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M13 - comments please!

Black Knight

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Black Knight

Black Knight

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Hi all,

Took this one the other night - the first properly clear night for me for ages :eek:. Anyway, I would be grateful if you guys could take a look and perhaps make a few suggestions/comments.

Explorer 200p newt

Canon 500D, Skywatcher coma corrector

24 lights, 120s at ISO 800

10 darks, 10 bias, 20 flats (although I think the flats were um, slightly overexposed)

Guided using QHY5 and PHD.

Stacked in DSS, no post processing in Photoshop

The guiding seemed to go mostly OK, although I did lose 2 subs to the same sort of huge guiding peak in RA that swag72 saw in her thread the other day. The star shapes are not round. This appears in all the subs I examined. Does this look like coma (I am already using a coma corrector), guiding, field rotation or collimation? Or maybe Flexure?

I seem to have overblown the core. Could the core be "rescued" in Photoshop, or were 120 second subs simply too long for this target?

Comments welcome :)

post-19904-133877639073_thumb.jpg

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terrym2002uk

terrym2002uk

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Hiya

Thats not too bad. Did you have some light pollution/local lighting to the right? Maybe the moon?

Not sure whats causing the eggs, im sort of having this problem at the moment which i working on. Like a barn in some of my photos!

Also I wouldnt use GIMP as it only handles 8bit and you end up throwing away all the quality. Try paint.net if your on windows.

Have a look at my first effort, I used 30s/800 and pretty much the same kit as you. http://stargazerslounge.com/imaging-image-processing-help-techniques/149987-my-first-imaging-attempt.html

Stick at it, its all in the processing.... well most of it.

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Black Knight

Black Knight

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The moon was indeed coming up by the time I had finished taking the lights which could explain the gradient. As far as my non-round stars go, well I don't really know. I had a look at your image. Very nice :). The stars are nice and round and the cluster looked very crisp.

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terrym2002uk

terrym2002uk

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Andy

The star were not round. I had to fix them. On close inspection mine loook like eggs with a flattened bottom. I think its my secondary alignment or offset. Haven't had a chance to look at it yet but will let you know. Tis bugging me.

Keep at it.

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terrym2002uk

terrym2002uk

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Hey Andy,

Heres my attempt with my limited skills. All this stretching biz hurts my head :) so I wont be offended if you think I have made it worse :eek:

As you say the core is a little burnt out, but can I ask did you stretch it in DSS before you saved it? I personally found its best to stick to streching in something else that offers better control. If you did maybe worth stacking them again and not doing the stretch in DSS.

Also,did you notice the faint galaxies you had capatured top/right quadrant? Cool :)

Tried to sort some of the eggs out but like you i need to try and nail the problem at source.

Anyhow heres is a link to the tif http://dl.dropbox.com/u/36405099/M13c-final.tiff

and a thumb attached. [Edit - With right files this time!]

post-26647-133877639623_thumb.jpg

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Black Knight

Black Knight

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Hi Terry,

Thanks for that. Nope, I didn't do any stretching in DSS, in fact no processing at all. Nice re-work :). Actually I hadn't even noticed the galaxies so I'm kinda chuffed you found them :eek: Can I ask what technique were you using to sort out the "eggs"?

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terrym2002uk

terrym2002uk

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Actually I hadn't even noticed the galaxies so I'm kinda chuffed you found them :)

There you go. Even if you think your picture wasnt that great, often or not there are some nuggets of information in there. Go and find out what there called and ring them up on your picy. Also apart from getting better definition than my first attempt, those orange stars came through rather nicely.

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JoLo

JoLo

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Very nice image, great work. My first two attempts at M13 weren't nearly as nice...blowout on the core, I need to redo with shorter subs. I use Carboni's tools for the eggy stars, works well, sometimes needs several iterations. I have done the manual process in PS as well...works better, but takes much longer, I am going for the convenience.... I also use GradientXTerminator, which I find to be an excellent tool...enough leeway on the settings so it can handle big and small gradients, with a little practice.

Great image, nicely done.

Joe

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Black Knight

Black Knight

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Eggs seem more around the edges of the image, did you use a flattener/corrector?

Yeah, I did use a coma corrector, the Skywatcher one. To be honest I have no idea whether I'm seeing field rotation, coma, collimation issues or something else. :)

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terrym2002uk

terrym2002uk

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Yeah, I did use a coma corrector, the Skywatcher one. To be honest I have no idea whether I'm seeing field rotation, coma, collimation issues or something else. :)

Yep tell me about it. I've got an MPCC and its bugging the hell out of me too. I really suspect it might be the secondary rotation, but need a nice clear night to sort it. Taking some fast pics of bright defocused star's in various feild postitions with and without the corrector may help to pin point it, or rule things out.

btw does your secondary have a slight flat beveled edge to it on one side?. Mine does.

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