With IRCAL the pixel scale is so small that twilight flats can be done while the Sun is up. This is especially true for J-band flats. Typical exposure times for flats done while the Sun is up are (though can vary, so use these only as a general guideline):

Ks: 30 seconds
H: 10 to 30 seconds
J: 10 seconds

Dome flats can be done with IRCAL, though sky flats are recommended. Turn on both the super blue and the blue CCD flat field lamps. Typical exposure times for flats are (these can vary, so use these only as a general guideline):

Ks: 1 second
H: 1 second
J: 1 second
BrG-2.16: 10 seconds
H2-2.122: 10 seconds
CaF-Kgrism: 30 to 60 seconds

As always with NIR dome flats, you should take images with the dome lamps on and another set with the lamps off so you can properly subtract of the thermal component from the dome.

IRCAL does not get focused on the sky, but instead gets moved (on a linear stage) to bring it to the same focus as the NGS WFS. To focus IRCAL you need to use the AO internal white light source and the imagesharpen script, selecting the focus mode. Note that focusing is typically done by the AO operator as part of the afternoon setup.

Focusing can also be done manually using the focfit function in the ircaldisplay software.

1. Have the AO operator put in the white light source and close the tip/tilt and AO loops.
2. Move IRCAL's filters to BrG-2.16 Open Open.
3. Determine the proper exposure time so that the white light internal calibration source does not saturate IRCAL, but still gives high signal-to-noise.
4. Check the auto fwhm checkbox in the image browser window.
5. Take an exposure with IRCAL.
6. Enter the current IRCAL focus position in the focval entrybox.
7. Push the focfit init button.
8. Change IRCAL focus (IRCamFocus window in AO software).
9. Take an exposure with IRCAL.
10. Enter the current IRCAL focus position in the focval entrybox.
11. Push the focfit button.
12. Repeat previous 4 steps until you get a good focus. After 3 focus positions a plot will be displayed in the IDL 31 window and the best focus estimate will be printed.
13. Move to the best IRCAL focus (IRCamFocus window in AO software) and take an exposure to check it is indeed at the best focus.
14. Open the tip/tilt and AO loops.

Image sharpening is a technique to fine tune the internal AO alignment to get the highest possible Strehl on IRCAL. Image sharpening is typically done by the AO operator as part of the afternoon setup and calibration of the AO system.

AO observing is not too disimilar from regular NIR obsering. The main differences are finding the natural guide star for each object, field steering the AO system with telescope nods, and PSF stars for calibration. None of these will be discussed in much detail, however the basic steps of an observation are listed below.

LGS observations are similar to NGS observations for the observer. The main differences for the IRCAL observer are the way in which the GS is acquired.

LGS observations occur from 11pm until 5am. The hours of laser use are limited because of heavy air traffic in the Bay Area (particularly San Jose Internation Airport). The switch from NGS to LGS mode should begin sometime around 10:45pm for greatest use of LGS time. Typically laser alignment and calibration will take anywhere from 30 to 60 minutes, depending on seeing conditions and laser performance (we are striving to reduce this time, but for the time being, the observer should be patient).

When moving to an LGS science target we use the following general procedure.

1. Point at an 9th magnitude star within ~1 degree of the science target. There is significant flexure in the system between the tip/tilt sensor (LTT), the WFS, laser launch telescope, and acquisition camera. The 9th magnitude star is used to align these elements for science observing.
2. Close LTT loop on the star and let the telescope "offload".
3. Open LTT loop and send light back to the acquisition camera to mark LTT boresight position.
4. Steer laser to the boresight position.
5. Send LGS to the WFS and close LTT loop on the TT star.
6. Close uplink TT and AO loops on laser. Adjust WFS focus to the sodium layer altitude using the Back WFS.
7. [optional] Image sharpen on the sky. This is a useful option on the first target of a laser guide star run, but only if the seeing is good.
8. Open loops and move to science target guide star.
9. Propagate laser and close all loops.
10. Field steer to science target.
11. Take science data.

The low resolution CaF Kgrism is mounted in the first filter wheel in IRCAL. The slit used with this grism is the 100um-H mounted in IRCAL's aperture wheel. The aperture wheel motor is not very accurate in positioning the slit, but the Jog function allows you to move the slit to approximately the desired position. The following is a cookbook of steps for doing low resolution spectroscopy with IRCAL and AO. There is significant flexure between the WFS and IRCAL, so the object will move off the slit in long exposures (i.e. more than 10 minutes). Flexure moves the object down on IRCAL's chip over time. This limits the amount of time one can spend exposing before having to reposition the object on the slit. A flexure compensation program has been written to account for this, allowing observers to take longer exposures.

