Mercury’s Sodium Tail
Accepting the high challenge of shooting the currently significantly well-capturable Mercury’s Sodium tail, I tried to make the record with no narrow-band filter, but only with full spectrum Baader BCF modified camera. Considering the bright short wavelengths are highly scattered due to the atmospheric extinction low over the horizon, the only colours to be captured then–with the modified camera–could be oranges and red (plus green and red rims of Mercury itself). And that should be helpful enough to detect the Mercury’s tail. This evening on 17 May, 2021, was absolutely perfect conditions as perfectly clear air after cold front over the Czech Republic (main picture) allowed me to follow Mercury just to the horizon, still bright. When moving lower, I started the sequence of 27 exposures (each 30s, ISO 2000), then stacked in one and tried some more aggressive processing (dark contrast, low key filter, detail enhancement, selective colour brightness enhancement…), and truly the tail appeared there (the inset; zoomed about 9 times to background image). Not much impressive as with a narrow-band sodium filter, not so far, but still a big success, I think! This just proves the Mercury’s tail can be truly bright. Used Canon 6D Baader IR modified, Tamron 70-200@200mm, f2.8, from tripod and Vixen U mount.
