Skywatcher 80 ED Backfocus

[Stu-Wales]

Hi all I have the skywatcher  Evorstar 80Ed, as yet I don't have a field flattener, I have two cameras I would like to be able to connect to it without the star diagonal their both Zwo, ASI 120mm-S and the 224MC, I cant seem to find the information regarding the correct back focus anywhere, any help will be gratefully appreciated, thanks in advance.

[fozzybear]

20 minutes ago, Stu-Wales said:

ASI 120mm-S and the 224MC

Hi,

According to the Manuals both Camera's Have 12.5mm back focus from sensor to M42 Flange. As you currently don't have a FF for the scope you could use a 50mm extension in it's place for now

Edited January 16, 2022 by fozzybear
added text

[Stu-Wales]

23 minutes ago, fozzybear said:

Hi,

According to the Manuals both Camera's Have 12.5mm back focus from sensor to M42 Flange. As you currently don't have a FF for the scope you could use a 50mm extension in it's place for now

Thank you, that's  helpfull

[mackiedlm]

Back focus is only an issue once you add the ff/fr. Its the reducer that has a set back focus. Until then you will be able to focus just by moving the focus knob. 

[michael8554]

Hi Stu

The ED80 Pro has a 600mm focal length.

So roughly measure 600mm from the objective, with the focuser halfway through it's travel. 

The distance from the rear of the focuser to the 600mm point is the distance you need to fill with spacers, minus the 12.5mm Flange Distance of your two cameras.

You can alter the scope focuser to allow the nearest standard length spacer to be used.

Michael

[Stu-Wales]

Sorry this is late but thank you for your help.