Three_C

Main Menu - Telescope Control - Telescope Functions II

Telescope Functions II is the second list of ten telescope control functions that three_c can perform. A horizontal menu will appear that looks like the following:

F1-HP

F2-IL

F3-ST

F4-SOP

F5-PLT

F6-SYS

F7-NG

F8-SC

F9-PC

F10-DC

The first item is a help screen, which simply translates the mnemonics of the menu into phrases that explain the functions. They are:

The hot keys for the Telescope Function menus are the function keys.

Integration Length (F2) permits the user to specify integration times for the three channels. Input is in seconds, is two digits long (so enter 05 for 5 seconds), and has a maximum value of 60. All channels use the same integration length. The reduction program uses counts/sec for all of its calculations. The general rule of thumb is that a reading will have an internal precision of 1% if the total counts of sky+star exceed those of the sky only by at least 10,000 counts.

Set Time (F3) uses the same procedure described above for setting the time from either the Most Accurate Clock or manually.

Select Observing Program (F4) allows the user to select one of the built-in filter sequences or create a customized program. A window appears containing the following:

Observing Programs (Filter-Object)

A. Doubled - One Pass

VVBBUU:

B. Single - Continuous

VBU

C. Single - One Pass

VBU:

D. User Defined

Enter Choice:

Option A is currently the default. Two types of programs are available. Options A and C are single pass programs, i.e., the steps are executed and then the user is asked to select a new group. Option B is an example of a looping program, i.e., one that repeats the same steps continuously. Option D allows the user to build a customized observing program. Character checking is done so that only valid filter codes are accepted. In order to make the customized program single pass, make the last filter a colon. Omit the colon for a looping program.

Change Catalogs (F5) will provide an on screen plot of the accumulated data. The data file for the current group is read and graphs are presented for each color. Different symbols and colors are used for the three channels. A key press moves to the next color. Of course, if no data have been collected or the I/O channel to the hard drive has not been opened, this option will fail.

System Changes (F6) will bring up the following window.

The entries are:

(A) The telescope tracking frequency in hertz.

(B) The ratio of the gear ratios on the two telescope axes.

(C) The motor acceleration in microsteps/sec².

(D) The motor rate acquired with the paddle in the slew position or the top speed during automatic moves in microsteps/sec.

(E) The motor rate acquired with the paddle in the set position in mircosteps/sec.

(F) The motor rate acquired with the paddle in the guide position in mircosteps/sec.

(G) Automatic moves to the east are programmed to overdrive and then come back west to compensate for the backlash in the worm gear. This item is the string segment that accomplishes the backlash correction. The numerical value is the number of motor steps issued for the correction.

Changes are accomplished by using the cursor keys or ENTER to get to the item of interest. You must then move to the last entry and press ENTER for the change to take effect. Since all automatic moves in both axes rely on the track rate, changing the track rate will produce a compensating change in the declination factor. The declination factor, on the other hand, only affects moves in the declination axis. Changing the basic rates and acceleration is not recommended unless you have experience with the Superior cards or similar stepping motor controllers.

The backlash compensation can be adjusted by moving between two catalog stars in close proximity to each other. With the more easterly star centered, make the west move to the other. Since no backlash correction is required here, the new star should be in the center of the field. If necessary, adjust the track rate. The move to the east will incorporate the backlash compensation, which can now be adjusted for precision moves.

Next Group (F7) will bring up the selection set window that will allow you to select a new star. A group is composed of the variable star, the comparison star, and a sky position. Once again, only stars that have altitudes of at least 20° will be on this list. The telescope will move to the variable star position of the group (the central channel). A pop-up window will appear that gives you a choice as to whether the offset stages are to be moved. The offset stage positions are computed by the RA and DEC of the comparison star and sky and the known geometry of the photometer. When selecting these objects, consult the section on catalog generation for criteria.

The last three items in the Telescope Functions II group control I/O devices. They are Screen Control (F8), Disk Control (F9), and Printer Control (F10). Each is a simple toggle controlled by pressing the appropriate key (C for screen, D for disk, or P for printer).