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My very first CCD image...'pac' to basics?


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Mornin all

its been a frustrating week...the other night i managed to frame and focus ngc6888 on the laptop, via my new, but secondhand, atik 314L...but i couldnt get guiding going (forgot to plug synguider cable into mount, duh!), but finally tonight i managed to capture 7 frames of 900sec each, with Ha filter 1x1 bin...again on the equinox 80....which i also got secondhand recently. guiding was thru the equinox 66. i had to chuck 3 frames due to poor visability...grrrrr! had hoped to flip, and get a few hours of s2 and 0111, and get a poor man's hubble pallet, but messed the framing up....or rather, i couldnt find the subject matter! then cloud, so packed up....and it cleared again! still, ive rammed the 7 subs thru DSS and just a quick stretch in pixinsight....just wanted to know if my investments were working properly.....will do a proper process tomorrow.

please let me know what u guys and gals think....

cheers

bob

ps....many thanks to:

Angus...for fixing my tube rings etc.

AndyUK...for your expertise.

Pete...for generously giving me your manual filter wheel.

......................................................................................................right, where's my oscar?

post-3512-0-23098800-1350611275_thumb.jp

Edited by cloudbuster
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I would say that you are definitely on the right track Bob. The noise will improve with the addition of more subs and you need some flats to help deal with the gradient. Pretty good stars and the focus is looking like you're getting there indeed. Well done!!

Onwards and upwards!!

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Nice one Bob - I would say that's a bit of a result with the new kit!

I agree with Sara - More subs will get rid of the noise... but I'm intrigued by the gradient - We'll have to look into that. There's no moon about and Ha wouldn't be picking up any LP :icon_scratch: but otherwise it's got great promise... :smiley:

(We'll also have to look into the Meridian flip issues as well :wink:)

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Nice one Bob - I would say that's a bit of a result with the new kit!

I agree with Sara - More subs will get rid of the noise... but I'm intrigued by the gradient - We'll have to look into that. There's no moon about and Ha wouldn't be picking up any LP :icon_scratch: but otherwise it's got great promise... :smiley:

(We'll also have to look into the Meridian flip issues as well :wink:)

Hi andy

sara says that better flats might improve the gradient...i do hope so and that its not equipment failiure?!

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Pixinsights DBE process should help with the gradient - have you got a light leak somewhere perhaps?

Frustrating though it is that you haven't got all you wanted I think you should be pretty chuffed - apart from the gradient the image you have looks pretty good to me. I tend to concentrate on getting just one channel per night which usually means I can avoid the temptation to switch to another filter too soon and that helps me get loads of subs in each channel but of course it means a complete image can take a long time :smiley:

James

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Hi Bob (my apologies to everyone else on this thread - Bob also sent me a fits file of this...)

The good news is that your flat looks fine - The ADU is okay and it will definitely be subtracting all that rubbish out!

Looking at your image, I was anticipating (perhaps) possibly seeing a large dark area towards the top LEFT corner as that's the area far lighter in your image. My first thought was that perhaps the flat might be subtracting too much... But no - I don't think that's the issue. As there's no gradient on the flats, I doubt that the flats are your problem.

I don't think it'll be LP as normal Ha bandwidth is WELL away from LP, and there's no moon, so it's neither of these. By deduction, as James has suggested, I think you may have some light ingress into the imaging train. This COULD be light somehow shining into the filterwheel (perhaps the thumbwheel area?) or even light getting in at the lens objective end... Are there any lights that could have done that? I have a piece of insulation tape over the thumbwheel on mine, as I don't want any light from the moon, extension or streetlights getting in...

Another thing you could try is doing a restack of just the lights (no flats) and seeing if the gradient is still there - My bet is that it will be, in which case that's another pointer towards light ingress...

