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Filter changes

Look on the white board and in the WWW filter page ( quality/filter/newfiltdoc.html) to see if the filters you need are already loaded in the JAG, or if they are currently somewhere else. If your science requires a filter change then your Support Astronomer will load up the wheel for you. If necessary, up to three wheels can be loaded, each with 6 filters.

If the JAG filter wheel contents have been changed, you will have to update the corresponding information in the ICS. The ICS stores for each filter its name, type (Harris/interference/etc.), unique ID (serial number), thickness, focus offset, and its position in the wheel. The WWW filter page lists all the necessary information. The focus offset introduced by the main filters goes as 0.03mm focus change per 1mm filter thickness.

Figure 5: Focus offset versus thickness of the science filters. These offsets are taken into account when pressing the CALCULATE button in the CHANGEJAG command

Additionally, the ICS stores for each JAG filter the names of the filters that need to be put into the autoguider light path, in order for it to remain in focus when switching from one science filter to another. The two autoguider filters that are in the beam should have roughly the same combined thickness as that of the main filter, such that the autoguider is in focus while the detector is in focus.

To update the filter information in the ICS you type

         SYS> changejag
which will pop up a small window that allows you to edit the contents of up to five filter wheels, and to choose which wheel definition is active. To make a new wheel definition a separate window will pop up. For each filter you will have to supply its name, type, unique ID (serial number), thickness, and its position in the wheel. The focus offset and the corresponding autoguider filters will be calculated when you click the `CALCULATE' button. Don't forget to click `SAVE CHANGES' before you exit this editing routine. Then choose which wheel is active, click `SAVE CHANGES' on the small pop-up window and click `EXIT'.

Note: All filter movements across the site should be logged into the ING filter database by your Support Astronomer, using the FILTER program on lpss1.

Always issue the command

         SYS> zeroset mainfilt
after the JAG door to the filter wheel has been opened and closed (even when the filter wheel has not been touched).

Table 3: Available autoguider filters
Autoguider ND filters                    Autoguider Colour filters
no. filter thickness (mm) glass type                    no. filter thickness (mm) glass type
1 clear 1.0 UBK7                    1 clear 1.0 UBK7
2 ND1 1.0 NG4                    2 UV 1.0 UG1
3 C5 5.0 UBK7                    3 Blue 1.0 BG38
4 ND5 5.0 NG4                    4 Red 1.0 RG610
5 C8 8.0 UBK7                    5 clear 2.0 UBK7
6 ND8 8.0 NG4                    6 UV 2.0 UG1
7 C11 11.0 UBK7                    7 Blue 2.0 BG38
8 ND11 11.0 IG4                    8 Red 2.0 RG610

next up previous contents
Next: Mounting CCD filters Up: Afternoon activities Previous: Closing and restarting the