Bending Model Data Taking (TPoints)

These are the basic instructions how to take data for the bending model. You will receive a schedule for the night which includes for each star:

• star name
• the number of image to be taken
• offset to be applied for dark images in degrees

Use the CDM interface to take the images. Please always wait for the end of a series of images to modify parameters. Near the "Take Images" button you find a small field where you can set the number of images to take, the exposure time field in milliseconds, and the star name. For all modification you must push the "Set" button at the end to apply the changes.

In the schedule, some stars can be close to the moon, and some can be listed several times with different procedures. This is normal, the main objectives is to test the bending model data taking during moonlight and test the impact of some parameters. Please consider the star which are present two times as completely different observations and make the complete procedures two times.

For all images, the SIS needs to be moved to the center of the camera through the CIC. You also need to be familiar with the procedures to switch on and off the Starguider LEDs from the CIC, and the OARLs from the Auxiliary Devices GUI

Standard Procedure for Stars

• Track the position of the star
• Switch on the LEDs from CIC (intensity = 255) and switch on the OARLs
• Change the name of star in the CDM interface to StarNameLED, with StarName replaced by the name of the current star
• Take 10 pictures with 20ms exposure
• Verify on the image taken you see OARLs on at least one image (sometimes the OARL spots switch on and off randomly), if you couldn't see them on any image retake 10 more exposures until you could see them in some images
• Switch off the LEDs from CIC and the OARLs
• Change the name in the CDM interface to StarName (remove the "LED" part)
• Take n images of 1s exposure, n is the number of images written for the star in the schedule
• Track the position of the star with the offset for the dark (there is a field in the Semi-Expert Drive GUI to apply offsets to tracking)
• Change the name of in the CDM interface to StarNameDark (add "Dark" to the star name)
• Take n images of 1s exposure, n is the number of images written for the star in the schedule

Special star procedure

• Star with the hysteresis procedure
  • Move the telescope first at least 30 degree away in azimuth to a fixed position
  • Track the star and follow the standard procedure
  • Move the telescope at least 30 degree away in azimuth to the other side to a fixed position
  • Track the star and follow the standard procedure
  • Please specify in the StarName field in the CDM interface from which position in azimuth you have moved the telescope

• Star with the exposure time procedure
  • First follow the standard procedure
  • Redo the standard procedure, doubling the number of images for star and dark, using 500ms exposure
  • Redo the standard procedure, quadrupling the number of images for star and dark, using 250 ms exposure

Procedure for the Zenith Scan

• This needs to be done for several azimuth 0, 90, 180, 270 degrees
• For all this test you only need to point the telescope at a specific position and not track this position
• Switch on OARLs and LEDs
• For each azimuth
  • Do a scan on zenith angle from 75° to 0° in steps of 5° (for the star name in the CDM interface use "Scan3Az[..]Zen[..]Up", replacing [..] with the current azimuth and zenith angle)
  • For each position take 10 images of 20ms exposure. Before any movement of the telescope please verify you have at least one image with the OARLs, if not, take another 10 images
  • Then do a scan on zenith angle from 0° to 75° in steps of 5° (for the star name in the CDM interface use "Scan3Az[..]Zen[..]Down, replacing [..] with the current azimuth and zenith angle)