Astrophotography

Just a little timeline chronicling my astrophotography dabblings so far.

July 27, 2018

I bought my first telescope! I opted for the Astronomers Without Borders Onesky – a collapsible 130mm (5in) reflector. I opted for this telescope because:

  • Relatively cheap at $200 – and I’m no stranger to the tendency for people to buy expensive telescopes that wind up collecting dust.
  • Good for visual – I knew I’d want to get into photography, but primarily to start, I wanted to just see some planets and learn the sky.
  • Compact/portable – easy for me to take places with less noise pollution (I live in the heart of an urban red zone).

I also bought a celestron kit w/ a variety of eyepieces, a 2x barlow, and a T2 adapter + 1.25” adapter for my Sony A7S II. This camera is not ideal for astrophotography, really, despite its low light performance. It has a large full-frame sensor and relatively few pixels, making for a general lack of detail in tiny objects through a telescope.

My first night I took it out to my parents’ place in Castillian Springs, where they live on a hill with unobstructed skies and much less light pollution. Spent some time getting acquainted with visual scoping, but didn’t have much luck with photography: I had trouble getting the focal point of the telescope on to my camera’s sensor – i.e. I couldn’t quite focus to infinity.

August 3, 2018

Skip forward a week, and I realized I could unscrew the barlow lens from its barrel and screw directly into the 1.25” adapter threads, which allowed me to give prime focus photography a try. Success! My first photo of jupiter and its moons, with uh … minimal (aka terrible) processing:

The following morning with fresh eyes I took a stab at reprocessing it with much better result – in this you can see all four moons! Barely!

August 4, 2018

Took my first stab at Saturn:

Not amazing, but definitely Saturn! The moon was rising late that night, so I gave that a whirl, with pretty good results:

On this night I also experimented with eyepiece projection – a different method of photography where you use an eyepiece and barlow in between the telescope and the camera to “project” the image from the eyepiece onto your camera sensor. I didn’t have much luck with this, unsurprisingly, as between the adapters involved and the small eyepiece lenses, the light actually reaching my camera was cut to nearly nothing. This explains why eyepiece projection is generally regarded poorly by most astrophotographers. Live and learn!

August 10, 2018

I ordered a 3X barlow, hoping to get a bit more detail from Saturn:

Not bad: bigger, but not much detail.

August 11, 2018

My first attempt at stacking!

This actually (surprisingly) worked quite well! This is a method where you take a video and use image stacking software to analyze the frames, discard the poor/blurry frames, and combine the remaining frames – generally for a boost in detail and reduction in noise. I didn’t have a lot to work with, because Saturn was projected as a very small dot on my sensor. Nonetheless it was able to pull out a decent amount of detail!

  • AWB Onesky
  • 2x Barlow
  • Sony A7S II
  • Stacked in Autostakkert
  • Wavelet/sharpened in Registax 6

August 12, 2018

Emboldened by the success with Saturn, I gave Jupiter a try, with the 3x Barlow – tracking manually with the 3X barlow is pretty challenging, but I managed to get it in the frame long enough to take a few videos and stack them:

Not bad! I had some weird issues with banding at first, which I alleviated by tweaking the color detection in Autostakkert. I am not entirely sure why I lost all the color in stacking, but it’s probably because there just wasn’t much color to begin with.

  • AWB Onesky
  • 3x Barlow
  • Sony A7S II
  • Stacked in Autostakkert
  • Wavelet/sharpened in Registax 6

August 14, 2018

Here’s something fun: around 10 years ago, my family went to Cape San Blas, FL for a week. I was just getting into photography – I had a Canon 20D, a wide angle lens, and no idea what I was doing. But the views of the Milky Way from the beach were spectacular. I tried taking some long exposures, but between the noise of my relatively old crop sensor and the heat, the results were riddled with noise and hot pixels. I gave up and never posted any of the shots I got that night.

Skip forward ten years, and here I am playing with astrophotography and learning all about image stacking. It occurred to me I might be able to salvage the original data. I had the 10 original raw images and I gave it a whirl. I was stunned by the results!

Before After

On the left is an example of an uncorrected frame I got that night. On the right, the result of stacking & cleaning up. Modern software is pretty cool.

  • Camera: Canon EOS 20D
  • Lens: EF-S 10-22mm (shot at 10mm)
  • ISO: 3200
  • Aperture: f/3.5
  • Shutter Speed: 30”
  • Total Exposures: 10
  • Software: DeepSkyStacker for stacking, darktable for levels correction & post-processing.

August 20, 2018

Another attempt at moon photography. It’s been rainy/cloudy all week, but there was a brief moment of clear skies before some storms moved in.

I played around with stacking/processing the photos of the moon with both PIPP/autostakkert and Pixinsight. Pixinsight, from what I can tell, is not really designed for planetary imaging, but I wanted to learn the tool and it was an easy place to start:

Autostakkert Pixinsight

You can see that there’s some weird fringing/ringing around the moon in the pixinsight version – still a lot of learning to do with that tool, but not a bad start!

