Telescope not square to mounting plate

[AlistairW]

Hello,

My scope has tube rings that are attached to a mounting plate via 6 screws. The gaps the screws go through allow a fair amount of wiggle room. But what I was wondering was, what if, when tightened down, the scope is not square to the mounting plate. How would that affect the image 

Thanks

Alistair

 

 

 

[Starlight 1]

I can tell you, I like to see a photo . I thinking cone err that when you move the mount RA from left to right.

[MarsG76]

Aside from cone error.. while tracking I dont imagine there would be too much if any problem... as long at the non perpendicular scope is rigid, the tracking path will still be the same.

 

[alacant]

Hi. I notice it after a meridian flip by having to crop around the edges of the stack where the angles before and after don't agree. It's small enough on my dovetail to ignore though. HTH.

[Peter Drew]

Not 100% sure about this, but I would have thought that cone error would be due to the axes of a German equatorial mount not being exactly at right angles to each other. If that is the case, the out of square fitting of the telescope to the axis, within reason, would not be important.  

[IanL]

On 08/10/2017 at 20:48, Peter Drew said:

Not 100% sure about this, but I would have thought that cone error would be due to the axes of a German equatorial mount not being exactly at right angles to each other. If that is the case, the out of square fitting of the telescope to the axis, within reason, would not be important.  

No, cone error is entirely due to the optical axis of the OTA not forming a right angle with the Dec axis. The only problem it causes is with the target not being in the FOV after a Goto. Even then most mounts can compensate if a three star alignment is done. It is fixed by raising one end of the OTA to square with the Dec axis. Either shim one of the tube ring to dovetail bar attachments with washers, or use the cone error screws if the dovetail has them.

In terms of tracking, cone error has no effect. You could literally mount the scope pointing out along the Dec axis and it would track, or anywhere in between.

If the mount axes are not square you have a whole bunch of other problems!

[Peter Drew]

Obviously not a problem for us visual guys!  

[Freddie]

Nice vid on cone error here