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Please Help! Deep Sky Stacker Woes

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#1 Astrolamb

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Posted 08 April 2021 - 11:21 AM

I have been have been having an odd issue with DSS recently.

 

For some reason when I register pictures, subs with blatant star trails are registered and scored higher than subs with little to no trailing at at all.

 

When I attempt to stack with all subs checked, DSS will stack what registered best and throw out any outliers as expected. The problem with this is that the majority of the frames that get stacked are ones with trailing. Using Kappa-Sigma stacking I can eliminate most of the trails but I know that this is cutting into the data as well.

 

When I attempt to stack with only the best subs checked(very little to no trailing at all), DSS will still not register any pictures that I can visually identify as the best and when stacking it will only use a couple of frames. 

For example, I took 20 3m unguided subs of the Monkey Head nebula last night, when letting DSS do its thing on its own it stacked 10 frames.

When I only used the 9 best subs, DSS only stacked 2 frames. 

 

I try to register the pictures to find at least 50 stars, I have registered with and without the median filter enabled, I have used the "Raw/FITS DDP Settings" to change the baseline brightness when registering to find even more stars, and I have changed almost every other setting I can find trying to get the registration and stacking to play nice and use the best frames. 

 

I have also tried stacking with the "Stack After Registering" option enabled at 100% to try and force DSS to use all of the best frames but it never works for me. 

 

Any help, comments or suggestions would be greatly appreciated.. I was already planning on buying PI but if this keeps up I may make it a bit of an emergency priority. I don't want all of my good data to go to waste especially since the Monkey Head Nebula is setting in the sky for me right now and I really wanted to try and get a good stack of it before its gone for the year.  

 

If it will help I can share subs, details of acquisition and equipment or anything else needed.  



#2 bobzeq25

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Posted 08 April 2021 - 12:16 PM

Any help, right?

 

Astro Pixel Processor.  Like PI it calibrates/stacks/processes.  Has an excellent gradient reduction tool.  Gives fine results.  It's useful to think of it as PixInsight Lite.

 

Much easier to learn, and time spent with APP is not wasted if you later move to PI, much will transfer.


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#3 Astrolamb

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Posted 08 April 2021 - 12:49 PM

Any help, right?

 

Astro Pixel Processor.  Like PI it calibrates/stacks/processes.  Has an excellent gradient reduction tool.  Gives fine results.  It's useful to think of it as PixInsight Lite.

 

Much easier to learn, and time spent with APP is not wasted if you later move to PI, much will transfer.

Yes, any help lol!

 

Even that is really appreciated, my hesitation on going ahead with PI is just shelling out the funds right now. I will look into APP and see how it fits as far as budget goes. I have seen lots of people using it and I have seen some great pictures processed with it so I am not opposed to considering it as an option.

 

Thank you! 



#4 Mike in Rancho

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Posted 08 April 2021 - 01:19 PM

You could also try to figure out what is causing it.  I don't know APP, PI, or if there's any guarantee that they would force-stack frames that DSS refuses to.  Or if that would even be a good thing.

 

That said, there's probably no harm in trying a trial version, depending on how hamstrung it might be.  You might like the overall package better too.

 

But back to DSS.  I tend to aim for 90-110 stars.  Some targets that is not possible, of course.  Can you tell why frames are being rejected by looking at the file list?

 

Try changing the option to stack immediately after registration.  Just register, and then look at the info it gives you.  Run compute offsets if those columns are not already filled in.  Also review what stacking mode you are using (standard, intersection, mosaic, etc), and the alignment mode.

 

DSS should score and rank the subs by stars found, sky brightness, FWHM, and whatever else.  I think it should stack if at least 8 common stars are found.  Note that when you run compute offsets, subs that are not computed are ones DSS does not like.  Now, is it because there aren't enough round stars, or common stars?  What do the offsets look like on the rejected subs?  Is it possible you had a lot of field drift?  If that is the case, you might be able to try selecting a different reference frame - one that is more in the middle of any drift over time.

 

Apart from buying new software or trying a trial version, Sequator is a fairly simplified free stacker.  ASTAP is a more complicated free stacker.  You might see if they are more forgiving of your subs.  But again, there's bound to be a reason that DSS is doing what it is doing.


