The "day" started as we left bed, around 12:00. That means 4 hours of sleep, while the CCD camera was left making dark exposures. We started by taking calibration flatfields for the end of the previous night (for the corresponding spectral range), and then made the same stuff for the begining of the night to come (different spectral range).
Our nights are broken in two parts: WR140 observation, with wavelengths around the bnlue-green area (grating position on 9.3 micron), and the H-alpha region for all other targets (grating position at 10.5 micron).
The night was great! Humidity had given us a break for the second consecutive night!
We pointed to some targets and made some spectra of them, but they were not many. We stumbled across a problem: Some images were superimposed with strange emission lines! We spent a lot of time debugging the problem, from over-taping the spectrograph with opaque anti-lightleak adesive stuff, to carefully putting a black bag around the spectrograph and then wrapping it in a double black bag (those used for storing garbage). We then identified the emission lines as those from the calibration lamp, and took the power plug out, to make sure no photon was comming out of the lamp.
The problem would only be correctly identified at the end of the night: RBI (Residual Bulk Image). To make it short the CCD memorizes strong information from the previous integration it made, and also adds it to the next integration. A problem for which we knew not how to choose among solutions. Thos would only be attempted on the next day/night...
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment