Focuser on 127 Mak

[Beardy30]

Fries anyone know if it’s possible to fit a Crawford style Focuser into the 127 Mak rather than having to use that awful Focuser knob ?? 

Edited March 3 by Beardy30

[Steve Ward]

I have something like this on my Mak180Pro , you'd need to speak to someone at FLO to check the thread sizes on the focuser and the OTA though ... 😖

https://www.firstlightoptics.com/astro-essentials-focusers/astro-essentials-v2-2-dual-speed-crayford-focuser-for-sct-telescopes.html

[Zermelo]

Yes. Though I have read that it can shift the focus position and consequently reduce the image quality a little. Catadioptric scopes have a large range of focus, but they are designed to focus close to the optimum distance between the mirror and corrector for their particular design. Introducing the focuser throws that off a bit.
I've not done it myself, others may have experience.

[Beardy30]

Yea I thought that might be the case - think I’ll avoid a Mak in future for this reason 

[Steve Ward]

14 minutes ago, Zermelo said:

Yes. Though I have read that it can shift the focus position and consequently reduce the image quality a little. Catadioptric scopes have a large range of focus, but they are designed to focus close to the optimum distance between the mirror and corrector for their particular design. Introducing the focuser throws that off a bit.
I've not done it myself, others may have experience.

Never been a problem with mine ... certainly not that I've noticed anyway , a vast improvement over the standard coarse adjuster.

[Louis D]

There used to be a 1.25" Crayford focuser available as well, but I think it's been discontinued.  Fitting a 2" focuser on a 127 Mak would be tight for space up against the native focus knob.

Either way, you'd need a Synta Mak thread to SCT thread adapter ring.

You'll see your focal length grow from 1500m to about 1700mm.  There may also be a bit of added spherical aberration due to the non-optimal mirror separation.