celestron c8 corrector

[sparky68]

hi just starting out a bought a celestron c8 about 1973 ser 340525 paied good money good mirrors but cant focus it at all every thing good exept i think the corrector has been replaced with window glass ,no etched number on it at all and green when looked edge on ..

could this be the prob ? and can any one help me on where i may be able to get a corrector for an old celestron c8 ?? i need a wedge as well

[rowan46]

It will have to go back to celestron then. the mirror and corrector are matched at the factory

[sparky68]

that would cost lots .. do you know if they sell matched mirrors and correctors because i live in australia and it would cost to muct to send to usa

[rowan46]

not as far as I know, it's possible your main dealer has something in the spares bin it might be worthwhile trying them, certainly wouldn't harm.

[John]

As I'm sure you realise, yes, it is a really big problem.

You will need to approach the main Celestron dealer for your region regarding the possibility of a replacement mirror / corrector set. My guess is either i) they would not have one available for such an old scope or ii) if they do the cost, including installation, will be more than it would cost to replace the tube.

If you bought this recently I'd approach the seller as, if the corrector is window glass, you have been completely duped - if you bought through E.Bay you may have some redress.

Getting a suitable wedge will be much simpler than sorting out the corrector plate, in fact you have a totally unusable scope until that is sorted.

[Peter Drew]

Early C8 correctors were made from "green window" glass but they were of course figured as a Schmidt corrector and as already mentioned, matched to the other optical elements. There will be an immense difference in the image if it is indeed just a basic disc of window glass, this could not possibly have been overlooked by the seller. You should still be able to reach a focus as the corrector has little effect on the focal length but the aberrations of an uncorrected F2 primary would give a pretty awfull star image. I hope you are able to redress this situation with the seller.

[sparky68]

thanks guys i will try and see if i can get a mirror corrector set ,, sorry peter i can get focus with a 40 mm eye piece in day light but ( rainbow and fuzzy edges is this aberrations ? ) i have a 2011 c8 and the mirror and corrector look like there the same and will fit but im not going to pull that good tube apart

[sparky68]

yes e bay seller wont reply to me at all

[Stephen]

yes e bay seller wont reply to me at all

I wouldn't even bother then, get on PayPal and file a claim

[sparky68]

is there any way of telling if the corrector is a real schmit corrector or window glass ???

[RobH]

Take a good photo of the front of the tube, and a couple of close-ups of the area where the corrector meets the tube edge, and the area around the central secondary holder and post them up here.

Rob

[rowan46]

It is possible that the corrector has been removed and not replaced in its correct orientation but I think that most celestrons have a number etched onto them.

[E621Keith]

Use Ebay buyer protection to claim your money back.

SCT primary mirror is spherical and rely on the corrector to compensate for the aberration. The two need to be matched.

From reading the CN CAT forum, it will cost more to send the scope back to Celestron and have the corrector replaced than to buying a new tube. Those were comments from owners in the USA. I'd guess the repair will cost considerably more for us in the UK.

[Peter Drew]

From your description of the image you have achieved I think it's obvious that the component is unfigured window glass unfortunately. A figured corrector plate will look just as flat as the curves are very subtle but vital to correct the primary mirror.

[sgazer]

if you paid by Paypal, raise a dispute right away, sounds like you've been ripped off. If he still doesn't reply, Paypal will refund you, otherwise it's going to cost megabucks to pay Celestron to make a new corrector plate to match your telescope.

[sparky68]

some pics of corrector

[sparky68]

best i can do prime focus 2 mp agent v5 web cam bright sunny day 500 mtr tv antena

[sparky68]

same thing new c8

[sparky68]

Take a good photo of the front of the tube, and a couple of close-ups of the area where the corrector meets the tube edge, and the area around the central secondary holder and post them up here.

Rob

here are some pics rob

[Peter Drew]

The photos you show reinforce my opinion that it is a plain glass replacement. The early Celestron green glass correctors actually were not as well edged as yours, often having bits missing from relatively rough cutting out, they were also anti reflection coated which is not obvious in the photo. I was a Celestron dealer/servicer in their early days.

[JamesF]

If it's plain glass then it should lie flat on a table both ways up. I assume the proper corrector would not do this?

James

[sparky68]

think it will lie flat ether way the correction is so small and concave i think ?

[JamesF]

If the concave section is face down, there should still be a small gap between the table surface and the lens, surely? Or you could rest a steel rule across the face to see if there's a gap anywhere?

James

[sparky68]

is this what it should look like

[sparky68]

found this looks like corrector fake this is 4 old c8""" Serial number is 6072 appears in three places, as shown above, scribed on edge of corrector plate under retaining ring, and on back of secondary mirror at www.flickr.com/photos/edhiker/4925860244 .