endless-sky

When all you have is a 384mm at your disposal, galaxies (except for maybe two or three particularly big ones) are no bigger than a dust mote... 🤣 I also have a Celestron C8, but that would require probably a better mount, an OAG, and a different guide-camera. I have just started with the basic "wide-field" setup, so I am not there, yet. That's why, for now, I dread galaxy season!

I feel you. I have only managed 5 targets of the many, many more I would have like to capture, since October of 2020 when I finally got my imaging refractor. Now dreaded galaxy season is coming and won't be able to do much until May, when the Summer arm of the Milky Way starts to rise. And guess what? I had a whole week of clear, beautiful nights right across this last New Moon. Right when I didn't need them and couldn't do anything with them. Ain't Murphy a b***h?! 🤣

Thank you for the kind comment, Lee! Glad you liked it, too! And thanks to everyone that liked the images!

After a 20 year long hiatus - my last astrophoto was captured with a film camera in 1997 - at the beginning of 2020 I decided it was time to start again. So, January 25th 2020 I brought home my used Sky-Watcher NEQ6 Pro and I immediately started taking photos. Obviously, my first target was M42 in Orion. This was my first digital astrophotography. 31 subframes, 30s each, taken at ISO800 with my unmodified Nikon D90, Nikkor 70-300mm at 300mm f/6.3 - January 28th, 2020, home front yard, Bortle 5/6 sky, no guiding, no filters. A grand total of 15.5 minutes... A couple of weeks later, me and my wife went to spend Valentine's weekend in the mountains. Of course I couldn't avoid taking advantage of the Bortle 4 sky and I took all my gear with me. Same target, 52 subframes, 45s each, taken at ISO800 with my unmodified Nikon D90, Nikkor 70-300mm at 300m f/5.6 - February 14th, 2020, Tonadico, Bortle 4 sky, no guiding, no filters. 39 minutes total integration. After I finished post-processing the second photograph, I was so happy with the result. It felt amazing that I was able to capture so many details and more nebulosity compared to the photo taken from home. Months passed, gear was changed. First one being the camera: at the end of February I bought a Nikon D5300 and a couple of months later I astromodified it on my own, adding a UV/IR cut filter in front of the sensor, after cutting it to size. In October the rest of the setup finally arrived: Tecnosky 80/480 APO FPL53 Triplet OWL Series imaging telescope, Artesky UltraGuide 60mm f/4 guide scope and ZWO ASI 224MC guide camera. Also, an Optolong L-Pro 2" light pollution filter. After months of imaging and getting more experienced with PixInsight, it was just a matter of waiting before I could have another go at one of my favorite targets. And maybe give it a little more justice. This project took me more than a month, due to the rare clear nights opportunities I have had here lately. I started acquiring in January and finished a couple of weeks ago. M42 taken over 8 nights, under my Bortle 5/6 sky. Total integration time: 18h 04m 00s for the nebula. 714s (14s subs) + 2065s (35s subs) for the Trapezium and the core. Here are the acquisition details: Mount: Sky-Watcher NEQ6 Pro Telescope: Tecnosky 80/480 APO FPL53 Triplet OWL Series Camera: D5300 astromodified Reducer/flattener: Tecnosky 4 elements, 0.8x Guide-scope: Artesky UltraGuide 60mm f/4 Guide-camera: ZWO ASI 224MC 2021/01/12: Number of subs/Exposure time: 33@300s. Notes: L-Pro filter, no Moon 2021/01/13: Number of subs/Exposure time: 33@300s. Notes: L-Pro filter, no Moon 2021/01/15: Number of subs/Exposure time: 38@300s. Notes: L-Pro filter, Moon 8% illuminated 2021/01/18: Number of subs/Exposure time: 36@300s. Notes: L-Pro filter, Moon 30% illuminated 2021/02/13: Number of subs/Exposure time: 30@300s. Notes: L-Pro filter, Moon 4% illuminated 2021/02/14: Number of subs/Exposure time: 23@300s. Notes: L-Pro filter, Moon 9% illuminated 2021/02/15: Number of subs/Exposure time: 51@14s + 48@35s. Notes: L-Pro filter, Moon 15% illuminated 2021/02/17: Number of subs/Exposure time: 11@35s + 38@180s + 1@300s. Notes: L-Pro filter, Moon 30% illuminated Total exposure time (main integration): 65040s = 18h 04m 00s. Total exposure time (35s integration): 2065s. Total exposure time (14s integration): 714s. Pre and post-processing: PixInsight 1.8.8-7. Full HDR Version: Masked Stretch Version: Blended Version (50% HDR + 50% Masked Stretch): To my personal taste, I like the blended version the most. I think it brings out the best of both worlds (HDR and soft, less contrasty but more colorful look). I must say, I am very pleased and happy with the result. Not to boast, but I think I have come a long way since I started. Obviously the better gear and the much, much longer integration time helped. I think I actually spent more time post-processing it than acquiring it. Especially since I had to do the work almost twice: I post-processed the HDR and the Masked Stretch images separately, making sure I used the same processes and with the same strenght in both, so that I could combine them effectively, if I decided I didn’t like the look of the HDR alone. I also think I managed to tame the stars a lot more, compared to my previous post-processing attempts. As usual, here’s a link to the full resolution image(s): Orion Nebula (M42), De Mairan’s Nebula (M43) and Running Man (NGC 1977) Thanks for looking! C&C welcome!

