Report on the installation and testing of the new medium resolution gratings for DIS: ------------------------------------------------------------------- The new medium resolution gratings for DIS have been fabricated and Alan Uomoto brought them to the site last week for installation and testing. We have been doing some testing of the gratings and potential users of the new gratings will find the following information useful: Blue Red Lines/mm 600 300 Resolution ~3.18 A/pix ~3.53 A/pix Coverage 1628 A 2824 A Blaze 4000 A ? If the medium resolution gratings are in: Low res slots High res slots ------------- -------------- blue red blue red ---- --- ---- --- Step position 796 649 748 648 Angstroms per step 16.2 28.1 9.8 20.1 Central wavelength ~4763 ~6826 4471.7 6825.8 Minimum wavelength ~3950 ~5414 3960.3 5414.4 Maximum wavelength ~5576 ~8237 5583.0 8237.1 For a single setting the wavelength coverage is: 3960 to 8237 Angstroms The above wavelength coverage is for the medium resolution gratings in the high resolution slots with a central wavelength of 4472 in the blue and 6826 in the red, which yields a range of about 3960 to 5583 on the blue side and 5414 to 8237 on the red side. I have found that this gives sufficient overlap between the red and the blue sides and minimizes the amount of spectral coverage with low S/N near the dichroic. If the medium resolution gratings are in the low resolution slots, then the coverage is about 3650 - 5576 in the blue and the same in the red. Note that the Remark interface is set up to handle specific gratings, so setting the grating tilts for the new gratings is not trivial. In theory, if the medium resolution gratings were in the low res slots then one could simply multiply the central wavelength by 600/300 in the blue and 300/150 in the red. Similarly if the medium resolution gratings were in the high resolution slots, then you would divide the desired central wavelength by 1200/600 in the blue and 830/300 in the red. IMPORTANT: The above formulas do NOT work. However, we have empirically determined the tilts. If the medium resolution gratings are in the high resolution slots, then to get a central wavelength of 4772 in the blue, then set your grating tilt to 739 STEPS. Similarly, to get a central wavelength of 6826 in the red, then set your grating tilt to 649 STEPS. If instead the medium resolution gratings are in the low resolution slots, then for similar central wavelengths set the blue side to 795 STEPS while the red side is still 649 STEPS. Note the use of steps here in concordance with the previous note regarding the repeatability of DIS grating tilts. For different central wavelengths one can use the fact that there are about 9.8 Angstroms per step in the blue and 20.05 Angstroms per step in the red if the new gratings are in the high bays. If the new gratings are in the low bays then it is about 16.2 Angstroms per step in the blue and 28.1 Angstroms per step in the red. We hope to have throughput numbers sometime in the near future. Gordon Richards Alan Uomoto APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 40 in the apo35-dis archive. You can find APO the archive on http://www.astro.princeton.edu/APO/apo35-dis/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-dis@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO