From: Terrence Redding <tredding@mac.com>
Date: October 28, 2009 6:55:33 AM MDT
To: alpo_Jupiter@yahoogroups.com
Cc: astro_IIDC@yahoogroups.com
Subject: Imaging Io against Jupiter
As some of you know I have been doing a series of Mutual events looking for an indication of a extended atmosphere associated with Io. Information on this project can be found here.
http://www.iop.org/EJ/article/0004-637X/563/2/1063/52792.text.html Through photometry, it appears we may have been able to detect the corona exposure. Quite surprising really
Where Io's gravity dominates over Jupiter's, within about 6 Io radii (6RIo), there is a corona (or exosphere) consisting of atoms and molecules that aregravitationally bound to Io. The density is much lower than the near-surface component, and there is little interaction between the constituents. The inner boundary of the corona is defined by Io's exobase, the distance from Io at which collisions between atoms are no longer important. Constituents that leave the exobase with velocities greater than the escape velocity or are accelerated to escape velocity by interactions with plasma torus ions can escape from the corona. A mapping of the sodium corona (Schneider et al. 1991) has shown that this region is roughly spherically symmetric about Io.
A question posed to the research group is whether any images of Io transiting Jupiter show this corona or exosphere? More to the point, if one wished to image the corona during an Io transit, what would be the best approach?
This season I have been learning how to image Jupiter, while participating in the Mutual event study. But now the task has changed somewhat. How should one configure a system for imaging the Io transit of jupiter with an interest in detecting an indication of Io's atmosphere, and especially the extended corona?
I am using a 14" LX200R on a permanent pier in a backyard observatory. I have a seven position USB controlled seven position filter wheel, so I should be able to easily try several different filters during a transit. I have the Baader's new LRGBC anti-reflection filters, and Schüler photometric filters for CCD photometric measurements and color CCD imaging. I also have a methane filter and an IR cut filter. I am very new to this notion of amateur astronomers collecting data suitable for science and so would appreciate any guidance and comments this group is able to provide.
It appears I should seek an Io transit at a time when Jupiter is at zenith, and that I should be looking for a filter that shows sulfur or oxygen. I am working my way through Warner's text, Lightcurve Photometry and Analysis, and Budding & Demircan's Introduction to Astronomical Photometry - but still would greatly appreciate all the help I can get.
I am looking forward to the response.
Sincerely,
Terry - W6LMJ - 14.287
Terrence R. Redding, Ph.D.
Redding Observatory South, West Palm Beach, Florida
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