ASI 290mm - Canon 18-55mm
Occultation of the star Betelgeuse by the asteroid Leona (319).
I had an incredible experience on the night of the occultation of the star Betelgeuse, by the asteroid Leona. A very difficult occultation technically for the reason that the star was very bright and with a very short exposure time the photo was "burned" and as a result a no reference star was captured in the photo. Therefore new techniques were used to overcome this problem. The weather was not an ally and in fact all the forecasts showed clouds for the whole evening. However, around 1:00 the weather cleared up and allowed us to set up the cameras. But the shocking thing was that at 3:00 the fog that had covered my town of Ioannina, came up to the area where I live and covered everything, so we started to pack up the telescopes in frustration. However 5 minutes before the occultation the sky cleared and we managed to get the recording right! Anyway the phenomenon was not visually visible although several people noticed a slight drop in the brightness of the star( reportedly somewhere around 1.5 mag ).
Completing the study of the rare phenomenon of the supergiant star Betelgeuse being occulted by the asteroid Leona I was anxious if my measurements were reliable and correct, in order to draw accurate conclusions that would help the international community about what happens to such a large star just before it explodes and goes supernova. The data was processed and I was very pleased to find that the recordings were correct and fortunately there was no point where the photos or video were beyond the point where they were scientifically unprocessable. The data will therefore be sent for more thorough analysis to Paris to be used along with the measurements taken in Spain, Italy and Turkey. I think that in America the weather did not allow measurements to be made. Congratulations to the amateur community in our country (and of course congratulations for all the people who participated to this campaign from the other countries Spain,Italy,Turkey,USA!) for participating so actively in this very important event, and to the Aristotle University of Thessaloniki for their support.
* A video showing the drop in brightness of Betelgeuse which was estimated at about 1.5mag. The occultation as recorded by my location is at about 01h 12m 33s to 01h 12m 38s, UTC .
Occultation of Betelgeuse by the steroid Leona (319). File *.mp4.
A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS4 measured from stellar occultations
A major campaign aimed at determining the size, shape and geometric albedo of the dwarf planet candidate 2002 MS4 through the analysis of nine stellar occultations conducted between 2019 and 2022. Using 13 selected chords from the occultation of 8 August 2020, the elliptical edge of 2002 MS4 was determined. The body has a semi-major axis of 412 ± 10 km and a semi-minor axis of 385 ± 17 km. The results show an object that is ≈138 km smaller in diameter than prdicted from thermal data, possibly indicating the presence of a previously unknown satellite. More information on the results of this campaign here:
https://arxiv.org/abs/2308.08062
and here where the existence of a huge crater about 45 km deep and 320 km in diameter, with τhe rim of the crater has height of 25Km!:
Occultation of the star TYC 1401-00444-1 by the asteroid Melpomene (18). The duration of the occultation was calculated at 5.72sec, while the decrease of its brightness at 1.3 mag. Skywatcher telescope 250mm and ASI 290mm (cooled with special construction). The acquisition program SharpCap (*.ser file) was used and for the curve extraction the programs PYMOVIE and PYOTE. The occultation took place on Wednesday 19 May at 21:23:10 UTC 2021 in the constellation of Cancer.
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VTI construction and affordable setup for asteroid star occultations
During the quarantine era, an important project was successfully completed and involved the capture of time in a video file. The accurate recording of the occultation of a star by an asteroid as well as the measurement of the time of fall of a meteor-diaton to calculate its velocity, is for a professional as well as for an amateur a very important parameter. For this reason, various devices have been manufactured and marketed which are called Video Time Inserters (timestamps). Devices that are used not only in astronomy but also in many other fields. A short list is given below:
http://occultations.org/observing/recommended-equipment/iota-vti/
https://www.blackboxcamera.com/pic-osd/sprite.htm
https://www.shelyak.com/produit/pf0063-timebox/?lang=en
These devices import the exact time into an *.avi file making it easier to record the event correctly. Choosing the most economical way, but clearly the most difficult, I decided to build such a device based on the Arduino platform. A device that without the help of a friend of mine in two specific points I would not have been able to realize. Cost of implementation? 68 euros. A very small amount compared to the above implementations. The materials were purchased from Greece and eBay. The idea on which the whole construction was based was based on a proposal by Piotr Smolarz made in 2017 at an IOTA conference. This device achieves an accuracy of msec since it is connected to GPS (1pps). It has been compared with the previous devices and the accuracy it provides in measurements is the same. There are of course several points that need attention to complete its construction, which were resolved over time and with a small change in the program code. Also needing attention is the digitization of the OCR time so that the software (Limovie, Pymovie, AOTA) can capture the correct time from the video to make the correct graph-curve of the occultation. Cameras for recording the phenomena for this purpose are available for all budgets. A Google search is enough. Besides, there is a corresponding thread on Astrovox for video astronomy. The best ones of course are WATEC for this purpose. It's just that their focusing, especially when talking about Newtonian telescopes, is a problem because they need to be placed further into the focuser in some cases. This was solved in two ways: by using various counterparts (which I happened to have in my possession) and secondly a patent on PVC pipes, there is the way to build them on their site https://occultations.org/, sent to me by Ted Blank from IOTA. As I found out he is finally using a 3D printer for more convenience. The setup was tested with great success with the 10'' Skywatcher. So on a small budget, you have a decent system for recording star occultations from asteroids as well as meteor observations that depending on the circumstances may cost less than the camera itself, especially if you are talking about WATECs. In the market, the QHY174GPS with built-in GPS is a middle-of-the-road camera. Its combination with SharpCap seems to be working very well.