Thank you, Lee! As long as I succeed sometime in the future, it doesn't matter how many times I fail until then. I'll keep trying!

Thank you, Martin. Yes, they do look kinda nice, but I would like to tone them down and reduce them just a bit. I am not a fan of a completely starless image, but I do love when people manage to get the "narrowband effect" on their star sizes.

Lee, I tried this method and while it works great on the stars, reducing the stretch and their size, I don't really like what it does to the "part of the image I care more about". Let me explain. If I check the "Rescale result", the stars are blended in nicely, but the main nebulosity loses a lot of stretching and gets toned down. It's almost like the nebulosity matches the stretch of the stars, which - with the main goal of rendering it as clear, bright and apparent as possible - defeats the purpose. If I don't rescale the result, the stars are still somewhat smaller, but their core looks completely saturated. Maybe I need to play with coefficients, instead of a direct 1+1 sum (for example, A1 + 0.5*A3, or 2*A1+A3) and try with Rescaling on and off and see what combination comes out the best. I haven't looked at the video, yet, but I am planning on doing so, soon. Thanks again for the tips, but it looks like I haven't found the light, yet.

Fantastic guide, Lee! Thank you very much! I'll definitely give it a try tomorrow. If you managed to get such a good result on a JPEG, I should be able to get something decent with the original data. Thanks!

Thank you very much, Giorgio! I tried, but then I don't really know how to work the stars back in, with different levels of stretching. I would like to see a detailed tutorial or guide. It's one of the steps that would definitely improve my post-processing, if I knew how to do it.

Thank you for the kind comments, Lee! Much appreciated!

I would like to share my fourth image. With my "lucky week" of imaging, along with M33, I managed to finish also this project. This is my longest integration to date. These are IC 405 and IC 410, also known as the Flaming Star Nebula and the Tadpole Nebula, respectively, taken over 7 nights, under my Bortle 5/6 home sky. Total integration time: 18h 29m 00s. Here are the acquisition details: Mount: Sky-Watcher NEQ6 Pro Telescope: Tecnosky 80/480 APO FPL53 Triplet OWL Series Camera: D5300 astromodified Reducer/flattener: Tecnosky 4 elements, 0.8x Guide-scope: Artesky UltraGuide 60mm f/4 Guide-camera: ZWO ASI 224MC 2020/11/18: Number of subs/Exposure time: 41@240s + 1@300s. Notes: L-Pro filter, no Moon 2020/11/21: Number of subs/Exposure time: 48@300s. Notes: L-Pro filter, Moon 46% illuminated 2020/11/24: Number of subs/Exposure time: 48@300s. Notes: L-Pro filter, Moon 75% illuminated 2020/12/07: Number of subs/Exposure time: 15@300s. Notes: L-Pro filter, no Moon 2020/12/13: Number of subs/Exposure time: 22@300s. Notes: L-Pro filter, no Moon 2021/01/10: Number of subs/Exposure time: 37@300s. Notes: L-Pro filter, no Moon 2021/01/11: Number of subs/Exposure time: 18@300s. Notes: L-Pro filter, no Moon Total exposure time: 66540s = 18h 29m 00s. Pre and post-processing: PixInsight 1.8.8-7. This image was particularly hard to process, since there are many bright stars and stretching the nebulosity while taming the stars was quite difficult. I am sure I didn't manage it as well as I would have liked. Here's a link to the full resolution image: Flaming Star Nebula (IC 405) and Tadpole Nebula (IC 410) Thanks for looking! C&C welcome!

Well, good to know, thank you! I'll definitely try it. Yes, good tip on the rotator screw, I noticed as well that if I do it too tight, it introduces tilting to the image. I have always turned it with my fingers, without forcing it, just enough that it doesn't come loose on its own.

Thank you! I must admit that I have never spotted it naked eye, but I took a look at it with my C8, from home. I would definitely like to see it - and Andromeda - just with my eyes!

Thank you, Giorgio! I thought the backfocus was supposed to be 55mm and I have been struggling to get it right. But then I saw on the website of teleskop-service in Germany that the backfocus for their 4 elements reducer is actually 61mm. Mine looks a lot similar to that one, despite it being a different brand. You saying that it needs to be 61mm also confirms the theory. Next Full Moon I will give it a try increasing it to 61mm and see things get better, thanks!

