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Yiannis. I’ve been lucky enough to get to quite a few very good dark-sky sites around the world. I have been to the Spaceobs site in the Atacama a couple of times, San Pedro de Atacama is one of my favourite places and the skies at Spaceobs are the best I have ever seen. It is a long slog to get there from the UK but definitely worth it. If you go in the southern hemisphere winter you get the centre of the galaxy overhead which just adds to the majesty of the sky.
This is a stacked set of 10s exposures with a 50mm lens from Spaceobs: https://www.flickr.com/photos/nickdjames/48273525482/in/album-72157709616722002/
There is a wide selection of telescopes to use too: https://www.flickr.com/photos/nickdjames/48273530247/in/album-72157709616722002/
La Palma is a very good choice for dark skies too and a lot easier to get to!
Your images from Sikinos are very good. A good excuse to spend a few days on Santorini too.
Nonsense? On the Internet? Never!
The C14 is f/11 whereas the C11 is f/10 so for extended objects he is sort of right but only for sensors with the same pixel size. The same does not apply to point sources since aperture always wins there. Even for extended objects, as you say, the larger aperture will always provide more signal. It is up to you how you distribute that on your sensor. Things were different in the days of film where you didn’t really have any choice in the matter.
Discuss…
Hi Chris,
That’s really great stuff and really important too.
I think it is really important not to conflate conventional light pollution from badly designed lighting and the effect of satellite mega-constellations. The two impacts are very different. For most people living in towns and cities the former has a much greater impact than the latter. The satellite constellations really only impact imagers and there are (usually) ways to mitigate the trails on images. I have been to really dark sites recently where the Milky Way looks like an illuminated cloud and visually the satellites don’t have any impact on the view event during late astro twilight. They are all over my images but there are ways of handling that.
We should be concerned about both of course but the former has a much greater impact on the vast majority of people (including most amateur astronomers) and we need to be careful not to equate the two from an amateur astronomy perspective since I think that weakens our argument when it comes to bad lighting. Bad lighting has no positive benefit to anyone but satellites certainly do. The impact on pros is much worse of course and so our advocacy is certainly very important in terms of getting operators to mitigate the effect of their spacecraft.
Nick.
Comet C/2023 P1 Nishimura has been in the STEREO-A HI1 field of view since September 17. It left it on October 3. A timelapse movie showing all of the frames over that period is here:
https://nickdjames.com/STEREO/comets/2023p1.mp4
Note that the frame rate changes through the movie since the cadence of frames from the spacecraft was doubled at certain points.
The comet is still visible in the STEREO HI images but it has faded considerably and it is moving much more slowly as it pulls away from the Sun. It should theoretically be visible from the southern hemisphere but the elongation is still small and it is no longer very bright so very few observations have been received.
https://britastro.org/cometobs/2023p1/thumbnails.html
The two bright objects above the comet are Mars and Spica.
Looks like Storm Agnes is on the way:
At least twice it seems…
How many more times- I am not a cosmologist part time or otherwise!
I know that but it was a convenient way to get back at you for your comment on my comet lightcurve. It did get a laugh.
STEREO data for the 19th and 20th:
https://nickdjames.com/STEREO/20230919.gif
https://nickdjames.com/STEREO/20230920.gifThe comet has been in the STEREO HI1 field of view since 17th Sept. The full res data is now available for the 17th and 18th.
Here’s an example for Sept 18:
http://nickdjames.com/STEREO/20230918.gif
Two nice tails.
Nick.
By coincidence I’m on La Palma at the moment. Last night I went up to the visitors’ centre which is around 2100m to look for the comet. Unfortunately there was a lot of cirrus out over the ocean in that direction but I did get a few images of the comet through thinner gaps. This one:
https://britastro.org/observations/observation.php?id=20230916_102938_2de129e1ecfdd06f
is a single 2s exposure with FoV 4×3 deg. The comet was 0.25 degrees above the theoretical horizon but refraction and my altitude made it appear more than a degree up.
It certainly wasn’t spectacular and it wasn’t visible in binoculars but it does show a bit of a tail if you zoom in.
I’m not expecting that C/2023 P1 will look anything like this but there have been reports of bright objects near the Sun in the past which may have been comets. A nice example is the object of 1921 seen from Mount Hamilton and possibly other places that is reported here:
https://adsabs.harvard.edu/full/1921JRASC..15..364P
Anyone who has been to Lick Observatory on Mount Hamilton can imagine that party looking out to the west towards the Pacific and seeing this mystery object appear briefly at sunset. We’ll probably never know what it was but they were experienced observers and a comet is a good bet.
This is a periodic comet which has been close to the Sun many times. Such comets tend to have a low dust/gas ratio which doesn’t bode well for a bright dust tail post-perihelion. It certainly has an impressive gas tail at the moment and it will be interesting to see how that develops over the next few weeks. Jaeger’s image shows it at 10 deg long so it might be visible in darker skies once the head has set.
Yes, you’re right, the media have hyped this comet up a lot and for most people it would be a real challenge since it is so close to the Sun in the sky. The elongation is now rapidly decreasing as it heads for perihelion so you will need very clear skies and a very low horizon and, preferably, a convenient mountain to see it over the next couple of weeks. It is an interesting object though and it does have a relatively short period (440 years) so I really should get a news item on the website. I’ll have a go at preparing something over the next few days.
This amazing image of it showing a 10 degree tail was taken from Austria this morning (Sept 7):
https://groups.io/g/comets-ml/message/31656
Michael Jaeger is one of the best comet imagers in the world and he has an excellent site.
Hi Duncan,
This comet is really close to the Sun in the sky so even if it does get bright it will be hard to find. It is currently very low in the morning sky in Leo but will soon move to very low in the evening sky as it approaches perihelion.
There was some discussion of it in the forum and on the comet section mailing list here:
https://britastro.org/forums/topic/a-good-year-for-japanese-astronomers
https://www.simplelists.com/baa-comet/msg/23154034/and there are plenty of images in our archive here:
Having a storm named after you is a great honour I guess and Skibbereen would be a good place to experience it!
I see that Met Éireann have also included Jocelyn after Jocelyn Bell Burnell, born in County Armagh, and the discoverer of pulsars (with some help from Tony Hewish).
I got another image of this comet this morning. It shows a faint ion tail to the west.
https://britastro.org/observations/observation.php?id=20230820_044052_9ecf5aeb201e50dfThe Japanese are very dedicated observers. The key strategy for amateur comet discovery is to scan the morning twilight since if a comet is in the right orbit it may appear here without being detected by the surveys. The attached plot shows the elongation of this comet, i.e. how far it appears to be from the Sun in the sky, as the purple line. The comet’s distance from the Sun and distance from the Earth are shown by the green and blue lines respectively. These lines are based on astrometry of the comet up to August 18 assuming that the orbit is a parabola, i.e. e=1.
You can see that the comet has been at an elongation of < 40 deg since the beginning of May and that Nishimura discovered it as it reached around 34 deg rising out of the morning twilight. As it approaches perihelion in September the elongation will drop rapidly and when the comet is at its brightest in September it will only be 12 deg or so from the Sun. To see it then you will probably want to be high up a mountain but we'll see. The surveys could have picked it up back in April when the elongation was much larger but it was then over 3au from the Sun and so would have been much fainter. I would expect that, once we have a better orbit, we'll find it somewhere in the survey data.
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I use a cheap barbecue cover bought from Amazon for my NEQ6 when it is left outside. It has survived some pretty torrential rainstorms this summer.
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