Drilling a Skywatcher MAK OTA

[Macavity]

Drilling a Skywatcher MAK 127 OTA. Has anyone had a go?

My MAK127 came with an AZ-3 mount. My idea is to replace a (long lost!) tripod attachment bar with a standard dovetail bar. This requires new holes that are (obviously) offset by 90 deg around the OTA. Heck, while I'm on, I wouldn't like a few more holes for (sundry) finder bracket(s) etc.

Are there any major pitfalls in removing a MAK corrector plate. I have recently discovered e.g. the whole containing CELL is (multi-start?) threaded onto the tube. Can this be safely unscrewed and re-screwed. I guess it worthwhile to RECORD the rotational match of the OTA and corrector cell, before and after removal. Of course guard against drilling swarf etc. is a no-brainer...

£64K question: I still a little unconvinced re. this (internet!) idea that the corrector plate curvature might be "rotationally" MATCHED to the mirror in a mass-produced item. Is this REALLY true? Hey I am willing to be told, either way... and take appropriate precautions!

[Rob]

This maybe a silly answer but hey!... I had a Skymax 127 many years ago (great OTA). Could you not redrill the dovetail bar to match the current tripod attachment bar holes, then if required buy some longer screws/bolts to bolt straight on. You don't need to open the OTA

Rob

[Macavity]

This maybe a silly answer but hey!... I had a Skymax 127 many years ago (great OTA). Could you not redrill the dovetail bar to match the current tripod attachment bar holes, then if required buy some longer screws/bolts to bolt straight on. You don't need to open the OTA

Rob

Indeed, and thanks for reminding me! I suppose it's only my purist notion that I can have the focussing knob on the right side and greater flexibility for adding finder brackets. Also, there is something that slightly "worries" me re. supporting a scope of weight (modified at 5kg) on two m4 self-tappers... But then, I sometimes worry about my kitchen cupboards too!

[johninderby]

Hi

Taking off the corrector cell is no problem, just mark it so you put it back in the same place. When I did it on a 127 that I used to own there was no effect on the collimation.

However unscrewing the rear cell from the tube is a bit more of a problem as there is a thin rubber O ring between the cell and the tube which invariably breaks when you unscrew the cell. Also the cell may be very reluctant to start turning. Better to cover the mirror while drilling. I used cling film.

I took it apart to fit a dovetail and a carry handle.

John

[Rob]

Good job. Those 2 bolts will hold it fine.

Rob

[Macavity]

Taking off the corrector cell is no problem, just mark it so you put it back in the same place. When I did it on a 127 that I used to own there was no effect on the collimation.

Many Thanks, John - Splendid stuff... AND precisely what I intended (To retro-mount on a Skywatcher GoTo!). Can I crave some further information: What bolts did you use? Size? Roundheads, Countersunk from the inside? Painted black? Drilled and tapped? Something else...

Yes, I was going to leave the other end well alone! Really looks GOOD though.

[johninderby]

I used some M5 countersunk head bolts through the dovetail with nuts on the inside of the OTA. I painted the nuts black before putting them on and then touched them up with more black afterwards.

I think you might want to countersink the boltholes in the dovetail so that the bolt heads are out of the way.

You can get the bolts cheap on eBay, just look for M5 countersunk bolts.

John

[Macavity]

Thanks for that John. I'll use my initiative now! <G> Just had a go at unscrewing the corrector cell. "A firm grip between the knees and presto"! LOL. Moreover it does return to a marked position easily enough. Thanks for the thought re. cling-film. Didn't think of that - Substantially better than odd pieces of card, (hairy) paper towels etc.