Nexstar GT mount problems

[sojourneyer]

i am in an unusual conundrum. 

My mount is from a Nexstar 90 GT scope but the hand controller says ADVANCED GT which means it came most likely from Celestron's Advanced VX line of telescopes.

I purchased the controller because there was none when I purchased the used scope, and I did not know that they are all different. 

Whenever I try to align after finding a star I press "enter" and the scope raises to almost Zenith..

Is there a way you can get around this such as clearing out the memory, etc?

Any input is appreciated..

 

thanks

[Cosmic Geoff]

It's possible that if you reprogram the handset with software that's compatible with the 90 GT, it will then work.   This may not be a task for the faint-hearted, as you may have to buy cables or USB-serial adapter, download and install various bits of software, and then download the software for the handset. 

Last time I did this, I updated the software on a Nexstar* (not Nexstar+)  for a Celestron C8 SE.  On the first attempt, I got it wrong and downloaded the latest software for an equatorial mount (as I presently saw on the handset), and had to start the update process over and select the right software (for alt-azimuth).  

I also had to hunt around for an older installer, as the preferred one, Celestron's CFM, wouldn't work for some reason.

If you visit nexstarsite.com, you may be able to figure out whether your mount and handset are potentially compatible. 

[sojourneyer]

I found out that the version is

HC:  GEM 5.31.9102

MC: 5.21  5.21

 

[sojourneyer]

they definitely are not compatible.  I wonder if I could change the firmware on the controller.

[Cosmic Geoff]

I see that the 90GT is an alt-azimuth mount (it looks like an earlier version of the SLT mount), and the AVX is an equatorial mount, so that combination definitely won't work.   My point remains, that it may be possible to reprogram the handset with alt-azimuth firmware that works with the 90GT.   Is the handset a Nexstar* (older) or a Nexstar+ ?

I found a quick setup manual for the 90GT online and it seems to show the Nexstar+ handset, but that doesn't mean a Nexstar* handset wouldn't work.

As an aside, I have found that I have three different types of Celestron handset, and I have three different Celestron mounts, and I can swap the handsets around at will, BUT all are alt-azimuth. 

[sojourneyer]

Thanks .

I know the handset came from the Advanced VX line of scopes which are all equatorial mounts..   ..... sadly.

Actually the GT mounts came after the SLT was first introduced. The difference is that the GT does not have an on/off switch, no aux port and the batteries go into an external pouch rather than the plastic mount hub.  The actual motor, etc is the same.

My handset is Nexstar+

I just worry that the handset will not accept 4.0 firmware and then I have a useless handset as well.   One thing i can do is slew the mount with that handset and manually find objects but the software to find objects does not work.

 

 

[Cosmic Geoff]

I should think it likely that your handset would be compatible with the 90GT if reprogrammed.   It's a Nexstar+ and apparently that's what the GT is sold with. 

If you look on nexstarsite.com, it says that if your GT mount has version 5 firmware, then it's the later model and should be used with a Nexstar+ handset, and the handset firmware is version 5 as used for the 4/5 SE mount.

I don't know if you are a technically adept person.  If the detail of reprogramming the handset is over your head, your best course would be to sell the mount and handset on, and start again.