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HunterHarling

Software for aligning and stacking planetary nebula images?

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Last night I captured 1700 1 second exposures of the cats eye nebula with my new ASI1600MM PRO. Since the exposures are so short the only thing in the image is the nebula itself and I am wondering what software will be able to align these images without any stars.

Thanks in advance! 

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You could try Autostakkert which is very good for stacking video frames of planets. It will work with fits files too which is what I assume your ASI images are. After clicking open just select all your fits files in one go. The files may be too large to process that many at once, in which case use PIPP beforehand to crop your images to just include the nebula part of the images. Both programs are free to download. You may have to play around with the edge detection options in Autostakkert to get it to 'lock' onto your nebula edges. I believe that PIPP will also register the images to some degree if you have a part of the nebula that is suitable to 'lock' onto. It's normally used when cropping planetary images where the planet moves around the frame between images. It may not work with your images but it's worth a try. :smile:

Alan

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I've only used Siril for images that had lots of stars, but it might be worth a go. I know they have several alignment algorithms from which to choose and tweak. It's perfectly happy with FITS images, in fact it converts other sorts to that before doing anything else with them.

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The fastest stacking software I know (and it's also my favourite) is AstroArt. http://www.msb-astroart.com/

You can try a free download version, though it won't allow you to save the output.

Olly

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3 hours ago, michael8554 said:

1 second exposures seems excessively short, even for an unguided setup?

Michael

I was trying to freeze the seeing but it didn't turn out so well, nothing will align  these images! I'll probably be better off ditching the whole set of data and capturing longer exposures:sad2:

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On 05/05/2018 at 21:17, HunterHarling said:

I'll have a go at autostakkart and also see what astroart and siril can do.

Siril is now almost dedicated to short exposure deep sky shoots. It is possible to preprocess, aign and stack directly the SER file. You can have 60000frames with no problem.

Moreover, you have many way to do it:

- automatic alignment tool with detected stars (could fail using a barlow and with only faint stars) -> align with rotation and translation

- one star registration ->align with translation

- planetary alignment (could be use ONLY if the two methods failed) ->align with translation

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From memory, I think registax will work on FITS files. It also has a 'centre of gravity' option so it won't concern itself with a lack of stars.

It also has the ad advantage of being free so it will cost nothing to try.

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The rate at which the seeing fluctuates is called the 'greenwood frequency'.

https://en.wikipedia.org/wiki/Greenwood_frequency

Wikipedia says it can range from tens of hertz to kilohertz. This means that to beat the seeing you either need adaptive optics that can keep up, or a lucky imaging frame rate high enough. 16-32ms exposures are probably as long as you want to go except in nice steady conditions, a whole second is almost certainly too long for real 'lucky imaging'.

That said, do try using Autostakkert!3. Find any frames with a few stars showing and put alignment points on them too - they will greatly help aligning the background.

When I see how much live video can 'boil' it amazes me that long exposures show anything!

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