The gas giants have still been hard to observe from my home recently (only at a late dawn), but on June 14th I finally met good conditions.
Last winter I found an ASI462MC and I spent some time to review the filters that can be used to exploit the huge IR sensitivity of the camera. It is not a legend, since I have been able to image Jupiter in CH4 at 20 fps in binning 1x !!
My choices so far are:
- The Astronomik IR740 as the main longpass filter, to reach the highest resolution and SNR (the Baader 685 can be used as well, but I prefer the 740 for Jupiter at least)
- The Sloan z' will catch all the monochrome part of the sensor. The Astronomik 807 would be slightly better here, but I'm interesting in trying photometric calibration. These two filters are a better choice than the IR850 commonly recommanded here.
- The usual CH4/890,
- And the Y filter, whose purpose will be to exploit the very end of the chip sensitivity, with more efficiency that my good old RG1000. The Y filter corresponds to an intermediate photometric band in an atmospheric window between two H2O bands ; it is also well centered on another CH4 band, that one at 1 micron, and also on the thermal emission band of the venusian surface
Here is a graphic that displays the transmission of the filters along with the albedo of Jupiter (that of Saturn is very close, with only deeper CH4 bands).