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Hi Giovanni,
We discussed the lunar occultations of Uranus and Mars in this thread
https://britastro.org/forums/topic/occultation-of-uranus-during-lunar-eclipse
and we have a thread for the imminent occultation of Mars
https://britastro.org/forums/topic/full-moon-occults-mars-on-2022-december-8
The DB and RB are relatively long-duration events, about 35 s, so any measurements from amateur images or timings will be approximations to the high-quality NASA JPL ephemerides
https://ssd.jpl.nasa.gov/ephem.html
Clear skies,
Alex.
Hi Duncan,
The dynamics of solar eclipses are very well known, although that’s no reason why you shouldn’t measure the obscuration for yourself.
The Observers’ Challenge and the BAA Handbook listed the obscuration percentages for various locations, whereas the article in the October Journal gave the magnitude values (fraction of diameter obscured by the Moon). Some casual observers were put off by the small obscuration percentages, not realising that the magnitude values signified impressive partial phases. I prefer that ‘eclipse magnitudes’ are quoted in eclipse work.
Some teams observe total solar eclipses to measure the Sun’s radius, aiming to determine any evidence of long-term change in its diameter, e.g.
‘Estimating the Eclipse Solar Radius from Flash Spectrum Videos’ in
https://www.iota-es.de/JOA/joa2022_2.pdf
(17 MB download)
Cheers,
Alex.
Hi,
Locations in Asia for the Uranus occultation (txt file)
Lunar diagram showing locations’ chords.Computed by Occult.
Cheers,
Alex.
Attachments:
Hi,
World map for Uranus event attached.
A month later, on December 8, Mars will be occulted by the Full Moon. (World map attached) and see p. 39 of the 2022 BAA Handbook. Observers in the British Isles will be well placed to see it, although it’s an early hours show.Alex.
Hi Dominic,
Have a look at this message on the IOTAoccultations forum
https://groups.io/g/IOTAoccultations/message/72766
and the discussion thread.
Cheers,
Alex.
Hi Peter,
If you look at the region (from about 155 deg. to 170 deg.) in my earlier limb profile, I think it also matches the images from other observers’ high-resolution stills and GIFs.
Alex.
Hi Peter,
Here’s an extended profile for York at 09:53 UT. If we look at too wide a limb segment, we’ll get bamboozled with all the peaks and troughs.
Cheers,
Alex.
Hi Paul, all,
I attended yesterday’s TA AGM and the illumination in the church hall was ‘spot on’ (pun intended). Dark enough to clearly see the presenters’ impressive graphics, with enough light filtering through the curtains that there wasn’t a safety hazard.
(Thanks to William Stewart for giving me a lift from-to Birmingham New Street station. Even then it was a long day, 16 hours 50 minutes door to door).
Clear skies,
Alex.
Many thanks for recording the AGM business proceedings and the very interesting talks. Our speakers spend a lot of time assembling their presentations, yet I see that the IoP continues with its policy of floodlighting the audience and directing spotlights at the display screens, washing out the finer details. Thumbs up to Nick James when I attended last year’s AGM, who kindly reduced the intensity of the illumination. (I’m slowly developing cataracts, and extraneous light impairs my viewing).
This ‘light trespass’ isn’t unique to the IoP, London. At other venues organisers and attendees have been aghast when I’ve suggested that we close the blinds and dim the lights. However, at last Saturday’s autumn meeting of the SHA in Birmingham, they only retained the inobtrusive safety lights on the theatre steps, so we could all enjoy the fine graphics on the screen.
It’s much clearer for me to watch talks on YouTube, and the few meetings I now attend are to meet friends and contribute documents to the BAA’s archives.
Clear skies,
Alex – The Commission for Dark Lecture Theatres 🙂
Limb profiles often require some mental gymnastics. Transposing the plot L-R, so that the PA (Watts Angle) increases from L-R, gives the attached image. Does it match James’ Silhouette?
It’s tricky to identify the required PA when we need to work from the N point of lunar images presented at various orientations, such as from my alt-az mounted Mak.
Alex.
Hi Peter,
If this is unsuccessful, please let me know a site location and time, and PA of the Moon’s limb and we can try that.
Alex.
Hi Peter,
Here’s an inverted plot of the lunar limb generated by Occult from LRO/LOLA data. It’s for the location of Cirencester at 09:50 UT on 2022 October 25 to compare with James Weightman’s ‘Lunar Mountains Silhouette’ image.
https://britastro.org/observations/observation.php?id=20221025_124443_d85bceb02058323a
Note that the Occult plot has a linear baseline, whereas the lunar limb is curved.
I might not have used the correct limb angle in Occult, and as you view the limb in fine detail any discrepancy in the site location and altitude, or error in selecting the cusp angle, can cause a significant difference in the resulting limb profile.
Alex.
Attachments:
Hi Peter,
The comprehensive occultations software suite Occult
https://occultations.org/observing/software/occult/
can generate a lunar limb profile for Baily’s Beads analysis (see attached)
I’ll have a look tomorrow to see if I can extract a limb profile matching our observers’ images.
Alex.
Attachments:
Hi Denis.
It’s only on for two nights and thankfully they’re not blazing lasers into the sky like they did in 2020. My meteor cameras shouldn’t be plagued this time, hopefully.
Here’s their plans for other cities:
Cheers,
Alex.
Hi Nick,
Yes, it’s likely that a body with higher density or cohesive strength would be far less affected. The NASA news release says:
“The recoil from this blast of debris substantially enhanced DART’s push against Dimorphos – a little like a jet of air streaming out of a balloon sends the balloon in the opposite direction. To successfully understand the effect of the recoil from the ejecta, more information on of the asteroid’s physical properties, such as the characteristics of its surface, and how strong or weak it is, is needed. These issues are still being investigated.”
We still need to wear our tin hats…
Alex.
We almost take for granted the amazing guidance and control systems required to hit a celestial bullseye at those high velocities – and that the camera will be set to the correct ‘shutter speed and f-stop’.
https://www.nasa.gov/feature/dart-s-final-images-prior-to-impact
Looking forward to seeing the images from the CubeSat which was also monitoring the impact!
Alex.
NASA TV will be presenting live coverage from 6pm Eastern U.S time, which (I think) equates to 11pm BST.
Amateur and professional astronomers in the southern hemisphere have been asked to obtain photometry of the Didymos+Dimorphos system
https://groups.io/g/IOTAoccultations/message/72575
Alex.
