Do you recognise this vintage 80mm/910mm f/11,3 refractor?

[West83]

So quick update, haven't been really active in the forum in the past year or so, but have been active under clear skies

I have bought an AZ GTI mount, mainly since my light polluted skies don't allow for relaxed starhoping. I have also bought the telrad, which I placed on velcro tapes and use it on both my scopes.

So new gear includes:
- AZ GTI mount
- Telrad
- Astronomik UHC filter
- Maxvision 24mm EP (got this second hand but in pristine condition)
- Concenter for Astromaster 130 collimation

I use most of this with both scopes. But at this stage I am becoming more accustomed to stargazing and can see the shortcoming both the frac (focuser and diagonal ) and of my Astromaster 130 - the focuser is crap and getting an aftermarket one is a pain in the nose, since I would need to cut and drill the tube, which is more than I am willing to do. Optics could be better (sharpness towards the edge progressively dropping), I have already centerspotted my mirror, flocked the tube and the focuser tube.

I am now looking to upgrade the focuser and diagonal on my refractor. This is proving to be another solid expense, as I am looking at upwards of 140€ for the focuser and no less than 80€ for a respectable diagonal. So that brings me to 250€ for this, and would like to know if it's worth it at this stage. I definitely plan on getting it replaced, just not sure if now is the time.

I would definitely need advice on selecting the right focuser here.

At this time, I am willing to budget 450€ for a new scope and was looking at Skymax 127, which my mount can hold. Any advice if it's better to buy a new scope or invest in the frac?

Thanks!

[John Baars]

Question is if another focusser and prism wil improve the images you see. I don't think it will. An F11 system is already very forgiving for a focusser and a prism is quite optimal for a refractor from the 80-ties.(the refractors of those days were calculated on their prism or vice versa)

[helicon]

Agree with John - not sure if this will be useful

[West83]

So currently, the diagonal seems to be the weak link. It has a tendency to rotate around it's axis, it's quite light and the eyepiece doesn't feel secure.
The stock focuser is only problematic due to the fact that it's operation is far from smooth, and I am looking to improve my experience. I wouldn't expect much better views due to focuser, but generally a more pleasing experience.

[Lady Fraktor]

These basic focusers can be updated a bit to make them better in use.
Inside they used poor grooved teflon strips to support the drawtube. These could wear down or fold over time producing slop in the drawtube.
Look for a source for solid PTFE strips (one side glued) of the same thickness and replace the factory strips.
At the top of the drawtube there are 2 grub screws and the tension screw which pushes against a plastic strip.
Replace that with a same thickness PTFE strip as well.

With the focuser off of the tube, you can check the drawtube slump by putting a diagonal in it.
The pinion acts like the fulcrum of a teeter-totter so at some point you will see the diagonal drop down when racking it outwards.
I usually make a block of wood and epoxy it in that spot above the tube inside so it cannot move upwards.

The only thing you cannot really correct with these focusers is the slight shift from the gearing which is inherent to the R&P focuser.

[West83]

Thank you for the advice @Lady Fraktor, I would of course benefit from an illustrated step-by-step process

Do you reckon, this article has all the bases covered (I do notice it's a newt focuser, but I reckon the process might be replicated):
https://www.practicalpolymath.com/uncat ... -much-rock

[Lady Fraktor]

That tutorial is very close to what I did.
I used the PTFE to replace the factory strips instead of covering the entire drawtube area.
Experiment a bit to see what will work.

[LDW47]

I had the C102 HD the follow up to the C102, it was an excellent scope. Ed Ting had high praise for those post 1995 line of Celestron scopes. No reason the 80mm model isn't the same. I realize my comments are long after the original post !