Thank you! I am mainly interested in nebulae, since right now I have neither the mount nor the scope to capture small galaxies. But M33 is fairly large and I gave it a try anyway. One hour here, one hour there (that's why it took me so long to finish it), while I was waiting for other targets to be high enough in the sky to begin imaging them. However, I was particularly pleased and had a wonderful feeling when I started seeing H-alpha regions (nebulae) appearing in the galaxy itself, as I was post-processing it. It is amazing that I can capture nebulae that are on a galaxy 2.9 millions light years away from us!

I would like to share my third image. I finally had a "lucky week", since my last session, December 18th. I managed 5 clear nights out of the past 6 (has to be a record, at least for me and my area) and I was able to finish a couple of projects I had started long ago and start a few new ones. This is M33, also known as the Triangulum Galaxy, taken over 10 nights, under my Bortle 5/6 home sky. Total integration time: 10h 14m 00s. Here are the acquisition details: Mount: Sky-Watcher NEQ6 Pro Telescope: Tecnosky 80/480 APO FPL53 Triplet OWL Series Camera: D5300 astromodified Reducer/flattener: Tecnosky 4 elements, 0.8x Guide-scope: Artesky UltraGuide 60mm f/4 Guide-camera: ZWO ASI 224MC 2020/11/08: Number of subs/Exposure time: 11@240s. Notes: L-Pro filter, no Moon 2020/11/09: Number of subs/Exposure time: 10@240s. Notes: L-Pro filter, no Moon 2020/11/20: Number of subs/Exposure time: 15@240s + 4@300s. Notes: L-Pro filter, Moon 30% illuminated 2020/11/21: Number of subs/Exposure time: 22@300s. Notes: L-Pro filter, Moon 45% illuminated 2020/11/24: Number of subs/Exposure time: 20@300s. Notes: L-Pro filter, Moon 75% illuminated 2020/12/13: Number of subs/Exposure time: 12@300s. Notes: L-Pro filter, no Moon 2020/12/14: Number of subs/Exposure time: 8@300s. Notes: L-Pro filter, no Moon 2020/12/18: Number of subs/Exposure time: 6@300s. Notes: L-Pro filter, Moon 20% illuminated 2021/01/10: Number of subs/Exposure time: 9@300s. Notes: L-Pro filter, no Moon 2021/01/11: Number of subs/Exposure time: 15@300s. Notes: L-Pro filter, no Moon Total exposure time: 36840s = 10h 14m 00s. Pre and post-processing: PixInsight 1.8.8-7. Image was Drizzle Integrated and then cropped to original sensor size (6016x4016), without resampling. So, it appears as if taken ad double the focal length (768mm instead of 384mm). Image scale 1.04 arc-sec/pixel. Here's a link to the full resolution image: Triangulum Galaxy (M33) Thanks for looking! C&C welcome!

Thank you, Mark, for the thorough explanation! I'll give a try to those PixelMath expressions on my next post-processing. The L-Pro is a relatively "mild" filter, but yes, there are pictures of color checker cards taken with and without and there is indeed some noticeable difference. All my images of emission nebulae are red instead of pink, so I guess "true colors" are out of the window...

Thank you both! Lots to read and digest. As for your workflow, Mark, I am lost after point 1: PhotometricColorCalibration, which I already do - and that's about my stopping point... 😅 You also mentioned light pollution subtraction. I am assuming DBE (or ABE) - I prefer the former. I have been doing this as step 1 (well, maybe not exactly 1, but after master integration and dynamic crop to get rid of the edges). Then I do PCC and also check Background Neutralization in the same process (used to do BN before, but then I saw it already built in and started doing it along with PCC). Does this sequence sound "correct" so far? Would absolutely love a detailed tutorial on the following steps, if you can spare the time, as I have no clue on how to adjust for CCM. Assuming D5300, would I pick the values given by Color Response --> CIE-D50 in the link you posted? Also, other point: I astromodified my camera and put a UV/IR cut filter in front of the sensor. I assume the same matrix doesn't apply anymore? Even more so if there's a light pollution filter (L-Pro) in the imaging train. Correct?

Hi Vlaiv. I use PhotometricColorCalibration for all my RGB images (taken with the D5300). Could you explain me why it doesn't work as expected? Are there some other methods I could use in PixInsight to get to a more correct white balance?

I wouldn't say it's the same type of comparison. When we do astrophotography and processing, we don't invent data, we don't take the healer brush and make parts of a nebula disappear, because they don't match a standard of what a beautiful nebula should be. We work with the data we have and we try to bring the signal (the object) as high as possible, while trying to render the noise as low as possible. Without creating artefacts. We are manipulating the data that's there. But smoothing out the "skin" of a nebula would be something counterproductive, because we would actually get rid of details, instead of showing them more.

