positions are available for filters. These will include the standard broadband filters J, H, K, K0, and
8QUIRC User Guide
H+K. In addition there will usually be several narrowband and other special purpose filters installed. Below is a list of the current filters as of the date of this manual. These are subject to change; the most recent configuration can be obtained by using the fi command in the qcdcom program, or by checking the QUIRC WWW homepage. The focus offsets for f/10 and f/31 are also given. The nominal focus positions are 4450 (f/10), 200 (f/31), and with HIPPO they are 5620 (f/10) and 500 (f/31). These are to be used as starting points, the values will shift significantly with temperature, especially at f/31.
Table 2. QUIRC filters, thicknesses and focus offsets
(Focus setting correlates with )
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Setting# | Wheel | Pos | Filter |
| thick (mm) | f/10 | f/31 |
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1 | 1 | 1 | J |
| 3.442 | +60 | +20 |
2 | 1 | 2 | H |
| 1.969 | +10 | +3 |
3 | 1 | 3 | K |
| 2.134 | +10 | +3 |
4 | 1 | 4 | K0 |
| 1.080 | 0 | 0 |
5 | 1 | 6 | H&K dual (1.8 | m) | 2.794 | ||
6 | 1 | 7 | H2BP23 (2.12m) | 0.914 | +2 | +1 | |
7 | 1 | 8 | 2260BP60 (2.260 | m) | 2.794 | ||
8 | 2 | 1 | 1560BP120 (1.56 | m) |
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9 | 2 | 2 | 1710BP120 (1.71 | m) |
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10 | 2 | 3 | 1.989BP50 (1.989m) |
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11 | 2 | 4 | 1.506/60 (1.506 | m) |
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12 | 2 | 6 | 1.107/50 (1.107m) |
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13 | 2 | 7 | BrGamma (2.166 | m) | 0.965 |
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14 | ... | ... | LOWFLUX (0.000 m) |
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| ATLAS Dichroic |
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| IN BEAM (<0:75m) | 4 | |||
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5.1Focusing
The command focus hniis an efficient way to focus QUIRC without taking many separate images. This routine opens the shutter n times between detector readouts to allow recording several focus images on the array. One can then directly compare the image quality at the different focus settings. The program pauses after each shutter open/close to allow the focus setting and position of the star to be changed. The telescope must be moved so that the images of the star do not overlap. See the qcdcom command section below for more details. There are two advantages to using this procedure. The first is that one can avoid the overheads with many different images and array readouts. The second advantage is that all the focus images are in the same image, which makes it easier to compare the different focus settings to choose the best one.