New wide field gear with DIY autofocus adapter (Arny)

New wide field gear with DIY autofocus adapter

FMA 230 as wide field scope
with Asi2600mm pro with 7x2“ EFW
and Zwo OAG for Asi220mm guiding camera
on the marvellous precise and lightweight AM5 harmonic drive.

Autofocus with Zwo EAF on a 3d printed rack with drive belt to control the manual focus ring of the scope. Biggest challenge was to print an adapter for the scope focus ring that fits belt toothing.

Backfocus of a dedicated camera with OAG and filtwr wheel vs a DSLR on a T2 Adapter os a bit tricky, as FMA anly allows for screwed on.
Camera angle can thus only be adjusted by turning scope in its brackets.

Also adjusting OAG or filter wheel means disassembly of image train.

Working with LRGB filters was a challenge at first, as I had not spread the current 5 filters evenly across the 7 slots, which made the drift during exposure. Also autofocussing newded a tweak of changing defaults to 10 second exposure for the filters (vs 2sec) and stepsize to 100 (vs 30).

Counterweight is not really necessary for this light scope, but the bar makes carrying easier, and the weight was still on from the 8“ Newtonian session beforehand.

The AM5 is really impressive by its light weight but also its guiding accuracy of 0.4-0.6 arc seconds.

AsiAir plus does a great job in orchestrating all of the above components and thus automating night session with a setup of only 15 minutes including its polar alignment routine.

Final
Original
B

B

Title: EAF adapter plate detail

Description: Printed in PLA of self made design.

The plate is sloped to allow for better tightness of belt.
Also a second piece holding down the EAF reduces backlash.
Third piece is an adapter to the manual focus ring of the scope that connects with the drive belt. Toothing was difficult as belt would slip due to imperfection. Creating a tooth only every jew millimeters simolified design and worked perfect.

Design was inspired by third party vendors solution I stumbled upon.

Making it perfectly work took about 8 iterations from first to final 3d print.

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