  • Camera: Sony A7S II
  • Telescope: AWB Onesky 130
  • ISO: 125
  • Shutter Speed: 1/40
  • Total Exposures: 20
  • Software: PIPP/Autostakkert and Pixinsight

August 21, 2018

I got my first equatorial tracker mount! I don’t want to spend a ton of money before I have to (cough cough in theory cough), so I bought one of these – it’s a tiny little DIY type equatorial tracker. I had tested it out on a cloudy day and verified it mostly worked, even though I couldn’t see Polaris to align it very well. Last night the skies were clear for the first time in weeks, so despite the Very Bright Moon, I gave it a whirl in the opposite direction. Since I was mostly just testing the functionality of the tracker, I used a Jupiter-9 85mm – partially because it’s relatively light, fast and long, and partially because I was morbidly curious how bad it’d look (narrator voice: very bad).

I just pointed it randomly in the sky away from the moon, so nothing of note necessarily – but astronometry knows what it is. So as you can see there’s quite a bit of light pollution and noise, but still: the center stars are (mostly) stable! The stars on the periphery suffer badly from coma, due to my poor choice in lenses. This was my first chance to learn more about processing photos as well: specifically, the value in using flat frames to correct for lens vignetting/fall-off (in addition to dark frames) when stacking. Not particularly amazing results, but good confirmation that the gear works and some processing experience under my belt!

  • Camera: Sony A7S II
  • Lens: Jupiter-9 85mm f/2.0
  • ISO: 125
  • Shutter Speed: 2”
  • Aperture: f/4
  • Total Exposures: 100
  • Dark frames: 30
  • Flat frames: 20
  • Software: DeepSkyStacker and Darktable for levels adjustment

August 28, 2018

A day of unexpected success! I hadn’t planned on doing any shooting tonight, but the skies were remarkably clear, so I gave it a whirl. First I wanted to try my equatorial tracker again, with the goal of producing a basic wide starfield free of as much noise as can be expected in the city. I’d previously been having a lot of trouble with post-processing. Specifically, my flats were overcorrecting the final stacked image. This time around, I shot the flats outside by putting a white t-shirt over my hood and aiming a diffuse LED flashlight at it. Still not ideal, but it yielded much better results. No overcorrection!

  • Camera: Sony A7S II
  • Lens: Canon 85/1.8
  • ISO: 160
  • Shutter Speed: 2”
  • Aperture: f/2.0
  • Total Exposures: 80
  • Dark frames: 30
  • Flat frames: 10
  • Offset frames: 30
  • Software: Pixinsight proprocess batch script

Still nothing amazing – I just pointed the camera straight up and away from the rising moon, so that’s Vega on the left completely blown out. Still some trailing, of course, because my polar alignment wasn’t quite perfect. Still, encouraging results.

After this, the moon rose, making any further starfield attempts kinda pointless, so I figured I’d try to get Mars (so far my white whale) again. I’ve had a lot of trouble with Mars – never getting much beyond an overexposed blur. I think it’s just so bright I kept consistently over-exposing it. I made an effort this time to expose it properly and had some moderate success for a change! First, I stacked the entire wide field w/ Mars in DeepSkyStacker so I was able to get a shot cropped with some stars around it:

I then used PIPP and Autostakkert to stack just the planet itself. Pretty blurry but you can see a tiny bit of detail and, if you squint and really believe, the polar ice cap on the bottom.

  • Camera: Sony A7S II
  • Telescope: AWB Onesky 130
  • Barlow: Celestron 3X
  • ISO: 640
  • Shutter Speed: 1/500
  • Total Exposures: 60
  • Software: DeepSkyStacker for wider field image, PIPP + Autostakkert for planetary stacking

August 31, 2018

I got a new mount! Despite my intentions to not go overboard and spend a ton of money, I decided to go ahead and go overboard and spend a ton of money. I got a Skywatcher EQ6-R Pro mount. Why? In the pantheon of Things You Can Buy For Astrophotography (which I am learning every day is bigger than I thought), the mount you use seems to be what everyone recommends to start with. In addition to equatorial tracking, it can also do go-to navigation for telling it what to point at (after some alignment/calibration), and allows for fairly heavy loads (with a capacity far exceeding anything I’ll be using short-term with my camera or Onesky 130). The EQ6-R Pro is a newer and very well-regarded mount that comes highly recommended – and if I get bored of the hobby, it should hold its value and be pretty easy to sell. “Mount first” is a mantra I hear from a lot of people, because I think stability and tracking are paramount over anything else, so I decided to get the mount and learn how to use it before deciding if/how I want to proceed upgrading the telescope and other parts of the optical train.

Tonight I did a test-run of the setup/teardown and polar alignment on my deck (seen above along with my assistant Emma The Dog). It was not easy (more on that later), but it worked. I was able to point my telescope at Saturn and leave it tracking as long as I needed. I took some shots and stacked – probably the best result I’ve had for Saturn so far:

You can see the cassini division in this one, at least! At this point, the limiting factor for planetary photos is clearly optical – the collimation of my telescope and the tilt (the weight of my camera pulls it and the focusing ring away from the focal plane a bit) combined are reducing my ability to get shots with better focus. This may be improved if I collimate better, but probably it’s not going to get much better without a different telescope better suited to photography. I did also manage to point the telescope at Andromeda, M15 and a few other things, but I won’t humiliate myself from posting the photos I attempted from the city, since the sodium vapor lamps near my house mostly stole the show.

