Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-06-28
Astronomy and Astrophysics
Astrophysics
Accepted by A&A (20/06/2005)
Scientific paper
10.1051/0004-6361:20042565
Historically, long-slit spectroscopic observations were carried out using the parallactic angle for the slit orientation if slit loss was an important consideration (either to maximize the signal-to-noise or to do spectrophotometry). This requires periodic realignment of the slit position angle as the parallactic angle changes. This is not possible for multi-slit observations where one slit position angle must be chosen for the entire exposure. Common wisdom suggests using the parallactic angle at the meridian (HA=0). In this paper, I examine what the best strategy is for long, multi-slit exposures. I find that in extreme cases (very long exposure time) the best choice is to orient the slit \emph{perpendicular} to the parallactic angle at the meridian. There are two effects to consider: the increasing dispersion with increasing airmass and the changing angle between the parallactic angle and the slit. In the case of \emph{traditional} slit orientation, the two effects amplify each other, thus rendering a significant fraction of the observation useless. Using the perpendicular orientation, the two processes work against each other, thus most of the observation remains useful. I will use, as an example, our 8 hour Lockman Hole observations using the Keck telescope, but generic methods are given to evaluate a particular observation. I also make the tools available to the community.
No associations
LandOfFree
Optimal slit orientation for long multi-object spectroscopic exposures does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Optimal slit orientation for long multi-object spectroscopic exposures, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optimal slit orientation for long multi-object spectroscopic exposures will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-435235