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#5 RedLionNJ

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Posted 08 April 2021 - 01:22 PM

Not to probe unintentionally too deeply - but 3 minute unguided exposures at 1200mm FL?  Isn't that asking rather a lot from the mount?

 

If you "pixel peep" in DSS, are your stars genuinely small and round in the majority of your frames?


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#6 TelescopeGreg

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Posted 08 April 2021 - 01:42 PM

What I've found is that DSS is telling you something about your image that needs to be fixed, and changing the stacking tool is not going to fix it.  The trick is figuring out what the issue is. 

 

Can you post a couple of examples of the images it likes, and doesn't seem to like?

 

A couple of thoughts...  When you lower the % of subs to stack, it's likely changing which sub it's using as the "reference frame".  As a diagnostic, not a fix, you might sift through your subs and try to pick a better frame as a reference.  Another diagnostic might be to try stacking with Sequator (yes, a different tool, but it's free); it's a lot less fussy about star shapes, which I think is the root issue.

 

Bottom line, you do need to figure out how to capture subs without any trailing of the stars.  That's probably the root problem.  I made a breakthrough some years ago when I got DSS to stack more than *one* sub.  The issue was star shape, and the answer was a combination of a bunch of things, including better focus, better polar alignment, and ultimately, adding an autoguider.  Each improvement increased the number of subs DSS would accept.  That's a crude way to evaluate star shape, but ultimately it's the one that matters.


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#7 rj144

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Posted 08 April 2021 - 02:20 PM

It only stacks what it can align.  It's not stacking based on quality if you have pictures stacked to check.

 

Pick a different photo that's in the "mean" positon of all the best photos as your reference frame.


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#8 Astrolamb

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Posted 08 April 2021 - 03:37 PM

You could also try to figure out what is causing it.  I don't know APP, PI, or if there's any guarantee that they would force-stack frames that DSS refuses to.  Or if that would even be a good thing.

 

That said, there's probably no harm in trying a trial version, depending on how hamstrung it might be.  You might like the overall package better too.

 

But back to DSS.  I tend to aim for 90-110 stars.  Some targets that is not possible, of course.  Can you tell why frames are being rejected by looking at the file list?

 

Try changing the option to stack immediately after registration.  Just register, and then look at the info it gives you.  Run compute offsets if those columns are not already filled in.  Also review what stacking mode you are using (standard, intersection, mosaic, etc), and the alignment mode.

 

DSS should score and rank the subs by stars found, sky brightness, FWHM, and whatever else.  I think it should stack if at least 8 common stars are found.  Note that when you run compute offsets, subs that are not computed are ones DSS does not like.  Now, is it because there aren't enough round stars, or common stars?  What do the offsets look like on the rejected subs?  Is it possible you had a lot of field drift?  If that is the case, you might be able to try selecting a different reference frame - one that is more in the middle of any drift over time.

 

Apart from buying new software or trying a trial version, Sequator is a fairly simplified free stacker.  ASTAP is a more complicated free stacker.  You might see if they are more forgiving of your subs.  But again, there's bound to be a reason that DSS is doing what it is doing.

 

I honestly cant tell what is causing it since the differences are so extreme.. 

While only using the best subs that I hand picked....

I normally aim for about 50 because I found a question about the number of stars needed that was answered by the dev. of DSS. Apparently it maxes out at about 50 stars for alignment purposes.  

I went back over the registration to use about 90-110 stars like you suggested and tried to stack after registration, also tried computing offsets several times but they wouldn't  compute, the boost in the number of stars let me stack 3 frames instead of 2 on the Monkey Head Nebula so its possible it helped it find a few more stars on some of the worse subs.

I like to use intersection for for stacking and automatic for alignment. I like to see how well the data is pulling through pretty early in the acquisition so I might only be stacking <10 frames or 50+. 

There was essentially no drift at all except for a very gradual drift from PE and some shifts from the wind. Before beginning my imaging session I polar aligned to <1" on both the altitude and azimuth. 

 

The last quote on this reply worked to force them all to align and stack, pretty shocked but also happy it worked. 

 

Not to probe unintentionally too deeply - but 3 minute unguided exposures at 1200mm FL?  Isn't that asking rather a lot from the mount?

 

If you "pixel peep" in DSS, are your stars genuinely small and round in the majority of your frames?

