CPWI and Sharpcap RA/Dec Do Not Match
Posted: Fri Nov 15, 2019 7:14 pm
I just got a CGX-L mount and have been trying out the Celestron/PlaneWave CPWI mount control software. I also use Sharpcap to control my camera and collect images. Since SC can also connect to the mount and control the mount GoTo, Polar alignment and Plate solve I have connected SC to the mount through the CPWI software without an issue using the CPWI driver under Hardware/Mounts in SC. I can move the mount with either the CPWI or SC Up/Down/Left/Right buttons without any problem.
What puzzles me is that CPWI and SC both display the mount's Alt/Az and RA/Dec coordinates but while the Alt/Az coordinates are exactly identical between CPWI and SC, the RA/Dec coordinates are consistently off by ~30min in RA and ~7deg in Dec. It doesn't matter if I connect CPWI to the mount through the HC or the mount USB connection, the offset is there and similar in size. This offset is pretty repeatable if I shut down both SW and re-start them and if I shut down the PC and re-start everything including the mount. CPWI indicates the RA/Dec are J2000 coordinates. My understanding is that SC gets the coordinates from the Ascom driver, in this case CPWI, so I cannot understand why they would not agree exactly. I used an on-line calculator to convert the CPWI J2000 coordinates to JNow. In that case the RA/Dec are now nearly identical.
Does SC display the RA/Dec in RNow or J2000?
I have attached screen captures showing what CPWI and SC report first for the connection through the HC and second for the connection through the mount USB port.
Regards,
Curtis
What puzzles me is that CPWI and SC both display the mount's Alt/Az and RA/Dec coordinates but while the Alt/Az coordinates are exactly identical between CPWI and SC, the RA/Dec coordinates are consistently off by ~30min in RA and ~7deg in Dec. It doesn't matter if I connect CPWI to the mount through the HC or the mount USB connection, the offset is there and similar in size. This offset is pretty repeatable if I shut down both SW and re-start them and if I shut down the PC and re-start everything including the mount. CPWI indicates the RA/Dec are J2000 coordinates. My understanding is that SC gets the coordinates from the Ascom driver, in this case CPWI, so I cannot understand why they would not agree exactly. I used an on-line calculator to convert the CPWI J2000 coordinates to JNow. In that case the RA/Dec are now nearly identical.
Does SC display the RA/Dec in RNow or J2000?
I have attached screen captures showing what CPWI and SC report first for the connection through the HC and second for the connection through the mount USB port.
Regards,
Curtis