1. Move IRCAL's filter wheels to Ks Open Slit-100um-H.
2. Take a short exposure (10s or so) to determine the position of the slit.
3. Use the Jog function in the Motor control window to move the slit to the desired position (typical moves are 500 counts).
4. Determine pixel position on slit where you wish to put the science object. Record the pixel position, because you should use it all night for easiest and most efficient observing.
5. Take an image of the science target with AO loops closed and use the fwhm tool in the Image Browser window to determine its centroid position. Typically the filter wheels are in the following position for this step: Ks Open Open. Also make sure that the image isn't saturated so you get a good centroid measurement.
6. Use the WFS Steering/Nodding window to move the object to the desired pixel position. The WFS steering is well calibrated and should put the object very near the desired position. Take exposures on IRCAL and fine tune the WFS steering to center object on the correct pixel. The AO loops should remain closed for the following steps.
7. Move IRCAL's filter wheels to Ks Open Slit-100um-H.
8. Take short exposures and Jog aperture wheel so slit is in the proper position.
9. Move IRCAL's filter wheels to CaF-Kgrism K Slit-100um-H.
10. Have the AO operator turn on flexure compensation.
11. Take spectrum of the science target.
12. Open AO loops and move telescope to get a sky spectrum.
13. Take a dome flat (have telescope tech move dome in front of telescope and turn on the Super Blue and CCD Blue flat field lamps). A reasonable exposure is 5s x 10coadds, though the flat field lamps vary in brightness from run to run, so it is wise to check the exposure time.
14. Turn off the flat field lamps and take another exposure (a dome dark, which will ultimately be subtracted from the dome flat during data reduction).
15. Move filters to Ks Open Open and take an exposure of the science target.
16. Determine approximately how many pixels the object moved during the spectrum exposure (this will help determine the flexure effects, even with flexure compensation, on your data).
17. Turn off flexure compensation.
18. Find a nearby SAO star for measuring the atmospheric absorption. Typically an A, G, or K star depending on the wavelength range and absorption lines of importance in your science data.
19. Close AO loops and take short exposure of star (e.g. 0.1 seconds for an 8th magnitude K5 star)
20. Use the WFS steering to move the star to the slit pixel position.
21. Move filters to Ks Open Slit-100um-H. Take short exposures and Jog slit to proper position.
22. Move filters to CaF-Kgrism K Slit-100um-H and take data (e.g. 1s x 20coadds for 8th magnitude K5 star).
23. Open AO loops and move telescope to get a sky spectrum.
24. Take another dome flat and dome dark.

High resolution spectroscopy is accomplished with IRCAL using the K-Silicon grism and cross dispersing the orders using the CaF-Kgrism. Instead of using a slit, a pinhole (usually pinhole-100um) is used as the aperture. Otherwise, the observing procedure is similar to doing low resolution spectroscopy.

A polarimeter is now installed for use with IRCAL. The waveplate is mounted just in front of IRCAL, while the Wollaston prism is mounted in a filter wheel. This is not yet a facility observing mode. Observers wishing to use the polarimeter should contact James Graham and Marshall Perrin at UC-Berkeley.

1. Point telescope to object of interest.
2. Close AO loops.
3. Move IRCAL's filter wheels to Ks Wollaston Half-field. Jog the aperture wheel to properly position the Half-field aperture mask.
4. Set the appropriate exposure time, number of reads, coadds, etc..
5. Use the polarim script to automatically rotate the Waveplate and take exposures at each waveplate position. Waveplate positions in the script are: 0, 45, 22.5, 67.5, 90, 135, 112.5, and 157.5 degrees.
6. Dither telescope using the WFS steering and repeat script.
7. Repeat on PSF calibration star, polarimetry standards, etc.

The waveplate rotation positions are not absolute, thus from one run to the next, the 0 degree rotation may shift. Calibration of the waveplate rotation is done through twilight flat field images because the sky is polarized.

The aperture wheel motion is inconsistent, thus when positioning the Half-field plate it is advised to position it properly using Ap Jog (typical steps 500 or 1000 counts), then not move it for the remainder of the polarimetry observing.

For more details on the polarimeter, refer to Perrin and Graham "The IRCAL Polarimeter: Design, Calibration, and Data Reduction for an Adaptive Optics Imaging Polarimeter," PASP 120:555-570, May 2008.

Note: This should only be done by a Lick Observatory support scientist or IRCAL support person from UC-Berkeley or UC-Santa Cruz. If there appears to be a problem with the IRCAL reference biases, please contact help instead of creating new reference biases.

1. Click on Exposure Palette - File - Update Reference Biases
2. Check createbias and coadd
3. Press Go. This will take a while, about three hours. Wait until this step is done before proceeding to the next step.
4. Uncheck createbias and coadd
5. Press Go. This is to check that the refbiases are actually ok and that there wasn't a bad read in one of them. This will take about 30 minutes.

Reference biases are located on ircalbox2 in /data/bias/YYYY.MM.DD/, where YYYY.MM.DD is the creation date code for the biases. The file /data/bias/biaslist.txt is a link to the biaslist file in the proper (usually most recent) reference bias directory.