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Crab and Veil

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#1 AstroMan0

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Posted 15 December 2012 - 02:03 PM

Here are the photos I took last night of the Crab and the Veil. I could only get about 19 minutes of exposure time for the Veil, as it was about to set below a tree. Also,my neighbors' bright lights were shining in the direction of the nebula. As can be seen from both photos, I clearly need practice on focusing and guiding. I also need to deal with dew on the objective. My photos lately have had mottled backgrounds, and I didn't know why. Then while handling dew covered equipment, I realized that the objective was covered with dew and spots resulting from it. Any recommendations for cleaning the objective?
Anyways, I exposed the veil for 19 minutes with the 29 filter, and exposed the crab for 30 minutes with the 29 filter.

Clear skies,
Noah

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#2 AstroMan0

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Posted 15 December 2012 - 02:08 PM

Here is the Veil... I think I might need a better scanner.

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#3 Michal1

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Posted 15 December 2012 - 04:12 PM

Hi Noah!

The standard solution of the problems with dew are heating belts. They contain a heating wire. They are sold by shops with astro equipment, but are quite overpriced, at least here. A fellow astrophotographer made a pair for me for a fraction of the commertial price.

There is something strange with your shots: why the vignetting isn't symmetric around the centre of the images? Do the images depict the whole film frames? Are they scans of the negative or the prints? Or can't there be a shaddow of something on the right sides of the images?

The stars are evidently blurred differently acros the image. This may result e.g. from that the film plane isn't perpendicular to the optical axis, or due to the field curvature of the telescope. What size of the image circle do the producer of your telescope declare?

Most of the people in this forum use their own scanners, because they can control the process. I always use the opportunity of a professional scanning service. I can get scans from high quality dedicated film scanners I couln't afford to buy. They've never messed it up. When I take into account the number of photos I take per year, it is more economical then buying a medium grade flatbet scanner.

M.

#4 AstroMan0

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Posted 15 December 2012 - 04:43 PM

Hi Michal,
I cropped the photos after I scanned them, so that may account for the uneven vignetting. As for the scanner, I used my grandparents' all-purpose scanner/printer. I should probably think about getting a dedicated film scanner, or getting professional scans. I don't know about the image circle size, but I do know that my guiding and polar alignment were far from perfect. Also, any tips for adjusting curves, etc. on the computer? So far, I haven't gained as much skill inn Photoshop as I have gained in the darkroom.

Clear skies,
Noah

#5 Michal1

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Posted 16 December 2012 - 07:34 AM

I'm sorry to say it, but it won't be possible to get significantly more from these images by postprocessing. They are too much grainy. If the scans are 16-bit per channel, the situation would be a little better. The first step should be the vignetting reduction in Pixinsight LE. Then I'd play with curves and maybe denoising.

If you want to benefit from computer processing, you will need better scans directly of the negatives themsef. Best in the 16-bit color depth. Dedicated films scanners are quite expensive. The people here use flatbed scanners. Someone could advise you a particular product.






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