Celestron NexStar 114GT User Manual download pdf (Page 2)

10.) The encoder constants of the 114GT and 4GT for AZ and ALT are 1059334. The encoder constants of the

60GT and 80GT for AZ and ALT are 0726559. Some NexStars have been shipped with the wrong encoder

constants so please check it. Otherwise you will not achieve proper alignment/Goto/tracking. Please note

selecting the model from the build in list does not work, instead you have to select "Custom" and enter the

constants given above. You must do this even if the correct model is shown in the display.

11.) After a reasonable good initial alignment as stated in 11.) and 3 hours time the alignment was completely

gone. Executing e.g. the command Goto AZ/ALT and giving the values 0/0 would tilt the telescope at least -10°

below the horizon.

12.) The GT version of the small NexStars cannot be controlled by the GuideStar software running on a PC.

Only the HC version does work. The GT version can be controlled by e.g. the Planetarium program running on a

Palm. Celestron works on fixing the GT controller.

13.) The enclosed Software GuideStar 2.1 cannot even be installed on a PC with German Windows. I tried

Windows 95 as well as Windows 2000 without success. The fix is: simply create a directory c:\program files and

copy the original guide star folder in this directory. Actually this is also necessary on US PCs because Guidestar

expects to be installed on C:\program files !

14.) I had some problems when using the Guidestar software together with my new HC hand-controller for my

NexStar114GT:

When comparing the calculated RA/DEC values with other programs I found quite some differences ... finally I

found the root cause: You must not set the Windows PC's country settings to German ! When changing to

English(USA) it seems to work fine. The difference can be seen in the RA/DEC values for a star in the windows

"information" and "change information". In the latter the values are consistent with the values shown by "the

sky" and "planetarium". However if the country settings are set to German these values are wrong converted to

the used RA/DEC values in the window "information".

Sometimes my NexStar114GT (controlled by the program GuideStar 2.1) starts slewing completely crazy until

the tube hits the base (= mechanical limit). Here are my settings:

PC running Windows 2000 with Country-code English(USA)

Location Frankfurt/Germany

Date 02/28/2001 Time 11:37pm Time-Zone 23 Daylight savings off

Altitude limits 0 and 65 Tracking on

Backlash settings AZM+=100, AZM-=100, ALT+=50, ALT-=50

After a dummy alignment indoor (accepting the centred 2 stars in auto alignment) I did a Goto to Sirius. It

should have been at an altitude of approximately 12°. Instead of going there the telescope slews towards

zenith until it hits the mechanical limit (tube hits the base). I did power off the telescope completely and started

from the very beginning: same result ;-(

15.) The RS232 cable for connecting the telescope to the PC is the same for the NexStars 4/5/8/60/80/114. A

very comprehensive description can be found at Mike Swanson’s NexStar Resource Homepage at

http://www.nexstarsite.com/PCControl.htm

16.) Maybe there is a similar effect of faulty memory for the location as in the NexStar 5 or 8: there only the

locations 0-4-8 or 1-5-9 do save the values correct. The reason is an overflow of memory i.e. saved data would

spill in adjacent memory locations. It is not yet verified that this is also the case with the NexStar114GT.

17.) When using the Goto function for a planet only the ALT value can be checked during tracking. The AZM

value is not available when toggling through the information menu.

18.) The NexStar controller does sometimes lock up:

13.01.01 at low outside temperature (-5°C) after approx 15min. during Goto command to new star (trying to

abandon old Goto command). Display shows only "1"s in both lines. (See next item 18.)

10.02.01 outside temperature approx. +5°C. After 2 hours of very good Goto performance (Saturn, Jupiter and

Orion nebula in the FOV of a 15mm EP) it locks. Display shows only the characters "b" in both lines.

19.) At lower temperatures the display reacts very slow. Celestron recommends to use a small heater (chemical

or electrical) attached to the hand controller when using it below the freezing point.

20.) How to do a daytime alignment e.g. for the sun: First do an Auto Align,. You need the date and time for

"finding" the sun. Just align the telescope north and level it horizontally. Then just accept where the scope goes

for the alignment stars and then do a Goto on the sun. You will most likely not hit the sun but should be

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Celestron NexStar 114GT User Manual Page 2

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