From: "Terrence R. Redding, Ph.D." <tredding@mac.com>

Date: October 29, 2009 5:16:48 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Imaging Io against Jupiter


Good morning Mark.


I believe I saw it several months ago.  Christopher's work has been part of the inspiration to learn to image the planets.  He demonstrates what is possible when you focus on the same task daily and you get better and better.  I think I will have to have to determine a way to compare filtered images of say Ganymede and Io to see if Io represents a difference that can be associated with the artifact of an extended atmosphere.  In this research I am sort of a mechanic and scope operator.  Others are working with the data I produce and using it to verify, or confirm still other data.  However, detecting an atmosphere during a transit must be near impossible - still a good problem to think about.


I will most likely go back to the images of the past to see how they configured their systems to emphasize Io's atmosphere and then use similar filters here.  It is not likely that we will capture anything.  But still worth the effort. 


Thank for pointing me back to Go's animation.


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?


American Association of Variable Star

Observers (AAVSO): RTN http://www.aavso.org/


On Oct 29, 2009, at 3:46 AM, Mark Gaffney wrote:

Hi Terry, 

I don`t know if you were aware of this incredible movie by Chris Go? It`s of an Io shadow transit of Ganymede on the 16th August 2009...You`ll have to scroll back a ways...

http://astro.christone.net/jupiter/index.htm

It may give you some idea what`s feasible in your case!


Mark.

On 29/10/2009, at 8:28 AM, Terrence R. Redding, Ph.D. wrote:

Milton, thank you for your kind and helpful response.


I have been looking through past images of Io transiting Jupiter and I suspect it would be impossible to image this artifact.  It appears we have detected a slight shift in the light curve outwards 6 Io radii on one side and 9 radii on the trailing side.  But to see a disruption of Jupiter's image by this tenuous material seems unlikely.  Especially when one considered that imaging process is designed to sharpen the image and this artifact by its very nature would diffuse and soften the image to some degree.  However, the question has been posed and so I need to work through the process and determine how I should approach the task.


A blue filter has been suggested as the most likely to display the sulfur as a darker component in the images.  I will try that but will also try other filters as well.  When I select images to stack I will have to consciously avoid selecting sharp images when considering the area surrounding Io.  It will be interesting to see if that allows me to detect a slight "fuzz" associated with the moons atmosphere. 


The task provides a practical issue around which I can organize my study and for that I am thankful.  Now that my filter wheel has arrived I will resume imaging Jupiter.  Hopefully with some preliminary results to share.


Thank you again for taking the time to respond.


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?


American Association of Variable Star

Observers (AAVSO): RTN http://www.aavso.org/


On Oct 28, 2009, at 3:02 PM, milton_aupperle wrote:

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/
>