Strange calibration behavior PHD2/EQMOD
Simmons
I seem to be getting very inconsistent calibrations in PHD2 when using EQMOD pulse guiding and I have no idea what in the heck is causing this. The guide speed rates for both DEC and RA shown on calibration vary by A LOT each time I calibrate pointed at DEC 0. The rates are always much higher (5x higher in some cases) than the expected rate based on the EQMOD pulse guide speed setting. I experimented calibrating with 0.5x and 0.9x (7.5 a-s/s and 13.5 a-s/s) speeds in EQMOD and ran several calibrations with various step sizes at DEC 0. The guide speed rates in the calibrations varied pretty wildly from close to expected to almost 100 a-s/s in one case on DEC. The guiding was quite poor with these calibrations. Guide log is attached.
I suspect this is an EQMOD issue because when I switch to ST-4 guiding, the calibrations work fine and guide speeds are consistently read by PHD2 to be close to a 1x sidereal rate. The ST-4 guiding produces much better results than EQMOD pulse guiding currently. In the guide log, I switch to ST-4 at 23:54 and tested calibration at DEC 0. Then slewed to target (Crescent Nebula) at 00:04 and calibrated there.
I'm using a WO 50mm 200FL guide scope and an ASI290mm for guiding on an EQ6-R mount connected by an EQDIR cable to a USB hub.
Has anyone else experienced this? Maybe there is some setting in EQMOD I have wrong? I'm using EQMOD HEQ5/6 V2.00w. I'm considering trying to reset all the EQMOD settings or just do a reinstall to see if that fixes it.
wave...@talktalk.net
Bruce Waddington
Yes, based on your tests, this looks like a problem with the EQMOD configuration. There are many UI controls in the EQMOD setup windows that are death for PHD2 guiding. So you should go through our configuration settings and quadruple-check that everything is set the way we recommend. Anything having to do with backlash compensation or any sort of guide pulse “modulation” needs to be disabled. You also need to be sure there is no cable plugged into the ST-4 guide port of the mount if you’re using EQMOD. If you decide to stick with ST-4 guiding, there is a far better way to do it than using this lame “ASCOM” driver from ZWO. You should choose “On-camera” in PHD2 then set a PHD2 aux-mount connection to EQMOD. This will allow PHD2 to get pointing information from EQMOD while not using the EQMOD pulse-guiding machinery. With that setup, you won’t have to repeat calibrations after every slew, won’t have to make any adjustments after a meridian flip, etc. But I think you should be able to get the EQMOD configuration sorted out, many hundreds of people are using it effectively.
Good luck,
Bruce
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