Uncle Burnout
super member
Reged: 08/06/03
Posts: 115
Loc: California (Bay Area)
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There was a space of fairly clear sky after dark last night, so I tried M42 with the ST80 again, this time w/o focal reducer. Conditions worsened as the night went on so my grandiose plan of guiding some really long exposures got ditched, but I still got a halfway decent picture of M42 in a pretty short time before switching to other targets.
My DSI-related main intent for the night was to get some more practice w/FITS format processing in Autostar IP, so it wasn't wasted, anyway. Using FITS versus BMP last time, I was able to get more of the surrounding nebulosity to show up in the final picture despite working at a slower f/ratio (f/5 versus f/2.8).
Notes:
ST80 w/Skyglow filter on SkyviewPro
Exposures: ~20x30s, ~10x42s, ~10x60s; images saved in FITS format and processed in Autostar IP, then tweaked pathetically in the GIMP.
Thanks,
Burton
Edited by Uncle Burnout (03/04/05 03:19 AM)
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Rushwind
Carpal Tunnel
Reged: 03/11/04
Posts: 2137
Loc: Newark, CA
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That's a pretty wide FOV for the DSI; nice!
Even though you had to shoot this one through that 400mm straw  , I cracked up when I thought of using a focal reducer with the little teeny ST80.  Effective focal length 224mm. I love it!
Jimbo
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Order of the Unblinking Eye
NJP 300D SSAG 8"f/5 (Rig)
Guidescope? What guidescope?
I used to shoot Nikon DSLR.
Before that, I shot film.
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Rammysherriff
Carpal Tunnel
Reged: 03/26/04
Posts: 1967
Loc: Lancs, UK.
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I'd say it was perfectly framed too. Good effort!!
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Simon.
One man and his shed: http://s211.photobucket.com/albums/bb288/Astroshed/
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Anonymous
Unregistered
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Hey that looks like the promise of becoming a great picture.
this one looks a bit out of focus but that might be due to bad conditions.
What i especially like is the equipment you shot it with; i have the same scope and filter. A replacement DSI is on it's way so i should be able to follow your footsteps (crossing my fingers that i will be able to get half decent traking with my poor EQ3-2)
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Uncle Burnout
super member
Reged: 08/06/03
Posts: 115
Loc: California (Bay Area)
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Quote:
Even though you had to shoot this one through that 400mm straw , I cracked up when I thought of using a focal reducer with the little teeny ST80. Effective focal length 224mm. I love it!
Jimbo, I really liked the focal-reduced ST80, too. M42 is a bit like the moon for practice: it's big, it's there, and it's bright, but it doesn't fit on the DSI chip with any normal focal length and the dynamic range is huge. I figure M42 is a good corner case for testing, not to mention the short fl's minimize tracking issues.
Quote:
I'd say it was perfectly framed too. Good effort!!
Thanks, Simon. I think I liked the focal-reduced view a bit better, but there probably aren't enough pixels to support it  .
Quote:
this one looks a bit out of focus but that might be due to bad conditions.
Hey, Peppe, those stars were focused to perfect X's! That kept the software alignment from working well. Also, to compound my problems, I summed the channels, leaving me with too much noise to run any kind of sharpening. Live and learn. I do think this combination (DSI/ST80) will do a decent job on M42 when everything is right.
Thanks,
Burton
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Anonymous
Unregistered
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did not mean to offend your hard workin' efforts! i know getting tack-sharp focus with the st80 is a b*tch; the focusser is not all that let alone that it is a refractor....
i found myself getting 'soft' stars most of the time, without color filters, on a refractor you most likely can't eliminate that completally.
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Uncle Burnout
super member
Reged: 08/06/03
Posts: 115
Loc: California (Bay Area)
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Peppe,
I didn't take offense at all -- there is not much of my ego in these images. I got out again last night (06 March) with some better transparency/seeing for a while and took the attached. Big improvement to my eyes, but I need some feedback. Just as I got tracking spot on up to 2M, the house got in the way:(.
30x30s; 15x60s; 2x120s
Thanks,
Burton
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jgraham
Postmaster
Reged: 12/02/04
Posts: 11575
Loc: Dayton, Ohio
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How are you combining the different exposures? I've been trying to do what you've done here; show the expanse of the nebula and still have some nice contrast in the core. I think I've got the source images to do this, but I just don't have the knack for putting them togteher yet.
-John
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-John
The best advice on imaging I've ever been given... don't forget to look!
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Uncle Burnout
super member
Reged: 08/06/03
Posts: 115
Loc: California (Bay Area)
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Quote:
How are you combining the different exposures?
Hey John,
I think what does the trick is to do a logarithmic stretch on the FITS files before RGB merge in AS IP. After exporting RGB images as BMP, I normalize them and adjust the levels as if they were final pictures, then stack them two ways: average and accumulate. This time I used the accumulated stack for the RGB (better saturation) and a desaturated average stack for a pseudo Luminance channel (it holds up well to sharpening). I use the exported BMP's for stacking because I have a program I wrote and feel comfortable using, but I suppose you could also do something similar with AS IP using the original FITS (I just haven't been able to get that working as well for me yet).
Lots of tweaking here and there, but that's the basic idea. Does that help?
Thanks,
Burton
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jgraham
Postmaster
Reged: 12/02/04
Posts: 11575
Loc: Dayton, Ohio
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Burton,
Ahah! That gives me some new things to try. The weather here it supposed to be lousy for the next several days and I have some great source images of M42 from last night to work with.
Thanks!
-John
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-John
The best advice on imaging I've ever been given... don't forget to look!
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