<div dir="ltr"><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div>We recently ran into a case where Obscore parameters are<br></div>either insufficient or ill-defined.<br></div>So, the question is: is this an issue that merits doing something<br></div>about or should we live with the ambiguity?<br><br></div>The case was a Chandra calibration observation taken pretty<br></div>far off-axis; we have quite a few of these and I don't expect us<br></div>to be the only ones engaging in this kind of thing.<br></div>The obvious purpose was to collect information on off-axis<br></div>behavior and PSF.<br><div><br></div></div>The first issue is that it would be helpful for unsuspecting users<br></div>to know that this was a calibration observation. Our database<br></div>knows that, but Obscore does not have a parameter that allows<br></div>communicating the type of observation. In addition to calibration,<br></div>one could think of observing modes, like pointed or scanning,<br></div>objective prism, grating, ...<br></div>Should Obscore be extended with information of this kind?<br></div>If so, how and to what extent?<br><br></div>The second issue concerns the coordinates, and is a question<br></div>of ambiguity.<br></div>The standard says "center of the observation".<br></div>Is that the pointing position (i.e., the tangent point) or the center<br></div>of the field of view? Both have their merits.<br></div>In the case at hand the tangent point fell well outside the FOV.<br><br></div>Just some more issues to mull over.<br></div>Cheers,<br><br></div> - Arnold<br><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><div><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr">-------------------------------------------------------------------------------------------------------------<br>Arnold H. Rots Chandra X-ray Science Center<br>Smithsonian Astrophysical Observatory tel: +1 617 496 7701<br>60 Garden Street, MS 67 fax: +1 617 495 7356<br>Cambridge, MA 02138 <a href="mailto:arots@cfa.harvard.edu" target="_blank">arots@cfa.harvard.edu</a><br>USA <a href="http://hea-www.harvard.edu/~arots/" target="_blank">http://hea-www.harvard.edu/~arots/</a><br>--------------------------------------------------------------------------------------------------------------<br><br></div></div></div>
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