As an aside, if you squint at a flat, you do have quite a few dust bunnies there (the darker blobs) which is especially prevalent on the right hand side (and especially top right and bottom right corners). Although it won't effect the gradient, it might be worth giving the filter a good clean and maybe getting one of those bulb air blowers just to give a good few puffs onto the camera chip and also, whilst you've got the case open, give that a good "puffing" too - Looking at the shape / focus of those dust bunnies, my first line of attack would be the filter - Don't forget to clean both sides :wink:

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Hi Bob,

Congratulations on the new camera. One huge benefit I've found of owning a cooled CCD is the ability to prepare dark frames ahead of time for a set of standard exposures. In my case 15 dark subs seem to work very well allowing me to get pretty close to the sensor's noise level and I was able to capture the dark subs during cloudy nights while I was deep in the arms of Morpheus. Have you had a chance to grab some darks yet?

Bob.

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In my experience with the 285 chip you'll not need darks. I've been running mine at 0 degrees during the warm weather, and really didn't battle with noise. While I have settled on a bias and flat calibration, darks certainly don't figure in my calibration routines with the 314L+.

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Ditto - I'm usually able to select at least -10C and sometimes more (if it's colder and I can get away with it :wink:).

Also, with this version of 314, there's no setpoint cooling - It's either off or -27C below ambient, so if you really wanted to get matched temp subs it would make it a bit trickier taking them at a different time.

You could always get a library together if you wanted to and then put them into different temp/exposure folders, but even if it's ambient 17C at night (I can't recall too many of those!), it would still be running at -10C, and at that temp (as Sara has noted even at 0C), the 285 chip seems pretty much noiseless even with 15 or 20 min subs (I've not tried 30 mins yet though!)

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According to the spec the Atik 314L+ has set point cooling. It's the cheapest Atik to have this feature which is why I am considering it for later on. I certainly find set point cooling a great advantage with my 1100D cooling system and I certainly wouldn't want to lose it in a CCD.

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I think that Bob has the 314L and not the 314L+ The latter has the set point colling, while the former, like the 16HR range just goes to maximum degrees below ambient. While this does make it tricky for darks, I'd be surprised if they were needed in all honesty.

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Hi Gina - Sara's correct - The 314L is the precursor to the 314L+ and doesn't have set-point cooling. Like the 16HR, all contain the Sony 285 chip and all have the capability of cooling to -27C below ambient, but only the 314L+ has the set-point option.

I too no longer use darks with my 314L+, even when set as "warm" as -10C. I did take a set of various exposures at -5C and -10C when I first got the camera, and also took a set of bias frames (which I do use). Whilst I can see some hot / dead pixels in the darks as the exposure times increase, I don't find these an issue with my setup. This could well be due to the natural dithering that seems to be inherent in my rig (ie differential flexure!). I admit it might be different if I had absolutely bang-on polar alignment and zero drift, but even then I might first look at the hot-pixel removal option before using darks - The Sony 285 chip does have a very low noise profile...

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I think that Bob has the 314L and not the 314L+ The latter has the set point colling, while the former, like the 16HR range just goes to maximum degrees below ambient. While this does make it tricky for darks, I'd be surprised if they were needed in all honesty.

Ah I see. I misread Bob's post and didn't notice it was the 314L rather than rthe 314L+ that you mentioned. That explains it - thank you :) Sorry for the confusion.
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thanks all for your expertize...appreciated muchos! yes...im hopin to get away with darks...and the LP culprit seems to be the thumbwheel opening, and thanks andy....will get some tape today. everything was going sooo well. the guiding was like a dream, the stars are not bad. framing could of been a bit better, with the subject being over to the right, but all-in-all, i enjoyed this session, and this resulting thread will improve my learning curve. i hope to get DBE to attack the gradient this afternoon, and i'll post the resulting image later.

cheers

bob

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That's a big improvement, Bob...! As you say, there is still a bit left across the top, but maybe another iteration of DBE would get shot of that too(?). Fingers crossed for the weekend weather - Saturday looks REALLY hopeful at the moment!

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