Blank Fields for LBC Twilight Sky Flats
The LBC blank fields on this page are based on fields chosen by the Nordic Optical Telescope (NOT). Due to the NOT’s relatively small field of view, in many cases their fields contained a few bright stars within the LBC’s field of view (the full LBC field of view is 23′ x 25′ vs. the NOT’s 5′ x 5′). Furthermore, the LBC sky flat script dithers by up to ±2.5′ to assist in removing bright, possibly defocused stars. To alleviate this, the blank sky coordinates have been adjusted to contain as little bright stars as possible. All of these blank fields are devoid of stars brighter than R=10 mag, including within the maximum 2.5′ dither in each direction. For stars fainter than R=10 mag, we denote the number of stars with R magnitudes between 10 to 11, and 11 to 12. There are a total of 27 blank fields covering all RA ranges to facilitate calibration data to be taken during any time of the year and at any time in the night.
This plot shows the RA distribution (x-axis) as well as the elevation (y-axis) for each of the blank fields. Since the relationship between hour angle, LST, and RA is given by
HA = LST – RA
blank fields with RAs greater than the current LST will be rising and hence in the east (e.g., negative HA), and vice versa. As an example, if the current LST is 1700 and a setting field (west) is desired to point away from the rising Sun, selecting a blank field around RA~14-15 would work. Note we do not recommend observing with the LBCs above an elevation of 85 deg. as rotational trailing will be much more apparent.
See below for the LBC footprint overlaid on a DSS image for each blank field coordinate. Click the image to expand the view and right click to save the image if desired. These images cover a 60′ x 60′ field of view and the y-axis of the LBC field of view points to the North. The red circles in each image indicate the stars with R magnitudes between 10 and 12.
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DSS image (60’x60′) with LBC focal plane overlay. PA=0, N-E along the LBC focal plane vertical and horizontal axes. |
Field | RA | DEC | N stars brighter between mag. range |
 |
Blank 00+07 | 00:24:00 | +08:05:00 |
10 < mR < 11: 0 11 < mR < 12: 1 |
 |
Blank 01+02 | 01:47:20 | +02:24:00 |
10 < mR < 11: 2 11 < mR < 12: 2 |
 |
Blank 02+13 | 02:20:40 | +13:12:00 |
10 < mR < 11: 1 11 < mR < 12: 1 |
 |
Blank 03+31 | 03:33:20 | +31:03:00 |
10 < mR < 11: 1 11 < mR < 12: 2 |
 |
Blank 04+25 | 04:48:13 | +25:29:00 |
10 < mR < 11: 0 11 < mR < 12: 0 |
 |
Blank 05-03 | 05:45:15 | -03:40:00 |
10 < mR < 11: 1 11 < mR < 12: 5 |
 |
Blank 05+52 | 05:29:15 | +52:40:00 |
10 < mR < 11: 5 11 < mR < 12: 5 |
 |
Blank 06+42 | 06:47:20 | +42:48:00 |
10 < mR < 11: 6 11 < mR < 12: 4 |
 |
Blank 07+64 | 07:38:33 | +64:08:00 |
10 < mR < 11: 1 11 < mR < 12: 5 |
 |
Blank 08+38 | 08:37:50 | +38:43:00 |
10 < mR < 11: 1 11 < mR < 12: 5 |
 |
Blank 09+46 | 09:10:40 | +46:26:23 |
10 < mR < 11: 2 11 < mR < 12: 1 |
 |
Blank 10+57 | 10:47:00 | +57:45:00 |
10 < mR < 11: 0 11 < mR < 12: 1 |
 |
Blank 11+51 | 11:09:00 | +51:48:00 |
10 < mR < 11: 2 11 < mR < 12: 5 |
 |
Blank 12+02 | 12:15:20 | +02:15:00 |
10 < mR < 11: 1 11 < mR < 12: 5 |
 |
Blank 12+54 | 12:21:40 | +54:12:00 |
10 < mR < 11: 3 11 < mR < 12: 3 |
 |
Blank 13+62 | 13:40:20 | +62:48:00 |
10 < mR < 11: 3 11 < mR < 12: 8 |
 |
Blank 14+17 | 14:12:00 | +17:50:00 |
10 < mR < 11: 0 11 < mR < 12: 1 |
 |
Blank 15+52 | 15:29:15 | +52:20:00 |
10 < mR < 11: 0 11 < mR < 12: 5 |
 |
Blank 16-15 | 16:51:20 | -15:21:45 |
10 < mR < 11: 0 11 < mR < 12: 0 |
 |
Blank 16+55 | 16:30:45 | +54:45:00 |
10 < mR < 11: 1 11 < mR < 12: 2 |
 |
Blank 17+33 | 17:27:40 | +33:30:00 |
10 < mR < 11: 6 11 < mR < 12: 9 |
 |
Blank 18+66 | 18:14:40 | +66:44:30 |
10 < mR < 11: 1 11 < mR < 12: 7 |
 |
Blank 19+59 | 19:10:40 | +59:44:00 |
10 < mR < 11: 6 11 < mR < 12: 17 |
 |
Blank 20-09 | 20:43:15 | -09:31:00 |
10 < mR < 11: 5 11 < mR < 12: 12 |
 |
Blank 21-10 | 21:12:40 | -10:00:00 |
10 < mR < 11: 4 11 < mR < 12: 0 |
 |
Blank 22-08 | 22:32:30 | -08:40:00 |
10 < mR < 11: 7 11 < mR < 12: 5 |
 |
Blank 23+10 | 23:37:00 | 10:15:00 |
10 < mR < 11: 2 11 < mR < 12: 8 |