September 2, 2018

This Labor Day weekend my parents hosted a family get-together for some birthdays. I decided to take the opportunity to haul the new mount and telescope out to their place, since they live in Castillian Springs, TN – which, while not perfectly dark still has far less light pollution. I setup the mount early in the evening before dinner while we waited for it to get dark:

(Warning: boring ranting about mount polar alignment and goto tracking to follow – skip ahead to avoid.)

So. Getting this mount aligned was a bit of an ordeal. I spent about 3 hours trying it over, and over and over. Sweat pouring down my face, making treks back/forth to the house to watch tutorial after tutorial on youtube. I could find no fault with the polar alignment, but when I attempted the initial alignment (with 1, 2, or 3 stars), it simply didn’t seem to be working: I’d pick Vega as the first star, and it would slew to a point way off-target from where Vega was. At one point I even thought I had accidentally aligned it with a star other than Polaris and went out into the dark to do some old-fashioned star chart/constellation navigation to make sure I actually had it pointed it at Polaris, which I did. In the end, when I was about to give up, I decided to just power through the 3-star alignment and manually slew the telescope to where the star should be. Et voila, it worked fine after that. What I realize now is that I think I was expecting a bit too much of the hand controller’s initial alignment star acquisition. I thought something was wrong because it wasn’t anywhere near Vega, when in reality that’s just how it goes (and why many people opt to use a computer and eqmod over the hand controller).

I’ve also learned the extent to which polar alignment is separate/different from star alignment. If the mount is aligned at the North Celestial Pole via polaris, the equatorial tracking will work, period, regardless of anything else. Aligning the go-to functionality by initial stars is, conversely, entirely relative based on your location, elevation, and time, so it makes perfect sense that the first-pass before alignment is not going to be great.

Anyway, tl;dr: I got it working.

It was about midnight by the time I finally got goto working, so I didn’t have a ton of time. I pointed it at Andromeda first and took some lights, darks and improvised flats (paper towel and LED headlamp) with my telescope, some wide-angle 10mm shots of the milkyway with my camera, and some 200mm shots near IC59 (basically just stars). I didn’t bring a computer with me, so all processing of the data would have to wait for the next day.

This was my first time trying stacking with data actually much more sensitive to flat/dark calibration and noise, and it was a good test to isolate some weaknesses in my gear for this stuff. To start with, I dumped the shots of andromeda into DeepSkyStacker (vs Pixinsight, because I am still learning it and wanted a quick test), and could see that for some reason adding the dark frames basically ruined the photo:

No dark frames With dark frames

I’m still not entirely sure what went wrong, but after some deliberation with people in the /r/astrophotography discord, it seems likely that the issue is with the data and conversion from my Sony’s raw format to TIF. Sony’s raw format is not supported by either Pixinsight or DeepSkyStacker, so for this processing I had been converting to uncompressed (in theory) 32-bit TIF from Darktable and using that as source data in pixinsight and Deepskystacker. There’s no way of knowing what darktable is actually doing – someone in the discord channel said the supposedly uncompressed TIF seemed to still have bad compression artifacts. I was able to salvage the data into semi-presentable photos by just not using the dark frames. The conclusion I’ve reached is that for future attempts, I am going to use the Sony compressed RAW format, which pixinsight does actually support, and should hopefully yield much better results.

The good news is the mount performed admirably. From the shots I took (most at 30”), there didn’t appear to be much trailing. I suspect anything much beyond 30” would have started trailing a bit (based on some subtle drift I could see from frame to frame), but once I tackle the mount’s periodic error correction, I expect it to do quite well.

  • Subject: Andromeda
  • Camera: Sony A7S II
  • Telescope: AWB Onesky 130
  • Barlow: Celestron 2X
  • ISO: 800
  • Shutter Speed: 30”
  • Total Exposures: 30
  • Software: DeepSkyStacker + Darktable

You really don’t appreciate how big andromeda is until you get it into view. Why didn’t I turn the axis of the camera so the horizontal sensor was in line with the plane of the galaxy? I don’t know!

  • Subject: milky way and trees
  • Camera: Sony A7S II
  • Lens: Voigtlander 10mm
  • Aperture: f/5.6
  • ISO: 640
  • Shutter Speed: 30”
  • Total Exposures: 30
  • Software: Pixinsight + Darktable

Sadly I had no flats for the milkyway. I was able to improvise flats for the telescope and 200mm shots with a paper towel and LED, but this lens’s hood is so short there was just no way. Thus, quite a bit of dust spots evident. Clean your gear, kids. Flats would have also corrected the pretty severe light fall-off. I’ll have to figure out some sort of softbox contraption or just get better at doing them during the day w/ the sun.

