Pointing/Setting Woes

Thursday, November 5, 2015 2:33 PM

Problem(s) Encountered:

Telescope seems to have a problem with pointing. Tried many ways to fix this, including pointing to bright sources, zeroing the zenith many times, etc. Finally had 2.4 meter observer come look at the tilt meter (I am observing remotely). Worked with 2.4 meter scientist for an hour fixing tilt meter readings, zeroing the zenith, and using the paddle to try to find where those guide stars could possibly be. JSkyCalc and TCS GUI have slightly different readings for positions, making my issues tonight sound very similar to the report filed on 10/10/2015. I have been unsuccessful in recognizing a single star field. System may need restart /reboot of some sort.


Found the TCS indicating that the telescope was at zenith (HA=0 Dec=31:57:12) but the tilt sensors were way off in declination.  They read -002,-131 when they should nominally be at -003,-008 when at zenith.  Moving the telescope to the zenith by zeroing the deviations seen in the tilt sensors gave values around HA=00:00:8.0 Dec=32:59:02.7, more than a degree off in declination.  I homed all axes, which brought the tilt sensors to reasonable values, but still the coordinates indicated that declination was closer to 33 than 32.  Performing a “point ha=0 dec=31:57:12 nodome” brought the tilt sensors back to roughly -002,-130.  

I then tried power-cycling the TCS and homing all motors, but I still got the deviation between coordinates and tilt sensors.  It might be worth noting that I did not shutdown/restart any of the telescope servers.

Next I simply pointed the telescope to zenith by the tilt sensor values, then drove east a ways and started tracking.  As I tracked through the nominal tilt sensor values (-003,-008), I used the zero command (zero ra=current sidereal time dec=31:57:12 equinox 2015.837) to tell the telescope it was at zenith.  This brought the coordinates into correspondence with the tilt sensors.  

Interestingly, after doing the zero command, I was able to home RA and Dec axes and get the values displayed for HA and Dec to correspond with the tilt sensors.

I am not sure what got the telescope into this state.  It is one of the unfortunate possibilities that leads to an almost unsolvable issue for a remote observer as there is [currently] no way for them to see the tilt sensors.  Hopefully tonight will go more smoothly.  I’d recommend after finding a bright star, that a new zero command be issued on that star.

Incidentally, I can set up a webcam for monitoring the tilt sensors remotely, if requested.