Hi folks, pleasant greetings
I got an RC 8 inch telescope GSO, a Zwo ASI2600MC, a Zwo EFW 2" five slot filter wheel. Without me actually swapping out extension rings and tubes to reach focus live , could someone help me calculate the theoretical distance to reach the focal point to focus image with my camera? Thanks much!
Back focus distance help
Started by
ferlinp
, Mar 23 2025 10:51 PM
3 replies to this topic
#2
bobzeq25
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ISS
Posted 24 March 2025 - 12:41 AM
It's a lot easier to just do this by trial and error. When you point at a bright star or the moon, and rack the focuser up and back, it should be obvious if you need more or fewer extensions.
#3
michael8554
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Fly Me to the Moon
Posted 24 March 2025 - 04:39 AM
Point at a distant landmark on a sunny day.
Move a piece of paper behind the OTA until you find a focused image.
That's roughly where the sensor needs to be.
#4
sharkmelley
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Cosmos
Posted 24 March 2025 - 05:34 AM
I'm seeing the following entry in the technical data for the TS-Optics GSO RC8
- Backfocus: 254 mm from the tube´s backside or 159 mm from the 2" receptacle of the focuser
- bobzeq25 likes this
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