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/