25 replies to this topic

[TheMagusMX]

I just rescued an old Nexstar 4GT and want to update the control but I'm completely new to this scope. Any ideas on upgrading this control?

 

Regards

 

TheMagusMX

[photoracer18]

Some can and some can't be upgraded. Original Nexstar like the 5 can't use a newer controller. I think the Ones that end in "i" like the Nexstar 5i can be but I can't confirm it. I am pretty sure everything newer can be upgraded to the Nexstar + controller. There is a person the sells those on here regularly and he can also reprogram them (Alt-Az goto scopes use a different program loaded than the GEM go-to mounts). They usually have a sticker on them telling which program is installed. I know the 80GT and the 4SE can use the "+" controller as I have both of those.

[TheMagusMX]

Thanks.

 

The 4GT I have must be really old. The hand control had wrong constants for both altitude and azimuth. There are some tips in http://www.dd1us.de/...rs tips 1_0.pdf and it seems that the early version of the HC is full of bugs. Just corrected the constants, there's a long way to go.

 

In a few minutes I'll take the scope to my backyard for a better collimation (originally had the screws completely loose, so my first collimation was made just carefully measuring the position of the primary baffle). Will report my experience later.

 

Good skies

 

TheMagusMX

[Michael_Swanson]

Hi,

 

Start here at my website for help with that "original" NexStar GT hand control:

https://www.nexstars...sGTOriginal.htm

 

If everything seems mechanically sound after you enter the correct encoder settings for that mount:

https://www.nexstars.../GTModelSet.htm

(which would be 1059334), then the first article at that first link explains that you can greatly improve the performance by picking up a version 4 hand control and loading the GT 4.03 or GT 4.04 firmware.

 

Best regards,
Mike Swanson
Author of "The NexStar User's Guide II"
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
https://www.NexStarSite.com

[TheMagusMX]

Thanks for the links, very useful. I checked and have the original HC, full of bugs. Already ordered a version 4.04 HC, should be here late this month.

 

To check the encoder constants I followed these steps:

 

1.- Point to a well defined point in earth. Tracking should be off and it is better to use a cross hair eyepiece

2.- Get the Azimuth and write it in a paper

3.- Enter the go Alt-Az to move the scope 90 degrees to the right four times, the last azimuth should be the same found in step 2

4.- If you have the right constant you should see the original point again exactly in the cross hairs, otherwise:

5.- Using the arrows put the original point in the cross hairs. The last button should be the right one to have a constant backlash.

6.- Get this last Azimuth and write it in a paper

7.- Calculate the correction to the original constant: new constant= old constant * (360+last azimuth-original azimuth)/360

 

I repeated the procedure several times and found a difference of 5.5' almost always. Instead of the original 1059334 constant used 1059604 and worked very well. It looks like some missing pulses. The rest of the night the GOTO function worked well putting the object in the telescope eyepiece.

 

Checking the RA and Dec of the different stars found some differences against the ones reported by the Star Walk II in my phone. Could this be a precession issue?

 

Clear skies

 

TheMagusMX

[Michael_Swanson]

Yes, almost certainly precession as the original HC used static J2000 coordinates.

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com

[TheMagusMX]

Thanks Mike, you are the best expert in nexstar telescopes.

 

The 4GT I rescued was in really bad shape. The star diagonal support was broken in three pieces (I made a replacement in a 3D printer), two of the collimation screws were removed, one of the encoder sensors was not working (replaced it with one taken from an old mouse), the battery holder was broken, etc. etc. One problem that I have not fixed is the missing baffle in the secondary mirror. There was a lot of glue hard to remove, only methyl-ethyl-ketone could dissolve it. I'm planning to make a replacement in the 3D printer but have no information about it. Do you have any pictures that show the baffle?

 

Best regards

 

Bill

[Michael_Swanson]

Hi Bill,

 

I just had a look through my archives and I do not have a picture of the back side of the meniscus :-(

 

Best regards,
Mike Swanson
Author of "The NexStar User's Guide II"
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
https://www.NexStarSite.com

[Geo.]

Well, if you are this handy, there's always this project.

 

 

This converts the encoders to work with a NXW435 motor board and thus the Plus and Ver. 4 hand controllers.

[Michael_Swanson]

Thanks Mike, you are the best expert in nexstar telescopes.

 

The 4GT I rescued was in really bad shape. The star diagonal support was broken in three pieces (I made a replacement in a 3D printer), two of the collimation screws were removed, one of the encoder sensors was not working (replaced it with one taken from an old mouse), the battery holder was broken, etc. etc. One problem that I have not fixed is the missing baffle in the secondary mirror. There was a lot of glue hard to remove, only methyl-ethyl-ketone could dissolve it. I'm planning to make a replacement in the 3D printer but have no information about it. Do you have any pictures that show the baffle?