  • Subject: widefield near IC59
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II
  • Aperture: f/2.8
  • ISO: 640
  • Shutter Speed: 30”
  • Total Exposures: 30
  • Software: Pixinsight + Darktable

This photo is not particularly impressive since it has no subject per se, but it shows pretty clearly that there was little to no trailing and that the 200mm is pretty impressive for this sort of thing – no visible coma in the corners at all. I wish now I had pointed it at andromeda instead of or in addition to using the telescope – I think it would have come out nicely, despite being a wider field of view (turns out Andromeda is huge).

September 4, 2018

Brief update: practiced setting up and tearing down the mount on my deck last night. I think I’ve got it down, at this point – was able to get it polar aligned and goto aligned in about 10 mins. Pointed it at andromeda with my camera + 200mm just to see what I could get. Despite the light pollution at my house, still came out pretty well! I think switching to compressed raw helped quite a bit.

  • Subject: Andromeda
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II
  • Aperture: f/2.8
  • ISO: 200
  • Shutter Speed: 20”
  • Light Frames: 40
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 10
  • Software: DeepSkyStacker and Darktable

Had some trouble with the pixinsight preprocessbatch script – it was complaining about inability to find stars. I’m not certain if it’s the light pollution or underexposure, but DSS had no trouble with it.

September 5, 2018

Minor update – turd-polishing edition. Clouds have rolled in, so I’m left to reprocess old data and hopefully learn some things. I took another stab at Andromeda from yesterday in Pixinsight this time. Everything worked pretty well and I was able to pull out a bit more detail, but I’m still stymied by the gradient from the plague of sodium-vapor streetlamps flanking my house. I feel like PI has a tool that can remove this, but I am not sure what it is yet.

September 13, 2018

The clouds have parted! After a week of heavy clouds, we finally had some clear skies last night. I might get lucky and have a few more days this weekend, too, despite the barrage of hurricanes currently off the coast. I setup the mount last night and decided to play with using just my camera, the Canon 200mm/2.8 and a Tamron 2X teleconverter. I knew the TC is not particularly great, but I was hoping the optical compromises would be worth the 400mm focal length and that I might be able to get some interesting stuff.

First attempt was M13 – it came out okay, all things considered. The TC added some horrendous coma in the corners, but I knew most of these targets would be in the center of the frame, so it looked okay. The good news is: I figured out how to fix the light pollution gradient! Turns out the Pixinsight tool I’ve been looking for is DynamicBackgroundExtraction (DBE). It lets you sample points along an image (avoiding actual data/stars) and develops a gradient that you can then subtract or divide from the master image. It worked great!

  • Subject: M13
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II w/ Tamron 2X teleconverter
  • Aperture: f/2.8
  • ISO: 640
  • Shutter Speed: 30”
  • Light Frames: 40
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - Color Calibration, DynamicBackgroundExtraction, Masked Stretch, Unsharp Mask

Next I tried Andromeda again because … why not. I’m sure it will be a frequent subject. This turned out okay, all things considered – not a lot of color or detail, but that’s to be expected given all the light pollution and the amount of glass it’s going through (including the cheap teleconverter). Still, glad I got a result without the awful gradient.

  • Subject: Andromeda (M31)
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II w/ Tamron 2X teleconverter
  • Aperture: f/2.8
  • ISO: 640
  • Shutter Speed: 30”
  • Light Frames: 40
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - Color Calibration, DynamicBackgroundExtraction, Masked Stretch, Unsharp Mask

Lastly I picked an arbitrary target before bed – the Triangulum Galaxy (M33). I thought this would be a long-shot, because I could hardly see anything in the test shots, but it turned out pretty well! I cheated and used the same darks, flats and offsets I took for andromeda since nothing else had changed, and I didn’t notice any detrimental effect – although there’s still some dust spots that weren’t eliminated by the flats. I’m not 100% certain why, but I should probably just clean my shit, really.

I was pleased to get a bit of color in this, and impressed that I got any detail in the galaxy at all – probably owing to its location high in the sky, so I was cutting through less atmosphere (and less glare from streetlight pollution).

  • Subject: Triangulum Galaxy (M33)
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II w/ Tamron 2X teleconverter
  • Aperture: f/2.8
  • ISO: 640
  • Shutter Speed: 30”
  • Light Frames: 40
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - Color Calibration, DynamicBackgroundExtraction, Masked Stretch, Unsharp Mask

All in all a pretty successful night – looking forward to having a chance to set this stuff up in some darker skies. I’m still deliberating on what path I want to choose for upgrading my optics – for now I am still enjoying learning how to use the mount and the processing tools. There are so many options to choose from between reflectors, refractors, etc – I’m still feeling out what I think the best path is. Using the AWB OneSky has somewhat lost its allure because it’s a tremendous pain to use (and obtain focus with), compared to the simplicity of mounting the camera + lens itself. But, I’m trying not to let this color my decision, since obviously the AWB OneSky is about as far as you can get from a telescope designed for imaging, and I know that better refractor setups are not without their annoyances (e.g. sensitivity to temp/conditions, etc).

