This is a rare and and high-value event. We've not sent a spacecraft near Titania since Voyager 2 in 1986. Central duration is 72 seconds. Titania is 32 degrees up in the SE, and Titania is 30" south of Uranus, which is about the same separation as the binary star Albireo. Should be able to get that with 8SE scopes (Karl), but take out the focal reducer after acquisition, to improve the image scale. Titania is 13.8, and should still provide some light during the long occultation. The drop is 2.2 magnitudes. V-R=0, both V and R are 11.75. The 59% half moon is about 80 degrees west of the target, and Uranus is halfway between the Plieades and Jupiter.
Uranus is at altitude 45 degrees Az=102, high in the East. To get 8SE scopes on it, just use the "solar system" button and scroll down to Uranus and "enter" to send the scope there. No need for RA/Dec. Finder pages are below, though.
We've gotten approved for doing an observing run on the MIRA 36" scope. We've got approval for taking the Cabrillo van and will take a couple of students if we can find interested students (extra credit!). If no students come (It's Thanksgiving week and travel plans, etc.) then in any case this Observatory run will provide valuable real data now that we're studying the Jovian planets in Astro 3 this month. I've got OccBox 3 finished and working, and now in testing. I believe it is now the best of our 4 OccBox rigs, but more testing to confirm. One test will be the 1999NU32 occultation Sunday night, which is supposed to be clear and warm. My proposal is to have my OccBox3 on the 36" with PAL time resolution and synched with the PAL time resolution of my PowerShot video cam as backup. Then, Kirk's gear on the 14" planewave SCT. Dan at MIRA has agreed the science value justifies commandeering the 14" Planewave for this event as well, and will remove his polarimeter when we arrive.
Science Value: A major science importance for this event, is to try and detect any atmosphere traces for Titania. There's been a good occultation of Titania already observed a few years ago (I'll track it down and link here) suggesting its atmosphere may be much thinner than Pluto's and only localized and episodic? That will likely require higher S/N than can be gotten on our 8SE scopes. But the 8SE scope (Karl at home) can get precision timings sufficient to see mountain topography and good shape measurement. So - getting detection of surface topography variance, given that Uranus' other moon Ariel looks badly beaten up, and Uranus unusual 90 degree polar offset from the ecliptic suggests past "blunt force trauma" may have occurred. Recommended cadence from Marcelo at LuckyStar is .05 seconds, which corresponds roughly with 2x for our Watec 910hx cameras. This should be quite do-able with such large light gathering as the 36" and 14" Planewave scopes will provide.
Updated info page from Dunham/IOTA
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Titania, photographed in 1986 by Voyager 2 |
The Uranus system at event time |
Temperature/Humidity:
It's 5,000 ft at MIRA. Not impossible that we could have temperatures in the 30F's, although mid 50's with 55% humidity are predicted as of Friday night. In any case we'll want to make sure our camcorders are warm and dry during recording. I suggest a heating pad but insulated directly from the camcorder as that may be too much heat. I have a heating pad which operates on AC which I will bring. Otherwise, perhaps Kirk you can use chemical handwarmer packs strategically at the right moment before observations.
If I can make sure I have all the required extra components, I may be able to run my backup OccBox on a 3rd telescope 8", but to monitor the data taking, that would have to be on the main scope floor and not remote placed. Any strange discoveries will want confirmations, after all. And, we know how easy it is to have one thing go wrong and data go lost. So far this year, Kirk and I have gotten pretty good at getting the data. Our batting averages are well over 90% (less than 10% where we fumbled something we shouldn't have, and data-taking failed). I'd have to run this 3rd setup on a telescope there on the main 36" floor to make sure all was well during the critical time and tracking was staying on.
Testing the new Watec PAL and Occbox3
The test1 image was taken with the target at 32 deg altitude, from a very highly lit apartment parking area, with a palm tree lit up partially in the out of focus field, and the stars not focused. High humidity and passing clouds, so it was a difficult grab of a couple of minutes. I did a Fourier finder and adjusted background/range and then labelled stars with their G magnitude from C2A. I'm happy to see that the vertical column noise is much reduced in this new Watec, and the depth seems to be good, given the conditions. This was done at 16x, gain=41, gamma=1, sharpness=4, no DNR, as per standard parameters.
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About 20s of light curves of selected stars. 4px static circular aperture "signal" in PyMovie. Even under these bad lighting conditions, the 14.4 star, given sufficiently long occultation of a second or so, could give a definite occultation. I'm happy with the performance. A better test under better conditions awaits on Sunday night. |
Our observations at MIRA on the 36" and 14" were a success. We had clear clean skies, and warm dry temperatures. However, the seeing was poor at the start of the night, but settled down to become rather good by 9pm and the Titania occultation.
