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Author Topic: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!  (Read 12966 times)

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Offline the fordster

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Well, of the 13,000+ posts I've got against my name, the two that I'm most delighted with (and that seem to have helped the most members) was my LPR filter comparison thread, and my focal reducer shoot out.

So earlier I had the idea of doing a third that you can ALL help with if you're actively imaging. It may well make 'scope choices for us all a lot easier in the future! -

But it will only be as good as you make it!


The idea came to me when I saw a few posts talking about colour correction, flatness of field, vignetting, off axis abberations (coma etc), field of view and the myriad other factors we face when choosing a new 'scope, so I thought - why not use the vast collection of kit our members have to compile a database.

Don't worry what kind of 'scope or camera you have - The more combinations the better (though I'm personally interested in 300D's and Apos :lol:)

Here goes:

Post up one of your unprocessed deep sky images, crop a 200x200 area from the edge of the field of view, and a 200x200 from the centre (don't resize!!!). Then just post these up too, with a short note of the 'scope and camera used (don't forget to mention focal reducers!). That's it! Why unprocessed? Because when we process images, we tend to crop the ugly bits or correct for abberations...

It may work and become a huge resource. It may well fall flat on its arse :lol: Main thing is, we all benefit hugely and only put in a wee bit of work!

 :mrgreen:

Offline the fordster

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #1 on: 08:53:48, 05 April, 2006 »
 :yakillinme: Not a single post - I should have known...

Note to self: Knowledgebases are grand if no-one has to do any work but everyone can benefit...

OK, I'll start digging through all my old images to kick this thing off - If you think it's worth it?

Offline GordonCopestake

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #2 on: 09:01:46, 05 April, 2006 »
I'm planning on doing an unguided shot of M42 tonight with my D70 DSLR at prime focus of my ED100. I'll post the results if it's any use but I can't promise it'll be something to be proud of!

Offline Dogman

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #3 on: 09:02:19, 05 April, 2006 »
I'll certainly join in Fordy - but not until the weekend - reet busy at the moment lad..........

Cheers
Dunc

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Offline the fordster

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #4 on: 09:04:56, 05 April, 2006 »
Sweet! 8-)

Offline gaelicstorm7

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #5 on: 09:14:50, 05 April, 2006 »
does it matter if any filters are used ? also is it important what length exposure or ISO is used?

Cheers

Alan.
Megrez 80mm SD II Semi Apo on EQ5 driven mount, Celestron G8-N, Meade ETX90, Canon 350D, Meade LPI, Astronomik CLS filter.

Offline the fordster

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #6 on: 09:18:00, 05 April, 2006 »
Hi Alan, doesn't matter if filters are used for comparing coma and flatness of field. Only thing that will prevent is an assessment of chromatic abberation...

Offline gaelicstorm7

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #7 on: 09:28:33, 05 April, 2006 »
ok will see what I can dig out  :)

Alan
Megrez 80mm SD II Semi Apo on EQ5 driven mount, Celestron G8-N, Meade ETX90, Canon 350D, Meade LPI, Astronomik CLS filter.

Offline robin_astro

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #8 on: 14:18:28, 05 April, 2006 »
If anyone is interested in quantifying the star shapes and sizes, Teleauto has a star modeling function (example attached)

Robin

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Offline the fordster

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #9 on: 16:01:15, 05 April, 2006 »
Now that's handy!

Offline dciobota

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #10 on: 16:51:31, 05 April, 2006 »
 Hey Fordy,

 Been sick, I just got to looksee this post.  Cool idea!  I think I may have one or two that show minimal star trailing, that might help you.  I'll dig through tonight and see what I can find.

 Now, by unprocessed you mean just the normal in-camera processing, right?

Daniel
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Offline Sam Scoggins

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #11 on: 17:13:11, 05 April, 2006 »
I think some of the comparisons Rich Best has done are usefull:

http://ukastroimaging.co.uk/forums/index.php?topic=14138.msg134131#msg134131

-Sam

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Offline rob uk

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #12 on: 17:20:21, 05 April, 2006 »
havent kept any of my old 300d+wo/tmb frames..dunno how much info could be obtained from the mx7 shots..? dont tell you much because of the FOV

Offline davenash

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #13 on: 17:24:37, 05 April, 2006 »
havent kept any of my old 300d+wo/tmb frames

What :shock:  Am I the only one who keeps EVERYTHING? :)

(on DVD-R)

Dave
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Offline the fordster

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Re: Coma and Chromatic Abberation Comparisons - Could Be A Winner!!!
« Reply #14 on: 17:38:13, 05 April, 2006 »
Cool guys, just post when you have the info!

havent kept any of my old 300d+wo/tmb frames..dunno how much info could be obtained from the mx7 shots..? dont tell you much because of the FOV

Not at all, mate - There must be others thinking of that combination...

 

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