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What can I do to improve my images? / What am I doing wrong?

beginner Celestron dslr equipment imaging reflector
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#1 18sampson

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Posted 10 July 2020 - 11:43 PM

Hello everyone,

 

Im having some trouble getting my images to turn out properly and am turning to y'all for advice. First I will provide a description of my equipment, then some of the photos I have taken. Let me know if theres anything you think I'm doing wrong / could be doing better. Any help would be much appreciated. I believe all my equipment is set up properly and I believe it has something to do with my exposure time / imaging specifically.

 

Equipment:

  • Telescope: Celestron 130mm x 650mm Newtonian Reflector
  • Camera: Cannon Rebel T5
  • Mount: Celestron AVX
  • Capturing Software: Backyard EOS
  • Stacking Software: DeepSkyStacker

Images:

 

https://ibb.co/Xp9QcTJ
https://ibb.co/D562rFj

 

157 x30 second subs @800 iso stacked 

30 Darks

30 Flats

50 Bias

 

 

 

 

I do believe I have corrected some of the significant coma and pinched optics by re-collimating and backing off my mirror clips. I am also under Bortle class 6 skies. I was wondering if there is anything I can do to improve my images further. To me they appear quite noisy and the color depth really isn't there. Any info would be appreciated. Thanks & clear skies y'all!


Edited by 18sampson, 11 July 2020 - 12:38 AM.


#2 bobzeq25

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Posted 11 July 2020 - 12:31 AM

Suggestions.

 

Flats.

 

More than 39 minutes total imaging time.  My rule of thumb is one hour minimum, two is better, four good.

 

Better processing.  You didn't list a processing program.  Processing is more than half the game.  Are you processing in DSS?  That's not a good idea.  This book is a good processing resource, explains the WHY, rather than just the what.

 

https://www.amazon.c.../dp/0999470906/

 

Dither.

 

Patience.  In five years, I've dragged myself up to a bit better than average. 

 

Study, this is a knowledge driven activity.  Here's your next book.

 

https://www.amazon.c...h/dp/1138055360

 

Minor point.  If that sub is unstretched, it has too many stars, indicating overexposure.  But not too bad, that's not your problem.


Edited by bobzeq25, 11 July 2020 - 12:34 AM.


#3 18sampson

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Posted 11 July 2020 - 12:42 AM

Suggestions.

 

Flats.

 

More than 39 minutes total imaging time.  My rule of thumb is one hour minimum, two is better, four good.

 

Better processing.  You didn't list a processing program.  Processing is more than half the game.  Are you processing in DSS?  That's not a good idea.  This book is a good processing resource, explains the WHY, rather than just the what.

 

https://www.amazon.c.../dp/0999470906/

 

Dither.

 

Patience.  In five years, I've dragged myself up to a bit better than average. 

 

Study, this is a knowledge driven activity.  Here's your next book.

 

https://www.amazon.c...h/dp/1138055360

 

Minor point.  If that sub is unstretched, it has too many stars, indicating overexposure.  But not too bad, that's not your problem.

Ah, sorry, I had some errors in my post. I took 157 Subs for 78 MINUTES of total exposure. I also did take flats, just mistook them for lights in my post. I'm not guiding so I dont think I can dither. Thanks for the resource recommendations. Also, I used photoshop to process and do the histogram stretch. 



#4 DanH.264

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Posted 11 July 2020 - 01:41 AM

It looks like you're trying to stretch too little signal from frames with low exposure.  I'd raise the ISO and/or exposure time until they become limits.  

Sure you get more noise overall with higher ISO, but at least the signal is easier to differentiate from the noise floor.


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#5 18sampson

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Posted 11 July 2020 - 01:43 AM

It looks like you're trying to stretch too little signal from frames with low exposure.  I'd raise the ISO and/or exposure time until they become limits.  

Sure you get more noise overall with higher ISO, but at least the signal is easier to differentiate from the noise floor.

Thats what I was thinking. Thanks!



#6 Kevin_A

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Posted 11 July 2020 - 07:34 AM

more signal needed.... 



#7 kathyastro

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Posted 11 July 2020 - 07:40 AM

A coma corrector.  At f/5, the scope really wants one, and it shows in the corners of you images.

 

Your mount should be capable of longer exposures even without guiding.  Try for 60s subs.  You'll have to make sure that your polar alignment is excellent.  60-second subs are possible even with a polar scope alignment.  With the electronic polar alignment aids nowadays, you should have no difficulty getting it that accurate.