Since my new Watec 910hx PAL version looked to be more sensitive and a cleaner pixel background than my older EIA Watec, and likely upgraded from Kirk's several years old Watec, I decided it should go on the 36", and Kirk would use his gear on the 14" Planewave. However, the downside of the 36" was the much smaller field of view and danger of not having a comparison star, and also the danger of saturated pixels. On the drive down to MIRA from Santa Cruz, I dictated a message for Kirk to immediately post on the IOTA Google message board, asking the pundits whether it was better to avoid pixel saturation by changing gamma, or instead changing gain and suggesting it was likely better to be reducing gain, and keeping the 2x setting. That's what we settled on. However, it was problematic that there was no usable ref star on the field in the 36" as I was testing. Testing was another problem - it required taping on the 36", then bringing the camcorder down, firing up the Vaio Win7 computer and firewire download, then xfer the test footage to a thumb drive, then inserting the thumbdrive into my Dell computer and run PyMovie on it. I had to do this whole sequence several times during the post-twilight pre-occultation time. Then, on the last test, I noticed that a nicely bright star had come into the field, suitable as a reference star. I then twisted the camera in the eyepiece to better get the target and ref star comfortably inside the side margins of the chip's field. But, the star was significantly brighter than the target star, and saturated at the settings I had settled on. So, more testing to try to reduce gain but not too much. I got that successfully done with only a few minutes till the occultation recording must begin... and then the real trouble. I had to set the camcorder out of its usual position in order to enable Jean, who ran the motorized focus, to live-watch the external monitor to achieve best focus. We settled on a defocused star and the combination of 2x setting, out of focus target, and gain=35 succeeded in avoiding saturated pixels. But again, up on the ladder, the camcorder was now on my left so Jean could access view of the external monitor, and after placing the camcorder in the OccBox, with only minutes now before the moment I needed to start recording, and did my checks but did not notice the now-hidden banana plug input not yet inserted this time. The result was: I saw the "REC" icon on the LCD, and the external monitor's view of the target, Uranus, and ref star, and assumed all was good. But no recording was actually happening.... At least, for insurance, I did video footage off the monitor using my hand-held PowerShot, and saw and recorded the sharp D and R of the target well. I will have to reduce the PowerShot video as substitute. The rendering of the brightness on the external monitor, and the auto-exposure on the PowerShot will mean that the photometry will only be useful for getting my D and R timings, not for photometric examination for anomalies. Fortunately, Kirk's data is excellent and will serve all these purposes.
RN's Data reduction:
I've run my PowerShot video data through PyMovie and PyOTE. The raw video file was read directly by PyMovie, and is in PAL cadence, just as the Watec 910hx was, so that makes assigning time stamps easy. The PowerShot was hand held, and not very steady; more intended as a documentary than for logging data. I had to take short clips around the D and again around the R, when the camera was sufficiently steady to permit good tracking. Then I used wide 8 pixel sizes for the target and reference star photometry apertures, and max=14 pixels for Uranus. I used Uranus as primary tracking since I worried I was also not holding the PowerShot camera at consistent orientation, and the reference star was much further from the target than Uranus. I used the refence star as a seconary tracking star. I adjusted the positioning of the aperture to be sure it would catch the R, and that worked. Both timings look to have been adequately done. I manually input time stamps into PyOTE. There were no dropped frames. The D and R were sharp and timings solid, as the brightness dropped to magnitude 13.8, still faintly visible during the video but harder to see on the frame-by-frame still look.
For Disappearance tape segment...
magDrop report: percentDrop: 84.5 magDrop: 2.027 +/- 0.204 (0.95 ci)
DNR: 7.42
D time: [05:19:37.7325]
D: 0.6800 containment intervals: {+/- 0.0052} seconds
D: 0.9500 containment intervals: {+/- 0.0118} seconds
D: 0.9973 containment intervals: {+/- 0.0249} seconds
For Reappearance tape segment...
magDrop report: percentDrop: 86.2 magDrop: 2.151 +/- 0.389 (0.95 ci)
DNR: 7.05
R time: [05:20:41.8826]
R: 0.6800 containment intervals: {+/- 0.0054} seconds
R: 0.9500 containment intervals: {+/- 0.0122} seconds
R: 0.9973 containment intervals: {+/- 0.0249} seconds
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PyMovie screen capture |
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Zoomed in on the D. The 1 integration partial is most likely due to the sharp D happening partway through the integration. Multiple partials would be a sign of a gradual event. But that's not the likely interpretation here. |
Same for the R. |
#/media/File:PIA00039_Titania.jpg){kind=link}