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Attempting M31 and need help

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#1 mjcastles

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Posted 13 October 2017 - 02:20 AM

This seems like a good time of year to try M31 and I have put together a small kit to  attempt image capture. Using a Nikon D7200, with a 70-300mm zoom mounted on a iOptron SkyGuider Pro. I have managed to capture M31 but need to work on the tracking, as I am only getting 45 sec per image right now. Not sure if that is long enough and even then only collecting just over an hours worth of images.

 

Using DSS to stack and have PS CC for final processing.  I can 'see' M31, but the it is weak and not sure what it should look like before processing. Have seen all of the great images on here and elsewhere but not really sure what I should be expecting from a single image before DSS and then the composite image out of DSS and before PS CC.

 

Any advice or links to videos would be appreciated.  I found a couple of videos but cannot find them now that seemed pretty good. So much out there and yet some of it is a little brief and hoping to find a little more detailed videos to watch over and over (will need to remember to save a bookmark once I find one that I think is good). 

 

Thanks in advance, as I know you guys see these questions all of the time.



#2 happylimpet

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Posted 13 October 2017 - 03:46 AM

Individual subs always look weak, dont worry about that. And 45 seconds sounds fine for a sub length - how dark are your skies? Just keep churning them out - its all about total exposure (and calibration frames: darks, flats).


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#3 baron555

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Posted 13 October 2017 - 06:42 AM

Collect many hours worth.  Don't worry about the individual frames.  Don't forget to do flats, darks and biases......very important.


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#4 mjcastles

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Posted 13 October 2017 - 08:48 AM

I should have mentioned in the original post that I am shooting from my backyard, in a red zone near a white zone, so not the best sky's. I did take darks and bias, but no flats which I understand from reading last night would help with the corners. Nearest dark sky is a little 2 hours away, and a little over an hour to an place that is a blue zone.  Have done some lunar, solar and MW which  while not easy have come out pretty nice.  DSO, like M31 are a whole new ball game. 



#5 RobawGT

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Posted 13 October 2017 - 09:06 AM

What focal length on the lens are you using?  A before and after processing picture might help us comment more accurately.  I'm in the same bucket as you with light pollution, but more / longer subs would help bring out detail. 

 

I got 12 minutes of integration (4 subs x 3minutes) of cloud free sky last night and captured this picture of M31, no bias, dark or flat frames.  With my canon piggy backed on my telescope. I was surprised what I could pull out in processing even with so little integration. Maybe you can compare?

 

M31_10-12-17_v3.jpg

 

Canon 300d Piggybacked (100mm focal length)

Astroview Pro Mount

ISO 200

12 minutes integration - 4x3mins

 

On a side note, were you able to shoot MW from your backyard?  If so, I'm looking for tips on doing that.  I would have thought that light pollution would prevent any decent picture from coming out. 

 

Good luck and clear skies,

Robert



#6 mjcastles

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Posted 14 October 2017 - 01:12 PM

What focal length on the lens are you using?  A before and after processing picture might help us comment more accurately.  I'm in the same bucket as you with light pollution, but more / longer subs would help bring out detail. 

 

I got 12 minutes of integration (4 subs x 3minutes) of cloud free sky last night and captured this picture of M31, no bias, dark or flat frames.  With my canon piggy backed on my telescope. I was surprised what I could pull out in processing even with so little integration. Maybe you can compare?

 

attachicon.gifM31_10-12-17_v3.jpg

 

Canon 300d Piggybacked (100mm focal length)

Astroview Pro Mount

ISO 200

12 minutes integration - 4x3mins

 

On a side note, were you able to shoot MW from your backyard?  If so, I'm looking for tips on doing that.  I would have thought that light pollution would prevent any decent picture from coming out. 

 

Good luck and clear skies,

Robert

Not able to capture MW from the backyard - well not very good. Can see a faint image of the core, but nothing special.  I have to travel a couple of hours to really see it in a dark sky area. Working on the stacked images now.



