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I got mine from Postie about a week ago (ca Oct 23). The packaging was battered, but the contents intact. It could be a post-office difficulty – not sure. Im wondering if the enclosed handbook causes a hiatus.
The occultation times in the table on page 337 are for an observer at Greenwich. See the HBAA page 39 and note under the table. Why the 0.1 minute precision? Well this is the format (as suggested by David) that is produced by Occult4 software. There is a routine that produced the tabulated data used by the Handbook. This format is historical, and goes back to the 1960s, but a good summary for two stations.
Predicted times can be computed to better than 1 sec if the observer coordinates are used in the software, so the tabulated times are only a guide. For other locations the times will differ by up to 2 minutes depending on how far the observer is from Greenwich.
Im grateful to Nick Hewitt for including Lunar prediction on his Sky Notes page. I find them fascinating to observe. The Lunar Section Circular contains predictions to 8th magnitude for those seeking more opportunities. The time format for these are dd hh mm ss.s for a single station – again a guide only.
I offer a service to keen occultation observers. In that i can produce predictions to 1 sec precision for their site via email.
Tim –
Lunar Section.When observing/recording, the event will occur near 2309 UT. so best to record video from 2308 to 2310 UT in the UK (see the graphic).
For most observers with access to NTP, it would be best to use the Meinberg software to keep the computer clock sync’ed to UT.
https://www.meinbergglobal.com/english/sw/The recording software of my choice is SharpCap, where SER or FITS images can be selected with recording between 10 and 3 fps. (dependent on the instrument and camera). With a 20cm and mono CMOS, an exposure of 100ms may be possible. All depends on transparency and light pollution levels, so the only way to tell is at the telescope. As long as the 12.6 mag target is detected clearly, a result is possible. The ARPS section can perform the analysis and help prepare a report.
Cheers – Tim
ARPS (Occultations)I have done some photometry and i aim to start with a nice clean sensor window. Any other shadows may be from the filters. I don’t clean the filters and if in a filter changer, are protected somewhat.
For sensor window cleaning, I use a Delkin-Devices Digital Duster kit (They can found on e-bay). The “wand tips” are of card-like material to which a few drops of cleaner solution is added (It soaks in). The damp wand is then drawn cross the sensor slowly in one direction. The tip can be cut down to fit the sensor. Then test the camera, or if you have a eyepiece or something under a bright light, its possible to see any dust or hairs. It may be an idea to used the blower, but the danger then is that you blow material back on the window.
If you have a camera serviced in the UK (Starlight Xpress, ATik) then it may be possible to send the camera to them for cleaning. I know Starlight used to do this. Its worth asking.
This link helps to identfy the source of shadows: https://astronomy.tools/calculators/dust_reflection_calculator
Yes! You might be able to blow some of it off, but i would use a DSLR camera sensor cleaning kit to remove the remainder.
-and keep the glass covered up !
Cheers – TimDavid,
Thanks for the alert for this TNO !
There are a some us in ARPS who hope to observe this, and the more observers we have, the better the chances of a success.If no occultation is recorded this is as important as a positive. From Oxfordshire the altitude is 12 degrees and with my mobile 8″ F/4 i should be able to reach this star in 0.5 sec on a CMOS mono camera (FITS is preferred by Pro-am). I will aim for a S/N of 5 at least, which is the minimum to clearly confirm a detection or not.
I have a rule-of-thumb (or eye), that provided the star image is above the noise (or transparency) threshold of the camera/scope and “visible” on the monitor throughout the recording period, this should provide the S/n desired. This can be tested by dropping the exposure down until the image is unclear and then increasing it enough to become a stable image. The mid-time for UK is 2218 UT and i would suggest recording for a minimum of 2 min either side (4 minutes in all). That would be about 240 FITS files. Test images on stars of mag 14 would be a guide.
Timing the frames can be done using the computer clock recently synched to NTP. Timing data will be put in the FITS header by the recording software.
Best of luck David, and to all observers,
Tim
Asteroids and Remote Planets Section (Occultations)Thanks Alan. This is a shock!
I was one of many, and shared a cabin on one of the upper decks. The full-board cost for the 2 week cruise was £140.
