Spectroscopy

- added effective resolutions R on the main grism page, now also for a 1-arcsec slit rather than just for a 0.5 arcsec slit.

- created He, Ne, ThAr, arc maps for new grisms gr#18-20 available for users on the ALFOSC pages

- Updated the grism-page tables with basic info (resolution, dispersion, sampled wave range) on the new grisms http://www.not.iac.es/instruments/alfosc/grisms/ and with a plot comparing the new grisms (gr#18-20) to the old ones that have similar resolution properties gr#7, gr#8, gr#16.

Due to the VPH technology the new grisms are consistently more transmissive over the full visual domain, than the old ones, with relative improvements of up to 40% in throughput.

- support for the 3 new grisms added to our on-line quick-look reduction

ETC!!! - Pedro made new storage rings for the new grisms, i bought new grism-storage 'containers'

- new grisms:

rules/mm cenwave disp R range #18 1086 VPH 4360 0.82 1000 3520-5190 #19 823 VPH 5640 1.10 970 4510-6670 #20 484 VPH 7850 1.95 770 5850-9840

Andrea Bianco and Alessio Zanutta (Merate, Italy) approached us via Emilio Molinari (TNG); as they are streamlining their new VPH grism design and fabrication process, they were looking for partners that are interested in obtaining VPH grisms cheaply.

The 3 new grisms were tested in ALFOSC. The green and red grism perfromed according to specification, the blue grism had its transmission peak at 470nm rather than the intended 430nm, resulting in poor transmission in the bluest part of the sampled wave range. The problem turned out to be a slight (on the order of 1-3 degrees) misallignment of the components of the VPH grism. The grism is back in Merate being re-aligned.

- The internal flatfield lamp of the calib unit is too red, and scattered light dominates the spectrum, making it impossible to properly get rid of the prominent wafer pattern in the blue spectra.

I found that for blue grisms the pixel-to-pixel variations (wafer etching pattern) are best corrected for by constructing a flatfield from UBV imaging sky flats. To construct a spectral flatfield the normalised UBV flats are interpolated according to the (expected) wavelength of the pixels along the dispersion direction.

- The Neon lamp broke in August. Two new ones have been ordered, and one He, to leave 3 spares of each.

ToDo:

- test re-aligned grism 18

- re-glue slits 1.0 and 1.8