#7 mjcastles

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Posted 14 October 2017 - 07:16 PM

I have not had much luck processing this in PS, but here is a jpeg of what I collected last night, stacked in DSS with lights, darks, flats and bias. Not sure if I am getting close or not, this is from 111x45s lights. If I get the darks where I want the highlights blow out and the lower left half seems to suffer from the light pollution as it is always a bit lighter.  Still looking for videos but nothing so far.

Attached Thumbnails

  • 101317_all_save.jpg


#8 RobawGT

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Posted 17 October 2017 - 07:03 AM

I've heard GradientXterminator for Photoshop is good, but here is a video that shows how to do it manually. This will help with the light pollution gradient. 

 

https://youtu.be/9weEol1aWds

 

I used to use photoshop, but my license ran out.  It's just one way to do it.  I am currently using the demo version of StarTools and it seems pretty easy to remove gradients (one click), however basic. 

 

Everyone keeps telling me that more integration time will help my images, but it seems like it will take hours and hours to get marginally better.  I really think I need to spend a night away from light pollution and see what I can get.

 

Regarding overstretching, Its pretty easy to overstretch an image (bringing the detail out blows up the bright parts).  I think the fix to this is again, more integration time or darker skies or both. 

 

I bet if you post a link to your stacked tiff file from DSS, you might get some help from someone who knows a lot more about processing.  I would give it a try as well, but can't say that I would be able to do any better.  

 

Best of luck to you,

Robert


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#9 bobzeq25

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Posted 17 October 2017 - 11:24 PM

I did a silly thing here, and processed your jpg.  It's silly because the jpg has blurred out information, in particular gradient reduction doesn't do well, and you had a big gradient.

 

Still, it does have a certain educational value <smile>, and I'm all about education.

 

M31newbie_ABE.jpg

 

As someone said, upload the stack as a tiff to something like Dropbox, ask people to take a crack at processing it.  As you can see, you captured more than you thought.  Processing is at least half the game, takes time and patience to learn.

 

The last 1/3 of this book (can be read separately) is a great introduction to processing.

 

https://www.amazon.c...n/dp/148180491X


Edited by bobzeq25, 18 October 2017 - 09:25 AM.

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#10 mjcastles

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Posted 18 October 2017 - 04:44 PM

Thanks for the input so far guys.  I can see that uploading a tiff will help, what you did with the jpeg is pretty amazing. I do have the book you mentioned, but have just started on it.

 

Here is a dropbox link (if I did it correctly - haven't used dropbox before) -  https://www.dropbox....l_save.TIF?dl=0



#11 bobzeq25

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Posted 18 October 2017 - 06:07 PM

Dropbox was fine.  I can only do a little better, because (this will take some time).

 

The camera records a "linear" image, where twice the data value is twice as bright.  Your eyes can't see the linear image.  It has to be "stretched", to be taken non-linear.  Thing is that's not advisable as a first step, things like gradient reduction work better on linear images.

 

The image you see after stacking in DSS is stretched.  DSS does that, so you can see what you've got.  But it does it very crudely, and as a first step.  What you want to do is save the stack as linear, and stretch it in your processing program, which gives you great control.

 

There are ways to do that.  What I like is simple, and reliable.  When you've got the stack, click "save to a file" on the left.  Then, in the save box check the box labeled "save with settings embedded, but not applied".  That saves the linear stack.  When you open it in your processing program, it will look very dark.  That is correct.

 

You then apply linear operations, stretch (go non-linear) and do non linear processing.

 

It's all very complicated, part of the charm for many of us.  Obviously, I can't explain in a few words, what the book says in 80-odd pages.

 

Bottom line.  That's a good start (better than my first M31), keep it up, go farther.

 

_101317_all_save_ABE_ABE.jpg


Edited by bobzeq25, 18 October 2017 - 06:12 PM.

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#12 mjcastles

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Posted Yesterday, 04:47 PM

Went pack to a previous stack and think I finally have something to show for more CC. I know it needs more work, but thanks for all the help. Now just to make more images and practice, practice, practice - oh, and probably ask more and more questions.

 

 

Attached Thumbnails

  • 101217_final.jpg

Edited by mjcastles, Yesterday, 04:48 PM.

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