Tube ring sizes

[MylesGibson]

I was gifted a while ago a Dynamax 8, and after having tested it out, was happy to see the optics still in great condition and getting some really nice, clear views through it, despite a few negative reviews of it online. However, the mount that comes with it is a bit old fashioned, although the tripod seems sturdy enough.

I was thinking of putting some tube rings and dovetail on it, then sticking it on an EQ mount. Every time I search for 8" SCT tube rings, I just get results for Newtonians. I would assume these are interchangeable, as the body size would be the same, but I don't have an 8" newt to check, I only have a 6". Can abyone confirm if it's possible to put 8" Newtonian tube rings on an SCT? 

[Cornelius Varley]

Can you measure the circumference of the tube and from that calculate the diameter ? If the circumference is about 738mm then 8" rings might fit.

[MylesGibson]

2 minutes ago, Cornelius Varley said:

Can you measure the circumference of the tube and from that calculate the diameter ? If the circumference is about 738mm then 8" rings might fit.

I would have done but my tape measure broke not long ago (lent it to an irresposible friend) and haven't got round to ordering a replacement yet!

[omo]

You want to use a cloth tape measure - metal wont take the shape so well and may not be so accurate. If your really lucky you have one that measures diameters - a pi rule as us winders used to call them

I would not assume all 8inch SCT use the same size tubes but Orion Optics UK can make any size rings may need

 

[fozzybear]

Maybe have a rummage in the sewing box for a "dressmakers" one or fail that use a piece of string and use on a metal tape measure (when you manage to get one)

[MylesGibson]

1 hour ago, omo said:

You want to use a cloth tape measure - metal wont take the shape so well and may not be so accurate. If your really lucky you have one that measures diameters - a pi rule as us winders used to call them

I would not assume all 8inch SCT use the same size tubes but Orion Optics UK can make any size rings may need

 

I don't have that type of tape measure unfortunately. I'll get round to ordering one. I wouldn't like to assume either, hence asking here before doing anything

31 minutes ago, fozzybear said:

Maybe have a rummage in the sewing box for a "dressmakers" one or fail that use a piece of string and use on a metal tape measure (when you manage to get one)

I don't have a sewing box anywhere here unfortunately

[fozzybear]

If this is the scope you might have problems attaching tube rings and achieving balance with the dovetail fitted to the tube rings  as there is an obtrusion on both sides for the fork mounting brackets on the scope,  so the scope ring would not be well spaced towards rear of the scope and be hindered by the L bracket for could you not attach a dovetail directly to the scope where the fork mounts are? You might need to drill/tap extra holes just a thought

[MylesGibson]

38 minutes ago, fozzybear said:

If this is the scope you might have problems attaching tube rings and achieving balance with the dovetail fitted to the tube rings  as there is an obtrusion on both sides for the fork mounting brackets on the scope,  so the scope ring would not be well spaced towards rear of the scope and be hindered by the L bracket for could you not attach a dovetail directly to the scope where the fork mounts are? You might need to drill/tap extra holes just a thought

That is indeed the scope. I haven't actually looked properly at doing this yet, I have only set it up once or twice and found it really good for planetary viewing, was mainly wanting to stick it on an EQ mount to improve planetary images, as the mount it comes with isn't the easiest to use!

Good point about the obtrusion, I hadn't considered that

[fozzybear]

26 minutes ago, MylesGibson said:

That is indeed the scope. I haven't actually looked properly at doing this yet, I have only set it up once or twice and found it really good for planetary viewing, was mainly wanting to stick it on an EQ mount to improve planetary images, as the mount it comes with isn't the easiest to use!

Good point about the obtrusion, I hadn't considered that

Could you remove the finderscope and attach a dovetail to the bolt holes ? But then no finderscope.   I've trawled the net seeing if anyone has converted from fork to dovetail but to no avail for this scope

just had a brainwave you can get sct saddles or botch something together and maybe use jumbo jubilee clips it will work 

2 x jubilee clips  plus dovetail and some form of saddle either 3d printed or bought for an 8"SCT ……...x2

 

https://www.jubileeclips.co.uk/products/high-torque/

Edited May 18, 2020 by fozzybear
added clips link plus other additions

[MylesGibson]

31 minutes ago, fozzybear said:

Could you remove the finderscope and attach a dovetail to the bolt holes ? But then no finderscope.   I've trawled the net seeing if anyone has converted from fork to dovetail but to no avail for this scope

 

Yeah, I trawled through the internet to see if there was anything about it and didn't find anything either. 

What are SCT saddles? Not seen or used them before, and how would a Jubilee clip connect them without causing an interference?

Edited May 18, 2020 by MylesGibson

[fozzybear]

those 2 pieces in the picture screwed to the dovetail as they are radiused  then 2 jubilee clips around the whole lot otherwise drill into to tube..... to attach a dovetail  take apart job ...

You have to think out of the box a little... 

you quoted"and how would a Jubilee clip connect them without causing an interference?"  I dont understand as per the picture the dovetail and the 2 supports rest on the scope and then you wrap the jubilee clips around the scope and the support at either end of the dovetail securing it square. hopefully 

Edited May 18, 2020 by fozzybear

[MylesGibson]

55 minutes ago, fozzybear said:

you quoted"and how would a Jubilee clip connect them without causing an interference?"  I dont understand as per the picture the dovetail and the 2 supports rest on the scope and then you wrap the jubilee clips around the scope and the support at either end of the dovetail securing it square. hopefully 

 

Ahh, I see what you mean now. The only reason I asked was I had a little look at your link and didn't see any that may possibly be big enough. But I am sure I could look around and find some. I haven't drilled into a tube before.... Would that not affect any images if there is a screw and bolt inside the tube? Jubilee clip is probably the best idea.