September 14, 2018

Friday night – you know what that means: astrophotography, wooooo party. I took delivery today of a 72mm light pollution filter I bought on a whim for my Canon 200mm/2.8. There wasn’t much research that went into this purchase: it was simply the only filter I could find that’d fit my lens. It claims it filters out 570-610 nm so I decided to give it a whirl. First, though, I setup my telescope and attempted to get prime focus (without the use of a barlow). I succeeded but gave up pretty quickly on any attempts at photography for the simple reason that there are two or three mega-bright sodium vapor lamps blaring into my yard, and while the OneSky 130 is good at a lot of things, blocking incidental light is not one of them. Since it’s collapsible, half of the telescope is exposed (just 2 tubes), which is not a problem in dark skies, but in the city, it’s a massive opening for light/glare. I used it to align the mount (which I’ve gotten down to a relatively quick process now, fortunately), and took it off and just rolled with my camera.

First target was the Dumbbell Nebula (M27) simply because it was high in the sky. It came out pretty well! This is my first attempt actually picking up any nebulosity from anything with color, so that feels pretty good.

  • Subject: Dumbbell Nebula (M27)
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II w/ Tamron 2X teleconverter
  • Filter: Breakthrough Nightsky 72mm
  • Aperture: f/2.8
  • ISO: 800
  • Shutter Speed: 20”
  • Light Frames: 80
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Masked Stretch, Histogram Transformation, Curves Transformation, Unsharp Mask

Next I tried Andromeda again because why not. I still struggle with processing Andromeda – DBE seems to work splendidly on other more remote targets, but Andromeda’s size means I was constantly struggling between eliminating the background noise and losing detail in the galaxy itself. I am hoping this will be a non-issue when I try again from darker skies. Additionally, I might have better luck if I waited till it was higher in the sky. Nonetheless this is still the best results I’ve gotten of Andromeda – and not bad considering I’m shooting from the middle of a white-zone urban area.

  • Subject: Andromeda (M31)
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II w/ Tamron 2X teleconverter
  • Filter: Breakthrough Nightsky 72mm
  • Aperture: f/2.8
  • ISO: 800
  • Shutter Speed: 20”
  • Light Frames: 80
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Masked Stretch, Histogram Transformation, Curves Transformation, Unsharp Mask

By this point I was getting tired and running out of ideas, so I just pointed at M33 again, to see if the light pollution filter yielded better results than the previous attempt. It came out okay – slightly better than my first attempt, though I think that’s owed more to my skill with postprocessing improving than any improvement in the actual data.

  • Subject: Triangulum Galaxy (M33)
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II w/ Tamron 2X teleconverter
  • Filter: Breakthrough Nightsky 72mm
  • Aperture: f/2.8
  • ISO: 800
  • Shutter Speed: 20”
  • Light Frames: 80
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Masked Stretch, Histogram Transformation, Curves Transformation, Unsharp Mask

It was around this time that I noticed the Pleiades had risen – which around here is a sure sign you should be in bed. Because I prefer to make bad decisions, I tried to photograph that as well. It seemed to be turning out okay, but postprocessing attempts fell apart due to some sort of data corruption. I am not really sure what the issue was (something with my darks and/or offsets, I think), but it was segfaulting Pixinsight and DeepSkyStacker both. I managed to coax DSS to actually stack them somehow, but the whole thing was kindof a mess and I wound up with some sort of green tinge (in stark contrast to the normal stunning blue through the nebulous gas in the foreground you usually see). Oh well, next time!

  • Subject: Pleiades (M45)
  • Camera: Sony A7S II
  • Lens: Canon 200mm/2.8 II
  • Filter: Breakthrough Nightsky 72mm
  • Aperture: f/2.8
  • ISO: 160
  • Shutter Speed: 20”
  • Light Frames: 80
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Stacked in DSS, Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Masked Stretch, Histogram Transformation, Curves Transformation, Unsharp Mask

October 2, 2018

It’s been a while since my last update, so I’ll skip forward a bit and spare you all a lot of testing, successes and failures. First, I got a new telescope! I know, I know. It was a responsible purchase. I long ago came to the conclusion that the AWB Onesky 130 – while an excellent beginner telescope – is basically atrocious for photography (see above for reasons). I had a lot more success simply using my Canon 200mm + TC, despite the awful coma. While I did still spend some time waffling on the eternal reflector vs. refractor debate, I was quickly becoming enamored with the convenience/size of my lens vs. the bulkiness/unwieldiness of the reflector. I had read a lot about the Astro-Tech AT72EDII already, as it has a pretty good reputation as a relatively inexpensive doublet refractor, but they were out of stock on pre-order waiting for the next shipment to arrive. My waffling ended when someone on the /r/astrophotography discord mentioned he had one for sale. Done deal! It’s not terribly different from my lens + TC combo, with the exception that it’s, well, designed for astrophotography. Chief among the improvements are a silky-smooth dual-speed locking focuser and a solid 2” mount with a 1.25” adapter. This means I can mount my camera directly with a 2” adapter and take advantage of its full-frame sensor without vignetting. The downside is that this 430mm refractor probably isn’t as good for planetary stuff as a big aperture newtonian would be, but I feel comfortable with this compromise. Planetary stuff is fun, but I feel like it’s a bit limiting (there are only so many planets to take photos of).

