TheSkySearchers

Hi,

I'm thinking of buying a used Celestron Nexstar 8SE, and btw I'm pretty new to reflector telescopes.

I won't be able to perform an extensive test on the device, just a few minutes of inspection in daylight and probably indoors.
So, I would like your advice about what to look for in the unit regarding its functional state. Maybe there is some test I can perform to check if the electronics in the mount are fully functional? Something to look for in the optics side?

Any advice will be very welcome!

Best,
Gustavo

I would check for chips/scratches on the corrector plate,check for mold aswell,these type of scopes can sustain moister in them when not dryed out and stored correctly after use in heavy dew, check that the focuser works well and the mirror lock .

yobbo89 wrote: ↑Mon Jan 23, 2023 3:07 pm check that the focuser works well and the mirror lock .

Thanks for your quick answer! I'll check for that!

According to the seller, the telescope isn't used, but the box is opened, and there is no warranty, so I'll check for those details and try some functions on the mount to see if it moves smoothly in all directions, etc.

Thanks again!

Make sure the mount is operational.
An easy test is to flip it on, (it uses 8 AAs) hopefully the seller has it ready for power up.

After a quick boot up it will ask for type of alignment, scroll (with the up/down on keypad, not with the 4 direction keys).

Select One Star alignment, it will then display the date that it was last used, this could be helpful if seller is telling you otherwise.
Just hit enter.

Then it will display location, just yes it to death, hit enter.

You can just hit enter, then scroll to any star using the four arrow keys, for a simple test, especially if it's daytime, select any star, I usually select Polaris, but that might not be an option near the equator.

Hit enter, then align.

For a test, press solar system or stars and select an object, it should slew, after it stops, put your ear near the mount arm and you should hear the motors tracking.

Here is a Fantastic site!
https://nexstarsite.com/

It's basically the end all on Nexstar, there's more info there than on Celestron's site.

You probably can download a manual and read the Quick Start page.

@Ylem

Thank you for all your tips and the link to nexstarsite!

I'll follow your suggestions!

Best!

Hi again,

Yesterday I had a chance to test the 8SE for a couple of hours.

Everything was perfect regarding the mount and the optics were super clear and sharp, even at high magnification. The tracking seemed to be working (test was at daylight so I can’t say it was tracking accurately but it was moving).

The engine reaction and ranges seemed normal too.

The only that did catch my attention was a slightly fluctuation in the engine’s rate when using the fastest speeds. I mean, movement was smooth but the engine’s pitch wasn’t super stable. Is this something I should worry about?

Any thoughts?

Best,

gbravetti wrote: ↑Wed Jan 25, 2023 5:34 pm Hi again,

Yesterday I had a chance to test the 8SE for a couple of hours.

Everything was perfect regarding the mount and the optics were super clear and sharp, even at high magnification. The tracking seemed to be working (test was at daylight so I can’t say it was tracking accurately but it was moving).

The engine reaction and ranges seemed normal too.

The only that did catch my attention was a slightly fluctuation in the engine’s rate when using the fastest speeds. I mean, movement was smooth but the engine’s pitch wasn’t super stable. Is this something I should worry about?

Any thoughts?

Best,

Not really, they all pretty much sound like coffee grinders. Don't get me wrong they are good, time proven mounts, mine is 8 years old and I still love it.

First, you have to make sure the scope is balanced. The best way to do this is put a broomstick on a table lay the dovetail across (like a see-saw) and try to balance, or find the centre of gravity of the OTA with the accessories on.
Then Mark the dovetail will a small dot.

Then remount the scope with the dot centered in the holder.
This will go a long way in keeping undo stress on the motors.

Edit, one more thing, run the mount at slower speeds, I think mine is set at 60%, it will be quieter and it will use less power.

Hope that makes sense.

Running at a lower speed also helps longevity of the motors as they have to produce a lot of torque when starting and stopping a mount slew