Videorecording Baily beads of the hybrid eclipse of 20 April 2023
ATel #15991; Costantino Sigismondi (ICRA, UPRA and ITIS G. Ferraris, Rome), Andrea Raponi (INAF-IAPS, Rome)
on 17 Apr 2023; 16:29 UT
Credential Certification: Costantino Sigismondi (sigismondi@icra.it)
Subjects: Optical, Request for Observations, The Sun
The analysis of the hybrid eclipse of 1567 observed by Clavius in Rome opened, in 1978, the debate on the secular variability of the solar diameter.
Anyone with a smartphone near the centerline of the incoming eclipse may contribute to our Baily beads' search for assessing the present value of solar diameter to 0.01".
In the smartphone camera a green ghost image appears when the Sun is slightly offaxis.
It can be exploited to record several Baily beads during a central eclipse, while their luminosity still saturates the direct image, and without using a solar filter.
The opportunity given by the incoming hybrid annular-total eclipse is to have many beads visible in the central phases, lasting in total nearly 10 minutes.
A video of 10 minutes around the central phase of the eclipse, at ISO 100, EV=-2, VGA resolution (640x480 pixels), 30 frames per second and zoom 4x, imaging the Sun and its ghost image, it is useful to individuate many beads in the ghost image, and following them near totality from the direct image.
On the same detector and on the same film, we have the brigth normal Sun and the ghost one, reduced in intensity by a factor of about 400.
The smartphone has to be stabilized during the whole video, and does not require tracking.
Several simulations have been realized to show the method and to prove its efficiency, e.g.:
1- https://youtu.be/0DOfl3QAe2I cloudless
2- https://youtu.be/3V0dHq2B_oE perturbed weather
3- https://youtu.be/wcMh3_n-pmM totality conditions.
The video in mp4 can be shared with the authors through Wetransfer.com, and they will be credited.
A short paper to help local media to encourage this observational campaign is linked to this Astronomer's Telegram.
1567 Hybrid Eclipse and Tutorial for 2023 observational campaign
