Less than 90 days to the Spectro conference. We’re still not at the telescope yet, although collimation is done (see last entry). Looks like the spectrograph was NOT properly focused. I visited the observatory of my friend Joe D who is an expert amateur spectroscopist and has the same equipment. Sure enough the spacing on his optical train was totally different. The adaptor on his measured about 42mm. Mine was only 30 -35. Way off. I went back to the bench testing, looked at all of the adaptors I had stored in various drawers etc and could not come up with any combination of sleeves etc that were not either too long or too short. I assumed the adaptor that came with the Lhires was correct when in fact it was not. So I checked with Francois over at Shelyak Instruments and he confirmed that my set up was incorrect. The slit on the spectrograph for Lhires is 23µ, and the camera pixels are 4.54µ (Atik 460 EX). Then the image of the slit should be ideally 23/4.54 = 5.06 pixel for 1×1 binning or about 1/2 that for 2×2. I was struggling to get just under 4 for binned images. What to do? Looked like there was an adaptor specific for Atik cameras on the Shelyak site with more appropriate spacing so I got one of those. The results are promising. For a 5 sec exposure of the calibration frames I am routinely getting 2.8 or so FWHM. Hopefully we’re good now. I have never had to fuss with spacing like this before for routine astroimaging. I mean we’re talking mm here! But apparently it is significant especially if in the future we plan to contribute to astronomical research!
So hopefully time to move on to the guider! Thanks for reading!