The telescope arrived, and brought with it, of course, a week of rain. Once it cleared this past weekend I spent some time testing it out. Thus I came to the next dilemma: the only skyglow/light pollution filter I had was 1.25”. I’ve long been conflicted on the actual value of light pollution filters. Are they really necessary? Are the compromises worth it? Do I really want to put a $100 tiny piece of glass in front of my fancypants new telescope – effectively dropping the quality of light reaching my sensor to it as the lowest common denominator? Well, no way to know unless I tested. So, Friday night I gave it a whirl with the 1.25” adapter and the skyglow filter. Andromeda, as always, is my preferred target because it’s big, forgiving, and high in the sky – perfect for testing the relative merits of these difference approaches.

  • Subject: Andromeda (M31)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • Filter: Orion 1.25” Skyglow
  • ISO: 1600
  • Shutter Speed: 20”
  • Light Frames: 60
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

So, it kinda looked like shit. I had a lot of detail lost and no color evident. This wasn’t entirely a fair test because it was also extremely gross outside (90% humidity with dewpoint hovering right around ambient temperature), and so I didn’t do a super long set of photos. Nonetheless, it seemed somewhat evident to me that the filter was working against me in this case. Also evident is a lot of coma, which was expected – this is largely fixable with a field flattener, which I’ve already ordered, so hopefully that will be solved soon.

Saturday night I gave it another whirl with better conditions. I opted to test with the LP filter again, since it didn’t get a fair shake on Friday due to bad conditions. This time I also tried a larger number of longer exposures – somewhat bold, since it’d mean I’d be burned for the night if I screwed something up. The results were very encouraging though! Turns out more data is better, who knew:

  • Subject: Andromeda (M31)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 640
  • Shutter Speed: 60”
  • Light Frames: 100
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

I also took a stab at the Veil Nebula:

  • Subject: Western Veil Nebula
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 640
  • Shutter Speed: 60”
  • Light Frames: 100
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

I was amazed I got any nebulosity, but here is where I started to run into a roadblock. After doing the normal background extraction, I was seeing a lot of leftover noise. Noise that I couldn’t explain as being from light pollution – it was weird, ugly red splotches of noise. Thus, the results I got of the nebula were compromised by having to clip a lot of signal to get rid of the noise. I am not certain what the cause is yet, but the pattern seemed to have a circular-ish pattern, leading me to think there was some problem with my flats:

Sunday night looked to be my last chance for clear skies, so I gave Andromeda another shot. This time I opted to finally try the 2” adapter sans filter. I had good luck with a much bigger data set, so this go round I went big for 120 exposures at 60”, which would about push the limit of my battery life. It came out pretty great, despite still fighting a lot of noise (more still on that below). I even managed to get some color from this, though I think that had as much to do with post processing as it did with data acquisition:

  • Subject: Andromeda (M31)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 640
  • Shutter Speed: 60”
  • Light Frames: 120
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

This is easily my best result so far, and so I’m proud of it, but this is where things started to go off the rails a bit. I had some time left, so I decided to try M33 (Triangulum) again. I did roughly the same process (100 lights at 60”, 20 darks, 20 flat, 20 offset). However, during post-processing I encountered the same noise problem – and because M33 is so much smaller on my sensor, it made getting anything usable out of the data almost impossible. No amount of background extraction or noise reduction could get rid of it:

There was probably something miserably salvageable from this data, but I ended up giving up. I even sent the source data to someone in the /r/astrophotography discord, who generously offered to take a stab at it and even he gave up. You can watch it here if you’re particularly masochistic.

I am a bit frustrated because this is a problem I don’t know how to solve. The aforementioned person indicated he thought my flats were bad over and over and I am inclined to trust him, though I’m not sure how/where I’m going wrong. My current process is:

  • Lights: (pretty obvious, point at stars, do exposures)
  • Darks: put the cap on the telescope dew shield, repeat exposures (I’ve been doing 20, maybe not enough, but I don’t think it explains this)
  • Offsets: set camera to lowest possible shutter speed (1/8000s in the case of my camera), do 20 exposures
  • Flats: I rigged up a cheap LED tracing pad inside its box with a hole cut out for the dewshield of my telescope so I could just place it on top of the dewshield to provide a flat white surface to take photos of. Set camera to Aperture priority mode, leave everything else the same, take 20 exposures.

Current theories:

  • putting the LED thing so close to the lens element means I have to dim it to its lowest so I can get at least somewhat longer exposed flats (usually around .125/.10s). the low LED setting is maybe causing subtle flickering resulting in variance in the flats (I can’t see any, but it’s still possible)
  • putting the LED thing so close to the lens element means I’m getting weird reflections inside the barrel from incidental light
  • some mystery setting or factor in my Sony camera’s compress raw data means the pixel math being done with the flats, darks and/or offsets is resulting in this weirdness (???)
  • … something else

I think my next strategy is going to be taking the flats by simply setting up the tracing pad a few feet from the scope and pointing it at it, rather than just plopping it on top, operating on the theory that one of or both of the first two theories is affecting things. Fingers crossed for next time!

