Observing & Reduction Tips

(NOTE: a major rewrite of this is in the works)

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(coming soon) The JEE Dissertation

 

How to calibrate video: http://scottysmightymini.com/JEE/HowToCalibrateVideo.htm

 

Good summary FAQ: http://scottysmightymini.com/JEE/2014IOTA_JEE2014CFO_Final.ppsx

 

GJEE – Europa water geysers

Discussion: Embargoed

 

TJEE – Io Torus Tip Transit

Discussion: http://scottysmightymini.com/JEE/IoTorusJEE_Discussion2014-Mar-08.pdf

 

 

 

The JEE Observing Program has now adopted an official camera:

 

(coming soon will be recommended settings for observing JEE with this camera)

 

The Imaging Source DMK 21AU618      DMK 21AU618.AS

 

http://www.theimagingsource.com/en_US/products/cameras/usb-ccd-mono/dmk21au618/

 

http://telescopes.net/store/dbk-21au04-as-dbk-21au04-as-bayer-color-camera-1.html

 

 

 

 

 

 

JEE_sunset

 

 

Introduction

 

JEE2012 is a great opportunity for amateur and professional astronomers to work together to accomplish something no one thought was possible. That is to actually detect and measure the tenuous atmospheres surrounding some of the moons of Jupiter as well as this same material that is captured in a torus ring around Jupiter, called the Torus of Io. The most exciting aspect of this project is since the moons of Jupiter are bright compared to most astronomical endeavors, the JEE work can be done in the smallest of telescopes, putting the ability to accomplish a real scientific measurement in virtually anybody’s hands. We have documented measurements of Io’s atmosphere in a small 80mm finderscope. Thus even the simplest amateur astronomer can perform some of the same measurements that our space probes have done flying out to Jupiter, and at a significant fraction of the cost. Add to that, the Juno Space Probe is on its way to Jupiter right now and they have expressed interest in some of our data. So here is the chance to actually contribute to real science. http://www.nasa.gov/mission_pages/juno/main/index.html

JEE stands for Jovian Extinction Event. This project has its roots in a discovery made in 2009 during the Jovian Mutual Event season where anomalous dimming and brightening occurred during the period of time outside of the actual mutual event. During this particular event of 20090807 Io was passing in front of Europa and occulting Europa with its body. But several 10s of minutes prior to the occultation a slow dimming occurred, and then following the occultation a reverse slow brightening began. Theorizing that this dimming and brightening occurred due to the extinction of the light of Europa by the tenuous material of the atmosphere surrounding Io, an observing program called the Io Atmospheric Extinction Project (IAEP) was launched to verify or refute this theory. Over a dozen folks from different countries submitted many dozen data sets and documented 28 events the indeed showed that extinction due to this tenuous material was being detected. We even then accidently discovered that Europa had an even larger and easily detectable atmosphere, as well as the Torus material that Io passes through constantly. This formed a new observing program we now refer to as JEE.

 

The results of IAEP were published here:

 

Degenhardt, S. et. al (2010), Io and Europa Atmosphere Detection through Jovian Mutual Events, The Society for Astronomical Science: Proceedings for the 29th Annual Symposium on Telescope Science, p. 91-100 

http://scottysmightymini.com/JEE/SAS2010_Io_Europa_Degenhardt.pdf

 

 

JEE Schematic cropped

 

The mechanics of the Jovian dust field

 

Without getting into specific technicalities, here is the basic understanding of how and where the material that makes up the Jovian dust is created and scattered. Io, the moon closest to Jupiter, is under a lot of stress from being so close to a super giant ball of gas. Io is geologically and electrically very active. Volcanoes constantly spew dust and gasses from Io, and the electrical and magnetic storm between Io and Jupiter trap this material for a short period of time. Io’s weak gravitational field will hold on to some of the material first, and our first order assumption is that we have detected this material out to about a dozen Io radii around Io. We have also found trails of it as many as 30 Io radii away from Io. Then the material slips away from Io into space. Some of it is trapped in a magnetic torus ring around Jupiter that Io passes through in its orbit, called the Torus of Io. It then eventually migrates out in space. Europa sweeps up some of the material and it is gravitationally bound temporarily out as far as 25 Europa radii. These numbers are preliminary and are what we hope to clarify and quantify with JEE2012.

 

 

 

The observation

 

The Jovian Mutual Event (JME) season occurs when the plane of the orbits of Jupiter’s four brightest moons is edge on so that they mutually eclipse and occult each other. This occurs at a frequency of about every six years and has about a dozen months of regular mutual events occurring. The difference and beauty of the JEE season is it lasts for years due to the outer reaches of the Europa and Io atmospheres. Actually the JEE season never ends because Io traverses through its torus nonstop, and about once a day is passing through the eastern or western tips of its torus where dimming are recordable.

