From: "milton_aupperle" <milton@outcastsoft.com>
Date: October 28, 2009 1:02:33 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: Imaging Io against Jupiter
I only skimmed the paper, but I didn't see anything in it that made me think anyone would be able to detect this corona or torus optically with an amateur scope. They appear to mainly be talking about using spectrometers and multi second exposures with huge scopes and very narrow band filters to detect it.
For example, have a look at:
http://www2.jpl.nasa.gov/sl9/image188.html
I found it using Google and the phrase:
Sulfur spectrum Io Jupiter
It shows the spectra they isolated in the far UV for Jupiter and Io Torus. Earth bound observers can't image that because the atmosphere won't pass UV light that low, so in this case it had to be taken with a satellite.
As to filters, you would need to know what sulphur / oxygen specie are going to be there (i.e. S, S02,H2S, S04, 0, 02, 03 etc.) and then find out what the peak spectra are for each in the visible spectrum band. After that, you basically need a narrow band filter that eliminates all light except in those specific bands. Then your going to need multi minute exposures of Io without it being in front of Jupiter so that Jupiter isn't influencing the received light.
And I'm certainly no expert in narrow band imaging, but it is used quite a bit for nebula imaging to isolate the nebula from the sky. But it requires large light bucket scopes and long exposures.
HTH..
Milton Aupperle
--- In Astro_IIDC@yahoogroups.com, Terrence Redding <tredding@...> wrote:
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
http://olt.net/learningstyle/Site_2/Learning_Style_Research.html
How do amateur astronomers learn?
http://www.youtube.com/watch?v=zSgiXGELjbc
American Association of Variable Star
Observers (AAVSO): RTN http://www.aavso.org/