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11/30/-1
    
Sunday, March 29th, 2009
I was able to get out for a short time tonight. Having a few issues I'm trying to resolve, but overall I solved a few problems and answered a few questions.

For instance:
  • I performed a more dialed in alignment with the guide scope.
  • I re-balanced the scope.
  • I tried to identify an anomaly with misshapen stars. It's still undetermined, but at least I know it's not flexure or drift.
  • I imaged using dithering to try and enhance the smoothness of the background.
  • I try to figure out the blue/green color problem from the other night
I shot a handful of objects while testing various things. M3 was actually worth posting so it's below as well as a screenshot.

UPDATE: The images of the in and out focus - mostly concentrating on the ripple in the diffraction rings, turns out to be heat current running up the tube. This is annoying to me because I'm not used to having to deal with heat current as a hindrance. I'm still considering going back to a medium sized (say, 100mm) refractor for imaging. I've still not fogured out the star bump, but it's likely collimation - which I'm not used to really dealing with that either.

M3 Image
Scope: Vixen R200SS 200mm @ f/4 w/Baader MPCC
Mount: Orion Sirius EQ-G with GoTo
Guiding:  Meade DSI Pro and PHD Guiding
Guide Scope: William Optics ZenithStar 66 SD
Camera: Canon EOS 20D (unmodified)
Special Settings: None
ISO: 1600
Exposure: 60 minutes - (20 x 180s)
Processing Software: Acquired in Nebulosity, Stacked in Deep Sky Stacker, Levels and Curves in Photoshop
See Gallery below for image



Image Gallery For This Session
M3 30m M3 Screenshot
z Collimation focuser in z Collimation focuser out
z Mis shapen stars
   

M3-30m.jpg
Click picture above for larger version
If the picture seems too bright or too dark, try adjusting the brightness below.
Brightness:
|
  



Comments:
On 04/07/09 at 01:31pm Neil Heacock wrote:
Jeff, yes that's what I'm referring to as dithering. A few revisions back Craig Stark implemented auto dithering into Nebulosity and PHD Guiding when used together. I tried it once before, but was not happy with the result. I think I understand it more now though and I plan on using it in the future.

On 04/03/09 at 05:57pm Jeff W. wrote:
When you talk about dithering, do you mean moving the mount, i.e. changing the framing, by a very few pixels between shots. Ive seen reference to this on the yahoo groups some. I dont have that problem, I dither every shot whether I like it or not, lol. Great glob by the way.

Jeff.

On 03/30/09 at 06:51pm Neil Heacock wrote:
Also, on this shot the background is considerably smoother then the previous shots (as I'm sure you noticed), and that has something do to with my experiment in dithering this session. I think I'm going to leave dithering as part of my future technique since it appears to work very well.

On 03/30/09 at 06:48pm Neil Heacock wrote:
I have considered that. But I don't have darks and bias frames for any other ISO setting right now and I didn't want to take the time to shoot darks for this session. Apparently, the optimal ISO for the 20D and astrophotography is 800. I'll start building a library of support frames for ISO 800 and then start shooting there. There is a technique to shoot a few frames at very low ISO like 200 to preserve star color and use that as a color saturation layer for the image. I think I'll experiment with that as well in the future.

On 03/30/09 at 06:37pm Barry wrote:
That's a nice M3. Well resolved. Have you tried reducing the ISO setting on the camera to maybe 400 ISO? I wonder if it would solve your smooth background problem......not that I see one in this image. Of course it would mean more exposure time.



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