rotating telescope tube

[philmac]

Hello,  

New user, with a Skywatcher 200p, EQ5, added motors later.  When I find a target, the eyepiece/finder needs to be rotated.  I loosen the 2 bolts, and the tube sometimes moves easily, sometimes is very stiff. On examination, the tube appears to be very slightly out of true,  ie. not perfectly cylindrical.  Can this be fixed?  The telescope was new, and as far as I am aware has not been dropped (at least not by me!)

Many thanks,

Phil

[Bugdozer]

I don't understand what you mean by "when I find a target, the eyepiece/finder needs to be rotated". Why? 

[orion25]

I'm curious about this as well.

Edited January 29 by orion25

[bosun21]

He means that the focuser can sometimes be pointing in very awkward positions due to using an EQ mount with a reflector. This can marginally be aided by when in the home position pointing the eyepiece straight up. This means that when you slew to either side of the meridian the eyepiece will be at a more respectable angle.

[NGC 1502]

51 minutes ago, bosun21 said:

He means that the focuser can sometimes be pointing in very awkward positions due to using an EQ mount with a reflector. This can marginally be aided by when in the home position pointing the eyepiece straight up. This means that when you slew to either side of the meridian the eyepiece will be at a more respectable angle.

Indeed, this is a particular problem with a Newtonian on an equatorial mount. When slewed to different parts of the sky the focuser/eyepiece can be in very awkward positions, like pointing towards the ground. Rotating the tube can make the eyepiece accessible.

The above is not a problem with refractors, SCTs & Maksutovs with a star diagonal on an equatorial mount. It’s easy to rotate the star diagonal/eyepiece to a convenient position.

This is one of the reasons why some of us prefer alt-azimuth mounts like Dobsonians, the focuser/eyepiece is much more accessible in any part of the sky.

 

Edited January 29 by NGC 1502
Edited for extra info

[wookie1965]

buy yourself these,

https://www.ebay.co.uk/itm/353919946975?hash=item526745d0df:g:gbwAAOSww-5iD7RC&amdata=enc%3AAQAIAAAAwPitE62sL1xBrB9fqOhVXJTMwCtsyEJE0YwiXRBEkBA%2F63CGkAmrMURtMpcjk%2F0b4xIxO7d0gEPVdOVORzw4FoD%2B7VyYbm3laZ9VozW%2B0NG3cpAkuDTWEfOHLMb2d0vu8TG2cZz9j%2BVi2oVdXze7XIhDRTkNnaYL6f4b01r4lr5QAdW%2FJDOVAW832aBixZpPQmm9mh3E5ntBnAWxP5DMmClJfVfP2dKrMcTGwNYkuIAzxUlkn%2Fsz6%2BoHh72yy%2F8jUQ%3D%3D|tkp%3ABk9SR8aXk8OqYw

https://www.screwfix.com/p/deta-tte-upvc-white-self-adhesive-mini-trunking-12mm-x-8mm-x-2m/262vt

use the front of the cable trunking around the tube on the outside of the rings top and bottom and make your own jubilee clips to fit. You can undo the bolts now and spin the tube it will not slip forward or backwards and unbalance the scope. 

Here is a picture of a 200p but at the time I used embroidery hoops but I got the trunking and jubilee kit as it made the tube spin easier. 

[John_D]

Thanks for this information. I have an additional problem in that the surface finish of the outside of my elderly TAL is more like that of a T34 tank that's been through the battle for Berlin ☹️ Rotating the tube is not easy even when the clamps have been loosened. I may need to get some PTFE tape and wrap it around the tube first and hope that the clamps still fit.

( I'm slightly surprised that there are no aftermarket kits to do this. )

[PeterStudz]

I have a feeling that it’s not unusual for some of these types of reflectors to have a tube that isn’t perfectly cylindrical. Especially if made of metal that’s rolled into a tube and joined with a seam. If I look closely (it was more obvious when I took it apart for flocking) at my SkyWatcher 200p Dob it isn’t perfectly cylindrical too. But then as a Dob it doesn’t need to be.

@wookie1965solution looks ideal as it means you can loosen the bolts far enough that it won’t matter if the tube is perfectly cylindrical or not. 

[RobertI]

2 hours ago, wookie1965 said:

buy yourself these,

https://www.ebay.co.uk/itm/353919946975?hash=item526745d0df:g:gbwAAOSww-5iD7RC&amdata=enc%3AAQAIAAAAwPitE62sL1xBrB9fqOhVXJTMwCtsyEJE0YwiXRBEkBA%2F63CGkAmrMURtMpcjk%2F0b4xIxO7d0gEPVdOVORzw4FoD%2B7VyYbm3laZ9VozW%2B0NG3cpAkuDTWEfOHLMb2d0vu8TG2cZz9j%2BVi2oVdXze7XIhDRTkNnaYL6f4b01r4lr5QAdW%2FJDOVAW832aBixZpPQmm9mh3E5ntBnAWxP5DMmClJfVfP2dKrMcTGwNYkuIAzxUlkn%2Fsz6%2BoHh72yy%2F8jUQ%3D%3D|tkp%3ABk9SR8aXk8OqYw

https://www.screwfix.com/p/deta-tte-upvc-white-self-adhesive-mini-trunking-12mm-x-8mm-x-2m/262vt

use the front of the cable trunking around the tube on the outside of the rings top and bottom and make your own jubilee clips to fit. You can undo the bolts now and spin the tube it will not slip forward or backwards and unbalance the scope. 

