P69-507: Probing the diversity of the smallest building blocks of the Solar System

ALFOSC photometry and low-res slit spectroscopy of fast targets requiring differential tracking.

NB! This program is going to use and test out an upgraded version of tcs.asteph. Info pending.

Instrument setup required

• FASU filters: g'r'i'z' (#120,#110,#111,#112)
• Grism wheel: Gr#4
• Aperture wheel: Slit_1.8"

Daytime and twilight calibration instructions:

• Standard twilight flat fields for filters g'r'i'z'
• Biases and spectroscopic flats and arc lamps are taken as part of the automatic calibration script alfosc-calibs in the morning

Observing instructions:

• If you are not already using ALFOSC, go to the desktop where the ALFOSC Sequencer is running, and change the telescope settings with the command:
    tcs.setup-tel-alfosc

• Go to the directory
    cd ~/scripts/69-507
  List the available scripts
    ls -lrt

  All OBs to be observed will have tonight's date (i.e. start of the night) in their name.
  Note that in addition to the target there will also be standard star OBs

• Start the target script, when it tells you to do the pointing, go to another sequencer window and use either of these:

  tcs.asteph -m optimal-ll -n targetname (for fast targets, rates > 100"/h)
  tcs.asteph -m optimal-lr -n targetname (for fast targets, rates > 100"/h)

  these commands connect to JPL Horizon to get the actual position and the rates at this UT time.
  In the case of using the optimal modes you also get the best setting of the field-rotation to optimize guide star area for repositioning.
  You can use either of the two. Try first the one that involves less turning of the rotator. See examples below.

      
  > tcs.asteph -m optimal-lr -n K07S06Q
  ...
  Your input target is                        -  K07S06Q
  Your observatory is Nordic Optical Telescope, La Palma.
  Retrieving data from JPL Horizons...
  Data retrieved successfully from JPL Horizons.
  The object being searched for is  2007_SQ6
  Prefix for file names will be  2023-Oct-06.2007_SQ6
  Today is  2023-10-06
  Your computer says time is  10:11  UTC.
  ***************************
  These tasks should be given to the TCS:
  ***************************
  tcs.append-object 2007_SQ6-1010 03 20 02.18 +09 15 10.5 2000.0 0.0 0.0 17.709
  tcs.ag-off
  tcs.tcs-command "instrument-name ALFOSC ALFOSC-LR"; tcs.guide-object -f 57.173 2007_SQ6-1010
  tcs.reposition-guide-probe 241.628 -374.546
  

• Copy and paste into the command line the last four lines listed by the script - one by one.
  
• If this is a fast target, by the time you have arrived, the target has already moved. It is a good idea to repeat the steps again from the tcs.asteph command.
  When you get the prompt back after the 4th command (which sets the differential RA/DEC rates), the guide star should be in the box,
  the box should be close to one edge of the TV screen, and the contrast value for guiding should be larger than 1.0. The star+box will move across the TV screen at the non-sidereal rates.
  Differential tracking AND guiding is now running.

• Press return in the sequencer window where the OB is runnning. This will start the data acquisition.

  If the target is fast, i.e. RA/DEC rates > 100"/h, then the guide star will reach the opposite end of the TV screen before a ~ 40 min long OB terminates.
  NB! You need to reposition before the guide star reaches the opposite edge!
  This is done by repeating the 4th command, tcs.reposition-guide-probe .... before the edge is reached!
  TCS warning beeps are given when there is 120, 90, and 60 seconds left.
  Ideally, the telescope is not moved while the guide probe is repositioned, but if many short exposures are used, it is wise to do this while the CCD is reading out.

  For more general information on how this works, see the section "Moving Targets" in the ALFOSC Cookbook.

At the end of the night:

• When all the OBs are done (check also for standard star OBs with today's date ), please, close them.

• Pplease, fill in the ToO or SoftToO tracking log.

• Remember to run alfosc-calibs ALF*** in the morning, where the input parameter is the file prefix.

Should any of the observations have been carried out using the OB system, you will find additional information HERE