Slippage at focuser.

[Gordon]

Okay,
I'm going to be a newbee with this question and hopefully someone has an answer.


I'm having a problem with the following equipment.
1. Quark Daystar with ZWO ASI174mm-c

2. Explore scientific diagonal.

3. Explore scientific ES 80 ed-cf telescope.

Problem stems from the weight of the camera, and Quark sitting at a right angle to the telescope. Explore Scientific makes there 90 degree diagonal with a small taper where it would connect to the telescope. Why a taper? Who knows. The connection to the telescope uses 3 thumb screws and a brass ring to even out the pressure to make the connection. The brass is flat and using a 'taper' to make the connection makes for less surface. I have made a space to space the diagonal away so that the connection area is flat. This seems to help but doesn't fix the problem. With all of the weight at 90 degrees when the telescope slews the weight shifts and tends to cause slippage.
So far my method involves a pair of pliers and getting a bit 'crazy' with tightening the thumbscrews. I just wondered if anyone else has had this problem.

Here's some images showing the problem area.

Here's the scope you can see 2 of the 3 thumbscrews at the rear of the focus tube.

Here's the diagonal, you can see the small taper on the end that attaches to the scope. (I use a spacer to locate the diagonal further out.)

Here's an example of the quark attached to the diagonal, add a cooled ASI 174mm-c to the top of that and you can see the weight issue.

Hopefully somebody has some suggestions. Other wise I will keep using my pliers and clamp that sucker down!!!

[Bigzmey]

My question is why do you need to use a diagonal? Why not put the camera straight into focuser?

[AstroBee]

I understand the reason for the taper is for when you tighten down the three thumbscrews it makes it impossible for the diagonal to move in and out of the tube. Unfortunately, it doesn't do much to prevent the rotation problem you are having with the weight of the quark extending way out from the diagonal.
Baader and TeleVue use a small recessed ring area instead of a taper.

[StarHugger]

I would delete the diagonal and get a 2 inch adapter to t thread and use lightweight t thread spacers to a 1.25 eyepiece clamp for your quark and camera...

About 130mm of spacing is typical for a diagonal of 2 inches.


My 70mm has an R&P but because of having a disability and my wife lifting and carrying all my scopes I make them as light as possible for her.

The eyepiece clamp I use is the Svbony tri screw model, but 3 screws arent really nessesary so I use only one.

This should help.

[Gordon]

The reason I was using the diagonal was because its recommended to use an ERF filter in front of the Quark. I do have an idea however, I have a couple of 2" svbony extensions that should work. I will give it a try and let you know how it works. I'm using a rack and pinion focuser so weight isn't much of an issue.

[OzEclipse]

I presume you mean that the diagonal rotates not that the focuser is slipping.

Low tech solution- gravity. Provided you have goto and don’t need to exchange camera and an eyepiece. Rotate the diagonal so that it points vertically downward.
Joe

[Gordon]

Well, after a lot of trial and error, I was able to get focus!

No slippage now!

Thanks for the suggestions!

[JayTee]

Yay, you got it working. Now, you just have to worry about "droopage."

[John Baars]

Turn the brass ring so that one of the thumbscrews falls precisely into the opening of the brass ring.
Fix and centre: use the other two thumbscrews. Real locking: the thumbscrew that is not in contact with the brass ring.
No pliers needed.

[Gordon]

Thanks John,

I had thought of that but the telescope attachment with the thumbscrews is from Explore Scientific and the brass ring overlaps so there isn't a gap. I suppose I could swap it out for a different ring but the change to remove the diagonal seems to be working great.