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Frustratingly it was mainly cloudy in Chelmsford last light but there were plenty of Perseids around in the gaps. Pictures of a couple of the bright ones are attached.
These days I prefer to operate my DSLR in HD video mode with manual exposure and the ISO fixed at 400 I then adjust the exposure during the eclipse to suit. I use a Megrez 72 and x2 Barlow operating at around f/13. I tend to take my filter off around a minute before second contact and adjust the exposure so that I get correct exposure on the inner corona which is visible even before C2. This leaves an overexposed photosphere but generally works well then for the diamond ring and prominences. You can see an example of this at around 0:25 in to this video. For Baily’s beads You would leave the filter on until C2 and use the same exposure that you use for the thin crescent.
During totality an example exposure for prominences, inner corona and chromosphere at f/13 is around 1/1600 at ISO800 which is what I used for the attached image. This is a raw image just scaled to 50%. This would be good for the diamond ring at C2 and C3 without a filter but you would wind up the exposure to get more corona. Depending on your field of view of course since really long exposures are only worth doing if you have a shorter focal length.
A huge advantage of digital over film is that you can see things in real time using live view so you can adjust exposures to suit the conditions. If this is your first eclipse though I would strongly suggest that you don’t spend too much time imaging but use binoculars and the naked eye to enjoy the view.
It’s in outburst: https://twitter.com/SuperASASSN/status/889934384496640000
Looks a really interesting bit of kit. A kind of hybrid of visual observing and electronic. I expect it would appeal to a lot of people.
Wow, is it really 28 years ago! Yes, I remember the Titan/28 Sgr occultation very well, particularly the astonishing central brightening when light from the star was refracted around the limb of Titan by its atmosphere. I didn’t have any sophisticated equipment then and the attached photo was taken with a camera mounted on the back of a small refractor.
Cassini is a mission very close to my heart. I was there for the launch and will be raising a glass when it dives into Saturn’s atmosphere on September 15.
The orbit is still very uncertain but all the astrometry to date (a 25 day arc) implies that it is near parabolic with a perihelion at 1.8au at the end of 2022 or early 2023. This is much less interesting than if it had been in a shorter period orbit since it probably means the that the comet is dynamically new. Such comets tend to have significant activity far from the Sun but then the underperform as they move into the inner Solar System. Still, it is worth observing this comet if you have the equipment. It is very well placed and you don’t often get the chance to image comets which are 16au away.
That Youtube video is fantastic, particularly the thruster plume. Unfortunately I was distracted by other things on Saturday night so forgot all about it. I clearly missed a very nice display.
All three talks are now available to members via the meeting page here.
After yesterday’s meeting at Burlington House Peter Carson has obtained some more astrometry of this object. I’ve added that to the collection and the output from findorb is attached. As I said at the meeting yesterday the period and perihelion date are very poorly constrained at the moment and the residuals aren’t much different if you force the orbit to be parabolic. Astrometry over the next couple of weeks should start to resolve that so we should at least have a good idea of the orbit. It will be a few years before we can even guess how bright it is likely to be when it comes to perihelion in 2023.
Michael. We use a sony voice recorder and a video recorder that goes in the HDMI/VGA path between the laptop and projector. I can’t remember the model number of this but it wasn’t too expensive. Jeremy or Dominic will know the details if you need them. We then merge the audio and video together to produce the final recording.
It was a fantastic weekend with brilliant weather, excellent talks and great company.
Those at Winchester will know that I had set myself the challenge of imaging all four of the relatively bright comets around at the moment even though the pesky Moon was almost full. 41P and 2015V2 are the subject of our current Observing Challenge and they were relatively easy since they were near the zenith, 2017 E4 was a bit more difficult since it was only around 15 deg up at dawn and 2015 ER61 was the hardest of the bunch since it was only 5 deg up when the sky was getting very bright. I used a Megrez 72 refractor at f/4.8 with a Canon EOS600D on a Vixen Sphynx mount set up on the lower football field. I’m pleased to say that after an alarm clock malfunction on the Saturday I managed to get them all on the Sunday. The attached montage shows them all at the same scale. A full-res version of this picture is available via the link.
This comet is running much brighter than expected and it is now reasonably placed for the UK as a morning object low in the east at the start of astronomical twilight. John Toone found it by accident this morning while observing AG Peg and described it as looking a bit like a globular cluster in large binoculars.
Glad you saw it visually Peter. This IC is relatively easy at 8 deg elongation. I have seen Venus at previous conjunctions when the elongation was only 5 deg. You need to be really careful and have a very clear sky. In fact, I also remember trying to see a comet very close to the Sun using one of Denis’ telescopes. We were very careful and one advantage of a dome is that we could block out the Sun so that there was no chance of getting it in the telescope. There is a picture of me doing that somewhere but it is probably best not published for health and safety reasons.
Yes, it was almost certainly in outburst when discovered back in 1952. Unlike today, there were very few people doing astrometry then so the orbit is based on only 7 position measurements over an arc of 26 days. That, and the fact that the orbit will have been changed by relatively close encounters with Jupiter mean that it is very unlikely to be recovered with a specific search. The fact that it has not been picked up by the big professional surveys means that it must be intrinsicly very faint. I’m not sure where Guide 9 gets its data from but it could do with being revised.
The attached ephemeris is from JPL Horizons however, as Martin says, the orbit is very uncertain and it isn’t likely to be near these locations.
