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Hi,
My replacement BAAJ arrived a couple of days ago.
Thank you Andy and the BAA office staff,
Best wishes,
JohnAs mentioned by Martin, the IUAA had their General Assembly in Dublin in 1978. Also there, Patrick Moore gave a public lecture in the Mansion House. I remember it well, as this was my first time to attend an astronomical talk! I am afraid I cannot remember the actual title of Patrick’s talk. I did not attend the excellent IUAA event itself as I had not yet joined the IAS.
Quite a few of the IAS members were involved with the IUAA. My memory was that James Kelly, Ciaran Kilbride, Eamonn Ansbro & Vincent Deasy were the IAS representatives.
The IAUU had very laudable ambitions of setting up worldwide observing sections. However, one problem was they were overlapping (in part) with organisations like the BAA and the AAVSO etc which were already doing a good job.
John
Hi,
That is great news about finding a picture of Birmingham.
Thanks for sharing it Ronan. And also for your link about your recent talk to the private star party.
John
Gary, thanks for the heads up. I made it (visually) mag 13.9 on 2020 Oct 9 at 01:38 UT. I used the AAVSO chart. Yes, it is a rich field, but easy enough.
John
Hi,
Thank you for the replies. I did find a link to the value of Delta T that (pre-Covid) was updated every month:
ftp://cddis.gsfc.nasa.gov/pub/products/iers/
See the file deltat.dat
The latest value they give is for 1st Feb 2020 (69.3752 seconds).
In my lunar phase program I give the result to one minute (just like the BAAH), which is why I was looking for Delta T. It’s nice to be able to compare the predicted and actual values.
John
Hi,
Yes Peter, that’s the USNO link I relied on for years, but in my brower (Firefox), it’s broken.
Just to be clear, the quantity, I was after, is Delta T = (TT – UT), where TT is Terrestrial Time and UT is Universal Time.
In J.Meeus Astronomical Algorithms 2nd Ed page 77 he states “The exact value of the difference Delta-T = TD – UT can be deducted only from observations”. I assume, for my purposes, TD and TT are interchangeable.
John
Hi Lee,
My understanding of preceding/following is that it only refers to celestial west/east respectively. This is independent of any rotation of the planet.
If you turn off the power on a telescope drive, a planet will drift in the Field of View in the preceding direction.
John
Hi,
Derek, that’s a nice photo from a fixed tripod. It’s good to see a Tamron lens still in use, I used one many years ago on my Olympus film camera. What focal length setting did you use?
The position in your photo is consistent with JPL Horizons. It would appear Stellarium uses the MPC comet elements.
John
Hi Nick & Derek,
Yes, that’s a relief, JPL Horizons gave a better position. Please see the attachment for a JPL Horizons overlay in Guide 9.1 every hour (UT). By the way, when I checked JPL Horizons, the comet was in fact near TYC 4029 694, not TYC 4029 714.
I look forward to your images, Derek. It was a nice object visually in my 28 cm SCT at 80x, much better than C/2019 Y4 ATLAS.
Thanks, John
Hi ,
Sorry for the confusion. I meant to say October 2019, not October 2018.
As Alex says its under the Journal Archive. This can found by following Publications tab –> Downloads menu item –> Journal Archive thumbnail. See:
https://britastro.org/downloads/3844
John
Hello James & David.
My thoughts
1. An eclipse is when we see a body in the sky passing into the shadow of another body. Examples are lunar eclipses and eclipses of Jupiter’s satellites. This does not include Solar ‘Eclipses’ as the Earth is not in the sky.
2. Yes, transits occur when a smaller body is silhouetted against a larger body in apparent size. Examples include the Transit of Mercury and Annular ‘Eclipses’ of the Sun.
3. Occultations occur when a larger body covers a body with smaller apparent diameter. Examples are Total ‘Eclipses’ of the Sun and Asteroids occulting stars.
John
Hi Ronan,
That brings back memories of hearing Paul Mohr’s talk at the first Galway Astrofest. In fact, it spurred my Interest in John Birmingham and in particular in T CrB, I have given a number of talks over the years on Birmingham and his recurrent nova in both Ireland and the USA.
It shows how obscure Birmingham’s name was, in that as a teenager with my copy of the 16th edition of Norton’s, I thought Birmingham was a reference to some observatory in the city of the same name 🙂
Thanks for bringing the video to our attention.
John
Hi,
I find the sky continues to darker after the end of astronomical twilight when observing in Topsfield, MA, USA. I would put this down to the turning off of lights over the region.
By contrast when in Rush, Ireland I do not see this sharp decline. There, lights are no longer turned off.
An interesting article, Some Thoughts on Twilight, from Sky & Telescope (Oct 1960 p.207) by Joseph Ashbrook talks about this subject. I believe this can be found at archive.org.
John
Hi,
Thank you for your responses.
Jean Meeus gives a time of the spring equinox in 2019 to be 21:59:34 TD in his Astronomical Tables of the Sun, Moon and Planets, 3rd Edition (p.151). Taking Delta T is be 69 s currently and subtracting this value gives 21:58:25 UT. Rounded to the nearest minute this is 21:58 UT.
John
Hi Emil,
I have a copy of the The Sky 6, which I am willing to sell. The disks are in my house in Ireland, but I am out of the country until late March. It is currently not installed on any computer.
If you are interested please PM me.
John
Hi Dominic,
Many thanks for sorting that out. I was able to pay via Paypal (without signing up to them). I was and am using a PC with Win 7.
All the best,
John
