Quote:
Originally Posted by bmitchell82
its to do with your draw tube length and what you need to make it clear the inside of the OTA. if your draw tube is say 100mm and you specify your imaging plane at say 90mm from ota it will drop 10mm into the light cone.
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Thanks, so does this height need to be the length of the drawtube inside the ota when retracted as a minimum, plus whatever you need for filter wheels, oag, etc?
so the focal point is the same whether you use an eyepiece or camera.
Looks like I'll need a 2.5 inch focuser as the minimum focuser ID without vignetting for my mirror shows 58mm.
I'm going with a 4 way push pull secondary adjustment similar to the primary mirror where i'll have two sheets separated by 15mm with 4 spring loaded bolts facing upward. one sheet close to the 45 deg mirror holder, and the other closer to the end of the OTA.
so for collimation, i'll be tightening or loosening the nut on top of the second sheet.
are there any disadvantages to a 4 bolt secondary vs 3 bolt traditional ones?
Thanks for the pics Brent. that is simple but effective, but have you thought of using velcro just at the ends of the flat rather than through the middle as then you'd have the proper 6 point support?
Just ordered a 3mm CF sheet for the focuser plate, and carbon fibre tow to try out a string spider.