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A quick and dirty M101

Catanonia

By Catanonia
in Imaging - Deep Sky

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Catanonia

Catanonia

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It has been so long what with the bad skies and my mount and CCD both dying with board issues.

Eventually I got up and running again, but have loads of issues with flats to be sorted out, amazing how much you loose track if you haven't imaged for about 3 months

So anyways, here is a quick and dirty M101 taken on the TS SuperNewt @F2.8. 1 hour per channel LRGB @ 5min subs

I think I am getting internal reflections off the secondary and primary mirrors, so I am going to strip and darken the mirror edges in a hope to resolve my flat issues having wierd lines on them.

post-16631-133877774049_thumb.jpg

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Catanonia

Catanonia

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Great to see you back with everything fixed again Cat. Any thoughts on upgrading that scope yet? You were thinking about the 12" weren't you?

A few issues with work etc, so need to get through these next few months and then who knows, may plump for the 12 incher and take it to the next level.

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Spikey

Spikey

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A few issues with work etc, so need to get through these next few months and then who knows, may plump for the 12 incher and take it to the next level.

I know the feeling mate :)

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Catanonia

Catanonia

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Thanks all, was nice to get back into the imaging after such a long lay off. The whole system went bang 1 week before the last 7 day clear spell and I was fuming, close to throwing in the towel at that stage.

I really wish I could solve this flats problem, all of the calibrated images have some horrid lines / arcs over them that I cannot see in the raw or the flats, but they appear after calibration. Really racking my brain to work out what the issues are. Hopefully it is internal reflections off the 2 mirror edges, so that is the next job. Already covered the primary with a dark cloth to stop stry light getting in that way, but hasn't worked.

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Gina

Gina

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I'm really struggling with M101 - such a narrow band of brightness I can't seem to resolve to more than about 5 levels :) Might try with some different software.

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Catanonia

Catanonia

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I'm really struggling with M101 - such a narrow band of brightness I can't seem to resolve to more than about 5 levels :) Might try with some different software.

Can you explain more Gina, not quite with you on "5 levels" ?

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Gina

Gina

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Can you explain more Gina, not quite with you on "5 levels" ?
Yes, after stretching the histogram in GIMP to clip some of the noise and increase contrast, the histogram showed only 5 spikes indicating that the image had been converted to just 5 brightness levels.
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AndyUK

AndyUK

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I'm really struggling with M101 - such a narrow band of brightness I can't seem to resolve to more than about 5 levels :headbang: Might try with some different software.
Hi Gina - By all means try different software, but I don't think it's a software issue. M101's a fairly faint target anyway (although you wouldn't know it from THIS image!), but don't forget that Catanonia's imaging at f2.8, and he's also using a more sensitive mono CCD camera. To get a similar image depth (with the same mono CCD) on your f7.5 ED80 the exposures would need to be nearly 7x longer (if my maths is correct?), which would equate to c. 35 min exposures... :).
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Catanonia

Catanonia

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Yes, after stretching the histogram in GIMP to clip some of the noise and increase contrast, the histogram showed only 5 spikes indicating that the image had been converted to just 5 brightness levels.

Gina,

What you need to realise is that M101 is extremely faint and that although I say quick and dirty for my images, it is still 5m per RGB channel subs at F2.8 !!!!! Take a Skywatcher MN190 @ f5.3 it is nearly 4 times quicker or 8 - 10 times quicker than an average refractor.

Looking at your subs, you have definately got M101 there, you just need MUCH more exposure time per sub and of course guiding with it.

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Catanonia

Catanonia

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Hi Gina - By all means try different software, but I don't think it's a software issue. M101's a fairly faint target anyway (although you wouldn't know it from THIS image!), but don't forget that Catanonia's imaging at f2.8, and he's also using a more sensitive mono CCD camera. To get a similar image depth (with the same mono CCD) on your f7.5 ED80 the exposures would need to be nearly 7x longer (if my maths is correct?), which would equate to c. 35 min exposures... :).

Yes using a CCD as well.

My F2.8 compared to your F7.5 is probably close to 8 times as fast and of course I have 200mm apeture so probably more than that.

So my 5m subs would equate to lests say 40min + on your DSLR and probably more.

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Gina

Gina

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Actually I'm running at f6.3 as I have the focal reducer but that's still over 3 stops as I calculate it and will need well over 8x the exposure of f2.8! So, I'm better using longer exposures even if I can only manage fewer of them? I've been wondering if a few long subs would be better than many short ones. Seems it is - is this right?

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Catanonia

Catanonia

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Actually I'm running at f6.3 as I have the focal reducer but that's still over 3 stops as I calculate it and will need well over 8x the exposure of f2.8! So, I'm better using longer exposures even if I can only manage fewer of them? I've been wondering if a few long subs would be better than many short ones. Seems it is - is this right?

Seems right give or take a small order of magnitude.

Faint objects need much more time to gather the photons on the chip. Of course this means more exposure time, harder guiding and of course more noise so the need to take more to reduce them. A vicious circle :)

Your effort on M101 is good for the limited exposure times at your F Stop and I think you are expecting too much from the data.

I noticed that someone managed to pull out a good image from your data, so processing skill also helps a great deal here.

Hope you work it out, perhaps try another target to practice on 1st, M101 is faint and small.

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Anweniel

Anweniel

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At F2.8 I guess everything is pretty quick (comapritively!) but if this is dirty my attempts must be stinking awful!!!!!! (which they are haha :))

I SERIOUSLY love the work you are pumping out of that powernewt - fabulous

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Catanonia

Catanonia

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At F2.8 I guess everything is pretty quick (comapritively!) but if this is dirty my attempts must be stinking awful!!!!!! (which they are haha :))

I SERIOUSLY love the work you are pumping out of that powernewt - fabulous

thanks mate, gives me encouragement even with all the flat issues are am having at the moment.

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