Noob in Deep Sky Dreaming of Galaxies - Forums

Topic starter

Oct 23, 2023

Hi fellow astrophotographers!

I've been mainly doing planetary photography, however deep sky, and specifically galaxies interest me a lot.

I tried looking into acquisition and processing - however it turned out to be way more confusing than I could ever imagine.

1. First of all, I was shocked to discoverer that you need different types of calibration frames like: dark, bias, flat, dark flat etc. This literally exploded my mind. Now Ive seen this in regard to nebulas - so I wanted to clarify that I dont care about nebulas, for me the main target are galaxies. Would I still need to go thru all of those calibration frames for a galaxy?

2. The next thing is acquisition itself. How should I ideally do it? Lets say Im trying some faint galaxy, like M74, or something brighter but still barely visible like M33. How many hours of integration would I need as a minimum? Furthermore - lets say I need 2 hours - so should I do 2 hours of exposure in 1 go? Or do I separate it into lets say 120 times by 1 minute? Or 24 times by 5 minutes? Which would be optimal?

3. And then processing. Ive installed DeepSkyStacker, however Im still very much confused about the interface. I did watch some youtube guides, and it gave me some basic understanding of it. However all the guides were in realtion to nebulas - so if you guys know any video where they specifically look at galaxy processing in deep sky stacker - please send it.

Thanks in advance for you help! Plz reply to each bulletpoint to make it easier to structure the answer.

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Konrad Krebs

Oct 23, 2023 · Edited: Oct 23, 2023

Hello Alien,

that is indeed a lot to learn in the beginning. I will try to pass on what I have learned in my 3 years of deep sky astrophotography:

Basically, it doesn't make too much difference whether you are photographing nebulae or galaxies when it comes to pure imaging.

1. You need either BIAS or Flat-Darks frames. Overall, it depends on what kind of equipment you have. With some modern cameras you can do without darks, also flats are not always necessary. For example, if you use a telescope that covers a much larger field than the galaxy, you could simply crop the vignetting. Of course, it almost always means at least a slight loss of quality if you work without correction frames.

2. This also depends very much on your equipment and your location. in principle, you ideally take several single images, which you stack. if you have strong light pollution, I would prefer shorter single images, if you have very dark skies longer ones. I personally never shoot longer than 2 minutes per image. At some point, the stars would also burn out. But that is, as said, also dependent on the camera and the telescope. If your telescope has f2.8, much more light comes in than at f11, so you should use a shorter exposure at f2.8.

3. I would personally recommend that you first do the same as with a nebulae and then try something around. Because at the core, galaxy and nebulae are relatively similar. I seem to remember that Adam Block had some videos where he processed galaxies, but with Pixinsight. I think Astrobackyard had an article on his website about the DSS.

I hope this has helped you a little bit overall.

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Joe Linington

Oct 23, 2023

1. Flats get rid of dust spots and vignette. If you want to have them, you should shoot them while you are set up, either right before or right after your imaging. They don't take long and they are hard(almost impossible) to make later. I often only use 15 flat frames but more is better and some people will argue that you need much more.

Flat darks OR bias frames go with flats. If you don't take flats, you don't need biases. Bias frames take seconds to take and can be taken later.

Darks get rid of amp glow and hot pixels. Some cameras need them more than others. You can often take these later but the closer the temp to your lights the better. I have a library of darks for my uncooled cameras with a set taken at about 5-10c intervals.

Realistically you can stack an image without any calibration frames. Depending on your gear it may look pretty bad and it may not. I have gone through a few different phases of using cal files including trying to be as lazy as possible by skipping the darks and using synthetic bias so I only had lights and flats. This mostly works with some of my cameras and make a mess with others. Flats make a huge difference and can't be taken after so it's best to always get flats and then you can play with the rest later.

2. You should take many shorter images (subs) and stack them. How long is it's own long topic and really depends on your gear but 30 seconds is not to short, 1 minute is my goto for galaxy type targets and 2 minutes may not be to long (but could be depending on gear and light pollution). Integration time greatly depends on your goals. There is a whole discipline (EAA) that is dedicated to shorter integration times. On the other hand the only question is how much patience do you have.

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Howard Richard

Nov 24, 2023

Planetary and Deep Space are two entirely different things.

The mount and telescope that you have for planets are the same, but from that point on, it will be brand new rabbit hole.

1. Embrace the journey. The flats, darks and bias frames are the cost of doing business. If you are creating planetary images, you certainly are able to create deep space ones too.

2. Consider a computerized assistant for acquisition. I use the AsiAir to automate targeting and light image acquisition. In addition, it can automate darks, flats and bias frame creation.

Good luck, and welcome to the rabbit hole…

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Oscar

Nov 24, 2023

1. You want to do astrophotography, you got to work for it. Just think about it, galaxies so so far away, galaxies that were never meant for human eyes to see. You need to work for it, you'll get better at it and it will become easy peasy at some point. It is well worth it.

2. This topic can get very scientific (to me). What I would do is experiment with combinations (such as more subs less exposure vs less subs and longer exposure) and see what gets the best result. Check out my gallery, you can still do stuff with 1 second subs.

3. Galaxies and nebulae are stacked the same way in DeepSkyStacker. The important part is the stars, not the object; the software uses the stars to align all subframes and stack them. Just follow any youtube guide for deep sky objects.

Dan_I

Nov 28, 2023

Since you are not tied yet to any stacking software, I advise you to learn to use Siril rather than DSS. It gives much better results IMHO. Plus it has scripts to automate everything (pre-processing and stacking).

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Alien_Enthusiast

Topic starter

Dec 2, 2023

Since you are not tied yet to any stacking software, I advise you to learn to use Siril rather than DSS. It gives much better results IMHO. Plus it has scripts to automate everything (pre-processing and stacking).

*** Atm im using DSS nad siril - do you mean that siril can also do what DSS does? Like stacking and stuff ***

JBNZ

Dec 2, 2023 · Edited: Dec 2, 2023

Yep :-)

Check out Deep Space Astro's beginner video …

www.youtube.com/watch?v=9K-V2VIcwfQ&t

It covers everything Siril can do and he gets into stacking at around 4:20.

It is very much an overview of the software, he deep dives into the features in other videos, but this is the one I started with to at least get an understanding of what Siril can do.

I have tried DSS but prefer Siril for stacking.

CS John

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Marcelof

Dec 2, 2023

One of the main differences between planetary imaging and DSO is light pollution. Planets are so bright that they are practically immune to it, for DSO it is the opposite. Fighting it is one of the most important things to do.

One of the best ways to do it is total integration time and you need a lot of it. To start getting decent results in galaxies you are probably going to need between 10 and 20 hours of integration. And it gets worse.

To efficiently combat light pollution you need a lot of frames of very short duration, between 15s and 30s each. That means that you need a lot of these frames, we are talking about thousands and this also implies a lot of power for the pre-processing, i.e., you need a powerful pc.

It is also very important to combat background noise to have a cooled camera.

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