October 4, 2018

Had some clear skies this last Thursday, so I gave the dumbbell nebula a whirl, hoping taking flats differently would help with my noise issue. tl;dr it didn’t, but the photo still came out okay nonetheless!

So, whatever issue with noise I have is not the result of flats, or at least if it is, my attempt at taking them differently didn’t help.

October 5, 2018

With clear skies in the forecast and being a Friday night, I decided to take my gear out to my brother’s place – about an hour east of Nashville, blessed with much darker skies. It was rather remarkable, the difference – silly as it sounds, this was my first expedition into dark skies while actually knowing what I am doing – at least a bit. We spent a little time just doing some visual through his telescope and mine, before I set up my camera to take yet another stab at Andromeda – an obvious choice for my continued testing: it’s bright, easy to find and provides a good baseline for improving my data acquisition and processing.

  • Subject: Andromeda (M31)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 2000
  • Shutter Speed: 60”
  • Light Frames: 120
  • Dark Frames: 40
  • Flat Frames: 20
  • Offset Frames: 40
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

Next I wanted to take a stab at the Orion Nebula, but it hadn’t risen yet, so I took a shorter set of photos of M33. M33 never turns out particularly well for me – it’s fairly dim and so I think I’d need a lot more integration time to overcome all the noise, which is quite evident in what I got:

  • Subject: Triangulum Galaxy (M33)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 2000
  • Shutter Speed: 60”
  • Light Frames: 80
  • Dark Frames: 30
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

Not terrible, but not great – M33 is so small in the center of the frame with my not-so-long 430mm focal length field of view, it’s hard to combat the noise. I think a much longer set of exposures would help. Once done, the Orion Nebula finally rose, and I was not prepared for how big/bright it is. It’s normally obscured by trees/buildings from my house, so I had never seen it before. It’s huge! Even single shot frames were blowing me away:

The final stacked result was pretty impressive (to me):

  • Subject: Orion Nebula (M42)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 2000
  • Shutter Speed: 60”
  • Light Frames: 120
  • Dark Frames: 40
  • Flat Frames: 20
  • Offset Frames: 40
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

So, some pretty good results. What does all this mean for my Noise Problem? I am not sure. I am not even sure I still have a Noise Problem so much as just normal noise and a Signal to Noise problem – i.e. it’s entirely possible I just need more integration time in clearer/darker skies, and to lower my expectations for the noise likely to result from a fullframe mirrorless Sony on a relatively hot night. There was still plenty of noise in the image as clearly seen here in this autostretched preview of the integrated data:

So while I was able to get a pretty cool photo, you can see from the above preview that there was actually a lot more nebulosity/dust-lanes that had to be discarded because I couldn’t quite separate it from the noise.

A few takeaways though:

  • It seems likely that dithering would help – this is a process by which you literally move the object in your camera’s frame by shifting and rotating it. The result is that the data you are integrating is located in different parts of the image so there’s less of a tendency for noise itself to stack.
  • More data is better. This should go without saying at this point – while it’s fun to try to do multiple targets, I think next time I will try for a much longer data acquisition process on one target. (Although Orion is tricky because it rises so late).

October 15, 2018

Just a quick update here – mostly grey skies as we move into fall, but I did a bit of experimenting over the last week. First, I gave some more thought to my “noise problem” such as it is. I realized that when I first embarked on this hobby, I was shooting Sony uncompressed RAW (as I always had), and as noted in an earlier update, I quickly realized that none of my software supported this particular format. I switched to compressed RAW on the (I think now flawed) assumption/premise that Sony’s “compressed” RAW wasn’t really compressed so much as it was just a smaller RAW file with, I dunno, less dynamic range or something. (Insert an interlude here about how little I know about RAW file formats.) I think this was probably wrong, and I did some testing with my earliest uncompressed data by using Adobe’s RAW conversion tool to convert it to DNG. The results seemed somewhat promising! But, I didn’t really know what I was doing with processing back then, so I didn’t have a lot to compare to.

If I were a good scientist I would have done a test run with just uncompressed RAW but leaving everything the same. Alas, instead, I am impatient and tried shooting uncompressed RAW in addition to trying some manual dithering/rotation. You can see below a comparison of my original integration from dark skies a few weeks ago – the results are otherwise unprocessed and autostretched to show the noise profile. On the right are my recent results – far less good data (clouds mostly ruined most of the exposures and it was in the city anyway), but good enough for a comparison:

You can clearly see there’s none of the weird ribbons of striated noise and a much more “normal” noise pattern. There’s still a disappointing amount of noise in general, but perhaps more manageable. I didn’t spent a lot of time processing it further since there wasn’t enough signal it’d be worth it. Still, it’s progress. Ultimately I suspect that shooting uncompressed RAW didn’t help much (but is probably still nonetheless worth doing) and that it was mostly the dithering that avoided the weird patterns in the noise. What I don’t know yet is if this will actually make it any easier to remove. Further experimentation is necessary!