#8 Huangdi

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Posted 11 July 2020 - 07:47 AM

Hello everyone,

 

Im having some trouble getting my images to turn out properly and am turning to y'all for advice. First I will provide a description of my equipment, then some of the photos I have taken. Let me know if theres anything you think I'm doing wrong / could be doing better. Any help would be much appreciated. I believe all my equipment is set up properly and I believe it has something to do with my exposure time / imaging specifically.

 

Equipment:

  • Telescope: Celestron 130mm x 650mm Newtonian Reflector
  • Camera: Cannon Rebel T5
  • Mount: Celestron AVX
  • Capturing Software: Backyard EOS
  • Stacking Software: DeepSkyStacker

Images:

 

https://ibb.co/Xp9QcTJ
https://ibb.co/D562rFj

 

157 x30 second subs @800 iso stacked 

30 Darks

30 Flats

50 Bias

 

 

 

 

I do believe I have corrected some of the significant coma and pinched optics by re-collimating and backing off my mirror clips. I am also under Bortle class 6 skies. I was wondering if there is anything I can do to improve my images further. To me they appear quite noisy and the color depth really isn't there. Any info would be appreciated. Thanks & clear skies y'all!

There are a few significant issues with your image. First of all, get a Nikon, the banding will be gone.

 

Just kidding...But banding is a serious issue in your image, that is why dithering is so important. Sooner or later you will want to autoguide anyway. But even without guiding you can manually dither. 

 

Another big issue is coma, like kathy said you will need a coma corrector. Please keep in mind that not only the stars are elongated and out of focus, but also all of your details get smeared and blurred.

 

The key to getting good images is having good data to start with. So I suggest you get round stars, then you can start worrying about processing.

 

 

More integration time will obviously help, but I'm not sure what you're expecting to get. When imaging emission Nebulae, modded or unmodded, the RGB only image usually is going to be largely red and will have a lot of stars. If you want to really get glowing colors and lots of nebulosity, then sooner or later you will need narrowband filters.

 

Your setup works best for big galaxies, such as M101, M31, M33...not nebulae. 



#9 the Elf

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Posted 11 July 2020 - 12:10 PM

The AVX is not the best choice for imaging. I used one for about one year and happily upgraded to an EQ6-R. The difference is like night and day. But this is not what is wrong with the image right now. For a DSLR dither is very important. Most objects need several hours of exposure time. With 30 sec subs this is a huuuuge amount of data. Rather sooner than later you have to get into auto guiding so that you can take longer subs and dither. As you are already using a computer PHD is the logical option. Get a guide camera, make sure it is a mono. ZWO ASI 120MM is a good choice in the low price segment. With a newton OAG might be impossible, I recommend you start with a guide scope. I like this one very much:

https://www.teleskop...inderscope.html

It is sold under different brand names in many countries. It is often called "de luxe".

ISO 800 is a good choice for your camera. As long as you shoot targets small compared to your field of view and can crop off the bad corner stars. If you want to use the full field of view, you need a coma corrector. But beware, some newts have very little back focus. Make sure you find someone who is using a DSLR with that particular scope and coma corrector before you pull the trigger. In a DSLR the sensor is deep down in the body. An astro camera has it's sensor much closer to the front.



#10 Alen K

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Posted 11 July 2020 - 12:43 PM

Exactly which model of Celestron 130mm f/5 (650mm focal length) Newtonian is it? Actually, it might not matter because I am not aware of any with 2-inch focusers, but maybe I missed one. If yours has a 1.25-inch focuser, then a coma corrector is not an option. And many (most?) of Celestron's 130mm Newtonians actually use spherical primaries. I was astounded to learn this but Celestron for many years now has just been a brand name for Synta. Quality has gone out the window. If yours has a spherical primary, there is nothing you can do to improve image quality. 

 

The only good 130mm Newtonian I know of for astrophotography is this one from Sky-Watcher. But you would need to import it from the UK or Germany. By all reports it is very good for a Newtonian. Baring that, if your current 130mm Newtonian lacks a 2-inch focuser and/or lacks a paraboloidal primary, the best thing you can do is replace it with something like an 80mm ED refractor. Your AVX mount should do okay with that. 



#11 the Elf

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Posted 12 July 2020 - 02:41 AM

 

Your AVX mount should do okay with that.

Well, maybe. The AVX is very problematic when imaging near the zenith. Dec is oscillating when guiding. At medium alt it works when you keep it at a short leash, i.e. very short guiding intervals. For unguided you need to train PEC first. This is probably the only great plus of this mount. Not many come with permanent PE correction in this price class.




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