Quote:
Originally Posted by AdamJL
Great stuff, Rodney. Glad you got it all sorted out. Thank you for the write up as it will help me when I switch to mono this month.
It’s a wonderful adapter as well. Really well engineered.
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Very good. Enjoy the journey with your new set up Adam
Quote:
Originally Posted by sunslayr
That's interesting, just to clarify you originally you had
Adapter: 12.5mm +
Filter wheel: 20mm +
ASI6200: 12.5mm +
= 45mm - 1.00mm filter = 44mm
and that didn't work, but
Adapter: 10.5mm +
Filter wheel: 20mm +
ASI6200: 12.5mm +
= 43mm - 1.00mm filter = 42mm
did work? I'm a bit confused  |
Edit: A quick edit to this post after the event David to confirm that your sums were correct. I shall leave my response below for posterity 
The default set back distance out of the box for the Astromechanics adapter is 11.5mm. This doesn’t make any allowance for the filter. As noted, I had incorrectly set this at 12.5mm rather than adjusting it down to 10.5mm.
The inclusion of a filter in the light path moves the focal point away from the OTA which, if not accounted for, will place the focal point behind the sensor (or further into the camera if you like). In other words, it
adds optical distance into the equation which needs to be treated the same as a mechanical distance. Your example shows it subtracting which is incorrect. This is the correct sum:
Adapter: 10.5mm +
Filter wheel: 20mm +
ASI6200: 12.5mm +
= 43mm
+ 1.00mm filter = 44mm
Usually our goal is to find the correct length for an adapter that we need to place into our imaging train with a view to obtaining the correct set back distance. The information that is on hand as the starting point is the set back distance that we are trying to achieve, the mechanical distance of the existing components and the optical thickness of our filters. If we approach the problem this way we have:
Target set back distance = 44mm
Components in image train:
* Filter = 1.0 mm
* Filter wheel = 20.0 mm
* Camera set back = 12.5 mm
These components add up to 33.5mm. To work out the correct length for my adapter then I subtract this from my target set back distance thus:
44.0 mm - 33.5 mm = 10.5 mm