We are continuing the acceptance and development tests on the telescope begun in July, 2000. The work planned for the next trip, scheduled for late April, 2001, has to do with finishing a number of details we haven't been able to get to in the past, with continuing to test and perfect the telescope control system, and with putting the secondary mirror into the telescope and testing it as a Cassegrain system. This work was still contingent on getting the secondary back from Torus Optics in time to do the work in April, and, to avoid wasting any more time, we decided to take delivery of the secondary from Torus in spite of the fact that they could not produce an optical test showing the mirror is figured to the specified shape. Eaton and Williamson drove a truck from Nashville to Arizona to carry a number of parts of the telescope.

The work planned falls into four categories as follows:

1. MECHANICAL ADJUSTMENTS and augmentation of the telescope structure.
1. Finish the duct work around the observatory. This includes putting the feed-through in the north wall, adding the auxilliary fans to the back of the telescope tube, wiring the auxilliary fans for power, running the duct to the north wall, and documenting these features for our maintenance pages.(We put the feed-through into the north wall on 26 April, hooked up the duct to it on 30 April, put the auxilliary fans on the back of the tube and wired them up on 29 April, and have documented these tasks as we did them.)
2. Discuss further with Boyd the way in which he is automating the motions of the telesocpe enclosure.(Boyd has made considerable progress in automating the roof/front flap of the telescope enclosure. He has put limit switches on the roof, designed and started builting an encoder to measure the position of the roof, and got a computer to run the roof and monitor the air compressor and UPS. Epand has written a computer program to run the roof, and we have discussed extensively with Boyd the protocol for communicating between the computers running the roof and the telescope.)
3. Make a video tape of the telescope in operation.(We made a recording of the telescope in motion on the nights of 25 and 26 April, using a spare VCR graciously lent us by Susan Eaton.)
4. Move most of the remaining spare parts from TSU to the observatory. (We drove a truck out to the site carrying the secondary mirror, its cell, the instrument head, and numerous boxes of spare parts. The remaining spare parts should wait until we move the spectrograph to the observatory.)
2. ELECTRICAL WIRING.
1. Wire in the distribution for protected power in the control room, hook all the computers and monitors into it, and measure the current drawn by this circuit. (We wired the power bus into the control room on 26 April and tidied it up on 27 April. The two computers and video equipment now running off this circuit draw about 4.0 amps when both are running X-windows. They should draw less than 3 amps in unattended operation. Other circuits took power as follows: oil pumps: 11.3 amps, telescope computer and associated electronics: 1.5 amps, drive amplifiers: appx. 0.14 amps each idle, 0.25 amps standby, and 0.50 amps in normal operation [azimuth moving with a demand of 15% maximum]. Values for the spectrograph measured since then are 4.2 amps for the CryoTiger, 0.84 amps for the CCD control electronics, and ?? amps for the control computer.)
2. Switch the computers over to the new Internet link. Set up a gateway computer for the AST, and get communications between the observatory working over an encrypted link.(Boyd got the new Internet connection for Fairborn Observatory by way of a radio link to Mt Hopkins set up in early April. We connected our computers to it through a gateway computer on 25 April and had all the network addresses changed and working in time to observe that night.)
3. Work on MIRRORS.
1. Put secondary mirror and instrument head into the telescope and get the secondary to focus on the instrument head. [This could involve modifying the supports for the secondary-mirror cell, a potentially time-consuming process.] (We put the secondary in the telescope on 27 April and assessed the focus by observing the Moon and Sirius. Since the telescope focused about 6 inches above the desired nominal focal position, we needed to move the mirror in by about 0.21 inches. We decided to do this partly by shimming the attachments for the secondary mirror cell by 0.125 inch and by running the secondary in by the rest [since it was at its far limit when we measured the focus position]. We put the instrument head with its guide camera in the telescope on 28 April and reran these tests. We had to shim the secondary mirror another 0.125 inch, which was a little too much, but it did let us focus on stars and assess the secondary mirror. Further tests indicated that we should make a new primary shim for 1.39 inches thick, vs. the original 1.31 inches, and shim the secondary mirror 0.125 inches with respect to its tripod. The primary shim will probably have to be shimmed about 0.1 inches on one side to compensate for a slope in the plate in the top-end structure to which it attaches.)
2. Colimate the Cassegrain system. (We did this first by tilting the secondary mirror to make an extrafocal image of a bright star as symmetrical as possible and then by tilting the secondary to remove the coma in images of fainter stars.)
3. Take images with the full Cassegrain system to assess quality of the complete optical system. Make and use masks to isolate various parts of the secondary mirror to assess them separately. (We took various images of stars designed to show the effect of optical imperfections in the secondary mirror supplied by Torus Optics. At full aperture, these images all showed a fairly bright halo around a central blob. The halo would focus byond the blob, i.e, closer to the primary mirror, because it was intercepted by the fiber feed projecting through the pickoff mirror when we centered a star on the feed. On 29 April we masked off various parts of the secondary mirror to determine just how much of the outer rim is unusable. Specifically, we took images with the outer 0.25 inches masked [which showed no effect], with the inner 8 inches masked, and with the inner 6 inches masked. We continued these tests on 30 April, with images for the inner 8 inches and the inner 6 inches of the mirror, finding that the inner 6 inches or so of the mirror produces the halo, which we could bring to a focus by moving the secondary mirror back away from the primary. We did not have enough range in this motion to bring the light to a focus, but it appears that it would require 0.017 inches of travel. Images of the double stars alpha Gem and mu Dra give some idea of the resolution of the system for the outer 2.5-in annulus of the secondary.)
4. Take images to use in developing the guiding strategy. (We took several such images on 28 April and repeated them on 29 April. Specifically, we got images of Arcturus [dimmed by appx 5 mag because the secondary mirror was unaluminized and had 50% of its area masked] on the fiber feed with exposures of 2/30 sec and 0.5 sec showing light spilling over the edge of the feed. A somewhat lower exposure gave this image for another star. The guider seemed to be working gratuitiously well because these images changed hardly at all during five minutes of tracking. We repeated this test on 30 April, getting good tracking for much longer periods.)
4. Work on the DRIVES and CONTROL SYSTEM.
1. Run further tests to verify new routines for a) moving the secondary mirror and instrument head, b) automating the process of acquiring and tracking stars, and shutting down the telescope, and 3) communicating between the computers running the observatory.(We ran the secondary mirror and instrument head as part of tests of the Cassegrain system. Williamson has made some further progress in automating the control system and communicating among the various computers, although this trip was not primarily concerned with that task.)
2. Run acquisition/tracking tests with secondary mirror in place. (On 28 April we ran through the list of stars for TPOINT using the Cassegrain acquisition camera and found all of the stars that were observable. The pointing was of the order of an arcminute with the mount model derived from using the telescope at prime focus.)
3. Construct a mount model with the secondary mirror, and verify it by finding stars.(Given the results of the pointing tests, we decided the existing mount model is adequate.)
4. Run mechanical focusing tests with secondary mirror. (We looked at whether the focus is dependent on zenith distance, by observing the shapes of stars near the zenith and horizon during our pointing tests. There did not seem to be any effects of flexure in the telescope tube, and the focus did not seem to change during the 5-6 hours we observed on 28 April. We also tested the repeatability of the three axial actuators, finding that they returned a star image to the same place, to at least a few pixels, after they were run to their home positions and then back to their original places.)