In the end we had a great eclipse despite some local fisherman removing the buoys careful positioned on the center-line (no GPS then).
Alan Sidi made the film “Line to the Sun” Thanks to Martin for putting it on his channel. Great memories indeed.Pink Floyd had just released Dark side of the Moon, and some folk on board were raving about it. To my embarrassment I’d never heard of the them !
Tim.
The sub frame calculator is helpful. Thank you. When you plug in numbers i can see the range of possibilities to try
TimThanks to all for reporting. So far no positive events but there are -ve ones (to be confirmed), and some reports to come in.
Considering the difficult conditions, many thanks for effort to observer, its much appreciated. The -ve results will help restrict the orbit better
for the next prediction.
TimNot sure Robin. Molecular absorption will be in the IR 2-20 u looking at my university notes. Interesting thought though.
Images of the target star taken last night (May 01/2), have been added to the page. http://www.stargazer.me.uk/call4obs/29PUK20230507.htm
They indicates an aperture from 8 to 10″ could image the star with exposure 100 to 200ms, even in poor transparency.I hope some observations will be possible and we get some chords. This will be my last update to the page prior to the event.
To be clear, a “chord” across an asteroid profile is two time points: Disappearance and Reappearance of the star, as seen by the unique position of an observer.
Good luck and clear Skies !
UPDATE: The occultation was successfully observed by the Asteroids and Remote Planets Section in the UK. It was a good prediction with a small path shift to the south and within the errors expected. If anyone else made a recording or observed the event, please send us a report – thanks very much.
Congratulation to all observes – Tim
Lunar section circular archive is incomplete: There is a jump from 1973 to 2019 and 1972 is missing. Is this a work in progress?
Tim
LSThis is what i have found Grant. The local server version of ANSVR on my PC is controlled by AIJ. It can be blind, or restricted to the sky area of interest. I’ve not used it much so far but seems pretty fast when constrained to one area.
Im hoping to use AIJ for asteroid photometry, but i dont know if it can be used successful for moving objects. Perhaps someone has been down this route and can advise me ?
Thanks for the tip about Linux on W10. I will investigate this.
Thanks Xilman. i believe i have the answer now. The secret is on the AIJ WCS settings page, where there is a tick box to constrain the search area to RA-Dec and the radius. Turn this off. Also uncheck the tick box to specify the pixel size. One should be able to specify this exactly, but turning it off works. I also entered the correct RA-DEC centre and constrained the search. The solves is lot quicker, as one might suppose. Hopefully im now in a position to solve any field in AIJ
Another hint is to start “Watch ansvr.log”. This runs in a cmd window. From this i was able to see the progress of the solve. Im sure you’r already up to speed on this, but i note it here for anyone else ascending the same incline !
Cheers…
Alex. thank for explaining some of the concepts.
If S/N was important, with hind-sight i would not have used a red filter. Of all the observations i count 5 instances of the use of an R filter. My data seemed OK (the READING light curve), but might have been better without the filter. The logic was to improve the seeing and so the resolution planet/moon.I made some rough notes which were useful to me at the time, but some of links are now unavailable. On the whole i believe we followed most of the good advice that was on offer.
As the occultation time approaches i see observers planning to observe on Occult-Watcher. This is good and i hope every one gets to see this remarkable event. But what will the maximum duration actual be? To find out we need observers on or near the mid line of the prediction. So anyone in the following areas would be helpful:
Redcar, Tadcaster, Castleford, Sheffield, Burton upon Trent, Solihull, Cirencester, Chippenham, Warminster, Weymouth and anywhere in between.
Good luck to everyone….
Thanks Alex for the reminder. Im looking forward to monitoring this long event. I am in the shadow and it could be one of the longest durations. We will see. My PB is a 29 second event. There is also the slim possibility of detecting a moon. The more observers there are, the better we can probe the space around Medea.
Good luck.I see on Denis’s images that JWST is about 3′ arc North of the HORIZONS position at my location in Oxfordshire. This is what my college maths gives me: (300/350,000) x 57.3 x 60 = 2.9′ ( Denis is 300 miles north of me). I don’t expect any prizes, but its good to exercise the brain cells from time to time.