 

Oh definitely... I'm pushing it hard. I spent a lot of time working on the mount to get it to do as well as it does unguided.. The biggest problem right now is that I basically have a sail in the wind with my telescope. I am fairly certain that I am dealing with a good bit of PE in some frames but for the stars to be as tight as they are without guiding I am pretty happy.

I wouldn't be surprised if I backed off the exposure and boosted the ISO soon to get the perfect round stars I really should be aiming for. Whenever I get set up for guiding I'll obviously back it off to 200ISO again and expose until I hit the right spot in the histogram. 

 

I will post a couple pictures in the reply after this one to show the extreme of what DSS liked, what is pretty good, and what the stack turned out like after getting all the subs to stack.

 

What I've found is that DSS is telling you something about your image that needs to be fixed, and changing the stacking tool is not going to fix it.  The trick is figuring out what the issue is. 

 

Can you post a couple of examples of the images it likes, and doesn't seem to like?

 

A couple of thoughts...  When you lower the % of subs to stack, it's likely changing which sub it's using as the "reference frame".  As a diagnostic, not a fix, you might sift through your subs and try to pick a better frame as a reference.  Another diagnostic might be to try stacking with Sequator (yes, a different tool, but it's free); it's a lot less fussy about star shapes, which I think is the root issue.

 

Bottom line, you do need to figure out how to capture subs without any trailing of the stars.  That's probably the root problem.  I made a breakthrough some years ago when I got DSS to stack more than *one* sub.  The issue was star shape, and the answer was a combination of a bunch of things, including better focus, better polar alignment, and ultimately, adding an autoguider.  Each improvement increased the number of subs DSS would accept.  That's a crude way to evaluate star shape, but ultimately it's the one that matters.

 

I am still not positive what the root issue was but after testing every sub as the reference frame I was able to get them all to stack with 1 of them, using any of the others would exclude some of the frames. 

I think you are right that it is probably the star shapes being the root issue, but it doesn't make sense why it rates the extremely  bad frames so high.

 

Personally I cant wait for the autoguider, I just cant completely justify it yet. I wanted to focus on working through all the issues I would encounter one by one first before adding in small set of equipment and software. By doing that I am very happy with how familiar I have become with my setup so far and its helping me look forward to guiding that much more.  

 

It only stacks what it can align.  It's not stacking based on quality if you have pictures stacked to check.

 

Pick a different photo that's in the "mean" positon of all the best photos as your reference frame.

Thank you for this, I was wondering why the offsets were so drastically different or nonexistent. This really helped to narrow down why I couldn't force DSS to stack them all. Like I said in the reply above this I tested each frame as a reference frame and calculated the offsets for each one and finally found one frame where DSS calculated the offsets for all the frames. 

 

This is also great to know and keep in mind for future reference and it makes a lot of sense. It will really help me to select reference frames in the future better. I always chose the frame with the best star shape and size previously.


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#9 Astrolamb

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Posted 08 April 2021 - 04:31 PM

Best Sub.
Monkey Head LIGHT 180s 200iso HII Region ra(6.16423) dec(20.57145) 20210407 21h56m17s070ms 01
 
One of the bad subs, DSS ranks this one as the best photo and sets it as the reference frame. 
Monkey Head LIGHT 180s 200iso HII Region ra(6.16423) dec(20.57145) 20210407 21h47m03s583ms
 
Stack of the 8 best subs.
2021 4 7 Monkey Head Nebula HII008

 

These were all exported straight to JPG without stretching.

The subs are Nikon RAW to JPG and the stack was TIFF to JPG

 

Thanks everyone for all of your help! I'm pretty happy it stacked, even if it didn't turn out fantastic..

I have a feeling with a bigger number of subs the Kappa-Sigma stacking method would have helped to even out the stars a little more even with the small amounts of shift during the exposures in the best subs. 

 

Still cant wait to get into guiding so I can fix those star shapes and take really long exposures at my local dark site!


Edited by Astrolamb, 08 April 2021 - 04:33 PM.

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#10 rj144

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Posted 08 April 2021 - 05:13 PM

 

Best Sub.
 
 
One of the bad subs, DSS ranks this one as the best photo and sets it as the reference frame. 
 