In unrelated news, my field flattener arrived! Looking forward to testing this out.

October 17, 2018

One thing I forgot to post from the Oct 15th session. I also wanted to try eliminating my Sony camera from the mix entirely (and I still may pursue this), so I gave Andromeda a shot with my trusty Canon 5D mk I. Partially I was just curious to see if the noise problem was any different (it was – much more ‘normal’ noise) or better (it wasn’t – a 13 year old camera shows its age), but it was also amusing to me in a sense to use this camera for astrophotography.

This particular 5D started its life in the hands of a friend’s boyfriend who used it to take photos of some pretty spectacular coldwater ocean life. It then made its way to me, and was my trusty daily driver for around a decade as I got my footing with photography in general. This camera was a beast and near-indestructible, taking all manner of abuse and still performing admirably. I thought it only fitting that instead of collecting dust, I at least close out (?) its lifespan shooting some stars. So, here you have it: Andromeda shot from my deck with an original mkI Canon 5D:

  • Subject: Andromeda (M31)
  • Camera: Canon 5D Mk I
  • Telescope: Astro-Tech AT72EDII
  • ISO: 800
  • Shutter Speed: 60”
  • Light Frames: 60
  • Dark Frames: 40
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

I didn’t do a hugely long integration for this test, since I just wanted to get a feel for the noise, but still – the results go to show that even an old camera is no barrier to doing astrophotography!

October 20, 2018

My brother had a pig roast this weekend! We had a few guys orchestrating things for the weekend, and I saw this as a clear opportunity to volunteer for overnight pig-watching duty. Why? You can probably guess. Turns out astrophotography and pig-roasting have something in common: they both require staying up all night. So, I gave Andromeda and Orion another whirl. Now, I imagine you’re getting a bit sick of photos of the same targets – I am too. But, in the interest of PseudoScience, I am trying to target the same things over and over so I can appreciate the more subtle improvements. Also, the moon was high and bright, so I needed targets that were brighter lest I not get much at all. Orion was also a choice target for this particular weekend, as the Orionid meteor shower was peaking.

  • Subject: Andromeda (M31)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 2000
  • Shutter Speed: 60”
  • Light Frames: 240
  • Dark Frames: 10
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

Not as much color as I’ve gotten in the past, and not super great – owing both I think to the high and bright moon washing things out, and the fact that, well, I was drunk and distracted by monitoring a roasting pig.

  • Subject: Orion (M42)
  • Camera: Sony A7S II
  • Telescope: Astro-Tech AT72EDII
  • ISO: 2000
  • Shutter Speed: 60”
  • Light Frames: 240
  • Dark Frames: 20
  • Flat Frames: 20
  • Offset Frames: 20
  • Software: Pixinsight - DynamicCrop, DynamicBackgroundExtraction, Background Neutralization, Color Calibration, SCNR noise reduction, Histogram Transformation, Curves Transformation, Unsharp Mask

Same goes for Orion – not quite as much color/detail as I got from truly dark skies. Notable, however, is that the field flattener seems to have helped quite a bit – still not perfect, but you can see that the corners are much less distorted. Still a lot of noise making it difficult for me to pull detail out of the dust lanes which were definitely there, but just too comingled with noise :( The core was a bit overexposed, too – something I could correct by taking some shorter exposures and compositing with the rest, but I had my hands full managing to take darks/flats/offsets while dealing with the pig, so .. next time, maybe.

The meteor shower was pretty fun, though. I spent a good amount of time in the hot tub with a glass of bourbon watching meteors while the pig cooked and my camera did its work. Highly recommended. There were a few bright meteors I hoped passed close enough to Orion itself that they’d be captured in a frame – and I was right! One of them went right through the frame:

… and another towards the bottom of the wider frame. It might give you some appreciation for how bright these meteors were, since this one was visible at near daybreak:

And, just for fun, here’s an animation of my exposures of Orion as they were rudely interrupted by the rise of our brightest star, the Sun – quickly putting an end to my night of astrophotography:

Next up: I bought a guidescope! I am hoping to actually try guiding to see if it improves detail. Should be fun!

October 24, 2018

The moon continues to be high and bright, making any attempts at DSOs (especially with the light pollution at home) mostly fruitless, so here’s the moon, waxing gibbous:

  • Subject: The Moon
  • Camera: Sony A7S II
  • Telescope: Astronomers Without Borders Onesky 130
  • ISO: 640
  • Shutter Speed: 1/640
  • ~2400 frames (MP4 movie), best 600 stacked
  • Quality-estimated/weighted/cropped in PIPP
  • Stacked in Autostakkert 3
  • Pixinsight - Color Calibration, MultiscaleLinearTransform wavelets
  • Darktable - Levels, sharpening

I have to admit I forgot what a tremendous pain it is to take photos through the AWB Onesky’s focuser – such a nightmare compared to my new refractor. Still, much more suitable (for the time being) for moon photography, since I can use a 2X barlow.