Changes between Initial Version and Version 1 of Ask_an_expert

Timestamp:

May 8, 2009, 6:28:28 AM (17 years ago)

Author:

Sebastian Jester

Comment:

Create Ask an expert page with many new questions

Ask_an_expert

@@ +1 @@
+= Ask an expert = 
+
+== Existing data ==
+
+ * In `catdir.20090327`, i seems to be `nan` throughout, can that be
+   right?  or did I look in a region that has no i-band imaging? How
+   would I tell? (also see questions on `dvo catalogs` below)
+
+ * Eric Bell suggested: for synth.grizy calibration, compute only one
+   ZP per FPA not per chip - too few blue stars to caibrate on per
+   chip. Calibrate chip-to-chip variations via flatfield only. (For
+   uebercal with `relphot`, it's a different story!)
+
+== dvo (inc. addstar, relphot, uniphot, relastro, dvo shell) ==
+
+=== dvo catalogs & their generation, processing/stacking strategies etc. ===
+
+ * How do I make a lightcurve for a given object?
+
+ * We want to find dropout objects, which may involve identifying
+   objects in one filter (y, say) and then demanding non-detection in
+   another one or more (iz, say). How would I run a dvo query to find
+   all y detections without iz detections?
+
+ * The observing plan includes 2 images per field per night. Are these
+   stacked immediately, and objects detected on the stack? Or only on
+   individual images?
+
+ * Would it be feasible (space- and processing time-wise) to drop the
+   default 3pi detection significance threshold to 3-sigma, say, to
+   allow automatic catalog-level stacks (yielding ~5-6-sigma catalog
+   detections from a year's four individual visits)?
+
+ * In general, what is the plan for making stacks - at fixed calendar
+   dates, whenever a given region of sky has become unobservable for
+   the year, ...?
+
+ * At which processing stage, and on which timescales, will forced
+   photometry be run in all "other" bands based on detections in one
+   particular band? Do we have to do forced photometry ourselves to
+   get ''griz'' fluxes for ''y''-only detections within a few days or
+   weeks?
+
+ * What happens to negative fluxes (which will appear in forced
+   photometry) when they get converted to magnitudes? Luptitudes have
+   the correct behaviour for colours, but we have already decided that
+   they are not practical in a collection of surveys with different
+   and evolving flux limits, such as PS1SC 3pi + MDS + Andromeda. How
+   do I do a catalog search for flux ratios exceeding some
+   threshold (i.e. a colour cut) if I don't have luptitudes?
+
+ * What is the default stack optimized for? Is there a preconfigured
+   way (assuming the need) to do stacks optimized for other things,
+   e.g. for faint point-source photometry, for good seing only, ...?
+
+
+=== dvo shell ===
+
+ * How do I find out which filters/instrumental photcodes are present,
+   and to which photcodes they can be translated, in a given catdir? 
+
+ * When I plot image outlines with 'images' and/or use gimages to find
+   images overlapping a given coordinate, again how do I tell the filter?
+
+ * What happens when doing multiple avextract commands with different
+   regions? I'm asking because we tried many different avextract
+   commands with different regions, and somehow ended up with
+   (allegedly) 30,000 objects in (0.001 degree)^2 around
+   `(14.84438,0.05039)`. But maybe it was just because...
+
+ * ... the difference between `region` and `skyregion` is a bit
+   subtle, and it's not obvious which out of `avextract -region`,
+   `avextract -skyregion ra1 ra2 dec1 dec2` and "naked" `avextract` is
+   what one wants. I think it's because the names don't make clear
+   that one refers to the plot window and the other one sets the
+   region of interest for `avextract` etc. How about these
+   suggestions:
+   * Rename `region` to `plotregion`, and instead of `avextract
+     -region`, use `avextract -useplotregion` or similar
+   * Rename `skyregion` to `extr_region` (if one does that to
+     use with later avextract commands, one won't have to type it very
+     often per dvo session, so a long name is ok).
+   * Analogously, use `avextract -extr_region ra1 ra2 dec1 dec2`
+   * In any case, have `avextract` print out which region it used, to
+     give a visual check for the dvo user that s/he's doing what was
+     intended. 
+
+ * When using `avextract ... flag`, for which band do I get the "flag"
+   data?  If the flag is  not just for a single measurement , how is
+   the "object" flag computed from the "measurement" flag?
+  * It would be useful to have some sort of help text for the flags
+   from within dvo, and in the long run also to build in a simple way
+   to apply some set of flag cuts that are useful to restrict oneself
+   to reliable point sources, reliable galaxy magnitudes, etc.
+
+ * How do I open and address additional plot windows, e.g. to have one
+   for an image, one for CMDs, and one for plotting objects in sky
+   coordinates?
+ 
+ * Assuming a local image mirror, we would like to do things like:
+
+  * Plot a CMD, click on an object in the CMD and have its extracted
+    averages and/or measurements highlighted, or a light curve
+    generated, or the postage stamp pop up, the entire image loaded in
+    a tv display with all objects overlaid. In general, have some
+    action taken when clicking on a plot window or tv display window
+    that has objects near the cursor position.
+
+ * region -30 20 90 AIT leads to segfault? In any case, AIT, centered
+   on not 0,0 gives weird plot results
+
+ * How do I make axis labels?
+
+== ppImage ==
+
+ * How do I run `ppImage` from the command line with the
+   `PPIMAGE_OA_SOFT` recipe from
+   `ippconfig/sdssmosaic/ppImage.config` (which turns all steps off
+   except subtracting the constant software bias of 1000 counts via `OVERSCAN`)? We
+   tried 
+{{{
+
+}}}
+but it complains about not having been given a bias frame, even though
+`BIAS = FALSE` in the recipe. 
+
+== psphoth ==
+
+ * How is deblending of overlapping objects done?
+
+ * How is star/galaxy separation done?
+
+ * How do I get aperture mags, fluxes instead of magnitudes, etc. in
+   the output .cmf table - i.e. more or different outputs?
+
+ * How do I feed an external catalog to psphot for forced photometry?
+
+ * what's `PEAK_FLUX_AS_MAG` in the .cmf file?
+
+ * Is there a tool for doing quick overlays of the .cmf table on the
+   input image?
+
+== pswarp ==
+
+== ppStack ==
+
+ * Is there any rejection of cosmic rays based on outlier rejection in
+   stacking? Or does that mess up moving & variable object photometry?
+
+== ppSub ==
+
+== panTasks ==
+
+ * Where are the command lines stored for the individual analysis
+   commands that pantasks launches (e.g. the `ppImage` call for some
+   image I read about in ippMonitor)?
+
+== ippMonitor ==
+