Mirror travel due to focus of SCT Edge HD

[torsion (Bram)]

Hi,

Would anyone know the distance the primary mirror travels per turn of the focus knob on the back of a Celestron Edge HD scope?

This would be the pitch of the focus screw, I would assume. Next step will be to take off the rubber nob and see if I can make the screw stick out to measure the pitch.

I am in the process of installing a motorised focusser and need to select a stepper motor. Just wondering if I can get a straight one or one with gears (few or lots).

Thanks in advanced.
cheers,
Bram

[Astro_Bot]

You can estimate it by observing the full travel of the primary and counting the revolutions of the focus knob - that'll at least get you in the ballpark with whether to use gearing, maybe more.

[Kunama]

0.75mm travel per turn apparently .........
Sedat (bilgebay) on CN wrote the following:

"........ The thread pitch of C11 Edge HD's focus shaft is 0.75 milimeter. 1 complete turn of the focus knob moves the mirror 0.75mm. I have verified this by taking multiple measurements while turning the focus knob. "

[Kunama]

he also wrote more:

http://www.cloudynights.com/ubbthrea.../o/all/fpart/1

[el_draco (Rom)]

Originally Posted by torsion

Hi,

Would anyone know the distance the primary mirror travels per turn of the focus knob on the back of a Celestron Edge HD scope?

This would be the pitch of the focus screw, I would assume. Next step will be to take off the rubber nob and see if I can make the screw stick out to measure the pitch.

I am in the process of installing a motorised focusser and need to select a stepper motor. Just wondering if I can get a straight one or one with gears (few or lots).

Thanks in advanced.
cheers,
Bram

Have you thought of using a motorised micro-focuser from Starizona? The retrofit takes minutes and the fix is excellent.

See here: http://starizona.com/acb/Feathertouc...sers-C654.aspx

Rom

[Rod771 (Rod)]

+1 for the Feather touch focuser. A very valuable addition.

[torsion (Bram)]

Thank you for your feedback.

Originally Posted by Kunama

0.75mm travel per turn apparently .........
Sedat (bilgebay) on CN wrote the following:

Thank you Matt, and the link.

Originally Posted by el_draco

Have you thought of using a motorised micro-focuser from Starizona? The retrofit takes minutes and the fix is excellent.

Yes, but soon I will be a proud owner of a SharpSky Kit (kindly provide by wasyoungonce) and with my own motor.

cheers,
Bram