Re: [Utah-astronomy] Want feedback on my Orion Nebula picture flaws
Thanks all for the responses, the help is great ! I will definitely try the "Hat trick". My Nikon doesn't quite have mirror-lockup, but it does have a mode to flip up the mirror 1/2 sec. before the shutter opens. I'm not sure that is long enough. Maybe I will try a few comparison shots between the Hat Trick and the semi-mirror lockup. I looked up the "star-drift" tracking method, and will try it on my next clear night. I'm very hopeful that will solve one part of the problem. It will definitely work better than the "Oops! The stars are still moving, let's try this position" method I was using the other night. I would really like to be able to get 2-5 minute exposures ... which I expect will make me want 15-30 minute exposures. For focusing, I will definitely prefocus on a brighter object. I did look at some the pictures on the small camera LCD after taking some of the shots, but obviously didn't look close enough. I was mostly thinking about the bad tracking at the time. I can magnify the pictures on the camera LCD, so I will be more diligent about reviewing the focus. I will have to save the after-market focusers until I get some more time into the basics. (and the family appropriations committee gets a little more softened up) I'm a little hesitant to culminate the scope because I don't know what the before and after differences should look like, and don't want to make anything worse. I guess I will do some more reading on it first. About the "piggyback" suggestion, I have an adapter/mount partially built to be able to piggyback my dSLR on the telescope. I am hoping to finish that today. I saw a picture of a pier (mentioned by Patrick) on a forum the other day, and that is definitely on my list. I can build one without a big $ outlay. I already have a concrete pad in my backyard, and I'm guesssing that a pier bolted to that would give me about the best foundation I could hope for. I took golf lessons a while back, and felt that I had to remember and pay attention to 8 different things simultaneously while I was swinging the club. Right now this feels similar. I am having great fun, although I could use a few more clear nights. Wednesday 3am-6am is showing possible clearing in SLC, but I'm not sure if I am quite that dedicated to stay up for a "maybe" on a cold winter's night. Clear skies, and Happy Holidays, Gary Logan.
On 23 Dec 2008, at 14:13, Gary Bulk wrote:
I will definitely try the "Hat trick". My Nikon doesn't quite have mirror-lockup, but it does have a mode to flip up the mirror 1/2 sec. before the shutter opens. I'm not sure that is long enough. Maybe I will try a few comparison shots between the Hat Trick and the semi-mirror lockup.
Joe has more "hat trick" experience than me but I think if you cover up the front of the scope before opening the shutter and then open the shutter and then let the vibration settle out before removing the hat I don't think you need to lock the mirror up. Just be sure and cover the front again before closing the shutter.
I would really like to be able to get 2-5 minute exposures
Ummm, since the chip is not cooled I've a feeling that if you go more than a few seconds you're going to pick up an awful lot of background noise. Anyone here have experience with how long one can go with an uncooled chip before noise becomes objectionable? Also, is there some way to use a DSLR to make a master flat and use it to subtract the noise (like is done with CCD cameras)?
I'm a little hesitant to culminate the scope because I don't know what the before and after differences should look like, and don't want to make anything worse. I guess I will do some more reading on it first.
Best not to mess with it unless you have a manual to show you how (it's very easy to make a bad situation much worse). Might be best to bring it to a star party and have someone do it for you.
About the "piggyback" suggestion, I have an adapter/mount partially built to be able to piggyback my dSLR on the telescope. I am hoping to finish that today.
If that doesn't work, I donated tall and short C-8 piggy back mounts to SLAS for the loaner scope program. You could see about borrowing one.
I saw a picture of a pier (mentioned by Patrick) on a forum the other day, and that is definitely on my list. I can build one without a big $ outlay. I already have a concrete pad in my backyard, and I'm guesssing that a pier bolted to that would give me about the best foundation I could hope for.
Best to put the pier in the ground (dirt) such that it is isolated from the concrete. Concrete has the irritating habit of transmitting vibrations especially when using long focal length imaging systems.
I took golf lessons a while back, and felt that I had to remember and pay attention to 8 different things simultaneously while I was swinging the club.
But, as with golf, if you stick with it you'll get the hang of it. Cheers, patricjk
Patrick makes a good point about an uncooled chip generating "noise" on long exposures. A really cold winter night will help extend your exposure time, but probably not that long. Also be aware of excessive battery drain during long exposures, combined with cold temperatures. On Tue, Dec 23, 2008 at 2:13 PM, Gary Bulk <garybulk@the-logans.net> wrote:
I would really like to be able to get 2-5 minute exposures ...
On 23 Dec 2008, at 20:31, Chuck Hards wrote:
Also be aware of excessive battery drain during long exposures, combined with cold temperatures.
I seem to remember that Joan Carman came up with a way of getting around that problem by figuring out a way to power her camera with a large external battery. Joan, was that you? If so, how did you do it? patrick
That's an excellent idea, with just two things to keep in mind: 1. Know exactly what you are doing so as to not damage your camera. 2. Bear in mind that you could be voiding any warranty. On Tue, Dec 23, 2008 at 9:37 PM, Patrick Wiggins <paw@wirelessbeehive.com>wrote:
On 23 Dec 2008, at 20:31, Chuck Hards wrote:
Also be aware of excessive battery drain during long exposures, combined with cold temperatures.
I seem to remember that Joan Carman came up with a way of getting around that problem by figuring out a way to power her camera with a large external battery.
Joan, was that you? If so, how did you do it?
patrick
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On 23 Dec 2008, at 20:31, Chuck Hards wrote:
Patrick makes a good point about an uncooled chip generating "noise" on long exposures.
Tonight's sucker hole didn't permit doing anything serious but Chuck's message prompted me to shoot a "visual aid". First I shot a 1 minute exposure of a random galaxy. That's called the "raw" image. Next I shot 15 one minute exposures with the scope covered (called "darks") and then using software I median combined them into a single master dark. Then, again using the software I subtracted the master dark (which is basically a picture of the noise in the chip) from the raw and got the final image. All three shots are posted here: http://users.wirelessbeehive.com/~paw/temp/RAWMINUSDARK.JPG As you might expect this is a very simplified version of what's done to get Tyler-like images but maybe it will give an idea of what "noise" is and what's involved in removing it (and how important it can be to remove it). patrick
Patrick, You da man! What an amazing photo for just a demo. It's haunting to think of all those "island universes" out there, probably every one of them with civilizations. -- Joe ________________________________ From: Patrick Wiggins <paw@wirelessbeehive.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Wednesday, December 24, 2008 1:53:25 AM Subject: Re: [Utah-astronomy] Want feedback on my Orion Nebula picture flaws (visual aid) On 23 Dec 2008, at 20:31, Chuck Hards wrote:
Patrick makes a good point about an uncooled chip generating "noise" on long exposures.
Tonight's sucker hole didn't permit doing anything serious but Chuck's message prompted me to shoot a "visual aid". First I shot a 1 minute exposure of a random galaxy. That's called the "raw" image. Next I shot 15 one minute exposures with the scope covered (called "darks") and then using software I median combined them into a single master dark. Then, again using the software I subtracted the master dark (which is basically a picture of the noise in the chip) from the raw and got the final image. All three shots are posted here: http://users.wirelessbeehive.com/~paw/temp/RAWMINUSDARK.JPG As you might expect this is a very simplified version of what's done to get Tyler-like images but maybe it will give an idea of what "noise" is and what's involved in removing it (and how important it can be to remove it). patrick _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com
participants (4)
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Chuck Hards -
Gary Bulk -
Joe Bauman -
Patrick Wiggins