buying second hand

[red dwalf]

i`m thinking of buying a second hand sct scope, can anyone help me with some ideas of what i might need to look out for regarding mount and scope ?

[GazOC]

Someone with a good, verifiable selling history would be top of my list.

[red dwalf]

don`t know the guy i`m affaid, been after a 8"sct for a while but i know that you have to be carefull with the coatings on the front plate, i think, how can you tell if some of the coatings are removed, would i be able to see it ?

[GazOC]

IIRC the corrector should show a slight (purplish???) tinge when viewed from an angle.

[Doc]

Thats what I was thinking as well Gaz. Rob wants me to go with him on sunday to give a second opinion.

[RobH]

It will be obvious if the coatings have been damaged, as they should normally have a lovely purple/blue sheen to them ...if you are a member of your local astro club, someone is likely to have an 8 inch SCT you can have a look at.

Don't worry if the optics don't look clean though. A bit of dirt is inevitable, as are dew marks.

If you can pick up an LX200 classic, you will get a great scope, but whatever you buy, try to see it in action if you possibly can.

I bought a secondhand SCT a few years back, and although I'd seen it slewing when I viewed it, it had major DEC tracking issues, and I had to replace the motors.

The celestron scopes are also very good, but I don't have experience of them, just the Meades, but I'm sure someone will be along who has.

If you find a scope that's not in your area, and need it looking at, there are members of this forum all over who I'm sure would help.

Cheers

Rob

[GazOC]

If you look directly down the tube into the mirror you'll see all sorts dust reflected about and it can look quite shocking. Don't worry about it though, as Rob says, its normal and nowhere near as bad as it seems.

[red dwalf]

he chap is in the Solihull / Tamworth area area,

[RobH]

A long way from me I'm afraid....I'm on the south coast.

Cheers

Rob

[johninderby]

Download Rod Mollise's guide to buying a second hand SCT. It's a 151 page book in PDF form

http://skywatch.brainiac.com/used/used_sct.pdf

Probably more info than you will need, but a good read anyway.

John

[red dwalf]

thanks John

[John]

One of the things to look out for in an older SCT of 8" or more is mirror flop. Basically this means that the mirror shifts slightly as you tilt the scope - typically as you cross the zenith, and this puts the scope slightly out of collimation which is very frustrating whether you are observing or imaging. It's difficult to spot unless you get a chance to observe with the scope so the best you can do is ask if it's an issue with the scope concerned and hope the seller is open with you.

[RobH]

I know with Meade SCT's that there is an easily installed lock available to deal with mirror flop. You unlock, focus, and then lock the mirror.

They are pretty cheap too, which is always good .

I completely upgraded my 10 inch LX200 classic, after fixing the motors, and it was a great scope which I made a mistake selling later.

Cheers

Rob

[brantuk]

What budget are you looking at? The brand new Celestron SCT's are a good buy at the moment.