Forum Replies Created
-
Posts
-
I’ve reprocessed my images from last night and the two faint blobs were artefacts caused by some problems on three of the subframes. I’ve removed these from the stack. Updated image attached showing the prominent features to the east of the centre.
Attachments:
The inner bright coma is showing quite a bit more detail now. The attached is 4 arcmin square, N up, E left, taken using the Alnitak telescope in Spain at 1906 UTC on Nov 17. There appear to be two blobs of material north of the coma. Does anyone else have any images that can confirm this?
Attachments:
My latest image (and an image by Peter Carson at around the same time) does show some emerging detail in the bright inner coma:
https://britastro.org/observations/observation.php?id=20231116_205120_39e0a2e36927510e
The attached image is around 2 arcmin square, N up. The bright inner coma is now about an arcmin in diameter.
Attachments:
It’s cloudy here tonight but I’m getting some images from the Alnitak telescope in Spain. This outburst is different to the others and David is right that this does look like a mini 17P/Holmes. I’m assuming the faint larger disk is the gas coma which expands quickly and the bright inner disk is the slower moving dust but don’t quote me on that.
It would be an interesting object to try spectroscopy on while it is currently bright…
I’ve just imaged the comet again and it was mag 9.4 on Nov 15.72 in a 34 arcsec aperture. This is a really big outburst and the comet should be a fairly easy visual target in a moderate telescope at the moment.
Robert. You’ll find quite a lot of different date and time formats are used in astronomy. The decimal date format is quite common for things that vary (such as outbursting comets) since it allows fairly quick mental calculation of the time between events. The next step is to get rid of years, months and days altogether and quote in terms of Julian Date. This is used a lot too but it is more difficult for the average human to interpret. If we arranged to meet at a pub at JD 2460254.333 most people (except some variable star observers) would have to go and look up a more familiar date before leaving home.
The point made by Paul Leyland up the thread is important too. In science, when we talk about quantities, we don’t want to imply more precision than is actually present. If you took it literally, July 20.82 would be 19:40:48 but we clearly don’t know the time of the outburst to that precision. The use of two decimal places in this context is used to indicate the level of precision that we think we have, i.e. around one hundredth of a day or around 15 minutes.
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.
