Eyepiece orientation with an equatorial mount

[Guest]

My previous scope was a dobsonian but I've recently changed it for a newtonian reflector with an equatorial mount. The weather has been terrible since I got it but I've been playing around to familiarise myself with it. One of the things I've noticed is that unlike the Dob the eyepiece is not always in the right place as you move around the sky. So you end up having to rotate the scope in it's hoops to get the eyepiece in a convenient place. I don't know if all are like mine but it's quite a clumsy operation. It's not sufficient just to slacken the screws you have to undo them completely and lift one half of the hoops before you can rotate. Am I doing something wrong, is there a better way or do I just have to get used to it?

Cheers

Steve

 

[Ouroboros]

@woodblock It's one reason that I enjoy using my refractor. The eyepeice is always accessible and can b rotated to a more comfortable position if necessary. 

I've never done this but I know that some people buy and modify another ring which sits tightly around the scope tube but isn't connected to the mount. This third ring then rests back on one the 'proper' scope rings. The scope can then be rotated within the lossened scope rings without sliding out of the rings. I hope that makes sense. 

Someone might have a photo of such an arrangement. 

Edited November 15, 2019 by Ouroboros

[Ruud]

You can get  rotating mounting rings but they are expensive.

8 minutes ago, Ouroboros said:

Someone might have a photo of such an arrangement. 

Ouroboros is right. Here is a DIY project with photo's: http://www.astro-baby.com/articles/rotating rings/Rotating Rings Project.htm

Edited November 15, 2019 by Ruud

[johnturley]

4 hours ago, Ouroboros said:

@woodblock It's one reason that I enjoy using my refractor. The eyepeice is always accessible and can b rotated to a more comfortable position if necessary. 

I've never done this but I know that some people buy and modify another ring which sits tightly around the scope tube but isn't connected to the mount. This third ring then rests back on one the 'proper' scope rings. The scope can then be rotated within the lossened scope rings without sliding out of the rings. I hope that makes sense. 

Someone might have a photo of such an arrangement. 

In the 1970's Fullerscopes used to sell dedicated slip bands for their Newtonian Reflectors at a relatively modest extra cost, so that the telescope tube could be rotated without having to loosen the tube clamps and affecting the balance, and I purchased one to go with the 10 in Newtonian I had at the time, and found that it worked quite well. Few (if any) suppliers appear to offer them nowadays.

John

Edited November 15, 2019 by johnturley

[rwilkey]

Hey Steve, that's one of the reasons I changed my Newtonian to an AZ mount, wait 'til you have to do a meridian flip (flip right over haha).  To me it's AZ everytime esp. as I am now partially disabled since I bought my Newt. 

[John]

It is an issue with equatorial mounts. I believe that having the eyepiece pointing at the ground when the scope and mount are pointing toward the pole star minimises the issue although it does not remove it completely. This may sound odd but I think it might help.

Like Robin, as I don't image, I use alt-azimuth mounts for the vast majority of the time for this reason.

 

[wookie1965]

https://www.toolstation.com/d-line-3m/p57441

https://www.ebay.co.uk/itm/MAKE-YOUR-OWN-HOSE-CLAMP-KIT-ANY-SIZE-JUBILEE-CLIP-CLAMPS-METAL-BAND-SET-/174045181403?nav=SEARCH

Use the flat part of the trunking then make a jubilee clip around the inside.

Dont rotate the OTA until you have aligned it then just rotate to get perfect eye position.

I did this with the 200p I had worked brilliantly.

Paul

[Ben the Ignorant]

Another suggestion is this:

A couple strong O-rings on each side keep the mounting rings tight enough but the scope can be rotated or slid up and down to keep it balanced when you change between eyepieces of a very different weight. The screws are completely loose except when I carry the scope, their main job is only to keep the O-rings from sliding out. A few rubber bands do the same trick but they don't look techie like black O-rings do.

[Ben the Ignorant]

2 hours ago, woodblock said:

It's not sufficient just to slacken the screws you have to undo them completely and lift one half of the hoops before you can rotate.

That's not normal, maybe the felt Inside the rings is too thick, or they are nor perfectly round.

[Ouroboros]

I usually have to slacken off the rings so much that there's a risk the scope will drop backwards unless placed horizontal. Worse than that all the pulling and pushing has either misaligned the polar alignment or shifted the RA or DE axes despite having the clutches being tightened up. I must say that apart from imaging this is one of the main reasons I have stopped using my reflector for visual. 

