Nexstar 11 third hand?

a funny question, but we all know the answer to that :lol:

Anyway Neil, I think you've just stated the reason why he's selling the scope, if the "go-tos" are out by 8 degrees on average, then its pretty much useless. No eyepiece is going to catch any object with that level of inaccuracy.
The real question is, is this because of the owner been inept at setting up or is the mount some way damaged/misalligned. See if you can use it at night time, checking its accuracy and optical quality.
If the mount is damaged then it might aswell not have the goto capability, in which case I'd avoid it light the plague.

Hi guys. Im about to buy a third hand nexstar 11" gps. Im a little bit nervious about it. I think its roughly 6 yoars old. I was gonna get a C11-SGT (XLT) from astronomy ireland which is 3800 euro but the N11 is considerably cheaper. Im going to see it but dont know a huge amount about SCT telescopes. According to the seller its working fine. Is 6 years old for this kind of telescope? Is there anything i should be looking for when i see it?

Well, Celestron only brought out the 11 GPS in 2001 so definitely not 6 years old but it could be 4+ old and one of the first ones into the country. If so, check if the handcontroller chips were updated sometime in 2002 from the originals as this was a free update offered by Celestron after some minor initial problems which AI carried out (only takes a few minutes). If allowed, open the handcontroller and see if the two chips have a green (or white - can't remember) E and O written on them with a marker. If so, these are the updated chips. Of course, there have been many further revisions since then but no free ones. If the original chips, I may be able to sort this out as I think I have a set of the update chips somewhere.

Is the 8 degrees he's talking about refer to the accuracy of the GOTO or in locating the initial alignment stars? If the latter, that's not unusual, some were 15 degrees off before the new chips and correction procedures. If GOTO accuracy, then that's a major issue and needs to be looked at very carefully before parting with any money.

If you decide on a new scope (such as the C11-SGT XLT), as Dave suggested, phone AI in the morning and it will match any price available in the UK. The new CPC 1100 by the way (Nexstar 11 replacement) should be available in a couple of months.

Gordon

Thanks for all the advice guys. I definitely feel more confident about going to see the scope tommorrow and ill have a hole heap of questions to ask. Just one more thing. How accurate is goto? If the telescope is aligned properly and is funtioning properly should the object in question be in the centre of the eyepiece?

Neil

Thanks for all the advice guys. I definitely feel more confident about going to see the scope tommorrow and ill have a hole heap of questions to ask. Just one more thing. How accurate is goto? If the telescope is aligned properly and is funtioning properly should the object in question be in the centre of the eyepiece?Neil

Assuming a properly set-up scope and accurate star alignment, the object should be well within the field-of-view of a low power eyepiece but don't necessarily expect it to be dead centre. How close to centre can depend on a number of factors in setting up the scope and choosing the best alignment stars and that is in the hands of the person selling the scope. Can you bring someone with you who knows Nexstars?

With proper setup and star alignment, my Nexstar 8 GPS places objects close to centre FOV of a fairly high power eyepiece (about 150x). Use deep sky objects, not planets, to check GOTO accuracy. For some reason I never quite understood, early and even later Nexstars seem to place planets with less accuracy than DSOs.

If objects consistently fall outside the FOV of a low power eyepiece, have him switch off, redo the entire alignment sequence and try again just to check if the problem is human or electronic.

Gordon

Here's a way to check the hand control (without opening it) and motor control versions in this Nexstar:

Look for a Version item in the Utilities menu, i.e. Menu > Utilities > Version. If there is no Version item, then the hand controller is an early Version 1.2 which shipped with the original Nexstar 11 and really should be upgraded. If there is a Version item, select it and hit Enter. Write down the numbers which appear, e.g. 1.6 1.0 1.0. If 1.6, it must have been updated with the later HC chips, even better if a higher number. Incidentally, Celestron recently released a new upgradeable HC for all Nexstar GPS scopes with the latest Sky Align technology etc (costs $150 or $75 if you trade in your old HC).

The other numbers relate to the Alt / Az drives in the Motor Control Board and should be identical. 1.0 1.0 indicates the original MC version - again an upgrade recommended (replacement motor control board). Only if the MC numbers show 3.0 3.0 or higher can the upgrade be done via a programming cable and PC rather than replacing the MCB.

The Nexstar 11 is a fine scope and even if it has the early HC and MC, it may run very well but like all electronic scopes, later versions eliminated various problems as well as incorporating newer features.

Gordon

Thanks guys! Went to see the nexstar 11 yesterday. Seems i got it wrong. Its not out by 8 degrees at all. I misunderstood him over the phone. He was talking about magnetic north and true north or something. :oops: Anyway the scope seems to be ok. Didnt actually get to look through it but i was shown some recently taken images and they looked grand. The sellor never got the HC chips updated but got a new handcontroller a year or so ago so i presume the updated chips are in it.
I also rang astronomyIre. about the C11-SGT(XLT) price difference in england and they said they would match the price i got in england. They said they would sell it to me for around 3200 euro, given the shipping cost and the VAT difference over here. Sounds good.
So i suppose i have to decide between a third hand Nexster(although the first owner had it for just 6 months) or a new C11-SGT. Would the CG-5 mount perform as well as the nexstar mount? If so i think ill spend the extra money on the new scope. Thanks guys


Neil.