The cameras on both sides are all-refractive. The camera lenses are temperature controlled; focus is a function of lens temperature. The focal planes on both sides appear to be quite flat. You may observe some small-scale variations in the focus due to irregularities of the chip. Blue: The design range of the camera is 3000-7000 A. It looks good to atmospheric cutoff. Peak efficiency of the entire system including the telescope is between 5 and 20%, depending on setup. The blue side operates in first order, and due to the wavelength coverage, red leak should not be a problem. If you're imaging on the blue side, remember that the lens performance deteriorates past 7000 A. Red: The design range of the camera is 4000-11000 A. Peak system efficiency is in the vicinity of 30-40% (with the old Reticon detector, figures have not been calculated for the Hamamatsu chip), depending on configuration. Response is decreasing rapidly by 10,500 A, but successful observations have been made out to 10,830 A. You will need to suppress second order if you go beyond twice the effective cut-on point of the dichroic you use. Remember that the user, lower, and upper filter wheels are in common for both beams, so use the 5.5" round filters in the red camera filter wheel. The Hamamatsu detector shows little fringing until the very reddest wavelengths. For most objects, red exposures will probably go faster. Do multiple reds if necessary to avoid red saturation during one blue exposure. NB: Additional, more current, throughput data has been provided by Dr. Prochaska (UCSC): http://www.ucolick.org/~xavier/KAST_THRU/.

Shane 3 meter Kast Throughput

As the position of the telescope changes, the Kast spectrograph flexes. There is up to nine pixels of total shift on each side (depending on CCD), moving between extreme positions on the sky.

The blue side may shift as much as nine pixels parallel to dispersion, but fringing will not generally be a concern, and the shift may ordinarily be accounted for by reference to skylines.

The red side may also shift as much as nine pixels in the dispersion direction, and because of fringing this may be a more serious problem than on the blue side. The Hamamatsu chip is thick and thus fringing has been minimized, though may still be seen to a small extent at wavelengths greater that 9500 A. This may become a particular problem due to the flexure described just above, because if observations at large zenith distances are flattened with straight up flats, the object and flat fringes may not match. If this is a concern, you may with to take "local" flats.

The Ilex shutter technically has no minimum exposure time. However, exposures of less than 1 sec are not recommended (a 1 sec exposure will have a timing errors of a few milliseconds).

There is a separate controller for each side. They are in close proximity to the dewars. The power supplies for the controllers and CCDs are mounted above the instrument in the 19" electronics racks. These contain most of the temperature and readout electronics for the CCDs, and will be set up by the dome crew. The only things the observer need to be concerned about is the temperature readout on the power supply for each controller. It reads in degrees Celsius to the nearest 1/10th degree at a location in the dewar near the chip. It should be fairly stable, and very close to -105 C for the CCDs.

The long slit capability of the spectrograph is very useful for extended objects as well as collinear ones. For these sorts of observations, one nearly always wants to rotate the instrument TUB to some predetemined (or in some cases, determined on the spot from the guide camera or CCD direct frames) position angle. It's useful to know which diretions are which, for various position angles, in order to plan setups and verify that they are correct.

On the guide camera, the scale and orientation varies with diagonal mirror position. If the TUB is at the standard position angle of 90 degrees, then in mirror position 2 one sees a field about 2 arcmin across on the guider with north up and east to the left. When offset guiding in position 3, this remains the same. The slit runs left-right on the guide camera. At a position angle of 90 degrees, this means the slit runs E-W. In position 4, the field size is roughly halved to about 1 arcmin, so about half the total slit length is seen on the guide camera at a given guide camera position. The guide camera may be moved by the telescope operator on its stage to view locations farther along the slit if necessary.

On the CCDs, with the TUB at position angle 90 degrees, north is right and east is at the top for the blue side (note the dispersion direction is along rows). The red side dispersion direction is along columns, so it is rotated 90 degrees with respect to the blue side CCD, so that north is down and east is right. It could be worse; at least these are simple rotations of most charts. The slit is of course still E-W, so on the blue CCD the slit appears vertical with east at the top. On the red CCD it appears horizontal with east at the right. Note, these orientations are for when the data are displayed with the XVideo software used by the Kast data-taking system. Images are flipped top for bottom in DS9, IDL, and most other image display software (meaning that for PA=90 deg, east would be down on the blue side and north up on the red side).

For different position angles of the TUB, the relative orientations of the guide camera, slit and CCDs are unchanged, since they all move together. The effect of going to a higher position angle (that is, in the usual sense of north through east) is to rotate images on both the guider and CCDs clockwise.