From previous ObsParis / CDS meeting
Using Aladin prototype v10 (6/6/2017) and TOPCAT v4.4 on MacOS
Healpix generation from a table in TOPCAT
In TOPCAT load a table containing a list of observations located in lon/lat
(working example is a large table of VIRTIS/Rosetta observations of 67P)
1) Standard way:
• Open Plane Plot panel, go to Form panel
• Click on the big Forms button (green cross) and "Add SkyDensity" from the local menu. Uncheck the previous Mark Form
• Go back to Position panel, select Lon and Lat parameters (C1min and C2min for an EPN-TAP view)
• Back to the Form panel, select parameter to plot as Weight (will be weighted by density), select combine mode, and adjust scale. Healpix generation is performed on the fly.
• Possibly adapt color scale in the Aux Axis tab (left menu)
• In the Form panel, you can save the healpix map (cell #, plotting parameter) - saved at scale 12, apparently. You can also load an existing map from there.
• Add new synthetic column providing healpix cell number (right-click on table column header and enter new column description):
healpixNestIndex( 6, longitude, latitude )
(adapt scale to data in use, 6 provides a resolution of ~ 1° at the Equator)
• Open Skyplot panel, add New healpix layer, provide inputs
• Standard setup for planetary maps is (in Axis / Projection):
Projection = sin (sphere),
Don't reflect longitude axis,
Sky system: Equatorial,
(in Axis / Grid): uncheck sexagesimal
• In Skyplot / Style panel, use Degrade and Combine mode to reduce resolution on the fly.
Mars HiPS generation
• In Aladin, load file Mars_MGS_colorhillshade_mola_1024.jpg
(MOLA integrated relief map)
• Go to Image > astrometric calibration:
Coord = 0.,0.
pos x/y = 512, 256 (lon = 0°, lat = 0° at image center)
size = 21.1' (= 360. / 1024)
Symetry: No => this is mandatory to get the image in the correct orientation.
But this currently provides a W longitude frame (entering Yes results in a reverse image (seen from the inside), not in a reverse frame).
Edit > properties: ascending longitudes - does not change anything here
• Convert to HiPS :
Tool > Convert current image to a HiPS
• The hpx image should be saved on disk automatically
MOC use case
- Load Mars MOLA hpx in Aladin
- Select two large craters in Mars Craters service from VESPA client
- send as s_region from VESPA client (in Aladin) - s_region currently provided in this service as with W longitude, so this will work
- select them in Aladin with pointer
- Generate common MOC for these 2 craters (Coverage > Generate MOC > from objects)
• Then: test intersections with something else.
How do we do that?