8 replies to this topic

[Dart106A]

Okay -- newb question that has probably been asked, and answered -- but I cannot find it. Do these knobs on the front, and back of the dovetail of my Celestron C9.25 SCT serve a purpose other than preventing the OTA from sliding off the mount if the mount knobs become loose for any reason? I need to move my OTA forward just a bit more to get an ideal balance, but to do so I need to remove this aft knob. Probably a stupid question, but I'm new to SCTs.

 

Thanks, Mark

 

[Notdarkenough]

Safety stop, so the OTA can't slide all the through the clamps

[Dart106A]

Safety stop, so the OTA can't slide all the through the clamps

So, essentially I need to do some risk management by removing this knob to obtain a correct balance for the OTA. Gotcha.

 

Mark

[Couder]

you can put an allen bolt there, smaller head than the knob

[Dart106A]

you can put an allen bolt there, smaller head than the knob

That might work. I'll have to try it to see if I can get the correct balance. Thanks!

Edited by Dart106A, 28 April 2025 - 10:09 PM.

[ris242]

That might work. I'll have to try it to see if I can get the correct balance. Thanks!

you are heavy at the back.......yes? .....so you could remove the back one and slide forward............the front one could therefore stay.

[Kefka1138]

I had an OTA slip out on me once. Thankfully, I caught it in time but was scary AF. 

[Dart106A]

you are heavy at the back.......yes? .....so you could remove the back one and slide forward............the front one could therefore stay.

The photo is of the aft knob. Yes, I need to remove/replace it so I can move the OTA a bit farther forward. The front knob is not in play at all.

Edited by Dart106A, 29 April 2025 - 09:15 PM.

[Notdarkenough]

Using an EQ mount, your scope is pointed towards the North Celestial Pole (NCP). Unless you live on the equator, there is some angle your mount is pointed to. I am at 41° N, so my mount has a 41° angle from the horizon. When I mount my SCT, the OTA is at a 41° angle. The safety stops are designed to "catch" the OTA from sliding backwards from the mount clamps. Lots of rigs have a heavy back end - primary mirrors on an SCT, cameras, focuses, whatever - and have to ride the mount clamp at the rear of the mount to achieve balance. If your rear safety stop can't be used because that is where the mounting clamps are located, simply remove it. The other end should also be tapped for the same screw. Most dovetails don't have a "front" or "rear" end, they are bidirectional. So, they have the same safety stop at both ends, or at least the holes for it. You can put the stop in either hole, or don't use it at all; your choice. If there is some other problem, please attach a picture.