[fozzybear]

2 minutes ago, MylesGibson said:

Ahh, I see what you mean now. The only reason I asked was I had a little look at your link and didn't see any that may possibly be big enough. But I am sure I could look around and find some. I haven't drilled into a tube before.... Would that not affect any images if there is a screw and bolt inside the tube? Jubilee clip is probably the best idea.

Those jubilee clips go upto at least 12"+ Diameter for industrial evac/aircon units so good for you just have to speak to your local builders merchant. Drilling into the tube a little more complicated but why ruin a good scope if you can go the lazy man's route. And less invasive....  as per a couple of holes in the tube you would notice nothing

[MylesGibson]

2 minutes ago, fozzybear said:

Those jubilee clips go upto at least 12"+ Diameter for industrial evac/aircon units so good for you just have to speak to your local builders merchant. Drilling into the tube a little more complicated but why ruin a good scope if you can go the lazy man's route. And less invasive....  as per a couple of holes in the tube you would notice nothing

Think that may be the route I go down. Thanks for the help here!

[fozzybear]

2 minutes ago, MylesGibson said:

Think that may be the route I go down. Thanks for the help here!

the site I listed you might have got you confused for the jubilee clips they do them to 520mm diameter..... and your scope is 200mm 8"

https://www.jubileeclips.co.uk/products/high-torque/

[MylesGibson]

4 minutes ago, fozzybear said:

the site I listed you might have got you confused for the jubilee clips they do them to 520mm diameter..... and your scope is 200mm 8"

https://www.jubileeclips.co.uk/products/high-torque/

Ahh, it was me being silly. For some reason, I was reading the diameters thinking it was quoting the circumference! 

[fozzybear]

2 minutes ago, MylesGibson said:

Ahh, it was me being silly. For some reason, I was reading the diameters thinking it was quoting the circumference! 

let us know how you go on...

[MylesGibson]

1 minute ago, fozzybear said:

let us know how you go on...

Will do, will be a while before I get around to it, but will update this when I get round to it

[fozzybear]

Just now, MylesGibson said:

Will do, will be a while before I get around to it, but will update this when I get round to it

👍

[RT65CB-SWL]

1 hour ago, fozzybear said:

those 2 pieces in the picture screwed to the dovetail as they are radiused  then 2 jubilee clips around the whole lot otherwise drill into to tube..... to attach a dovetail  take apart job ...

You have to think out of the box a little... 

you quoted"and how would a Jubilee clip connect them without causing an interference?"  I dont understand as per the picture the dovetail and the 2 supports rest on the scope and then you wrap the jubilee clips around the scope and the support at either end of the dovetail securing it square. hopefully 

Hi @fozzybear

I have no objection to you or other SGL'ers using my image(s), unless it is in a Quote but please drop me a PM first out of courtesy.

Thank you in advance for your cooperation.

Edited May 18, 2020 by Philip R

[fozzybear]

Just now, Philip R said:

Hi @fozzybear

I have no objection to you or other SGL'ers using my image(s), unless it is in a Quote but please drop me a PM first out of courtesy.

Thank you in advance for your cooperation,

Sorry if I offended but thought if it was on SGL then they had the perpetual rights as already on the site and I just reposted an image already there... did not know I had to attribute it to an individual again Sorry

[RT65CB-SWL]

1 minute ago, fozzybear said:

Sorry if I offended but thought if it was on SGL then they had the perpetual rights as already on the site and I just reposted an image already there... did not know I had to attribute it to an individual again Sorry

Apology accepted.

[fozzybear]

2 minutes ago, Philip R said:

Apology accepted.

could you help or advise the poster on any other options?

[RT65CB-SWL]

Just now, fozzybear said:

could you help or advise the poster on any other options?

I will have a go!

[RT65CB-SWL]

After reading this topic and suggetions, I think @fozzybear suggestion about attaching a dovetail bar directly to the OTA appears to be the most feasible option, though as he says, it will involve drilling and tapping holes into the OTA or one of the side plates, (I would prefer the right side), that holds the backplate in place, but I do not know how secure that part is, if @MylesGibson is confident enough to attempt it, though it would involve a total stripdown and rebuild, to prevent any foreign object debris; [FOD]; swarf, etc., getting into the mechanics and/or on the optical surfaces.

But it is these side plates for the forks is the issue, as I think they are an integral part/piece of the backplate itself and that does concern me if they are/were to be removed or start drilling and tapping holes. 

@omo has suggested to contact Orion Optics which is an option. I would also get in contact with SCTelescopes and see what he would advise, before attempting anything at this stage. It is a triicky one to answer, unless you have an engineering or optical/mechanical engineering background, which I do not have. He has done restoration work on the late Sir Patrick Moore's telescopes and others.

Out of interest @MylesGibson what is the OTA's weight? - I feel that using Jubilee hose rings, (as I have done with my 're-modded' ETX105), may not be substantial enough to support the weight of your 'scope. However, if you do decide to go the Jubilee hose rings route, you will need to purchase some felt, cork or neoprene strips to prevent them from scratching the tube.

 

 

 

 

Disclaimer:

1. I have written/replied to this topic in good faith.
2. I do and will not accept responsibility for any injury, damages; (physical, mental, other); death, etc., to the end user or other persons that are using the telescope and/or damage or loss of any equipment, accessories, etc., during its operational use and/or modifications that are undertaken.