[joe aguiar]

wow this is weird i havent seen where you have to untighen the rings so much the ota will almost fall off, are scope made there different than here?

it doesnt have enough slack to unloosen the rings threads abit and turn the tube to a more better angle? i mean even a refractor will have some issue the diagonal  maybe at a weird or a downward angle,you can just loose diagonal and pointed up but its really the same for all eq scope regardless what they are.

if you are pushing/pulling so hard that its going out of polar alignment something is wrong, its either wrong size rings or the bolts that hold the rings closed is too small.

joejaguar

[Ouroboros]

@joe aguiar Well, I can only report what I've found. If the scope is loose enough to rotate then it's loose enough to slip in the rings. If it's not loose enough to rotate easily then in applying sufficient torque to the mount it can, I've found, muck up a carefully aligned mount.

 I tend to avoid rotating it if at all possible. When I first set up I tend to scan the mount and telescope about to the different parts of the sky I'm interested in to make sure I can reach the eyepeice. Then I align the mount. 

[Guest]

Thanks everyone, that's given me something to think about. I haven't used the scope in anger yet because of the weather.

The scope is a skywatcher N200PDS on an HEQ5 PRO mount. The material inside the rings is quite hard, very thin and not at all like felt. I tried again this evening and I do have to loosen the screws completely in order to be able to turn the tube but I also found that it rotates easily in one direction but not in the other. In one direction the hinged half of the ring tends to tighten up on the tube. In the other direction it stays loose. My plan, initially, is to mark up one of the rings in 6 or 8 segments. Roughly line up the scope with where I'm interested and make a note of where I want the eyepiece. Then turn the scope so that the tube is horizontal before turning the tube in the rings to the right position for the eyepiece.  At the moment it seems that the only position to safely rotate the tube is when it's horizontal. In that position in won't slip down and it's supported underneath.  I need to get more experience with it. I just need a few clear nights.

 

[johnturley]

54 minutes ago, Ouroboros said:

Well, I can only report what I've found. If the scope is loose enough to rotate then it's loose enough to slip in the rings. 

That's the whole point about the slip band, it prevents the tube slipping down in the rings when you rotate the tube.

John 

[Ben the Ignorant]

I bought the product so long ago, I'm not even sure that business is still around, but Car Lack 68 gives the tube's paint such great polish, the rings and tube get the right balance between stickiness and smoothness. It works on my brother's 150mm Celestron and my 130mm Sky-Watcher, which seem to have the same black color with an orange peel texture paint job.

[Jiggy 67]

It is possible to preempt the eyepiece position during setting up. If your plan for the evening is to observe in the South, then set up with the eyepiece towards the ground (as you will slew through East to get to South) then when you slew to the South it will be in a reasonable position.  The same applies to any direction, with a bit of thought you can pre-position the eyepiece  and with practice you’ll find your doing it without even thinking 

Edited November 15, 2019 by Jiggy 67
Typo

[Aramcheck]

8 hours ago, woodblock said:

It's not sufficient just to slacken the screws you have to undo them completely and lift one half of the hoops before you can rotate.

I had a similar problem with the rings on our SW 200dps, where the OTA wouldn't rotate easily. The felt hadn't been fitted correctly on the inside of the rings & had folded over slightly in a couple of places, so it was bunched up and some of the adhesive side was facing the tube.

I bought a 2nd set of rings & replaced the originals. Then I cleaned the OTA & cut away the faulty bits of felt on the original rings... Replaced the hinge bolt with a countersunk one (& drilled the ring so the countersink bolt would fit), then put them back on the OTA so that the one nearest the secondary butts up against the ring that's attached to the dovetail, and the other near the primary.

This has made it easier to rotate the OTA when slackening off the two rings that hold the tube in place without the OTA sliding about, and the one near the primary can be used as a fine tuning counterweight, when nearly balanced.

It's early days, but so far it seems to work ok.

Cheers
Ivor

[Ouroboros]

10 hours ago, johnturley said:

That's the whole point about the slip band, it prevents the tube slipping down in the rings when you rotate the tube.

John 

Exactly. 

[Alan64]

http://www.andysshotglass.com/wilcox_rotating_rings.html

[Paz]

16 hours ago, Ouroboros said:

@woodblock It's one reason that I enjoy using my refractor. The eyepeice is always accessible and can b rotated to a more comfortable position if necessary. 

I've never done this but I know that some people buy and modify another ring which sits tightly around the scope tube but isn't connected to the mount. This third ring then rests back on one the 'proper' scope rings. The scope can then be rotated within the lossened scope rings without sliding out of the rings. I hope that makes sense. 

Someone might have a photo of such an arrangement. 

I have seen pictures of this before and had wondered what was going on - now I know!