During an occultation JME the body of one moon occults or blocks our view of another moon line of sight to earth. So far we have documented Io and Europa to have a tenuous but measurable atmosphere of material. If Io or Europa is the moon in front occulting a moon behind it, then the light from the moon behind Io or Europa will experience a slow dimming the closer it gets to the occultation, and then a slow brightening after the occultation. The total magnitude lost to extinction is very subtle, about 0.1 to 0.2 magnitude, but very measurable with quality imagery and a few basic techniques. The most important technique is time. This is the reason this has been overlooked for the 400 years since Galileo discovered the moons surrounding Jupiter. The dimming, which is miniscule, occurs over many 10s of minutes, and in some cases many hours. So collecting images over the right period of time is one of the most important aspects of the observation. The predictions made for JEE21012 are designed to facilitate the understanding of the right period to observe. It is likely you will only be able to record data over a very small portion of a total event, but your data combined with others is what will make up a total lightcurve. This lightcurve is almost 50 minutes long and you see the extinction dimming was over 20 minutes before the occultation and the length of the brightening is unknown afterwards because of incomplete data.

 

20090807 IoIInIII O-C plot

 

 

The most important technique is time. This is the reason this has been overlooked for the 400 years since Galileo discovered the moons surrounding Jupiter. The dimming, which is miniscule, occurs over many 10s of minutes, and in some cases many hours. So collecting images over the right period of time is one of the most important aspects of the observation. The predictions made for JEE21012 are designed to facilitate the understanding of the right period to observe. It is likely you will only be able to record data over a very small portion of a total event, but your data combined with others is what will make up a total lightcurve.

The key to making a successful observation is a few basic methods. First and foremost, try to keep Jupiter out of the field of view of your recording at all times. Jupiter provides glare that makes photometric reductions more difficult (but not impossible). This is not always possible due to different observing systems, but try to keep that in mind.

Next, understand the predictions to know ahead of time which moon is the target, i.e. the one that will experience the dimming. Know which one is causing the extinction, i.e. the moon in front for our line of sight. In the early parts of the upcoming JEE season all you need are those two moons in the FOV if at all possible. At reduction time I will simply compare the intensity of the front moon to the back moon and get something like this:

 

 

So in some cases you will want high magnification to get just the target and front moon in the FOV and exclude Jupiter. In the case where a JME occurs, it will require a third or fourth moon in order to do a photometric reduction because your target and front moon actually merge to a single spot.

The past observing complain was imaged unfiltered in what is called photographic magnitude. We have desired photometry in other colors given that JEEs involve extinction phenomenon, which certainly implies varied colors are being extinguished by the dust and gasses that make up Io and Europa’s atmosphere. I would predict, for instance, that given the large amount of sodium and sulfur one would expect to see a deeper occultation in the red portion of the spectrum. But with Rayleigh scattering the moons may lose blue. B, V, and R imaging would help answer this. So it is desirable to have different spectrum data. If you are able to include filtered data, that would be bonus data for this round of observations in 2012. The AAVSO will likely participate in JEE2012, and they are quite capable of multicolor photometry. http://www.aavso.org/

You will see “wing data” length of time suggestions in the predictions. Wind data means taking measurements outside of an event before and after the event occurs in order to get a good baseline of the intensities. The longer you can record before and after the better, because one never knows what else exists outside of the predictions. This is in some cases unchartered territory and methodology. That is why it is an “experiment”.

The next concept to understand is saturation. If you make a recording or snapshot of Jupiter’s moons and the gain of the camera or the exposure is too long, the disc of the moons will saturate the pixels. The intensity profile of the moons will be clipped or chopped off at the top. When clipping or saturation occurs information is lost. It is important to know to back off from saturation when making a JEE data recording (or any photometric data run). Here is an example of a JEE that was accidently left in saturation. Note the small window on the right showing the intensity profile of the moons circle in the video image on the left and that their tops are flat or clipped due to saturation. If you are new to this concept you will want to make some practice runs to learn how to image out of saturation.

 

 

Most data acquisitions to date were done with streaming video. In the USA the NTSC video rate is 30 frames per second, and overseas PAL is 25 frames per second. The target front moon, the probing back moon, and preferably one other moon used for reference photometry are kept in the field of view at all times. We photometrically reduce the video with a software tool commonly used in IOTA called LiMovie. A measurement aperture is placed over each moon and a background aperture is configured as well so that a photometric intensity of each object is corrected for the underlying background noise. By carefully configuring the shape and position of the measurement apertures one can minimize noise from the signal. By placing the background aperture on either side of the object being measured at an angle tangent to Jupiter one can completely cancel out Jupiter’s glare effects on the background.