 
Stack of the 8 best subs.
 

 

These were all exported straight to JPG without stretching.

The subs are Nikon RAW to JPG and the stack was TIFF to JPG

 

Thanks everyone for all of your help! I'm pretty happy it stacked, even if it didn't turn out fantastic..

I have a feeling with a bigger number of subs the Kappa-Sigma stacking method would have helped to even out the stars a little more even with the small amounts of shift during the exposures in the best subs. 

 

Still cant wait to get into guiding so I can fix those star shapes and take really long exposures at my local dark site!

 

 

I would say to forget JPG.  Use all RAW images in DSS and export as TIFF.  Then stretch the TIFF and even after the stretch keep it as a TIFF if you want to work on it further.

 

Only the finalized image after all post processing is done should be JPG for easier sharing.


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#11 Astrolamb

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Posted 08 April 2021 - 05:18 PM

I would say to forget JPG.  Use all RAW images in DSS and export as TIFF.  Then stretch the TIFF and even after the stretch keep it as a TIFF if you want to work on it further.

 

Only the finalized image after all post processing is done should be JPG for easier sharing.

Thats exactly what I did! I appreciate you saying it though, I have realized lots of people don't know just how big of a difference it makes to shoot and save as RAW


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#12 rj144

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Posted 08 April 2021 - 05:23 PM

Thats exactly what I did! I appreciate you saying it though, I have realized lots of people don't know just how big of a difference it makes to shoot and save as RAW

Ok, but you said subs are Nikon Raw to JPG.  What does that mean?  To me it seemed like you were converting your subs to JPG first.



#13 Blackhawk163

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Posted 08 April 2021 - 05:23 PM

By the way Astropixel processor is fully featured as a trial so give that a go. You'll have 30 days to decide on that and the UI is very user friendly. It helped me a lot that instead of just going with the yearly sub, I bought it outright.

#14 Astrolamb

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Posted 08 April 2021 - 05:36 PM

Ok, but you said subs are Nikon Raw to JPG.  What does that mean?  To me it seemed like you were converting your subs to JPG first.

The first two of the pictures were subs, I just figured I'd specify that they went straight from RAW to JPG in case someone wondered about the color or something. 

After I realized DSS can read Nikon RAW files I just started loading them straight in, before that I was converting them to TIF to stack but I didnt know that was a mistake at the time.


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#15 Astrolamb

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Posted 08 April 2021 - 05:39 PM

By the way Astropixel processor is fully featured as a trial so give that a go. You'll have 30 days to decide on that and the UI is very user friendly. It helped me a lot that instead of just going with the yearly sub, I bought it outright.

 

Will do, now that I am much more comfortable doing post processing editing I feel like the free trials wouldn't be a waste. 



#16 Mike in Rancho

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Posted 08 April 2021 - 06:21 PM

Yikes!

 

Well, I'm glad the offsets offered a clue and selecting a new reference frame gave you some stacking anyway.  A KS rejection will help some no doubt, though everything has its limits...

 

Totally understand building up experience and confidence before adding more on top.  I did the same thing, and only now, several months later, have started guiding.  And then dithering, once I had a little bit of guiding under my belt.

 

However, you may be a special case here, whereby guiding is almost a necessity or too many things will end up sideways.  So might be time to start diving in.

 

I downloaded both those subs, albeit converted to jpg already, and DSS properly identified which was good and which was bad.  The offsets weren't terrible, at least between these two subs.  So, I'm confused why DSS told you the bad sub was the best when using the RAW versions.  There was a clear shift of field creating little peanuts.  Maybe in the RAW file there is separation such that DSS though you were imaging a giant field of double stars, and hence counted a whole lot of stars in that sub.  Either way, having that sub in there is bound to create problems in alignment.  Sometimes you do have to look at them and cull them out, either before feeding files into DSS, or afterwards if a frame is sticking out as an oddball.

 

The best frame itself looked like a bunch of footballs.  If you can't start guiding quite yet, might you obtain better results with shorter subs?  Maybe 30 to 60 seconds tops?  I think you might get a decent stack if you can keep mostly round frames and toss the footballs out, rather than keeping footballs and tossing the peanuts out.


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#17 TelescopeGreg

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Posted 08 April 2021 - 06:56 PM

What Mike said.

