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SkySafari Plus for Android gives "Connection Failure" with Celestron NexStar 8 GPS telescope via Bluetooth-to-serial adapter.

SkySafari Plus for Android cannot connect to my NexStar 8 GPS telescope via Bluetooth. The app returns the message "Connection Failure, SkySafari Plus can make a wireless connection to the scope, but the scope is not responding....". However, I _am_ able to control the NexStar GPS via Bluetooth by using the Celestron Handbox app (in insecure mode), so this confirms that my Bluetooth hardware and phone are definitely connecting to the telescope. Bluetooth telescope control also works correctly with my laptop PC.  The NexStar GPS has HC 2.2 and MC 4.06 firmware.

Is there possibly some setting which I need to adjust in order to get SkySafari to talk to the scope? SkySafari is set for Celestron NexStar GPS/SLT/SE. Also, upon trial and error I found that some of the other scope types seem to cause the scope to move briefly, but will not control it properly.

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14 comments

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    Tim Campbell

    It occurs to me that a friend of mine had this issue and it was because he picked the specific scope model instead of picking "Celestron Wi-Fi" as his scope model.

    What "Scope Type" choice did you select in Sky Safari's "Settings" -> (Telescope) "Setup" menu?

     

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    Bill Tschumy

    He is connecting via Bluetooth, not to the Celestron Wi-Fi device.  

    Please try turning off the "Set Time & Location" option if it is on.  Many mounts that have GPS don't like being told where they are.

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    Bill Tschumy

    Also where does the serial cable plug in when using the "Celestron Handbox app".  We require connecting though the bottom of the hand controller (and you need the appropriate NexStar serial cable for that connection).

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    Lemmingfactory

    Hi, thanks for your help!

    Scope type is set for "Celestron NexStar GPS/SLT/SE".  "Set Time & Location" was OFF; I tried turning it ON and it made no difference: no connection.  SkySafari Plus will not connect to the NexStar GPS either before or after it has been aligned via the hand control (I've tried both).  The (Bluetooth) serial cable is plugged into the bottom of the hand control.  Celestron Handbox (Android) and PC (Windows) telescope control both work perfectly via this same serial connection. 

    Do you have any direct confirmation that SkySafari Plus actually works with the NexStar 8 GPS?  One possible factor which comes to mind is that I am using the original hand control with HC 2.2.  Perhaps other NexStar GPS users have had success with newer hand controls with HC 4+ firmware? 

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    Bill Tschumy

    Lemmingfactory,

    I think it is the older firmware in the HC.  This is from our SkyFi page but it should also be on the SkyBT page since the same limitation exists:

    "The baseline requirement for Celestron support in SkySafari 4/5 is Celestron firmware version 4.0 or higher, which is basically everything sold since 2008. This excludes the older Nexstar GT series, the original Celestron Nexstar series and the Celestron Ultima 2000. Note, the GT hand controllers can possibily be replaced with newer versions that will then work with SkySafari 4/5. Consult a Celestron dealer for more information"

    If you can't upgrade the firmware (or HC), you can return the SkyBT to us for a full refund.

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    Lemmingfactory

    Thanks Bill!

    Mike Swanson from the NexStar site suggests that SkySafari Plus should work using BT-to-serial with any handset that is HC 1.6 or higher and has confirmed that an older version of the software worked with his HC 1.6 NexStar 11 GPS.  Are older versions of the software compatible with older hand control versions?  Are there serial commands being used in the recent software which are not present in HC 2.2, rendering it incompatible?  As I said, both Celestron Handbox (Android) and PC (Windows) telescope control work perfectly via Bluetooth.  I can purchase a newer version 4 or 5 Celestron hand control; however, I do not want to do so unless I know for certain that it will work with my NexStar GPS and SkySafari Plus via Bluetooth.  

