Monday, September 3, 2012

Venus Transit Aureole Captured

The new October 2012 issue of Sky and Telescope has an article by Jay M. Pasachoff entitled "A Glorious Transit of Venus."  One of the items explained in the article is the occurrence of an "aureole" around the polar region of Venus caused by sunlight refracting through the upper atmosphere of the planet.  The article featured the results of a team of astronomers on Haleakala who were specifically observing this phenomena.

Hey, that's were we were ... well, almost.  This group was in the astronomical complex on the next hill over from our location at Red Summit.  I am sorry that their location was restricted; I should like to have met with some of the observers over there.

The article motivated me to look more carefully at my prominence-detail exposures around ingress and egress.  Sure enough, several frames during ingress show a clear illumination arc which I presume to be the same phenomena as described in the S&T article.

The one below, taken at 17h20 GMT, just before second contact showed the best detail.  Images were taken with a Lunt LS60T/PS Hydrogen-Alpha telescope with a DMK41 monochromatic video camera.  Since I was primarily trying to get full-disk images, I was not using any additional optical magnification.  The resolution is not great on these enlarged images but you should be able to see the arc.  You may have to brighten your screen intensity to see it as the contrast is still pretty low.

and here again zoomed in with annotation in both grey-scale and false-color gradient which is easier to view on darker monitors.

Venus Polar Aureole - Greyscale image in H-alpha light 

Venus Polar Aureole - False-color gradient map

No such luck during egress.  I am missing the prominence-exposure frames that might have shown something.

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