Retro-fitting Celestron Fastar

[deanm (Dean)]

Folks: your advice sought - I've just received an insurance claim replacement 'scope for my horrifically-wounded C11.

My original C11 was Fastar-ready.

The replacement C11 is not (probably older stock).

Is it possible to transplant the Fastar fitting from one C11 to the other, without buggering around with moving secondary mirror or knackering collimation (original C11 Fastar has Bob's Knobs installed, which help)?

Dean

[casstony]

Assuming the steel backing plate for the secondary and the size of the corrector hole are the same on both scopes you should be able to transplant.
I think you'd need to remove the corrector from both scopes to get the respective secondary assemblies off, then swap the mirrors/backing plates over and reinstall the secondary assembly, then reinstall the corrector.

The most important point is to maintain the rotational orientation of the optical components. They should already be marked but it wouldn't hurt to add your own mark on the side of the corrector and secondary in line with the focuser.
You could also wear cotton gloves when handling the secondary mirror to avoid accidently touching it and leaving a fingerprint (which would need to be cleaned off).

Finally you'll need to collimate.

When I disassemble mounts or scopes I sometimes take digital photo's each step of the way; if I'm not quite sure of something during reassembly I can refer back to the photo's.

[deanm (Dean)]

Tony - I sit in awe!

I can't even contemplate pulling corrector or secondary apart - yikes!!

Dean

[casstony]

It's something learned slowly over years Dean. After you've successfully removed and replaced one corrector it's not scary anymore; next time you go one more step and remove a main mirror to regrease the baffle, etc.

Same thing with collimation or stripping down and regreasing a mount. After you've done it once it's no longer mysterious. Preparation and going slow are the key to success.

You could use your dead C11 as a learning tool. Carefully disassemble it, clean the optics, clean the grease off the baffle and replace with new grease, reassemble and it might be a useable scope. There are a few guides around the 'net.

[deanm (Dean)]

Sage words, Tony.

Dean