Altair Accent 70ED

[Ukjonathan]

Hi hope I’ve posted in the right place. I’ve discovered a rattling in my scope and it’s wen I tip it from one side to the other. It does not seem there all the time.

it sounds as if it’s coming from either the inside of the focuser unit or low down on the scope tube where the focuser is.. it’s only I think since I removed two studs that hold the small tripod mounting bracket on the bottom of the scope  to fit a longer dovetail on. The original one is too small to be held on my EQM 35 it’s only about 2.5ich long. I’ve looke indies by just removing the rear dust plug and front lens cover but there is nothing loose in there. It sounds  it sounds small if that makes sense. Any ideas?

john

[Marmot]

I must admit this has me baffled!

It may be worth carefully working your way through the moving parts to ensure everything works as it should: ie Does the focuser smoothly move out and in as it should and do the focus control knobs operate smoothly.

 

 

[Marmot]

PS.  Just had a thought:  could it be a loose screw of some description? There are several screws accessible from outside that are situated around the focuser and of loose they could make a slight metallic rattle. Eg I believe your scope has several screws for mounting a finder scope shoe. There is probably a largish thumbscrew on the underside of the focuser for  locking it in place (when used with camera etc). If your scope has a rotatable focuser there may be a locking thumbscrew for that also.

 

i may be clutching at straws, but worth a mention.

[Ukjonathan]

Hi Mamot,

                 Yes everything works fine, and checked everything on the outside. It sounds like it’s coming from just in front of the focuser. I’ve looked through the scope nothing in there but it looks like it has a inner tube so it could be between that but defiantly where the focuser joins the scope. It sounds very small whatever it is and it’s doesn’t sound like a nut but more like a light washer. The two studs that held the bottom dovetail only go into the tube that is threaded  about 4mm I’m baffled 

John

[AstronomyUkraine]

3 hours ago, Ukjonathan said:

Hi hope I’ve posted in the right place. I’ve discovered a rattling in my scope and it’s wen I tip it from one side to the other. It does not seem there all the time.

it sounds as if it’s coming from either the inside of the focuser unit or low down on the scope tube where the focuser is.. it’s only I think since I removed two studs that hold the small tripod mounting bracket on the bottom of the scope  to fit a longer dovetail on. The original one is too small to be held on my EQM 35 it’s only about 2.5ich long. I’ve looke indies by just removing the rear dust plug and front lens cover but there is nothing loose in there. It sounds  it sounds small if that makes sense. Any ideas?

john

Have you tried removing the focuser from the tube? It should be a straightforward operation. The focuser will either screw into the body of the scope, or be held by a number of screws.

[Ukjonathan]

Hi I have thought about removing the focuser unit and there are four small grub type hex screws that I assume holds it on. I must admit I am a little hesitant but I’m sure that will show the culprit. If I thought by just removing them it would come off without any other things on the inside connected to it I would try it. Reason I put it on here for suggestions as there are far more experienced people on here then I.

thinking about it it could have been there when I bought it as I’ve only had it out of its case a couple of time and I handled it very gently and this is the first time I’ve heard it when I tipped it over 

john

 

[Nightspore]

It might be something loose inside the OTA. 

 

 

Although, on some focuser designs, there is a tension knob often directly underneath the focuser housing. In most Crayford and Crayford-rail focusers, and even some rack and pinion focusers, the knob/screw is usually slightly loose in actual use and only tightened totally to lock the focuser completely.

 

 

The GSO Crayford-rail on the right has the tension knob on top of the focuser housing. You can see it directly underneath the 'TS' logo. A loose tension knob may be the cause. In normal use the knob needs to be slightly loose. When tightened completely the focuser draw tube is locked in position allowing the focusing knobs to turn freely. 

[Ukjonathan]

Hi I took the plunge and just lightly slackened the four small hex screws and the focuser came off between that and the tube is a thin gasket which I left in place. I found the culprit as I said small and in the focuser in the gap that’s around the focus tube that goes in & out when you turn the focus knobs. I took two pics of it it looks like something that is a kind of holding button it’s got a grave in it and I’m wondering if it’s supposed Togo honto the end of that nut and slides around the lip that the focuser rotates around. It may be part of that lock button that tightens onto the lip

if I could find a way of posting the pics I’m sure someone here would know. 
john

[Ukjonathan]

Hi could it be on the end of the focusing shaft that sort of put the brake on when you slightly tighten it to stop the knots going round?

[Nightspore]

Might be worth emailing Altair.

[Ukjonathan]

Hi yes I will do on Monday. It really does look as though the grove  fits around a shaft and it acts as a friction brake. The scope is no worse for it. Focus works & you can adjust the knots position ie before.

im please I got it out 

thanks all I’ll let you know if I find out

john

[Nightspore]

Good luck.

[MarkAR]

Looks like some sort of friction pad that a screw would push on.

 

[Marmot]

Although I can not judge the exact scale from the pic, it does look like the groove is quite small: this makes me think it may be meant to add friction to the axle between the focus knobs which, I believe, may be the case with some Crayford style focusers.

If your focuser does in fact have such a thumb screw for adding friction to the focus knobs, it may be that it will now screw all the way out without the friction pad attached to it. If it does in fact screw all the way out, you could then see if the photographed friction pad has in fact detached from the end.

I hope this makes sense. It may be another long shot, but thought I would mention it.

[Nightspore]

A lot of R&P focusers have screws to adjust tension levels.

 

 

They aren't usually captive. If I tighten this screw on my 102mm ED-R Starwave it tightens the tension on the focus wheels.  The idea being that the focuser could be effectively locked when carrying a heavy load. Although outside of AP I doubt it has much use. 

 

 

On Crayford and Crayford-rail focusers (above and below) the idea is the same but when the tension screw is tightened the focuser locks but the focuser wheels themselves run freely.

 

 

The screw controlling the tension isn't normally captive.

Edited August 22, 2021 by Nightspore

[Ukjonathan]

Hi all

          That’s what I thought it was, as it looks like it would fit around a shaft to brake & stop it moving.

The think that threw me a little though the white bit with the grove is made of  plastic & I would have thought a nylon which is slightly softer. It has a sale back and it’s the size of a paracetamol tablet.

ive had another look and if it fits there I can’t do it as the pressure bolt you turn to stop the focuser knobs moving has what looks like a plate sprig that  pushes against the shaft. It may goi their. & must rest on the small shaft at the back of the white  bit. It’s too tight to see but it’s not a good deign if it does just rest in there with the little shaft. I don’t want to take it apart again as I don’t think it’s good in case dust gets in. It’s very cheap part by the look of it.

forgot to say it seems to still work but I’m in the process of looking for another 80mm as I’ve put my Skymax 127 up for sale today so if the right one comes along I’ll buy it

john

Edited August 22, 2021 by Ukjonathan
Forgot something