Each year, certain changes need to be edited into the Forth TCS source code. This is an explanation of what needs to be done for the IRTF. For the 88", see the UHTF section of my computer log book.

A set of Year 2000 diskettes (Version 2000-A) has already been prepared and is in the TCS room. Someone should make backup copies. That version uses the XTERM type of TCS monitor display. To create a version of Year 200 diskettes that uses the old TV monitors, you will have to use the Forth editor to edit the 1999 version (1999-A) as described here. (I suggest you review the operation of the editor before proceeding further.)

The apparent sidereal time for the target year at January 0 from the Astronomical Almanac, Section B, Page 8, the table of sidereal times at Greenwich.

These are absolute block numbers in the system source section of the Drive 0 diskette. They are accessed by typing SYS-EDIT before starting to edit. Don't forget to type HEADING 22 AUG 1999 (whatever the current date is) before starting to edit.

Note the number on line 13 associated with JAN0, which is the modified Julian day number for January 0 of the current year. If the current year isn't a leap year, add 365 to that number to make it JAN0 of the target year and edit it into the line, also changing the year that the day number refers to in the comment on the same line.

This block is kind of confusing. Pay attention. Comment symbols are ( parentheses) with a mandatory space after the open paren.

Note line 4. That is a comment line, to tell you where to put the open paren for leap years.

On line 5, place an open paren at character position 8 (starting with 0). Note that there is a space after the line number, which is not part of the block text and is not counted. The close paren at the end of the line finishes the comment.

Remove any open paren at or near character position 8 on line 5.

The text in quotes in this block is displayed whenever the TCS is booted. It is for information only and doesn't affect the operation of the telescope. What we need to do here is change the version number for convenience in identifying the running version.

On or near line 5 is the text **** 1996-C2 **** or its equivalent for the diskette you are working with. Change the version number to the correct year and letter. This is fixed format, so don't move it or expand it beyond its current size. You can replace characters with blanks. This particular field is used whenever the version number is displayed by whatever TCS application.

The text in quotes in the rest of the block is reminders to telescope operators or anybody booting the system. Feel free to modify, remove, or add to the text. The guidelines are that there must be a space after the opening quote. The quotes work on single lines only. Use CR outside the quotes to make a newline. Anything after the ;S symbol is ignored by Forth.

You can test your work on this block by exiting the editor and typing PROG 221 LOAD . The boot startup messages will display.

There is only one source file block we need to modify. In UTILS type EDIT DATA.TCS . In Block 30, make these changes:

Line 3: You will see something like 6:35:48.75 D.SS

Change the number to the apparent sidereal time for the target year at January 0 from the Astronomical Almanac, Section B, Page 8, the table of sidereal times at Greenwich. This number is fixed format. Use leading or trailing zeros as necessary. Round the fractional seconds in the table to 2 digits. Also change the year in the comment further over on the line.

Line 5: The default epoch, which is the half-year point for the target year. Change it as necessary.