P72-501: Active Asteroids, Disintegrating Comets, and Other Unusual Solar System Objects

This is a ToO and SoftToO program for non-sidereal targets (rates < 50''/hour). All observations will be triggered via the OB system.

ALFOSC instrument setup:

• Gr #3
• Slit_1.0''
• B(#74), V(#75), R(#76), i(#12)

The corresponding commands to run the tcs.asteph for the different objects are:

• tcs.asteph -t comet -n 2017 K2
• tcs.asteph -n 2023 JN16
• tcs.asteph -t comet -n 12P
• tcs.asteph -t comet -n 2024 S1
• tcs.asteph -t comet -m optimal-ll -n 2024 S1
  
  
• tcs.asteph -t comet -n 2024 E1 (for the target Wierzchos)
• tcs.asteph -t comet -n 240P

Daytime calibrations:

Run alfosc.alfosc-calibs in the morning after observations. This provides biases for both modes with the window and/or binning used, as well as halogen flats and arc lamps for the spectroscopy mode used.

Observing instructions:

1. Go to directory: cd ~/obs/scripts/72-501/
   Do ls -lrt to see the scripts and run them as indicated in the trigger. Note the target "NAME" as given in the trigger for use below.
   
   
2. When the OB generator asks you to do the pointing and differential tracking in another sequencer window , do it as follows:
   
   
   • Use tcs.asteph -n "NAME" for imaging OBs
   • Use tcs.asteph -m para -n "NAME" for spectroscopy OBs (parallactic angle)

   this calls up JPL Horizons to get position and RA/DEC rates at the current UT. Check that the output given in the terminal refers to the desired object.
   

3. Cut and paste the sequencer commands output from tcs.asteph (the 4 last lines) one by one. The 4th line starts the actual differential tracking and guiding:
   tcs.reposition-guide-probe RA-rate DEC-rate
   and you can check that this is happening by noting that the star box is moved to one edge of the guide TV screen, and the guide star is entered.
   
   
4. Now press return in the sequencer window where the OB was started in order to continue the OB script and start the observations.
   
   The star box is placed at the optimal position on the guide TV screen, the differential tracking and guiding is started. The autoguider box will move at the differential tracking rates and guiding will stop when the box reaches the edge of the monitor (size is 70''). These targets have expected rates below 50''/hour, and the rates typically do not change over the time of the observations. Most likely the whole observation is possible without having to reposition the star box on the autoguider screen, but if you have to reposition, just repeat the above command:
   tcs.reposition-guide-probe RA-rate DEC-rate
   Note that the TCS will give a warning beep when there is 120 sec left before the star box reaches the edge, then again at 90 and 60. Make sure you reposition before the edge is reached.
   
   

• In order to locate the target, which should be close to the centre of the CCD, you may need a finding chart, especially for spectroscopy. In a browser on the Florence computer to your right, open either of the links:
  • The NOT Aladdin(it is usually displayed on the top screen of Florence)

  • Lowell asteroid finder (http://asteroid.lowell/edu/astfinder)

  Note that for the Lowell astfinder you can enter the target name, set observatory to "950 la Palma", FOV to 390'' for ALFOSC, and you have the possibility to set the time steps of the trajectory.

• In addition to comments in the OB queue, remember to fill the ToO tracking log of this program.

Program Tracking
Proposal	72-501
Semester	P72: 20251001 - 20260401
Principal Investigator	Jane Luu
Programme	Active Asteroids, Disintegrating Comets, and Other Unusual Solar System Objects
Instrument	ALFOSC
Time Allocation	6 hours ToO
Total Nights	6h
Type	ToO+SoftToO
Notes	Override
Total Time Spent	01:27 (hh:mm)

Proposal	Date	Time	Type	Targets	Files	Comments	Status
72-501	2025-10-10	00:34	ToO	240P, SA96-409	ALIj100111 - ALIj100122, ALIj100123 - ALIj100124	Observed with clear sky and seeing about 0.5''	Observed
72-501	2025-10-19	00:15	ToO	240P	ALIj190288 - ALIj190291, ALIj190294 - ALIj190299	Science observations completed. First attempt produced 4 good images, but had to be stopped due to weather. Second attempt successful - completed the OB (from the start), but the very last exposure cut after 60s instead of 100s, again because of weather. Std. star missed due to weather.	Observed
72-501	2025-10-27	00:19	ToO	SA110-506, 2025m2	ALIj270050-ALIj270055	Observed under clear sky and with fluctuating, but ok seeing (1"-1.4").	Observed
72-501	2025-10-29	00:19	ToO	240P, SA95-236	ALIj290091 - ALIj290098	Observed when conditions slightly worsened, but still good seeing and clear, dark sky.	Observed

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