Chandra Deep Field Observation with

I. Masks

          Chandra Deep Field IMACS Observation Masks
  Ranked in the order of priority, i.e. number of slit on the mask.

 N  Mask     Mask#     RA            Dec      Slit Hole Mag.range   obs  obx  ps  SMF  FC
------------------------------------------------------------------------------------------
 1  cdfs1    4198   03:32:28.000 -27:47:55.00  110   4  14.5-21.9   obs  obx  ps  SMF  FC
 2  a1332    4204   01:03:38.400 -21:42:00.00   76   5  16.8-21.6   obs  obx  ps  SMF  FC
 3  smc2     4201   00:55:24.000 -72:33:00.00   71   4  14.4-21.3   obs  obx  ps  SMF  FC
 4  a1331    4202   01:02:02.400 -22:06:16.69   68   4  14.3-21.4   obs  obx  ps  SMF  FC
 5  smc3     4203   00:50:24.000 -72:51:00.00   66   6  13.9-21.5   obs  obx  ps  SMF  FC
 6  smc1     4199   00:50:24.000 -73:15:00.00   64   8  14.4-21.0   obs  obx  ps  SMF  FC
 7  cdfs2    4200   03:32:49.735 -27:52:31.90   57   4  17.2-21.5   obs  obx  ps  SMF  FC
 8  a1333    4206   01:03:40.800 -22:06:00.00   54   8  14.6-21.5   obs  obx  ps  SMF  FC
 9  smc5     4205   01:03:48.000 -72:05:24.00   51   6  13.8-21.6   obs  obx  ps  SMF  FC
10  a851     4207   00:41:48.000 -09:20:24.00   41  10  13.7-21.7   obs  obx  ps  SMF  FC
11  smc4     4208   00:46:48.000 -73:06:00.00   38   8  13.8-21.3   obs  obx  ps  SMF  FC
12  fornax1  4209   03:38:24.287 -35:26:21.36   32   4  14.2-21.7   obs  obx  ps  SMF  FC
------------------------------------------------------------------------------------------
N:         Rank of priority.
Mask:      Mask name.
Mask#:     Mask number.
RA,Dec:    RA, Dec (J2000) of the center of the mask.
Slit:      Number of object slit on the mask.
Hole:      Number of alignment star hole on the mask.
Mag.range: Magnitude range of objects on the mask.
Maskfiles: obs, obx, ps SMF
FC:        Finding chart of 1X1 degree.

II. Elevation Chart

Astronomical twilight on 9/25: 20:59 - 06:09, duration 9h10m
1. smc is observable all night.
2. a85 and a133 are observable one hour after the start of the astronomical twilight.
3. cdfs and fornax are observable three hours after the start of the astronomical twilight.

Here is the Las Campanas Observatory 2021 Ephemeris.

III. Observation

1. On 9/25-27, the astronomical twilight durations are 9h10m, 9h8m, 9h6m, respectively.
2. There are 12 masks. Aim to observe 4 masks per night. Spend average 2h17m on each mask, including the overhead time.
3. Always start the night with one of the smc masks, since only smc is observable at the beginning of the night.
4. It's best to observe cdfs and fornax after midnight for lower airmass.

Here is the observation plan based on the above consideration and their ranking:

Night Date  mask1 (#)     mask2  (#)     mask3  (#)     mask4    (#)
----------------------------------------------------------------------
  1   9/25  smc2 (4201)   smc3  (4203)   smc1  (4199)   cdfs1   (4198)
  2   9/26  smc5 (4205)   a1332 (4204)   a1331 (4202)   cdfs2   (4200)  
  3   9/27  smc4 (4208)   a1333 (4206)   a851  (4207)   fornax1 (4209)
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