18 October 1999

This document is also at: http://www.ctio.noao.edu/telescopes/opteng/sideportseeing.html

An RCA camera (image intensifier tube) is installed permanently on the side of the rotator. It must be ready to use during ALL F/8 nights. The light is sent to that camera by putting the rotator mirror #3 IN and another tiny flat mirror OUT (switch is on the rack on the right side of the TCP sun).

• Typical telescope focus for the measurement is 172000 (at 14°C). WRITE DOWN the current focus used by the instrument before refocusing for the seeing camera.
• Use a mag. 3-5 star.
• The autoguider must be disabled to do the measurement.
• Make sure the switch on the black rack in the computer room is on the "seeing PC" position.
• Type "cd seeing" on the PC (same display and keyboard used by Iman), which will bring you to the start up screen and menu (use the ESC key to return to menu or quit)
• Press F10 to see the setup parameters and modify the entries so that:

- F2 scale is 0.13

- F4, F5 and F7 say no (toggle the F# key several times to enter the right field value)

- the rest is unchanged from the default values

- ESC to return to main menu

• Press key F2 "Select Star Manually''. Use the arrow keys to approximately center the box on the star (note that the "+'' key toggles between big steps and little steps for each use of an arrow key). Then press the "!'' key to automatically center the box, and ESC to return to the main menu.
• Press key F3 "Focus Aid''. You will see graphs showing FWHM, Star Peak, and Contrast, being updated in real time. If the scales on the graph are wrong, use the F10 key to change them.
• Adjust the TV signal level (gain, etc) so that the Star Peak level is clearly below saturation. Saturation appears to occur at 256 for the RCA camera (as shown in the F3 Focus Aid mode).
• Adjust the focus carefully by looking at the video display. In the Focus Aid, you need to make the FWHM as small as possible while making Star Peak and Contrast as large as possible. In practice, the FWHM graph is not very useful except that it becomes very noisy when you are way out of focus. The Star Peak is useful in good observing conditions.
• BEWARE: If the image is either out of focus or saturated, the result is not meaningful!
• Once you think the focus is as good as you can get it, press ESC to return to the main menu, then F9 to "Measure Seeing''. The computer will store a sequence of 256 frames, which takes about 17 sec, and then will analyze the frames. For 32 subsamples of 8 frames each, and also for the full sample of 256 frames, it will find the FWHM and the rms image motions in x (Sx) and y (Sy). When the analysis is over, the PC display should bring a new screen showing (if that doesn't happen, then quit the program and restart it):

"Whole sample RMS in x and y: Sx... Sy..."

"Whole sample FWHM: ..."

+ several lines showing the details of the calculations in each sub-list

Once observations are underway again, please fill in the log book: Date, Time, Airmass, Dome Azimuth, FWHM, Sx, Sy and appropriate comments. Use the "seeing monitor" pull down menu of the TCS workspace to log the data. Fill in with the "Whole sample" values.