Parfocal filter test #1
I always wondered this, but as I didn't have a motorized filter with readable steps (until now) I wasn't able to do any testing on my filters previously. Since the moon is lovely and bright tonight killing most of my imaging plans I figured I would do some focus tests with my new Moonlite focuser. After letting the scope cool to the nice chilly evening (whilst my toes froze nice and solid as well) I ran through my Astronomik set (LRGB and Ha,SII,OIII) and not only did FocusMax's "focus" button but then dug around a few steps each way to find the best focus for each filter. Happy to say that the "focus" button on FocusMax got the focus within 1-2 steps of best focus so gotta say that I am happy to use the automated routine in the future.
So, for my f/6.25 system the CFZ is:
Red: 124 microns
Green: 97 microns
Blue: 91 microns
Based on the measurements I did that showed each step was 16 microns, the CFZ in steps for each color (rounded down) is:
Red: 7 steps
Green: 6 steps
Blue: 5 steps
Not a lot of room for error, only 2-3 steps on either side of the focus point. Makes me even happier that I got the motorized focuser as finding that 91-127 micron sweet spot by hand was exceedingly difficult (even with a Bahtinov mask)
Note: These tests are done on my actual imaging system, not an "ideal" test setup. I find it hard to find results on average setups as "tests" are generally done on apochromatic scopes and very high-end equipment. That is why I like to share my test results on my modest equipment. These are not "scientific" and are done just as I state. I do them for others who have modest setups and would like to find results on setups similar to their own.
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