Having fun with old equipment

Roland Christen

Hi Astronuts,

Having recently purchased a ZWO CMOS camera and putting it thru its paces, I am impressed with how much easier it is to take great images. Download times are very fast, resolution is unreal. However, this camera produces such large files that it makes processing a real bear. Just trying to combine a large number of files causes my laptop to give up the ghost.

I have had an old SBIG STL11K sitting here unused for a long time, so I thought I would dust off this old monster to see what it could do. We do not have great conditions here for deep sky, so I have to image the brighter objects, like M57. I put it on the 17" F8 astrograph and immediately discovered that the tiny internal guide chip just won't show any stars in the star-poor regions away from the Milky Way. Can't use a guide scope with the 17" due to focal length, flexure etc. The solution for me was to fire up APCC and do a point map.

Easier said than done. Although the software is straight forward, the old STL11K has a hugely long download time, even binned 2x2. So to do a mapping run of 190 points took about 2 1/2 hours of precious dark sky. In the end it was worth it. Starting image runs at midnight, I still had another 2 + hours of imaging before the first hints of dawn. Fortunately the almost full Moon was far south, so I didn't have much in the way of gradients.

How did the scope track with APCC modeling with the 1600 encoder mount? Round stars at 4 minute and even 6 minute exposures for the duration of the session. And that's at 3454mm focal length at 0.5 arc sec per pixel. The mount drifted about 8 pixels during that entire session. Hats off to Ray Gralack for this wonderful program.

Take a peek:


(I did make one error at the beginning when I entered the wrong pixel scale. Old age or?)

Roland Christen

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