Preliminary information for observers proposing to use AO in semester 2003 Feb-July (JTR Aug 02)

AO is being offered on a shared risk basis starting April 2003. During this period only one user program per month can be supported. Since AO is still undergoing testing we can't guarantee performance. AO is only being offered with NSFCAM this semester. We plan to offer AO with SpeX in the following semester. Observers should keep in mind the following capabilities and restrictions when preparing proposals.

  • NSFCAM 0.056 "/pixel scale only (FOV 14.3"x14.3"). All listed filters, CVFs, and grisms are available, but no polarimetry. Observing in the L and L' filters is possible although the background with the AO relay in the beam is much higher due to the additional warm mirrors and baffles in the beam. In order to maintain precise alignment between the AO sensor and NSFCAM, we have found it necessary to fix the position of the NSFCAM dichroic which feeds the AO system. Starting February 1, 2003, the 0.95um IR transmitting/visible reflecting dichroic will be left in the beam. No open position will be available. As a result the average throughput of NSFCAM will fall slightly from about 35% to 32%, a 0.3% ghost will be created, and the short wavelength side of the IJH (asteroid grism) will be blocked (SpeX is more efficient anyway).

  • When using AO the position angle of the instrument rotator will be fixed at 0 degrees. Rotating to other position angles is not possible because this changes the mapping between the deformable mirror in the AO relay (above the instrument rotator) and the lenslet array (below the instrument rotator). Therefore it will not be possible to align the grism slit in NSFCAM to do both components in a binary for example. SpeX has this capability since it uses an internal K-mirror rotator. However, the spectrograph pixel scale in SpeX is not as fine (0.15"/pixel).

  • AO observations will be restricted to < 1.6 airmasses and hour angles to < |+/- 2 hrs|).

  • The FOV available to the wavefront sensor is 75" x 75" (square). The science object and guide star must lie within this FOV. The closer the guide star to the object the better the correction of course.

  • Guide stars should be brighter than R=10. Guiding on extended objects with diameters < 5" (e.g. Uranus and Neptune) is acceptable.

  • Guiding on objects moving at different rates to the science object is acceptable (e.g. guiding on Tethys for Saturn). This mode isn't working yet but we plan to have it ready.

  • Dithering on the guide star by up to 5" is acceptable.

  • Object-sky sequences are acceptable, i.e. nodding to blank sky and and resuming AO guiding when the telescope nods back to the object.

    Questions about AO proposals should be directed to John Rayner. Technical questions about AO should be sent to Professor Toomey.