Lick Shane 120 Pointing, Crashing Galaxies, and New Vulcan Stars

by Peggy Bernard


One of the TACO's had asked if the Lick Shane 120" used TP Point pointing software. Well the answer is no. The Shane uses custom software written by a member of the staff. Apparently, there just are too many custom variables to use a "off-the -shelf" program.

I've personally seen the Shane in use. The astronomer calls out the target of interest, then the telescope tech enters the target name into the targeting computer. The targeting computer calculates out the flexure, the worm gear variables, the atmospheric pressure error (yeah, the mirror is so big they have to compensate for this), dome slit position, and other variables I'm not privy to. Then the computer reports on screen the targets corrected RA and Dec. Then the tech takes this information and moves the telescope to these corrected coordinates using separate RA and Dec position controllers. As far as auto tracking, I'm not sure how they accomplish that but it appears to be similar in concept to that we are using over in Vulcan (CCD pixel counting feedback loops).

By the way, last nights (9/5) Shane work involved optically looking at radio galaxy fields. The goal was to find additional galaxies that were "traveling through" local groups of galaxies. I'd guess that these "travelers" were moving at higher speeds than the groups. Anyway, can't say much more than that.

My Vulcan work was exciting as we moved to a new star field. Good thing I arrived on site early Saturday evening as I needed all of the extra time to dry run all the new coordinates and scripts. Our new target star is (1 Perseus) just below Cassiopeia. Our reference star is Shedir in Cassiopeia. I had to re-verify the target coordinates twice and make a phone call down the hill to a co-observer because the MAXIM DL overlay for the new target didn't exactly match what I was seeing. As it turns out, the overlay shows two stars near 1 Perseus that do not show at all on MAXIM DL. I verified the correct star field in both my finder scope and with the "V" CCD images so everything turned out ok.

The 1 Perseus target has some really strange tracking as compared to the previous Cygnus target. Cygnus simply started in the northeast and traveled to the west, requiring only two major dome slit alignments and some very minor tweaks during the night. Well the 1 Perseus field results in the telescope doing a "corkscrew" pattern all night long. Since the slit isn't real wide, the scope movement required me to make adjustments about every 96 minutes, else the scope would image the inside of the dome! Needless to say, I was very busy all night long tending to my "baby" in the dome. By the time I get used to all of this, we'll be moving to another field.

The MIRA images of the star field display the double cluster in Perseus very nicely and I can clearly see the "catspaw" in the 884X component. This might give you a clue - the Vulcan Camera field of view is around 10X10 degrees. In trying to find ET's home planet, we are looking at a huge chunk of the sky. My next shift, I'll have to check to see if M76 shows in the MIRA field.

Well enough for now. Hope this is interesting to you all.