Commands are entered in OMICS window. Each step of this new system is approximately 1/4 step of the old focus system; the new focus range is 0 to 6446. There are no decimal steps.
| 1) | fp NNNN | Focus position, where NNNN is a four digit number. |
| Example: | fp 1664 | |
| fp is used to to set an absolute position for the focus. The parameter is a string containing a number with up to 4 digits. Any incorrect input causes fp to abort and returns a warning message to the user. | ||
| 2) | fpo +/-NNNN | Focus position offset |
| Example: | fpo +20 | |
| fpo is used to increment or decrement the absolute focus position. The parameter is a string which MUST have a leading '+' or '-' in order to be parsed, followed immediately by a number (up to 4 digits) which specifies the offset. If there is no leading sign, an error message tells the user the correct syntax and aborts the command, any other bad input causes the same message as in fp. | ||
| 3) | fp+ | Preset positive focus increment |
| fp- | Preset negative focus increment | |
| fp+ and fp- move the focus an increment of 50 steps out or in respectively. | ||
| 4) | fpz | Focus position zero |
| fpz sets the focus position to zero. | ||
| 5) | Nominal focus positions: | |
| CCD 2000 | 1660 (see No. 6 below) | |
| Grism | 2400 | |
| Photoelectric photometer | ||
| White Spectrograph | ||
| 6) | Change of focus with temperature | |
| Focus position increases with temperature approximately 5.3 steps per degree Celsius. An approximate starting setting is a focus of 1664 at a mirror temperature of 12 C for the standard 4mm thick filters. | ||
| 7) | Focus change for filters of different thickness | |
| For filters thicker than the standard 4mm UBVRI filters, such as the narrow band filters, decrease the focus setting by about 20 steps. | ||