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Stacking images with too few stars and detail? Effective manual stacking somewhere?

astrophotography beginner imaging
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#1 Bilbo Baggins

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Posted 17 April 2019 - 04:34 AM

Dear friends,

 

I have started learning astrophotography since a few months and now I have more questions than answers... grin.gif

 

What is your opinion: if there are many light frames but they have only about 5 stars at the most (for example vicinity of M51 or NGC5866-Spindle Galaxy) and very few details, how can they be stacked?

 

I am primarily asking for an advice about software and/or processing parameters as I cannot do much about taking better pictures. (I used to take BMPs but learned quickly that FITS is the only good solution :)) I use an Alt-Az mounted Celestron NexStar 8SE with ASI120MC cam, so my field of view and exposure times are limited and cannot eliminate field rotation.

 

DSS wants to stack only 1 of the frames no matter of the star detection treshold. I found a very promising software AstroArt which has a manual align function (I have to select the same star or detail on all of the light frames) so the frames can be stacked just the stars far from the reference star are 'smeared' along a circle line due to field rotation. I haven't found other solutions yet.

 

What do you think I should do? Any little advice will be highly appreciated!

 

Krisztian

from Hungary

 

PS: I suppose PixInsight can do this as almost everything else too but if there is a more simple solution suited for a beginner like me, I would try that one in the first time :)

 

 



#2 ShortLobster

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Posted 17 April 2019 - 06:54 AM

Welcome to the hobby and CN!

 

In DSS, try lowering your star detection threshold in Register settings. This may increase the number of stars that DSS sees. 

 

DSS is very sensitive to star shape, and an alt az mount that's tracking will very quickly add "stair step" shapes to your stars. If you are using the Celestron mount, you could try finding an "eq wedge" that converts the mount into an equatorial mode. You would then polar-align the mount. I haven't done this myself but you can find others that have on this site. 

 

I also started with Nexstar 8 and alt az mount and deep space photography is difficult. However, you can get good results on appropriately bright objects such as the moon and planets using "lucky imaging." Your camera, mount and scope are fine for that. I also got a recognizable image of Orion on that rig using Firecap, Autostakkert and Registax, the same software you'd use for planets. 

 

At an appropriate time in the future you will need an equatorial mount to get good results. 


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#3 Bilbo Baggins

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Posted 17 April 2019 - 08:10 AM

Welcome to the hobby and CN!

 

In DSS, try lowering your star detection threshold in Register settings. This may increase the number of stars that DSS sees. 

 

DSS is very sensitive to star shape, and an alt az mount that's tracking will very quickly add "stair step" shapes to your stars. If you are using the Celestron mount, you could try finding an "eq wedge" that converts the mount into an equatorial mode. You would then polar-align the mount. I haven't done this myself but you can find others that have on this site. 

 

I also started with Nexstar 8 and alt az mount and deep space photography is difficult. However, you can get good results on appropriately bright objects such as the moon and planets using "lucky imaging." Your camera, mount and scope are fine for that. I also got a recognizable image of Orion on that rig using Firecap, Autostakkert and Registax, the same software you'd use for planets. 

 

At an appropriate time in the future you will need an equatorial mount to get good results. 

Dear ShortLobster,

 

thank you for your informative message! Yes, I was aware that I will have to change my mount as I cannot make longer expositions than about 30 secs... Nevertheless I enjoy shooting and processing, it's always a happy moment when the progress bar jumps to 100% and the final image appears with an identifiable object :)) But I know I will have to move a step higher if I wish to advance.

 

Now I am trying to check the limits of this setup and I have had remarkable results on brighter DSOs - of course those are not comparable to a 20x5 minutes integration time and a precise EQ mount, of course...

 

My issue is that in certain situations I cannot get more stars in the FOV as 3-5, not even with an f/6 focal reductor, and those stars are likely too faint. I tried to lower the star detection limit but it didn't work in the case there are simply not enough stars or not bright enough. Frustrating, because I know where are those stars (or the center of the planetary nebula, or a nucleus of a galaxy) and would be able to tell that to the software, just there is no option of this. (Except of AStroArt but with only 1 star).

 

Thanks again for you comments!

 

Best:

Krisztian



#4 Pauls72

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Posted 17 April 2019 - 10:42 AM

Try using Nebulosity 4 for stacking. It lets you select the stars.



#5 44maurer

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Posted 17 April 2019 - 12:28 PM

Try using Nebulosity 4 for stacking. It lets you select the stars.


+1

#6 DuncanM

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Posted 17 April 2019 - 01:40 PM

Dear friends,

 

I have started learning astrophotography since a few months and now I have more questions than answers... grin.gif

 

What is your opinion: if there are many light frames but they have only about 5 stars at the most (for example vicinity of M51 or NGC5866-Spindle Galaxy) and very few details, how can they be stacked?

 

I am primarily asking for an advice about software and/or processing parameters as I cannot do much about taking better pictures. (I used to take BMPs but learned quickly that FITS is the only good solution smile.gif) I use an Alt-Az mounted Celestron NexStar 8SE with ASI120MC cam, so my field of view and exposure times are limited and cannot eliminate field rotation.

 

DSS wants to stack only 1 of the frames no matter of the star detection treshold. I found a very promising software AstroArt which has a manual align function (I have to select the same star or detail on all of the light frames) so the frames can be stacked just the stars far from the reference star are 'smeared' along a circle line due to field rotation. I haven't found other solutions yet.

 

What do you think I should do? Any little advice will be highly appreciated!

 

Krisztian

from Hungary

 

PS: I suppose PixInsight can do this as almost everything else too but if there is a more simple solution suited for a beginner like me, I would try that one in the first time smile.gif

You should buy or build a wedge so that you can turn it into an equatorial mount.



#7 Kendahl

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Posted 17 April 2019 - 02:15 PM

I use Nebulosity (version 3) for processing. To align and stack, select an alignment method (e.g. translation or translation plus rotation) and pick two unsaturated stars that are well separated.



#8 pfile

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Posted 17 April 2019 - 08:17 PM

pi has a manual alignment tool called "DynamicAlignment".

 

maybe you can post one fits file and someone can see if there is a way to tweak the PI star detector to make it work for you.

 

rob



#9 Eric Seavey

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Posted 17 April 2019 - 08:48 PM

Though I use ImagesPlus for my processing and highly recommend this very stable program, I would also take a look at astropixel processor.  I heard good things about it and it produces with ease good results.



#10 Bilbo Baggins

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Posted 23 April 2019 - 11:22 AM

Dear friends!

 

Many thanks for your kind advices, I hope I haven't made you angry with my noob question :)

 

Nebulosity demo did the trick indeed but I will check all of the software you mentioned, it seems there is a few...

 

Have a great day everyone!

 

Krisztian




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