LiMovie tracks each object for every frame in the video and gives you a CSV file of a number of parameters including photometric intensities corrected for background. This column of ADU intensities represents one data point for each video frame, so there are 30 ADU measurements per second for NTSC video and 25 data points per second for PAL. Ten seconds of video data is then binned to a single data point in an effort to eliminate effects of earth atmospheric scintillation, camera noise, and other random noise. Since AVI intensities are scaled from 0 to 255 and we are binning 300 frames for NTSC our effective intensity resolution is 256 times 300, or 76,500 (2x1016 bits). This significantly reduces the noise inherent in video and enables us to commonly resolve photometrically to 0.015 magnitude.

 

Fig9 limovie aps cropped

A screen shot of LiMovie and the configuration of the measurement and background apertures.

CCD data

 

For the first time we are receiving photometric data in multicolor. Members of AAVSO have submitted large amounts of data in red, green, and blue wavelengths. As of 2013 data is still being derived in a way to be combined with our unfiltered data. One lesson learned from the multicolor data sets is the cadence rate of image sequencing has to be sufficiently fast. Video offers superior coverage of long term photometric events because it provides an image stream of 30 images per second for NTSC and 25 images a second for PAL, and one can continually image for as long as your method of recording the video stream has capacity. Typical color data comes from still CCD imaging cameras. This may mean your image rate can be sporadic. Given that some of the trends like the potential Europa water geysers can occur in a matter of a few minutes one might completely miss a minima with standard CCD imaging rate. However it was found that most CCD cameras offer a pseudo video mode where the camera can continuously acquire and download images. Some of the JEE2012 AAVSO participants were able to convert their observing to this streaming image mode increasing their chances of capturing fast transient photometric events while also observing over long periods of time. There are still lessons to be gained in imaging methodology as we go into 2013 and beyond.

Color data is valuable in potentially helping us determine what wavelengths are suffering the most extinction and could help identify the materials involved in the extinction process. Spectrometry of a JEE event will be most valuable in identifying absorptive material but has not yet been achieved and techniques are still under development.

 

Ř  If you don’t have filter capability observe broadband unfiltered.

Ř  If you can only observe with one filter use B (BLUE).

Ř  If you can do two or more alternate between R-B, V-B, or I-B.

 

 

The next issue is time associated with your data. Given that JEE events occur over 10s of minutes to hours millisecond timing accuracy is not a must. But it is desirable that your intensity data be accurate to at least a second of UT. There are ways to accomplish this in crude manners. You could for instance log into the Naval Observatory Master Clock and record the screen prior to and after your video recording without stopping your recording (http://tycho.usno.navy.mil/what.html). Another preferred more accurate way would be to record a WWV time clock recording on your audio from a shortwave radio at 2.5, 5, 10, 15, or 20MHZ. Or if you own a GPS based video timestamp device like an IOTA VTI (http://videotimers.com/home.html) then you are as accurate as you can get for one of these recordings, as it will lay the UT time from the GPS atomic clocks onto your recording. As a last ditch effort your cell phone time is likely accurate to within a second, but only use that as a last resort. It is important in the end to report how you assigned the time to your recording, so keep good notes.

 

Here is an older page with some “How To” tips:

http://scottysmightymini.com/JEE/HowToJEE.htm

 

For advance observers with spectroscopy capabilities it is very desirable to get spectra of these JEEs to add to the understanding of the structures and components of the dust surrounding Jupiter.

 

 

What to do with your data

 

At this time Scott Degenhardt has a standing offer to reduce your data. If you take the time and effort make the recording or the snapshots he will reduce the data for you. He has tools he has developed that expedite the process while maintaining accuracy.

Contact Scott at this email scotty@scottysmightymini.com to discuss data reduction (or acquisition). All the data will go into a soon to be formed JEE database. Papers will be published so it is very important that you maintain good record keeping. Please be ready to provide the observers name, location, instrumentation, timing methods, and contact information and associations to go into a paper.

Mission statement

 

The call for observations for JEE2012 serves the main purpose of getting as many people to observe whenever they can and provide basic video or picture sequences over time during a predicted JEE so that the photometric reduction of those data samples may one day collectively yield a high resolution 3D model of the material scattered throughout the Jovian system. Anyone willing to do spectroscopic observations during a JEE may also contribute an accurate accounting of the specific molecules and their ratios in these clouds of material. We have also added the likely ability to detect Europa water geysers through the changing albedo to Europa’s reflected light via scattering from geyser debris of 500nm and shorter photons.

 

 

 


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