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Calculated object size much smaller than correct
#1
I'm scratching my head over this. 

Short description: Skytools 4.0d  calculates the image size much, much smaller than the actual case, even though the scope & camera appear to be correct. Most objects are 1x1 pixel and very large objects like M31 are 11x4 pixel. ST3 appears correct (sizes in hundreds of pixels or more).

Details: I have a Celestron 8" SCT with a 0.63x reducer and a ZWO ASI 294MC Pro camera. I entered or used the pool configuration and from what I can see, they are correct. (One oddity: I defined the 0.63 reducer but in the imaging system window, the value appears in teh Magnification Factors dropdown box, it even if I select it and click Done, the next time I open the dialog I see the "Magnification factors" text as the default value in the combobox. So it's not clear if the reducer is used in the calculations.

The camera I took from the pool but verified the settings, they appear correct (BTW, minor suggestion: under Camera Type, rename "Astronomical CCD Camera" to "Astronomical CCD/CMOS Camera"). It is the only camera associated with the scope.

The main issue is the size of the objects for the above telescope and camera as it can be seen in the screenshot. Even very large objects like M31 only occupy a few pixels - this is not the case in real life. 

Not sure if I did something wrong.

Help is much appreciated,
Thank you.


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#2
Hi Razvan,

I see that in your Imaging System definition you have the 'Optical Configuration' set to 'Camera Only'. If you are imaging through the telescope, you should set the 'Optical Configuration' to 'Primary Focus (normal)'. The 'Camera Only' option is intended for imaging using a camera + lens configuration. Open your Imaging System then click the 'Help' button at the bottom of the page to see what the settings do. The 'Camera Only' & 'Piggyback' configurations seem to be intended for imaging through a separate lens, not the telescope.

Hope this helps,

Phil S.
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#3
Thank you Phil, it's all good now and this has also restored the ability to choose the reducer. What an embarassing mistake.
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