    Mike Swanson's response:

    "I haven't used SkySafari with my version 1.6/2.2 HCs in a few years (and that scope is thousands of miles away at my son's house) so it is possible they are querying the scope for one of the newest commands, possibly the ones that set the date/time in the hand control though turning off the set date/time option in SkySafari should account for that.  Any of the other new commands are absolutely optional for the core functions of SkySafari (showing where the scope is pointed, directing a GoTo, and manually slewing with the onscreen buttons) so they should be able to easily recognize it is an older HC version and make the connection.

     
    If you do decide you want to purchase a NexStar+ HC, we have determined that the latest firmware will not work with the NexStar GPS mounts but I have some older firmware which will work.
     
    Best regards,
    Mike Swanson"
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    Bill Tschumy

    I can't recall exactly why we dropped support for firmware version < 4.0.  I think it was related to the fact that Celestron started renumbering the firmware when they released their USB StarSense HC.  When we ask for the firmware version we get back something like 1.4 and there appears to be no way to distinguish the new firmware from the old original < 4.0 firmware.  We have consulted with the Celestron engineers about this and they confirm it.

    There is also a possibility that there were a number of communication incompatibilities with the older firmware and we just limited support to > 4.0.

    In either case, we are not likely to reconsider this limitation of > 4.0.  Sorry.

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    Lemmingfactory

    Hi Bill,

    I'm not sure I understand. 

    There are two possible ways to interpret "we no longer support firmware below 4.0".  One is that SkySafari will definitely NOT work at all with HC firmware below 4.0 because lower firmware versions do not have the necessary hardware/software support.  The other is that SkySafari MAY work with lower HC firmware, but we will no longer provide any user support for those using lower firmware.  So which is it?

    I ask because Mike Swanson from the NexStar site seems to suggest that all of the necessary serial telescope control functions are present in HC 2.2 firmware and also that HC 2.2 has been confirmed to work with older versions of SkySafari.  Therefore, unless newer versions of SkySafari are using new serial commands which are _only_ present in HC 4.0 and higher, then the current version of SkySafari should still work with HC 2.2.

    Can you tell me, for certain, if the current version of SkySafari is indeed communicating with the telescope using new serial commands which are only present in HC 4.0 and higher?  If such exclusive HC 4.0 or higher serial commands are not being used by SkySafari, then there seems to be no reason why HC 2.2 should not work.  Moreover, if not, then purchasing a newer HC 4.0 or higher Celestron hand control will likely not fix the connection problem with my NexStar GPS either.

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    Bill Tschumy

    You can interpret it as it *may* work but probably not.

    We had multiple problems with firmware below 4.0 and we were not able to debug it properly because we did not have access to it.  It was a support nightmare and we decided on the 4.0 cutoff.  There was also the later problem that Celestron decided to reset the version numbering with the StarSense USB hand controller and it was not possible to recall figure out which device we were talking to.

    I can't easily tell you whether we use commands only available in 4.0 and higher.  It would take me hours to go through the commands and see when they were introduced.  Sorry.

    I know of no reason this wouldn't be fixed by a new HC.  We have lots of users with NexStar GPS scopes.

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    Lemmingfactory

    Update: Testing shows that SkySafari version 4 controls my NexStar 8 GPS with HC2.2 via Bluetooth/RS-232 without any obvious issues.  Guessing that something changed in the code for version 5 which broke compatibility with the older hand control.  Mike Swanson cannot suggest any good reason why the older firmware should not work correctly with the software as all of the necessary control functions are available.

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    Bill Tschumy

    We have dropped support for firmware below 4.0  I explained our reasons earlier.

     

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    Lemmingfactory

    My update was posted in part to let others know about the issue. I spent hours troubleshooting, thinking it was a hardware problem. However, the hardware works just fine. Celestron NexStar HC2.2 telescope control is limited to SkySafari version 4 and below.

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    Lemmingfactory

    NexStar 8 GPS Bluetooth/RS-232 control now confirmed to be working with SkySafari 5 plus using a newer hand control with 5.22.3280 firmware.

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    Keiron Smith

    Excellent upgrade!

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