ICEINSPACE
Moon Phase
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Waning Gibbous 82.1%
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06-06-2008, 12:52 PM
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Registered User
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Join Date: Aug 2006
Location: Western Australia
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Darks, lights ,light darks, dark dark and the meaning of Life
Can anyone please explain to me these terms so a layman could understand and why you need to do these things to produce a good image.
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06-06-2008, 01:24 PM
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Join Date: Oct 2006
Location: Adelaide
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lights = a normal exposure
darks = an exposure with the same settings as your lights but with the scope/lens cover on so basically all you are recording is the noise generated by the sensor without any light hitting the chip.
flats = exposing to an evenly illuminated light source across the entire telescope aperture to around 30% of your maximum pixel value (records dust/vignetting)
flat darks = if the exposure needed for flats is long enough you will need to take dark frames to be applied to them.
meaning of life, the answer is 42 (apparently)
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06-06-2008, 01:27 PM
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Starcatcher
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Join Date: Dec 2006
Location: Gerringong
Posts: 8,539
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Quote:
Originally Posted by monoxide
meaning of life, the answer is 42 (apparently)
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I don't know why that is, but it looks nice in binary. Add a leading 0 for best effect.
ps. thanks for the succinct explanation.
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06-06-2008, 01:30 PM
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Starcatcher
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Join Date: Dec 2006
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pps - what is a "sub"?
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06-06-2008, 01:46 PM
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Ah I know that one, it is a boat that swims under the water.
leon
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06-06-2008, 02:03 PM
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Starcatcher
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Join Date: Dec 2006
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or some sort of sandwich thingie?
OK, I'll expand. I think it's an abbreviation for sub-frame, one of a number of frames which are put together (stacked?) to create a final image? Have I guessed right?
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06-06-2008, 02:22 PM
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exactly
also its good to take the same amount of flats/darks/flat darks as lights
that way you get a better 'reading' of whats going on.
takes a lot of exposures for 1 image doesn't it
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06-06-2008, 02:23 PM
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Location: Hahndorf, South Australia
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Quote:
Originally Posted by leon
Ah I know that one, it is a boat that swims under the water.
leon
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No, it's a bus admiring itself in the mirror!!!
Serious question!
Do flats have to be taken at same FL and f ratio as imaging run? I'm thinking about lens imaging here.
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06-06-2008, 03:22 PM
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Quote:
Originally Posted by dugnsuz
No, it's a bus admiring itself in the mirror!!!
Serious question!
Do flats have to be taken at same FL and f ratio as imaging run? I'm thinking about lens imaging here.
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In answer to your question you may refer to Jim Solomon's Astrophotography Cookbook
Flat Darks- exactly same value ISO and Tv settings when collecting flat lights but with eyepiece cover and lens cap in place
I noticed that you are using a Pentax stD I have recently purchase the K100d super. What program do you use to stack photo's. Also is it a good idea to set ISO to 800 etc and do muliptle short shots
Last edited by TrevorW; 06-06-2008 at 03:36 PM.
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06-06-2008, 04:27 PM
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Quote:
Originally Posted by TrevorW
I noticed that you are using a Pentax stD I have recently purchase the K100d super. What program do you use to stack photo's. Also is it a good idea to set ISO to 800 etc and do muliptle short shots
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Cheers Trevor
Sold the ist-D a while back to fund the 40D purchase.
The pics in my gallery would have been stacked using either Registax (earliest widefield pics) and then Images Plus.
I found iso 400/800 to be good on the Pentax, but get as many subs as you can due to the noise generated!
Doug
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06-06-2008, 04:44 PM
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I found iso 400/800 to be good on the Pentax, but get as many subs as you can due to the noise generated!
Doug[/quote]
The K100d has built in noise reduction and supports ISO up too 1600 or would this be way too much
Regards
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06-06-2008, 05:41 PM
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Retired, damn no pension
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Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
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Doug, if you shift your focus between taking your lights and taking your flats or rotate your camera or do anything that alters your imaging train, then your flats will be no good to you. They must be taken with the same imaging train/layout/orientation/dust (yep don't even blow the dust away ) as your lights.
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06-06-2008, 05:48 PM
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Quote:
Originally Posted by TrevorW
I found iso 400/800 to be good on the Pentax, but get as many subs as you can due to the noise generated!
Doug
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The K100d has built in noise reduction and supports ISO up too 1600 or would this be way too much
Regards[/quote]
Not really too sure Trevor - there are a few devoted Pentax users on IIS.
Perhaps start a Pentax related thread?
I would just experiment with iso settings though Trevor.
You'll probably know quite quickly if the noise produced looks unacceptable.
I would add that the same rules apply to all astro dslrs (pentax, canon etc), take as many subs as possible of an image to obtain the best signal to noise ratio when stacked.
All the best
Doug
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06-06-2008, 08:47 PM
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A bit of experimenting then is on the cards
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06-06-2008, 09:57 PM
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Do you have autoguiding capability with your EQ5 mount Trevor?
If not is it driven in RA?
If polar aligned, a driven EQ5 will give you 30-60sec unguided exposure time. Probably closer to 30secs unless you're anal about the polar alignment!!
That will necessitate the need for multiple exposures.
If you have a Pentax remote shutter switch this is easy.
Set the camera to multiple exposure mode and the maximum exposure setting: 30secs. Put your remote switch into the hold mode - this will make the camera take one shot, do a dark then take another shot etc etc as long as the remote button is depressed.
Doug
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07-06-2008, 05:34 PM
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Beginner-ish
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Join Date: Dec 2007
Location: California, USA
Posts: 207
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Jeepers! I logged on to get some info about focal reducers and saw the subject of this thread (which made me laugh in empathy) and, of course, had to read the whole thing because I'm just learning about the subject. Now I'm too sleepy to look up focal reducers. LOL.
I love this place!!
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09-06-2008, 11:21 AM
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Join Date: Aug 2006
Location: Western Australia
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Welcome to America, it's gratifying too know we can help.
I'm not new to astronomy as a hobby but monetary restrictions have placed limitations on what I could do in the past but now I'm building up some modest equipment to try my hand seriously at astrophotography.
The advent of DSLR's and the like has widely opened this realm to the amateur in more ways than one.
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09-06-2008, 11:36 AM
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Moderator
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Quote:
Originally Posted by dugnsuz
Serious question!
Do flats have to be taken at same FL and f ratio as imaging run? I'm thinking about lens imaging here.
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Serious answer !: Yes
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