Celestron NexStar 4GT Problem.

I've just bought my first motorised telescope, a Celestron NexStar 4GT Maksutov-Cassegrain, which I bought to upgrade from my old Tasco 3 inch Newtonian.

I'm really impressed by how solid it all looks and feels, so I'm just waiting for some clear skies here in Roscommon to start testing it out.

During a brief break in the weather last night, I just tried a quick 'Solar-system align' using the Moon as a single point of reference. It seemed to align OK and tracked the Moon quite well in Alt-Az tracking mode. So I was delighted with that.

However, while trying to move the scope around using the 4 direction buttons on the hand controller, the left button did not seem to work. So I'm wondering do I have a problem with the motor, or is it just something dumb I'm doing. I could 'slew' (is that the correct verb?) the scope up, down and to the right, and holding those buttons down caused the rate to speed up nicely. However, when I pressed the left button the scope did not move, apart from the normal tracking at sidereal rate. The left button on the hand controller seems to be working OK, as the scrolling text moved faster when I pressed it, as it does when I press any of the other direction buttons. Also, a number '9' appeared on the LCD display when I pressed it, indicating the slew rate, I think.

Could I have a motor problem? This happened before and after I completed the solar system align. So at no point could I move left using the controller. The manual doesn't mention this problem, nor does Celestron's web site.

I bought it from the German web site www.telescope-service.com/ for 498 euro. Seemed like a great bargain. I hope it's not too good to be true!

If there is a fault the first thing you should do is contact Teleskop Service. I've bought some equipment from them and I've always found them very helpful if I needed to ask questions later.

The first thing that occurs to me is that it may be set to prevent the unit rotating more than 360 degrees (a useful setting when a power or data cable is attached) I disabled that setting on mine once so I know that if you look in the manual it says where to find it on the menu system.

Hi, is there any way to remove say a cover over the motors to have a look? At 9, the slew speed is high, maybe a wire has come loose??, I knoew that the internal wires on these motors are quite fragile...have a try first...
Keith..

Thanks for those suggestions guys. You're very helpful. I've sent an email to the supplier, so we'll see what they come back with. I'll check that menu option and see if I can remove the cover safely as well. Cheers, Liam.

Hi Lphil,
Contact Telescope Services before you remove the cover otherwise you may void any warranty.

Though, I suspect the issue is the backlash settings. Backlash is caused by the play between gears in your drive. Sometimes the gear may have to drive quite a bit in the opposite direction to engage, so try holding down the left button for a minute or so and see if the mount drives then. Back lash can be minimised by ending any manual alignments with the up and right movement arrows.

Also on many Celestron handcontrollers there is an option for adjusting the backlash setting under the utility menu, check the manual for doing this.

Regards

Thanks Martin. I will try pressing the button for around a minute and I'll look at the backlash settings also. The only other limit I could find in the menus is the slew limit, which restricts movement on the Alt (vertical) axis, as far as I understand, so I don't think this is relevant. John, (jhoare), do you remember which setting it was that you changed before? Telescope Service have said that they will get back to me tomorrow. I did a full 3 star align last night and the scope seems to be performing well other than that. It was able to go to several objects for me. But at no time did it move left, just up, down and right.