 

So, a reality check.  The "bad" frame I would toss outright, without even considering adding it to the stack.  There's no way it would help the final image be any better.  And note that I have a rather large tolerance for what sort of frame I consider keeping.  As Mike notes, even the good frame is kind of marginal, though if they were all like that I'd probably go ahead in order to see what sort of nebula I captured, just to learn as much as I could from what I got.

 

Bottom line - you need to be guiding.  Take a look at the short diagnostic "movie" I made of an imaging session, back when I was trying to get DSS to stack more than one frame.  This is a sequence of 30 subs, each only 20-30 seconds long, strung together at 1 second each.  This is what an unguided 1,000mm focal length Newtonian telescope on an unguided, and likely unbalanced AVX mount looks like.  (To be fair, I'd only had it a few months.) 

 

https://www.dropbox....acking.mp4?dl=0

 

Any of those subs look familiar?  I could probably pick out a frame or two and stack those, but relying on "Lucky Guiding" is going to get old really fast.  With the guider, the motion pretty much disappeared.  It was like turning on image stabilization on a Point-and-Shoot digital camera.  I still had a few bad frames, but 80% of them were better than your "good" image.  The guider doesn't have to be super expensive, but no post-processing software is going fix the star shapes once they're stretched and twisted.


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#18 Astrolamb

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Posted 09 April 2021 - 04:00 PM

Yikes!

 

Well, I'm glad the offsets offered a clue and selecting a new reference frame gave you some stacking anyway.  A KS rejection will help some no doubt, though everything has its limits...

 

Totally understand building up experience and confidence before adding more on top.  I did the same thing, and only now, several months later, have started guiding.  And then dithering, once I had a little bit of guiding under my belt.

 

However, you may be a special case here, whereby guiding is almost a necessity or too many things will end up sideways.  So might be time to start diving in.

 

I downloaded both those subs, albeit converted to jpg already, and DSS properly identified which was good and which was bad.  The offsets weren't terrible, at least between these two subs.  So, I'm confused why DSS told you the bad sub was the best when using the RAW versions.  There was a clear shift of field creating little peanuts.  Maybe in the RAW file there is separation such that DSS though you were imaging a giant field of double stars, and hence counted a whole lot of stars in that sub.  Either way, having that sub in there is bound to create problems in alignment.  Sometimes you do have to look at them and cull them out, either before feeding files into DSS, or afterwards if a frame is sticking out as an oddball.

 

The best frame itself looked like a bunch of footballs.  If you can't start guiding quite yet, might you obtain better results with shorter subs?  Maybe 30 to 60 seconds tops?  I think you might get a decent stack if you can keep mostly round frames and toss the footballs out, rather than keeping footballs and tossing the peanuts out.

 

Yeah I can see the limits of the KS stacking already being pushed so you are probably right about it being time to start guiding. I have considered it for awhile now but knew it wasn't a necessity until I had all my little problems worked out first. 

 

That's exactly why I was so puzzled! Your reasoning seems spot on to me though. I gotta say though if there really was a field of double stars like that it would be pretty cool.. lol

Going through them one by one seems to be the best bet to ensure a good stack the first time around. Its proven its worth on subpar frames and will only be that much more worth it when I've got really good frames with great star shapes.

 

Yes it does, it was partially from the wind. The wind was about 8mph at the beginning of the night according to Astropheric and as the night went on it was around 3mph by midnight or so. These frames were from the beginning of the night since the monkey head is already so low in the sky.

 

I can definitely obtain better results with shorter subs, I partially got into a bit of a habit of trying to push my mount as hard as I could to see what the longest unguided sub I could possibly take was but that was a bad habit to get into for just taking pictures. While I was trying to troubleshoot and tune the mount up properly it was good but I am past that point and need to just focus on getting good star shapes and filling the histogram to the halfway point. 

 

Are you using a guidescope or an OAG? I feel like I will need to go with an OAG for my FL but I am still not certain. I am also not sure what size pixels I should be looking for in an OAG camera since it will be using the scope.. Everyone suggests a 5:1 or lower for guidescope camera to telescope camera pixel resolution but no one really talks about what you should use for an OAG..

 

What Mike said.