 

Best regards

 

Bill

Hi Bill,

 

This at least gives you an idea of the shape and general size:

https://www.cloudyni...re-nexstar-4gt/

 

Best regards,
Mike Swanson
Author of "The NexStar User's Guide II"
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
https://www.NexStarSite.com

[TheMagusMX]

Thanks again Mike. The baffle I designed is 25 mm deep with an internal diameter of 28 mm in the meniscus side an 38 mm in the other side. The secondary spot is 30mm in diameter so the baffle will overlap 1 mm to avoid any light going between the secondary and the baffle. Will report the result. If anyone wants to 3D print this baffle I'll be glad to share the file.

 

Ragards

 

Bill

[TheMagusMX]

The telescope was tested yesterday night and made some Moon pictures with a Canon SL3 replacing the eyepiece (virtual image). As you can see there is small detail in this picture (good collimation) and has a good contrast (the secondary baffle is working well).

 

 

I received this scope for free. The owner took it to local (Mexico City) telescope repair shops but none could or wanted to repair it.Repairing this scope took me many hours but the end result is a nice little telescope.

[TheMagusMX]

Collimation of 4GT telescopes in annoying. You hace to remove the back cover and the diagonal support (there is a screw under the guiding rod), make a small correction, assemble all again and repeat this cycle over and over. For this reason I designed and made in a 3D printer an eyepiece holder that allows you to make adjustments without assembling and disassembling the scope.

I'll be happy to share the file needed to 3D print this piece.

[TheMagusMX]

Also designed made a new secondary baffle.

If someone need to make one I'll share the 3D printer file.

 

Regards

 

Bill

[Michael_Swanson]

Very nice work Bill!  Congratulations on resurrecting a baby NexStar :-) 

 

Best regards,
Mike Swanson
Author of "The NexStar User's Guide II"
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
https://www.NexStarSite.com

[MickTaurus]

Wow Bill, well done to quote Ian Dury and the Blockheads "There Ain’t Half Been Some Clever ****".

 

https://youtu.be/cY2GmYE_piE

[TheMagusMX]

I received the version 4.04 control and used it for a few nights. Usually in winter we have many clear nights, but this year is an exception. Anyway, this control is cool. The easiest alignment requires just to point to any three bright stars. Then it can find objects very well. If you have the version 1 control, should replace it with the version 4.04, it's great.

 

Regards

 

Bill

[Michael_Swanson]

Yep, a version 4 hand control makes a world of difference on a GT mount.  Besides having most of the cool new features of the more recent models, it improves tracking dramatically.  

 

For those coming from an older version of the hand control, you might find my "hand control version 4 user's guide" useful.  It describes all the newer features and is available as a free download here:

https://www.nexstars...com/Manuals.htm

 

Best regards,
Mike Swanson
https://www.NexStarSite.com

[MitchK]

For general info, I just completed upgrading an older costco GT mount (pre 2012) to a later GT mount that uses a nexstar+ hand control. The mod entails replacing the old board with a new style board, then removing one wire (yellow pin 4) from the hand control board, removing the wires from the hand control board plug and re-inserting them in the correct order. 

 

This allows the old GT mount to work with the celestron GPS module and the skyportal wifi. Nice to be able to control the mount via wifi from a mobile device. The old GT mount can not use those accessories. It still will not work with CPWI, but it works with other software ( skyportal, skysafari)

 

I'll post more info on the mod in the next few days. 

 

Mitch

[TheMagusMX]

Looks interesting. Hope you can give us more information.

 

Bill

[Michael_Swanson]

Looks interesting. Hope you can give us more information.

 

Bill

Here you go Bill; Mitch got to it the next day in a different post:

https://www.cloudyni...tar-controller/

[Sensei1956]

There is so much information on this scope!  How do I know what hand unit I have and if I can update it?

[Michael_Swanson]

There is so much information on this scope!  How do I know what hand unit I have and if I can update it?

Hi,

 

Are you saying you know you have a NexStar 4GT?  If so, on this page of my website:

https://www.nexstars...om/Firmware.htm

Click the link for "NexStar GT, Orion StarSeeker and Tasco StarGuide".  Scroll to the bottom to refer to the section on "Determining Versions".  Feel free to report back here with the results.

 

Best regards,
Mike Swanson
https://www.NexStarSite.com

[Sensei1956]

Mike, thank you for your response.  I have been to your page and read many pages of information.  Thank you for your time.

The HC version is 101.0

[Geo.]

That was the early Nexstar GT HBX. There's someone selling Ver. 4 HBXs on eBay for a nonce. Get two!

https://rover.ebay.c...l=loc,osub=osub