In May 2002 the Rigel telescope was delivered to its permanent site, the Winer Observatory in southern Arizona. We completed initial on-site acceptance tests during the week of 18 - 24 May. A brief description of the results can be found below. A more detailed account, written by the students who participated in the tests, is available here. The sample image at right (Omega Nebula, M17) was made using 30 sec images in B,V,R and combining using Maxim/DL.

In summary, we have confirmed the initial pointing and tracking tests done in early Spring at the North Liberty Radio Observatory,which were very positive. The new pointing mesh is very smooth, and an initial check indicates that RMS pointing errors well under 1arcmin. The tracking was equally impressive, with several long (3-5 min) exposures showing the FWHM increasing by only 0.5 arcsec or so. The only significant problem area is the focus positioning system, which Torus has agreed to upgrade, probably with carbon struts and a closed-loop positioning system.

A brief description of the test results are as follows.

1. Pointing. (Rigel spec: <30 arcsec RMS error whole sky). We ran a pointing mesh over most ofthe sky using an 8 deg grid interval. The mesh itself was quite smooth. After installing the mesh, the residual pointing errors were about 22 and 26 arcsec RMS in hour angle and declination respectively. Plots of the residual errors and sky coverage are shown here.

2. Tracking. (Rigel spec: <0.01 arcsec/sec error) Several long exposure (100, 300,580 sec) showed the tracking accurate to 0.001-0.003 arcsec/sec, easily meeting the Rigel specification.

3. Optical Quality. The star images were clean, round, and often under 3 arcsec FWHM, with some images having FWHM approaching 2.0 arcsec. There were no obvious optical defects such as flaring, ghosts, or non-roundness. After recollimating, out of focus images were uniform tori.

5. Spectrometer. The spectrometer system is a fiber-fed Ocean Optics S2000 with 2048 elements, a wavelength range from 350 nm - 1000 nm, and an effective spectral resolution of 0.5nm. The target fiber in the focal plane is 300 microns (15 arcsec). The fiber is fed using a 45 degree pick-off mirror located to the side to the CCD sensor. We illuminate the fiber by first locating the target star on the fiber, then reposition so that hte star is centered on the fiber. A sample spectra of the A0V main-sequence star Vega (1 sec exposure) is shown at right.

6. Focus subsystem. (Rigel spec: repeatable within 1 step (6 microns), focus from -20C to +40C). The focus subsystem did not meet the spec, probably because the home position was not resetting with the required accuracy. We attempted to determine the focus position vs. temperature curve, but got inconsistent results (see full report for details).

7. Limiting Magnitude, single image. We took a number of long exposures to test the tracking accuracy. The observng conditions were clear, moonless, and with average (2.8 arcsec) seeing. A small (3x3 arcmin) section of a typical image (100 sec, clear filter) is shown below with sample stars magnitudes marked. The magnitudes were obtained using GSC stars as photometric references, so the uncertainty may be as large as 0.5 magnitudes. This unguided 100 sec exposure has a limiting (3 sigma) detection limit near V= 19.0.

The predicted signal to noise ratio (SNR) for the Rigel system as a function of magnitude for a 100 sec. exposure and clear filter for sky brightness 15.5 mag. per square arcsec (red line) and 19.0 mag. per sq arcsec (blue line) is shown below, along with measured SNR of several stars in the image above.

It is not surprising that the data are consistent with a bright sky (15.5 mag/sq. arcsec), since the image was acquired under very bright full-moon conditions. Note that at a reasonably dark site (19.0 mag/sq. arcsec), the expected SNR for a 20th magnitude star is 6:1 in a single 100 sec exposure.