 

So, a reality check.  The "bad" frame I would toss outright, without even considering adding it to the stack.  There's no way it would help the final image be any better.  And note that I have a rather large tolerance for what sort of frame I consider keeping.  As Mike notes, even the good frame is kind of marginal, though if they were all like that I'd probably go ahead in order to see what sort of nebula I captured, just to learn as much as I could from what I got.

 

Bottom line - you need to be guiding.  Take a look at the short diagnostic "movie" I made of an imaging session, back when I was trying to get DSS to stack more than one frame.  This is a sequence of 30 subs, each only 20-30 seconds long, strung together at 1 second each.  This is what an unguided 1,000mm focal length Newtonian telescope on an unguided, and likely unbalanced AVX mount looks like.  (To be fair, I'd only had it a few months.) 

 

https://www.dropbox....acking.mp4?dl=0

 

Any of those subs look familiar?  I could probably pick out a frame or two and stack those, but relying on "Lucky Guiding" is going to get old really fast.  With the guider, the motion pretty much disappeared.  It was like turning on image stabilization on a Point-and-Shoot digital camera.  I still had a few bad frames, but 80% of them were better than your "good" image.  The guider doesn't have to be super expensive, but no post-processing software is going fix the star shapes once they're stretched and twisted.

 

That's mostly what I was doing, just trying to stack and see what I got. Pushing 3m on the unguided mount is a bad habit I got into though like I said in the reply to Mike. Its time to back off of the exposure time and bump up the ISO until I can guide. If I focused on getting good star shapes I would have way more usable frames and a higher total integration time than I would if I keep trying to do "lucky guiding".

 

Hey that's way too familiar! I'm sure you know exactly what I mean when I say I have to throw out about 75% of the frames I take with 3m exposures like that because of peanut frames. I wouldn't be surprised if by backing off of the exposure to 60s or 90s tops that I would be able to use 75% of the frames and only throw out the oddball.

 

Do you have any thoughts, comments, suggestions, or experience you can share on the OAG question I posed in the reply to Mike? 


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#19 han.k

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Posted 09 April 2021 - 04:17 PM

Why would expose 3 minutes?. Expose 3 times 1 minute will give you more or less the same signal to noise ratio and rounder stars.  If you expose 5 or 10 seconds you can work without guiding.  Unless you live in a super dark location, the sky noise is still overwhelming the read noise of the sensor.

 

Han


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#20 Mike in Rancho

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Posted 09 April 2021 - 04:32 PM

Lucky Guiding is a good term.  I must remember that.  lol.gif

 

I'm using a guide scope, but, being the silly person I am, made both the guide scope and guide camera out of excess junk I had around the house.  So far it is working decently well, although its FOV is rather tight so I have to change where it points to find a good guide star sometimes.  Maybe not the greatest, but I think it is within the recommended bounds and the reported RMS was good as far as I could tell.  Stars are round, even at 900mm with a pixel scale of just under 0.9" I think.

 

But that's still a refractor.  I think a big ol' bucket is better matched with OAG, from what I read.  There's a couple recent threads here discussing pros and cons of OAG, so they might be worth looking into.  For me, I like getting double use out of things.  So if I ever got a camera specifically for guiding, I would then use a guide scope with appropriate f/l, but would also hope to use that camera for other imaging tasks as well.  Maybe planetary, or perhaps a mono that I could use filters with.  Would all depend on the size and scale.

 

On your subs, yes for sure back down those exposure times for now.  For culling, it depends what you use.  DSS is not well-suited for that, unless it flags things as oddballs for you in scoring, stars, or skyglow.  For sure use that too.  For me I can use Backyard Nikon to review and flag lousy subs.  Something like ViewNX is also okay for quickly stepping through frames.


Edited by Mike in Rancho, 09 April 2021 - 05:08 PM.

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#21 Astrolamb

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Posted 09 April 2021 - 04:53 PM

Why would expose 3 minutes?. Expose 3 times 1 minute will give you more or less the same signal to noise ratio and rounder stars.  If you expose 5 or 10 seconds you can work without guiding.  Unless you live in a super dark location, the sky noise is still overwhelming the read noise of the sensor.

