Re: APPM Image Scale Question and Suggestions


Hi Marty

Just to confirm, you should enter the unbinned image scale, and then choose your binning in APPM

I'm not sure what you did in this regard


On Sat, Apr 17, 2021 at 9:12 AM mjb87 via <> wrote:
Hi everyone.

I have used APPM successfully with my Mach2 and 130mm Starfire GTX. I am now trying to build a model for my 1100 with a CFF 300 on it.  I have some specific questions about image scale. I'm using USNO A2.0.

The camera is a ASI1600MC-Cool with a 0.67 focal reducer on a 300mm f/15 Cassegrain. I calculate unbinned image scale at just under 0.26, which is of course pretty small. I binned 2x2. My initial run was not successful -- many failures, often reported as due to potential image scale issues. Later, using the image-link-test solve capabilities, I was able to get a couple of the earlier images to solve, but the estimated image scale in those calculations was reported just over 1.0. When I re-ran the image-link-test solving with that 1.0 entered for image scale I got about half the images to solve easily.

Question #1: Is this inconsistency because of the 2x2 binning? Does the plate-solve results in the Image-Link-Test display estimated unbinned or binned image scale?  The math works: 4 x 0.26 is about what was reported. 

Question #2: Just to confirm, then, that when I enter X-scale and Y-scale factors in the platesolve setup, I should enter the unbinned values, right (0.26)? The software will then adjust, I assume, for the binning.

Question #3:  What options should I play with to reduce the potential for failed solutions due to image scale issues.  How high can I set (realistically) the Image Scale Tolerance?  Is 50% too high?  100%?  I also assume it would be helpful to set Catalog Expansion to a higher value, maybe to the max at 0.8.  I'n not trying to get fast solutions, just more solutions.

Question #4: Any other suggestions for running APPM with such a small image scale?  I was worried about getting enough stars so I increased the exposure time on the camera (from 5 to 15) and reduced the sigma above mean (from 4 to 3). Anything else?




Brian Valente

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