Problems with RC-8 optics?

[moont]

Has anyone else experienced problems with the optics of a GSO RC-8 telescope (carbon-fibre tube model)?

I bought one new, the optics were horrible. Despite repeated careful attempts to collimate it (following the prescribed collimation process) I was unable to get even an acceptable image. We are not talking about some small degree of aberration at the edge of the FoV but misshapen star images indicative of gross collimation problems or misconfigured optical components.

The telescope was simply unusable so I've returned it to the supplier but wanted to 'poll' others to see if I've been unlucky or if there are frequent problems with these telescopes?

Tex

[Atmos]

Although I personally have not used one I have read a number of not so good reports on CN about the GSO RC-8, good things about the rest of the RC range however (everyone ditches the focuser).

[DJT]

Hi Tex
I have had mine for a few years now and its fine. Its was pretty close out of the box but maybe yours took a knock somewhere that put the main mirror out?

I am aware from previous posts and also from the supplier I used that GSO does bench test their ones using some Laser wizardry before they ship out.

Its certainly true that there are a number of forum posts out there on this but I don't think its an endemic problem. Interesting as I read it its the larger RC 10 that had more issues rather than the 8.

Cheers

[moont]

David,

Thanks for reply with your positive experience of this telescope. I may ask for a refund and try another supplier if not fixed.

Tex

[rustigsmed]

I have heard of someone having pinched primary mirror causing odd star shapes. think it was on IIS somewhere if you go searching.

[Satchmo]

But did you get nice star images in the centre after collimation exercise ? Its pretty hard to judge the edge as eyepieces usually don't perform well out there unless expensive . Natively those RC's suffer from astigmatism at the edge which can be cured with a field flattener .

[glend]

Do not use EPs with those RCs, they are not very good visually, they are designed to image.

I bought a new RC08 and it took me two months to properly collimate it. They are very touchy and if you disturb the primary in any way you are screwed. Too many people with a newt background try to mess around with the primary adjustment. You need to have the optional focuser collimation ring, and a good laser and Cheshire, even better the TAK collimation scope.
There is a fairly easy way to confirm everything - remove the centre baffle tube, this allows you to see all tge interior baffle rings and vanes from the rear. To remove the centre vaffke tube, 1. Take take the front ring off that is also the secondary mount ring, and make sure you mark one of the holes so you can put it back exactly in the same orientation. Now reach inside and unscrew the central baffke tube. I recommend the scope it sitting pointing up while doing this, i sat mine on a chair. The central baffle tube on the RC08 is a two piece item, don't just remove the top section, grab it down towards the primary to unscrew it. Be aware there us a primary lock ring that it screws into, this lock ring may rotate when you unscrew the baffle tube. Don't worry if it does because you can remive the mirror lock ring and put it back on the mount post when you get the baffle tube out. So with the baffle tube removed, make sure the primary lock ring is in place and secure. Then reinstall the secondary mount ring on the front, aligning it correctly. Now you can collimate with all the internal structure in view. Much easier that way. When properly collimated, reverse the process and reinstall the baffle tube. Do a star test, with your imaging train in place, for final tweaks. BTW, removing the front end is the easy way to clean the primary if you need to.

Good luck.