 

Han

 

It sounds hard to believe but 3 minutes at 200ISO on a Nikon D5300 gives about the perfect 1/3-1/2 fill of the histogram under my bortle 8-9 skies. So as I learned my mount and worked on it to tune it for my setup I kept that as the goal in mind figuring that if I got anywhere near close to good subframes with a 3m exposure it would only help me when I move into guiding finally. 

I do regularly drive out to a dark site near me with bortle 4 skies so being able to have everything well tuned helps that much more when I get to enjoy a relatively dark sky.

 

Lucky Imaging is a good term.  I must remember that.  lol.gif

 

I'm using a guide scope, but, being the silly person I am, made both the guide scope and guide camera out of excess junk I had around the house.  So far it is working decently well, although its FOV is rather tight so I have to change where it points to find a good guide star sometimes.  Maybe not the greatest, but I think it is within the recommended bounds and the reported RMS was good as far as I could tell.  Stars are round, even at 900mm with a pixel scale of just under 0.9" I think.

 

But that's still a refractor.  I think a big ol' bucket is better matched with OAG, from what I read.  There's a couple recent threads here discussing pros and cons of OAG, so they might be worth looking into.  For me, I like getting double use out of things.  So if I ever got a camera specifically for guiding, I would then use a guide scope with appropriate f/l, but would also hope to use that camera for other imaging tasks as well.  Maybe planetary, or perhaps a mono that I could use filters with.  Would all depend on the size and scale.

 

On your subs, yes for sure back down those exposure times for now.  For culling, it depends what you use.  DSS is not well-suited for that, unless it flags things as oddballs for you in scoring, stars, or skyglow.  For sure use that too.  For me I can use Backyard Nikon to review and flag lousy subs.  Something like ViewNX is also okay for quickly stepping through frames.

 

I see people use lucky imaging all the time when discussing planetary since for planetary they aim for having such a small pixel resolution.. Lucky guiding just happens to be the perfect description of what I have been doing lol

 

I was thinking the same from what I have read so far about OAG vs guidescopes, its time to start reading more I guess. Hearing a little about your makeshift guidescope helps put it into even more perspective though. Its nice to know that you can make guiding work from extra odds and ends even. 

 

I use BYN too and I like it quite a bit but if I am not out at a dark site I don't normally sit with my setup all night as the pictures are coming through, hence looking through them after I loaded them into DSS. I should probably take the time to go through them with BYN and flag them since its easiest to do there though and it actually changes the name of the file.


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#22 Mike in Rancho

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Posted 09 April 2021 - 05:08 PM

Oops!  Yes, "lucky guiding" was what I meant to type, since that's the amusing reference.  Lucky imaging is real.  lol.

 

Yeah as you probably know you can open up BYN into preview mode even after the fact, though it takes a little time to load everything in.  One cool thing is that if you zoom in deep, say to check how round a small star is, when you go to the next image it will retain that same zoom and location for comparison.


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#23 han.k

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Posted 10 April 2021 - 01:15 AM

It sounds hard to believe but 3 minutes at 200ISO on a Nikon D5300 gives about the perfect 1/3-1/2 fill of the histogram under my bortle 8-9 skies.

You better not use the histogram as a guide for this. There is no reason to fill the pixels 1/3 of their maximum value because you will stack them later.  5 to 20 seconds exposure is the way to go without guiding. You could stack them live with something like Sharpcap or ASTAP or later if your mobile.

 

Han



#24 Kzoech

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Posted 10 April 2021 - 02:51 AM

I was DSS with Star Tools, now I'm Astro Pixel Processor, the difference in the quality of stacked images is chalk and cheese. I'll try to find the pics of the difference in just default settings.
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#25 Mike in Rancho

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Posted 10 April 2021 - 04:57 AM

It sounds hard to believe but 3 minutes at 200ISO on a Nikon D5300 gives about the perfect 1/3-1/2 fill of the histogram under my bortle 8-9 skies.

 

Although it's of course just a rule of thumb, I believe that rule of thumb is 1/4 to 1/3 of the BOC (back of camera) histogram.

 

All good news!  You can cut down those exposures, reduce or hopefully eliminate the trailing artifacts, and fall in a more "perfect" histogram.

 

Right now I'm doing 120 seconds, ISO200, D5300, bortle 7-8, on Markarian's chain and hitting a bit over 1/8th histogram.  At least around zenith.  To the sides it starts edging over 1/4.


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