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Hello everyone, 

I'd say it's been about 6 years since I last posted on this forum, oops 😁

Anyway Ive been looking for a new scope something with abit more punch than the skywatcher 130m I have been using and came across this beaut on eBay, I won the auction and picked it up yesterday. The guy was selling it on behalf of an elderly gentleman man who couldn't use it anymore, (it's been sitting in an unheated garage for many years 😩) he had no idea on the make or model other than its a c8, I did a bit of research and found its a c8 super polaris. 

The mount has both RA and Dec axis motors but I have no way to power them, the action of the mount is buttery smooth. However I plan to mount this on my HEQ5 anyway... 

The scope its self seems to be in good condition some minor scratches on the tube but nothing too alarming, no finderscope or dust cover but I plan on adding my own finder anyway. The focus is super smoothe and can't see much if any image shift in use (not tested on a star yet due to preverbial clouds) 

My main concern is as its been in an unheated garage for some considerable time and there seems to be some minor mildew on the primary which I plan on cleaning... when I feel brave enough.. 

I don't think the secondary screws are original, should be Phillips head? Tested on a small light down the garden and it seems to be well collimated, but does have a small amount of mildew on it

I don't recognise the mounting bar, I would like to swap it to a vixen style bar so I can mount it on my HEQ5 maybe this?

Anyway that's where I am with it sorry its been so long since I last posted, I hope to be a tad more active on here. 





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i think those hex screws are oringinal before the cross screws came out.

the mirror is not too bad but ya get to that and just mark the side of the corrector plate inside andout with tape then a pen mark. the corrector HAS to go back the same place it went in.

thats the classicic 8" celestron cb on cg5 i think good scope.

for the dust cover i just did it on an old 6" refractor that also didnt have the dust cap. I went to dollar store they sell tin cans that you can put cookies in etc . you will need probally the largest ones they carry. i put 2 rows of foam to give it a fit as it wont be the perfect size u need, and then spray paimted the tin lid black. Its not so pretty but works or use a shower cap.


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Ah ok thats great, I was worried someone had forced some metric screws in there 😁. I saw a post on here collecting serial numbers and trying to date them (from serial number 1980 something??)

Yes ive been reading lots of tutorials about dissassembly and cleaning, especially with potential mould issues I don't want it to get any worse...

Ah good idea with the shower cap, It would do untill I find something a bit more substantial or get something 3d printed? 






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These were pretty good scopes as long as they were not made in the run up to the Halleys Comet return in 1986. Meade and Celestron relaxed their quality control to get scopes out in the run up to Halley.

You will need a dew shield if you don't already have one. SCT's are "dew magnets" with all that glass up the front end.

Celestron went through a number of patterns for the secondary screw heads - those hex ones being one of them. They may well be an imperial size.

The other thing to check for with those older SCTs is mirror flop where the mirror moves slightly as the scope moves around, affecting the collimation.


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That mirror will be ok, although the mildew is annoying I doubt that this amount will effect the view. It’s incredibly easy to damage a mirror when cleaning so bear that in mind if you do decide to have a go.  If you look at some pics of ‘dirty’ mirrors you’ll see that they’re a lot worse than yours and with minimal impact on the views given.  Nice scope!

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what may help is exposure to UV as that'll at least cull the mould hopefully, so it doesn't spread. A UV lamp and a decent exposure time would do if the sun doesn't want to help, don't point it at the sun tho!

As for cleaning it off, a soak with some hydrogen peroxide added perhaps? tho I've no idea how that'd aflict the mirror, others with more experience than me may be able to advise better re that. Might be fine with just the usual soapy water routine after a UV session to kill it off, but give the internals of the casing a treatment as well to remove any spores that might still be lurking.

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Hmm maybe I'll hold off on cleaning until after I get a decent viewing session in and put the scope through its paces. Check for mirror slop collimation etc 

34 minutes ago, John said:

You will need a dew shield if you don't already have one.

Yes dew shield is definitely top of my list! Always struggled round here with dew! 

10 minutes ago, DaveL59 said:

what may help is exposure to UV

As it doesn't have a dust cap at the moment I will leave it somewhere where it will get some sun (not direct, don't want to burn anything) in the hopes I will at least halt the mould growth 

Very excited to try this scope out! 


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If you must clean the mirror use isopropyl alcohol and distilled water. Some suggest a few drops of washing up liquid in the mix as well but avoid those containing lanolin. I use 25/75 mix, (alcohol/water), and pulling medical cotton wool over the surface without applying any pressure. Lastly I rinse with distilled water. Best done outdoors or in a very well ventilated area. Avoid cleaning unless it's really necessary. I hope you enjoy your new scope.


Edited by JimB

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Thanks for the advice,

I'll see what its like after I have used the scope. Other than the spots of mould on the mirror and corrector plate it dosen't seem too bad


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OK so I was able to test the scope briefly before the C8 was saturate with dew (dew shield has been ordered 😊

1st thing I noted was just how simple it was to colimate, I've never used a SCT scope before, it was all ready pretty close so I just found a bright star defocused slightly and tightened/loosed the correct screw untill I got nice concentric rings. 

I was only using low powered eyepeices and didn't notice much mirror slop focus was nice and smooth. 

I did notice dew on the inside of scope on the corrector (is this normal for use without a shield?) but it also highlighted a bit more of the mould growth I hadn't noticed before. 

Anyway, I'm really happy with this scope and really looking forward to using it more. 




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