• Target List
• Exposure Sequence
• Observation Plan
• Biases, Flats etc.

I. Target List

One main goal of this run is to map out the galactic center using 6 Mosaic pointing (GCs) to cover 47 Chandra observations near the Galactic center. So these 6 pointings are given the high priorities. Among these 47 Chandra observations, 30 are Wang's GC mapping, 12 are the SgrA* deep field, 5 are other observations. Mosaic field GC1, which covers 21 Chandra observations (8 Wang's fields, 12 deep SgrA* chandra observations and the Galactic Center Arc), will use twice the nominal exposure time and is given the highest priority. The rest of the priorities are sorted mainly by the number of serendipitous X-ray sources detected. 1 is the highest priority, 14 is the lowest priority.

Following is the target list sorted by increasing RA. The RA and Dec in the list are the telescope pointings, i.e. the center of the MosaicII (not the coordinates of the targets or the Chandra), based on the overlay of Mosaic II on ACIS. NO MORE OFFSET IS NEEDED.

                       Champlane CTIO 4m/MosaicII Target list   June 2-6, 2003

                                Telescope pointing
                                Center of Mosaic II                                          Chandra
Priority  Field			 RA         Dec(J2000)      l         b      NH(e22)   Exp   Instru  ObsID
-----------------------------------------------------------------------------------------------------------
  9     MSH11-62              11:11:57.38  -60:41:28.0  291.05262  -0.13461  1.4600   50.00  ACIS-S  2782
 10     G292.2-0.5            11:19:45.94  -61:40:13.5  292.28345  -0.70871  1.3000   60.00  ACIS-S  2833 3819
 11     CENX-3                11:20:49.67  -60:37:04.3  292.04094   0.32351  1.3000   40.00  ACIS-I    88
 14     MYCN18 unobserved     13:39:44.30  -67:20:27.0  307.57299  -4.90493  0.4270   40.00  ACIS-S  2576
 13     1RXSJ161411.3         16:14:53.00  -63:12:57.0  323.64926  -8.85357  0.1660   33.40  ACIS-I  2365
 12     MARS unobserved       17:00:41.15  -26:58:24.1  356.03416   9.30766  0.1590   30.00  ACIS-I  1861
  5     GC5                   17:43:04.80  -29:37:48.0  359.12038   0.10918  1.0900   24.00  ACIS-I  2267 - 2296
  2     GC2                   17:43:33.12  -29:01:48.0  359.68500   0.33677  1.0900   24.00  ACIS-I  2267 - 2296
  3     GC3                   17:45:44.88  -28:25:48.0    0.44816   0.24004  1.0900   24.00  ACIS-I  2267 - 2296
  6     GC6                   17:45:49.20  -29:37:48.0  359.43188  -0.39826  1.0900   24.00  ACIS-I  2267 - 2296
  1     GC1                   17:46:16.32  -29:01:48.0  359.99555  -0.17025  1.0900   24.00  ACIS-I  2267 - 2296
  4     GC4                   17:48:27.60  -28:25:48.0    0.75723  -0.26983  1.0900   24.00  ACIS-I  2267 - 2296
  7     BW unobserved         18:03:45.70  -29:57:15.0    1.11639  -3.92286  0.2960  100.00  ACIS-I  3780
  8     GALACTICPLANE         18:43:27.72  -03:58:12.0   28.49164  -0.03855  2.0700  200.00  ACIS-I  949 1523 2298
-----------------------------------------------------------------------------------------------------------

Click a object name to see the MosaicII & ACIS overlay on DSS image. This should help to identify the field. Click a Chandra ObsID to see the X-ray source plots by XPIPE. Note that the DSS images and XPIPE plots are E-left & N-up. But the MosaicII display at the CTIO is E-up & N-right.

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II. Exposure Sequence

Do dithered exposures for the long exposures are very important. Not only it fills up the gaps between the chips and eliminate bad columns to make a cosmetically clean image, it also greatly reduce the "bleeding" effect caused by saturated bright stars.

           Exposure sequence for each field

N  Filter  Frame         Exp   Exp+readout Total Timeline
                        (sec)  (min/frame) (min)   (min)
---------------------------------------------------------
1  R       single image     2       1.7     1.7     1.7
2  Ha      single image    30       2.2     2.2     3.9
3  R       dither 1x5     240       5.7    28.5    32.4
4  Ha      dither 1x5    1500      26.7   133.5   165.9
5  V       single image     2       1.7     1.7   167.6
6  I       single image     2       1.7     1.7   169.3
7  V       dither 1x5     180       4.7    23.5   192.8
8  I       dither 1x5     180       4.7    23.5   216.3
---------------------------------------------------------
1. N is the exposure sequence number.
2. Exp is the exposure time for each image in seconds.
3. Exp+readout is the exposure plus 1.7min readout time for each image.
4. Total is the total time ((Exp+readout) x dither) for each filter.
5. Timeline is the accumulated time for each field.

