Advice on buying used Celestron 8 Plus

[iwannabswiss]

I have the opportunity to a buy a used Super Celestron C8 Plus from someone but I've never bought used so i don't know what to look out for. I believe it's from the late 80s, it comes with a wedge mount. They say the optics are great condition because they keep it covered and it's between rarely used the last few years. So what should I look for or do?

[knobby]

Difficult question but if bit was me I'd be checking the front corrector plate was clean / undamaged, the secondary mirror was properly seated, the focuser moved smoothly and the main mirror wasn't damaged / peeling / fungi etc .I'd also look at the various screws to see if they're stripped buy clumsy hands and if possible have a look through it to see if it will focus on a distant object.

[scarp15]

Probably will be fine, both my scopes are second hand. Concerning my Celestron 1990's Celestar, I was able to arrange a visit  to collect and so got to have a good look, which was not the case with my dobsonian as I had to arrange for a courier. Usually instruments such as these are looked after, the build and optics on classic C8's  are generally very good and can provide very good value. In both circumstances I built up a rapport with the seller, in as far as communicating via email and also phone so asking plenty of questions and if necessary requesting additional photographs. Otherwise as Knobby has referred to.

[John]

Mirror flop is something to look out for on those older C8's. The causes the primary mirror to shift slightly as the scope crosses the meridian and you loose collimation. C8's focus by moving the primary mirror and the mechanism can get sloppy with age.

I'd also be a bit wary if it's one of the ones produced around the time of the return of Halley's Comet in 1986. A number of manufacturers apparently relaxed their quality assurance for a period to meet the demand to get scopes to the market. 

If the optics are clean and bright and the scope holds focus / collimation as you move it from one side of the sky to the other then it's probably OK.

[iwannabswiss]

Thank you both for the advice. I am planning on getting a night time demonstration, that way I can make sure the images look good. I'm going to get a different mount but I plan on using the scope to further my astrophotography skills. It is possible to use scopes on different mounts, I just need the right brackets right?

[iwannabswiss]

Thanks John. I'll be sure to have him cross the meridian.