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First real attempt at Deep sky imaging

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19 years 10 months ago #4219 by voyager
Replied by voyager on topic Re: First real attempt at Deep sky imaging

Thats a great image of tha galaxy, something to aim for.
Can you remember the exposure time ??
All I need is a 14 inch scope and the seeing on mount Wilson :wink:

I used 30 second exposures at iso1600,
I might try longer exposuresd at lower iso ratings to see if it prodices less noise.
Once i get the polar allignment fully sorted (wont bother until the dome in built) I'll try it with ds/o2 filters at much longer exposures.
I used the low image quality on fine detail mode, registax seemed to be ok with them, I wish I'd taken more shots, imagine what 100+ stacked images could produce.


I have to say I was shocked to get such a good image of the galaxy. Generally light polution messes up images from mount wilson. All it takes is just the tiniest bit of haze and the sky just lights up yellow with the lights from LA. The above image was a 2 minute exposure on an exceptionally clear night with absolutely no ligh polution. Most images have more noise than that!

My Home Page - www.bartbusschots.ie

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19 years 10 months ago #4222 by larrylart
Replied by larrylart on topic Re: First real attempt at Deep sky imaging
Or an RCOS 12.9 inch telescope :) www.rcopticalsystems.com/gallery/m57smith.html

I think it can be done with as much as an 8” lx90 :) and from light polluted Dublin as well. I will try prove that with the first clear night to come.

Dave, LP filters usually help only in certain nebulas by cutting off that part of the spectrum which commonly originate from public lighting systems. In case of galaxies, which emit in full spectrum these aren’t much help – for very dim objects will considerably increase your needed exposure time which means that you better have a very good guiding system so you can easy do five to ten minutes exposures. Lowering the iso on canon dslr series 10d or 300d from what I know wont make much of a difference either especially because lp noise is more of a problem then electronic noise. If you worry of electronic noise try take some dark shot with your camera lens covered 30 seconds at iso 1600 via 60 seconds at iso800 and see if there is much of a difference in electronic noise.

On the other side, with alt-az mount even field rotation isn’t visible at 30 seconds your still leaking light - some 30% I will say. Also a close to perfect focus makes a lot of difference. As for light pollution mobility is the key and that leads to the country side :)

Larry

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larryo.org

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19 years 10 months ago #4223 by dave_lillis
Replied by dave_lillis on topic Re: First real attempt at Deep sky imaging

Or an RCOS 12.9 inch telescope :) www.rcopticalsystems.com/gallery/m57smith.html


I'll have one please,
Oh, wait a minute, I didnt win the lottery THIS weekend, damn. :cry:
That page shows an incredible image og M57 and IC1296..

Larry, I figured as much about the galaxies and light pol filters, I'll get the guiding working as good as pobbible, I have tried before with accurate polar setup and feel its possible to get 10 + minutes tracking with this scope + mount setup although I must fully train the PEC and backlash on the drives for this, lots of work ahead here.
Camera noise is not really an issue for me, it hasnt been the main problem with imaging, but any edge (Ilike using lower ISO speeds) is benificial, especially if you have good tracking which I'm sure this mount has once its not overloaded and balanced, I've seen examples of this mount massivley overloaded on the web with not so good results. I reckon its near its limits as is.
As for moving to the country side, who knows what the future holds.??
To be honest, I'ver had it with hauling this scope around in the car, I'll be getting a more portable scope in the next year or so, maybe an ETX125 ???, something you can carry onto a plane as hand luggage.

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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19 years 10 months ago #4225 by johnflannery
Replied by johnflannery on topic Re: First real attempt at Deep sky imaging
hi guys,

many thanks for sharing those superb images with us and teasing the galaxy out of the raw data. I'd sort of suspected it was there on the original. I didn't really get a chance judge the light pollution from Mt. Wilson earlier this year Bart as we were there in the daytime but from Santa Monica I was able to glimpse LINEAR in the binoculars -- I was actually pleasantly surprised to see the comet 'cause I had thought the lights would be too bad.

the image of M57 from Tuscon is a real carrot now for everyone! Outer halo and a clutch of background galaxies that are probably not even in the UGC, etc. databases!

I've to still give the SkyMemo camera platform an outing so a long way to go to catch up with your good work! Happy imaging!

John

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19 years 10 months ago #4230 by larrylart
Replied by larrylart on topic Re: First real attempt at Deep sky imaging
Ok, I did a bit of digging and found that RC optics get their mirrors from a Russian company www.lzos.ru/en/glass_sitall.htm . There is a new type of glass sitall with very low(almost zero) thermal expansion. Which is probably why they have such a sharp image. Funny I never thought that small temperature variations could have so much impact on the final result. Anyway, maybe there is a way to get your hands on some good quality optics at a reasonable price … after all the mechanical part and electronics can be done in various ways at a tenth of price.

I don’t have PEC so my upper limit is pretty much 5 minutes (where 50% of my shots fail). Anyway, I would not go near that because at that exposure length my red channel fills up … all red :cry: .

As for a portable scope probably refractor, anything fluoride tak/apo, do very well for dso imaging and are considerably smaller.

Larry

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larryo.org

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19 years 10 months ago #4250 by dave_lillis
Replied by dave_lillis on topic Re: First real attempt at Deep sky imaging
Larry,
You really have your heart set on a RCOS scope, those optics are expensive from what I saw on the web a while back, but you get massive wide and flat fields of view, most of the reader pics in Sky and Telescope are done with this class of scope.

It would be nice to get one of those tak/apo scopes, but I just cant see myself spend a few grand on a 3 or 4 inch scope.
One of the guys in the club here has an etx90, the optics and mechanics are good, and I just cnat give up the goto features,although I presume you can get one of these refractrors with this feature.

BTW, after I was finished with M57, I slewed the scope over to M82 and got this shot.

homepage.eircom.net/%7Esac/graphics/deepsky/m82aug.jpg
I've since re-processed it to remove most of the bright background.
I was surprised to see any colour or dust lanes in it
I stacked 12 frames at iso1600, each 30 secs long. I also took pics of M81 and no matter what I did, the spiral arms just weren't there, they're much fainter then I thought.
I also got this shot of M13 using 14 frames, but the tracking let me down slightly on this one.

Dave L. on facebook , See my images in flickr
Chairman. Shannonside Astronomy Club (Limerick)

Carrying around my 20" obsession is going to kill me,
but what a way to go. :)
+ 12"LX200, MK67, Meade2045, 4"refractor

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