Under Frame: 

A. single image: take one short exposure for each filter.  No dither.

B. dither 1x5: Use command "mosdither" to do one set of standard dither pattern 
   of 5 positions for R, Ha and V filters.  Take one image at each position. 
   The standard dither pattern is at "ditherdb$todd.dat".

It looks like this:
===========
# Tod Lauer's canned dither scheme for the NOAO mosaic 

# Offset relative to current telescope position 

# RA (pixels) Dec (pixels) 

0 0 

160 -240 

-160 240 

80 120 

-80 -120 
==============

C. When short of time, dither 1x3 can be used for filters I and V: 
   Use command "mosdither" to do one set of dither pattern of 3.  Take
   one image at each position. Create and use a "ditherdb$dither3.dat"
   file like this:

===========
# Dither 3 positions.

# Offset relative to current telescope position

# RA (pixels) Dec (pixels)

0 0

160 -240

-160 240
===========

OR, simply use the standard dither pattern and stop it after 3 exposures.

D. For field GC1, double the exposure time for the deep
images.  Keep a single image for the short exposure but do two 1x5
dithers for each filter.  So there will be 10 deep images for each
filter.  Do the following exposure sequence:

N = 1 2 3 4 5 6 7 8   3 4 7 8 

where N is the exposure sequence number in the exposure sequence table

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III. Observation Plan

A. Since the first target of each night has lower priority than the second and third targets, please don't spend more than 216 min (3h36m) on the first targets. Otherwise it will shorten the observing time for higher priority targets in later night. Please move to the second target by 10:51PM each night at the latest. If it's necessary, shorten the time for the first targets as suggested in item B in order start the second targets by that time.

B. When time is running short, do the following to save time:

a. First reduce the number of I images to dither 1x3. (save 9.4 min)

a. Then reduce the number of V images to dither 1x3. (save 9.4 min)

b. Skip V and I short (2 sec) images. (save 1.7 min each)

c. Reduce one or two more I deep images, then V deep images. (save 4.7 min each) But keep at least one V and one I images.

When take only one deep V and one deep I images, the total time needed for a field is reduced to 175.3 min - a total saving of 41.0 min.

postscript and txt

Here is an observing almanac made for this run.

Here is the CTIO 2003 Ephemeris.

Here is a suggested observation plan for the 5 nights.

Night                   Do
-------------------------------------------------------------
6/2     MSH11-62        GC1 (this field takes 2/3 of the night)
6/3     G292.2-0.5      GC2             GC4
6/4     CENX-3          GC3             GC6
6/5     1RXSJ161411     GC5             BAADE'SWINDOW
6/6     MYCN18          MARS		GALACTICPLANE
-------------------------------------------------------------

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IV. Biases, Flats etc.

• Biases and Domeflats: Take biases and domeflats in the afternoon before dinner.
• Skyflats: Take twilight skyflats starting shortly after sunset at around 5:30pm.
• Pointing and Focus: Do telescope pointing and focus after the skyflats at around 6:10pm.

1. Biases and Domeflats

2. Skyflats

• Point the telescope to zenith at sunset at 5:59pm.
• Turn the tracking on during the skyflat exposures and turn the tracking off during the readouts so there will be an offset between exposures.
• Do the Ha filter skyflats first, then do the I filter skyflats.
• Start at about 6:10pm, take a 2 seconds Ha skyflats. Examine the image and make the adjustment of the exposure time so the flat has about 10000 counts.
• Take the first Ha skyflats with adjusted exposure time (remember to turn the tracking on during exposure and off during readout).
• Take the second Ha skyflats with exposure time twice as long as the first exposure (e.g.: first is 5sec, second one should be 10sec). The sky gets darker during the 1.7 min readout. To double the exposure time is just about to compensate the change in the sky.
• Take at least 3 Ha skyflats.
• Take at least 3 Ha skyflats.
• If the exposure time is still under 30sec, continue to take the Ha skyflats until the the exposure time is over 30sec.
• Take the first I filter skyflat with exposure time equal to 1/10 of the last Ha skyflat exposure. Examine the image to make sure it gets about 10000 counts. Adjust exposure time if needed.
• Take the second I filter skyflat with exposure twice as long as the first.
• Take at least 3 I skyflats.

3. Pointing and Focus:

• Stop the skyflats at around 6:40pm.
• Do the pointing and focus at around 6:40pm.
• Start to observe the first ChaMplane field at about 7:00pm.

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THANKS!

Ping Zhao: zhao@cfa.harvard.edu