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jmasin
sage
Reged: 12/22/08
Posts: 489
Loc: Murphy, TX (DFW)
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Hey all, probably a stupid question for you other Newt images, but how do you manage diffraction spikes when you image a given object across multiple evenings/weekends?
I don't have a fixed setup, so must take down every so often depending on work/weather. This means disconnecting the camera from the focuser. This also means the next time on the same object the diffraction spikes are not aligned the same.
Anyone have a trick to handle this?
Now that Orion is up, I'm really looking to generate a detailed mosaic, but there's no way I can do this in a single session (or single setup run).
Thanks (and sorry if this doesn't go here but there isn't really a general imaging forum and the Reflector forum seems to be mainly observing).
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Cheers,
Jon
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Orion Atlas 8" (203mm f/4.9 on Atlas EQ-G)
Tasco 60mm (~35 years old and still kicking!)
Nikon D300, 80, 70 & many lenses
http://www.pbase.com/jmasin/astro
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cdndob
professor emeritus
Reged: 07/28/06
Posts: 665
Loc: The Great White North
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That's a good question and I'm hoping to do some of my very first newt imaging as well, if it ever clears up!
I would guess the spikes would align as long as the OTA is in the same rotational position in the rings. This should keep the spikes in the same orientation relative to the object in the sky. I can't visualize anything else you'd need to line up though a good polar aligment might play a role here as well. This is just a guess but I hope to have some actual experience on this real soon.
Steve
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Nils_Lars
Post Laureate
Reged: 01/04/08
Posts: 3459
Loc: Santa Cruz Mountains , CA
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I personally leave my adapter attached to the draw tube and just take the camera off the T-ring like the scope is a big lens , then I put a lens cap on the T-ring to keep dust out.
The camera only goes back on the T-ring in one position so this should solve the issue I think?
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Erik
Orion Atlas Self Hypertuned (EQMOD)
Orion ED 80
Williams Optics VII reducer
Celestron 8" SCT
Orion Starshoot Autoguider
PHD guide
Canon 400D Hap Griffin Mod w/Baader filter
Astronomik clip-in LP filter and 12nm Ha
Stilleto CVF and Bahtinov mask
Tamron 75-300mm&28-80mm lenses
NexImage webcam
http://www.flickr.com/photos/31986095@N05/
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jmasin
sage
Reged: 12/22/08
Posts: 489
Loc: Murphy, TX (DFW)
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Quote:
That's a good question and I'm hoping to do some of my very first newt imaging as well, if it ever clears up!
I would guess the spikes would align as long as the OTA is in the same rotational position in the rings. This should keep the spikes in the same orientation relative to the object in the sky. I can't visualize anything else you'd need to line up though a good polar aligment might play a role here as well.
Steve,
I just got done typing up a reply explaining why you are wrong (  ) and I just deleted it. I think I feel a bit idiotic now. I was thinking camera orientation made a difference too, but you know, you are correct. As long as the vanes-object are aligned and don't change, the sensor doesn't matter since you need to align/rotate to stack anyway. All ya really need is the diffraction spikes consistent with respect to the object.
Which of course explains why no one else has asked this question
I pulled an all-nighter last night imaging (first clear night in 1.5 months!) - I guess my brain finally went to sleep.
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Cheers,
Jon
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Orion Atlas 8" (203mm f/4.9 on Atlas EQ-G)
Tasco 60mm (~35 years old and still kicking!)
Nikon D300, 80, 70 & many lenses
http://www.pbase.com/jmasin/astro
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cdndob
professor emeritus
Reged: 07/28/06
Posts: 665
Loc: The Great White North
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Jon,
It wouldn't have been the first time I was wrong about something . My first thought was the camera orientation played a role as well but then I thought back to my non-newt pics. Now I just wonder how critical the OTA/ring alignment will need to be but I'll leave my OTA in the same position so it should be ok.
Look forward to seeing the results to your all-nighter efforts.
Steve
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