Each noise reduction technique allows for a more aggressive stretch to be applied to the image. The autostretch will try to take advantage of this by pushing the image more, everytime you perform an action that reduces noise. If you actually like a stretch from a previous step, you can create an instance of it by dragging the triangle on the workspace. That way, if you accidentally perform a new autostretch and do not like the results, you can always go back. I used to rely on autostretch almost entirely. Now I try to use iterative approaches, masked stretches, and play with masks and HistogramTransformation in a more manual, controlled way. I feel I can achieve better results, this way. The autostretch is, more often than not, too much, for my taste.

I think it's a fine - and difficult - balance, but yes, details and amount of nebulosity / parts of the subject have a higher priority over colors (and their resemblance of reality). Going to the extremes, many subjects that are rich in H-alpha, would show their best with a monochromatic camera and a narrowband H-alpha filter. In that case, you would have no colors. But the highest amount of details your eyes can see (for that imaging train combination). This because your eyes have more "resolution" in greyscale than in colors.

Might this - T2-NikonS - work?

The line between art and science is very thin. Colors are most likely always an interpretation, and to be honest, I doubt they resemble the actual colors of the subject. Even when the photographer actually tries to do a white balance as close as possible to what the object might look like in reality. The bluish/golden renditions that you are seeing are probably been captured in narrowband (typically H-alpha, OIII, and SII), and then mapped to the Hubble palette: SII to red, H-alpha to green and OIII to blue. Of course, there are tons of variations of color mapping and those will all produce different results. Sometimes people only shoot with two bands and map one on one color and the other for the remaining two colors. These, including the Hubble palette, are not intended to render the true colors of the object, but rather to exasperate the contrast of the different gases and wavelengths in order to make them stand out more and be more visible. Even the same data, given to two different astrophotographers, will inevitably produce two different results, because they will be post-processed according to the taste of each. As far as me, I try to not over-saturate or over-stretch the image, but try to keep a more natural, soft and blended feel. But I am shooting with a color, astromodified DSLR. That might change, when I'll get into monochrome and narrowband territory.

Why isn't everyone an astronomer? I have asked myself the same question multiple times, but never gave it much of an answer. It would seem only natural to be in wonder of such a marvellous beauty that is our visible sky. However, if I had to try to answer, I would say: - because it's expensive; and the more into it you get, the more money is needed for the next "bang for the buck". You start visually, then binos, then a small achromatic refractor, then a 114 mm Newton, then a Celestron C8, then you want to get into imaging and buy an equatorial mount, an FPL-53 triplet, a dedicated DSLR (to astromodify it), a guide scope, a guide camera (till here, this is my actual path), then in the future you'll want a monochromatic, cooled astrocamera, filterwheel, filters, bigger scope(s), bigger mount(s), more cameras. As long as there's Universe to observe/photograph, there will really be no end on the amount of equipment you'll want to have. There's always something dimmer, smaller, and further away that you'll want to see/photograph and that your current gear won't allow you to - because it's not taught in schools; at least not when I attended, more than 30 years ago. I had to develop an interest into Astronomy on my own. I was fortunate enough that the son (older than me) of some family friends had an Astronomy book and let me look at it when we used to go visit. After the first couple of pages (if you don't count the cover and the first few blank pages/introduction), I was hooked (I was less than 6 or 7 years old) - because you need nights in order to enjoy it (unless you are only interested in the Sun); nights are when people usually sleep after work / spend time with their family / relax / watch TV. It's hard to find time for a few hours under the stars when you take all these into account - because it's weather dependent; if you are hardcore about running / cycling / doing activities that require you to be outside, you can still do them/enjoy them (maybe a little less), even if it's cloudy/raining. But no amount of money and gear will clear the sky for you to use it. You'll have to wait for a clear night. Then there's the Moon. Sometimes, a clear sky night with no Moon feels rarer than the Great Conjunction that we just had... - because it's light pollution dependent; and as time passes, light pollution is only destined to grow. 20-30 years ago I could find a dark sky in less than a 30 minute drive. Now I probably have to drive 1/1.5 hours to get to a dark sky. You can find a "solution" to this by doing narrowband, but then see the first answer above (monochrome, filterwheel, filters = $$$) So, you really, really need to be into it, for all of the above (and more) to not matter much to you and still allow youreslf to enjoy it. To me, everytime I see / photograph a DSO, a planet, the Moon or a comet, I still feel the same wonder / humbleness that I did at that first page with a photograph, of that book that I was lucky enough to see when I was still young enough that my age could be counted in less than two full hands. And I probably will keep feeling until I am too old to be able to see.