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RC GSO 12" Carbon Truss Backfocus

reflector equipment astrophotography
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#1 Fukinagashi

Fukinagashi

    Mariner 2

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Posted 24 January 2021 - 04:25 AM

I've just got my new GSO 12" RC Carbon with Esatto 3" focuser.

To select the right extension tube (to be placed between focuser and tube backside) I would need to know the backfocus computed from the tube backside and not from the focuser as the specifications says "The distance from the 2" connection of the focuser to the focal plane is 127mm".

Anyone?



#2 Tapio

Tapio

    Soyuz

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Posted 24 January 2021 - 04:38 AM

One simple solution suggestion which you can do in daytime - aim your scope at some distant object and then put a sheet of paper behind focuser, adjust distance until image in paper is sharp, that is your focus distance which you can measure.
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#3 Fukinagashi

Fukinagashi

    Mariner 2

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Posted 24 January 2021 - 01:44 PM

Done using an ASI 120MM. Total distance from tube backside is 300 mm +- 5 mm.




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