From: Mamoru Doi (doi@ioa.s.u-tokyo.ac.jp)
Date: Sun May 12 2002 - 20:48:30 PDT
Rob,
Thank you very much for your hard work, and I am sorry about
the situation. I now realized what happened.
I adopt the same dithering parameters which we used for March-
April Suprime-Cam runs (SS1-SS4) except for the position angle
of the field of view.
I changed the position angle of SDFe and SDFw so that rectangle
FoVs align with SDF center images (whose position angle was
already determined) so that the area covered with three shots
becomes compact. However, this made the difficulty, since the main
dithering direction becomes short side of a 2kx4k chip. We didn't
realize this becomes a big problem, since Japanese group usually
make a mosaic image from multiple CCDs once (One of the purposes
for dithering for us is to remove the effect of gaps between CCDs).
In any case we need more discussions for observational parameters
before Subaru next runs (fall big project) including standard star
observations. Since many targets are included in the big project,
we need enough time to negotiate with others Japanese people.
-Mamoru
>> Most of these are the new ones from yesterday; anything else has been
>> deemed to be extremely unlikely. I will try and go through and rate the
>> unrated Subaru supernovae. Indeed, that's what I had hoped to be doing
>> for most of the last two days, but somehow the search of SDFe fell
>> through the floor and I basically lost the last 24 hours to that.
>
>Since I made it sound like those of us doing the subtractions (i.e. Alex
>C. and myself) dropped the ball on this, I thought I'd explain. In all
>previous searches, we've used dithers small enough that we could just
>subtract the images of one chip in the search run from the images of the
>same chip in the reference run. (This is also how the FROGS work, I
>believe.) The dithers on the Subaru fields were much larger than
>anything we've used in the past. We were not fully prepared for the
>implications of this (i.e. the large lost area due to the intersectino
>of the dithers on one chip), and developing the hacks to our subtraction
>procedures to properly handle the large dithers without losing too much
>area is what ended up taking me out the last couple of days.
>
>As always, when we're developing the methods of dealing with things
>during the search it's much more stressful than when we're fully
>prepared for the search we're doing ahead of time. There was a
>fundamental difference this time around that we hadn't thought through
>going in.
>
>-Rob
Mamoru Doi
Institute of Astronomy
School of Science
Univ. of Tokyo
voice +81-422-34-5084
fax. +81-422-34-5041
doi@ioa.s.u-tokyo.ac.jp
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