Here is a picture of a 200p but at the time I used embroidery hoops but I got the trunking and jubilee kit as it made the tube spin easier. 

I tried this exact ‘anti-slip’ solution and it works fine, I have the ring clamp bolts permanently loosened so I can rotate the tube. Two things to watch out for though, you will probably need an ‘anti-slip ring’ at both ends to stop the tube sliding backwards and forwards, and you will also need to be careful that the ring clamp bolts are not at the end of their threads meaning the rings can pop open and the scope fall out! 

[doublevodka]

2 hours ago, John_D said:

Thanks for this information. I have an additional problem in that the surface finish of the outside of my elderly TAL is more like that of a T34 tank that's been through the battle for Berlin ☹️ Rotating the tube is not easy even when the clamps have been loosened. I may need to get some PTFE tape and wrap it around the tube first and hope that the clamps still fit.

( I'm slightly surprised that there are no aftermarket kits to do this. )

There have been scopes in the past that had rotating rings (Meade I believe) but they would be fairly expensive to produce and so fell out of favour.

There is another solution here - https://www.astro-baby.com/articles/rotating rings/Rotating Rings Project.htm Just need an additional ring and some diy

[johnturley]

3 hours ago, wookie1965 said:

buy yourself these,

https://www.ebay.co.uk/itm/353919946975?hash=item526745d0df:g:gbwAAOSww-5iD7RC&amdata=enc%3AAQAIAAAAwPitE62sL1xBrB9fqOhVXJTMwCtsyEJE0YwiXRBEkBA%2F63CGkAmrMURtMpcjk%2F0b4xIxO7d0gEPVdOVORzw4FoD%2B7VyYbm3laZ9VozW%2B0NG3cpAkuDTWEfOHLMb2d0vu8TG2cZz9j%2BVi2oVdXze7XIhDRTkNnaYL6f4b01r4lr5QAdW%2FJDOVAW832aBixZpPQmm9mh3E5ntBnAWxP5DMmClJfVfP2dKrMcTGwNYkuIAzxUlkn%2Fsz6%2BoHh72yy%2F8jUQ%3D%3D|tkp%3ABk9SR8aXk8OqYw

https://www.screwfix.com/p/deta-tte-upvc-white-self-adhesive-mini-trunking-12mm-x-8mm-x-2m/262vt

use the front of the cable trunking around the tube on the outside of the rings top and bottom and make your own jubilee clips to fit. You can undo the bolts now and spin the tube it will not slip forward or backwards and unbalance the scope. 

Here is a picture of a 200p but at the time I used embroidery hoops but I got the trunking and jubilee kit as it made the tube spin easier. 

I don't know why current telescope manufacturers don't offer 'Slip Bands' with their scopes as Fullerscopes used to do in the 1970's.

John 

Edited January 29 by johnturley

[John_D]

6 hours ago, doublevodka said:

There have been scopes in the past that had rotating rings (Meade I believe) but they would be fairly expensive to produce and so fell out of favour.

There is another solution here - https://www.astro-baby.com/articles/rotating rings/Rotating Rings Project.htm Just need an additional ring and some diy

Thanks for that, I'll have a look. If you Google for rotating rings then you end up at either expensive items or dead pages.

[saac]

x2 for the embroidery hoops - used to good effect on my 8 inch newt. A neat and inexpensive solution. 

Jim 

[orion25]

21 hours ago, bosun21 said:

He means that the focuser can sometimes be pointing in very awkward positions due to using an EQ mount with a reflector. This can marginally be aided by when in the home position pointing the eyepiece straight up. This means that when you slew to either side of the meridian the eyepiece will be at a more respectable angle.

That's what I thought but wasn't absolutely sure. Thanks!

[John_D]

One final thought is that when you do get the eyepiece in a comfortable position then, inevitably, the finder scope is then awkwardly placed. So rotating rings would be useful for that as well.

And while we're at it the finder scope on a Newtonian needs a star diagonal as standard because it can be a pain so look along the telescope to use it. ( Such a thing is probably readily available 😁 )

[Stu]

On 29/01/2024 at 08:23, John_D said:

I'm slightly surprised that there are no aftermarket kits to do this.

There are rotating rings available for newts; I’ve seen them occasionally available on the used market. They are pretty heavy though I think so the solutions suggested are probably better.

http://scopestuff.com/ss_arrs.htm

[dweller25]

21 hours ago, johnturley said:

I don't know why current telescope manufacturers don't offer 'Slip Bands' with their scopes as Fullerscopes used to do in the 1970's.

John 

As Astro Systems did in the 80’s and their anti-slip ring also acted as a camera platform and handle….

Scopes designed by people who used them 👍

Edited January 30 by dweller25

[Bugdozer]

On 29/01/2024 at 06:30, bosun21 said:

He means that the focuser can sometimes be pointing in very awkward positions due to using an EQ mount with a reflector. This can marginally be aided by when in the home position pointing the eyepiece straight up. This means that when you slew to either side of the meridian the eyepiece will be at a more respectable angle.

Oh yes of course, that makes perfect sense. For some reason I was imagining rotating the eyepiece within the focuser! 

[Neil H]

Hi I made a set of Wilcox rings that wookie told you about I also spray furniture polish on the telescope rings as they normally have a felt inside the rings  and this makes it slide nicely in the rings and the Wilcox rings stops any up of down movement