Forum Replies Created
-
Posts
-
John Mason send me a video of the event from Barnham, West Sussex. I’ve put a processed version here: https://www.nickdjames.com/meteor/2023/202302/2023cx1_20230213025922_jmason.mp4
This was shot using a Sony A7s and 20mm lens at f/4.
The bright fireball recorded off northern France at 02:59:20 this morning was the cause of these flashes. The object that caused the fireball has now been officially named 2023 CX1:
https://minorplanetcenter.net/mpec/K23/K23CA3.html
It is the seventh time that an object has been discovered just prior to entry. The previous ones being 2008 TC3, 2014 AA, 2018 LA, 2019 MO, 2022 EB5 and 2022 WJ1.
Unfortunately weather over most of the UK was poor but people along the south coast saw it.
https://fireball.imo.net/members/imo_view/event/2023/937
John Mason saw it from Sussex and has sent me a video. I saw the flashes through thick cloud from Chelmsford at 02:59:21.
Details of the astrometry so far.
Attachments:
Hi Alan,
The program isn’t that clever! You need to tell it the X,Y coordinates of a guide star and search radius using “-a x,y,r” (this is used to align the stacks) and then the comet offset rate and image scale using “-o rate,pa,scale”. You can also tell it the image orientation if it is not north up using “-A pa”. Have a look at the autostack script to see how I have automated this. Alternatively you can get all of these things manually. A valid example command line would be:
fcombine -C -N -a 1006,221 -A 1.37 -o 8.86,190.2,5.49 outputfile inputfiles
In this case -N says to normalise all of the input images to the same sky background before stacking, the guide star is at 1006,221 in the image (using the default search radius of 5 pixels). The image PA is 1.37 deg, the image scale is 5.49 arcsec/pix and the comet motion is 8.86 arcsec/min in PA 190.2.
If you just type fcombine with no options it will list the options that it can accept.
Hi Alan,
The “could not allocate output buffer” message occurs if the program can’t allocate enough memory to do the stack or if the star and/or comet offset pixel-shift lists are incorrect. Can you post the exact command line that you are using so I can see where it might be going wrong.
It looks as if I can’t attach scripts to the posts here but you can find it here:
https://nickdjames.com/astrolinux/
Nick.
You can provide the image coordinates of the guide star manually or use something like SourceExtractor to select one automatically. I don’t use a Paramount but it tracks the guide star frame by frame so you would need to have pretty awful PE for it to lose lock. The search radius is configurable and if some of the subs are trailed you can set a PSF threshold which is used to reject images from the stack.
As an example of how it can be used the attached script uses fcombine to automatically stack stars and comets. The STAR option is simple. The COMET option is a bit more complex since it uses a local version of astrometry.net to platesolve so that it can get the offsets right.
Grant,
It’s command line so will run fine under WSL.
It is indeed C.
It only translates images. There is no need to rotate with an equatorial that has decent polar alignment. Translation is by integer pixels. There is no sub-pixel interpolation since that would be bad for photometry. Alignment is done by centroiding a reference star.
Paul – That is why I have never liked fork mounts although the price I pay is meridian flips. The comet was really nice tonight despite the bright moonlight. I get it to be 5th mag now. Here is a picture of my telescope effortlessly pointing near to the pole taken while it was taking the picture in the inset. I don’t get many chances to take a picture like this!
Attachments:
David. Yes the ion tail is very active again. Your images are excellent. Your fast RASA is ideal for this.
Gideon van Buitenen has produced a really nice simulation of the comet’s appearance which you can find here:
http://astro.vanbuitenen.nl/resources/C2022E3_simulation.gif
It shows the PA of the ion tail swinging around very rapidly over the next few days.
Interesting. I let my iTel subscription lapse since their kit was unreliable and the cameras were mostly old and/or not well calibrated. If things improve I might be tempted back. I did try Skygems but many of their instruments are offline or broken at the moment. Does anyone have any suggestions for good, reliable, high-quality remote observing. I would prefer pay-as-you-go since I don’t use it that often.
A very nice event. I got it on two cameras from Chelmsford:
https://britastro.org/observations/observation.php?id=20230111_000436_356d03a9d87988cd
There is a video from a fireball camera in Lanzarote which shows a bright and slow fireball northwest of the Canaries at 23:18:50.
https://twitter.com/RedSpmn/status/1612727698048311297
Drop time was 23:09 so this is around 600s downrange. Virgin Orbit stated that the vehicle reached 4.9 km/s which is a long way short of orbital velocity but fast enough to ablate on re-entry so this is consistent with re-entry of the second stage and payload.
If anyone else has contacts in the Canaries please ask if they saw anything.
As Grant says, putting stuff in orbit is still hard. Falcon 9 makes it look easy but Space-X has had a lot of practice.
I didn’t expect to see anything from Chelmsford but I set up a video camera with a 200mm lens looking at the horizon in the expected azimuth. Nothing detected.
Yes, a real shame that the second stage failed well short of orbital velocity.
Grant/Paul,
Yes, ignore my comment about it being 500 km up over LP. I forgot that the altitudes in the flight profile plot are kft. 500 kft = 152 km so at SECO it is indeed around 160 km up.
Damned imperial/metric confusion again.
Attachments:
The ground track from the Virgin site shows the launcher crossing La Palma at around T+ 560s. The vehicle is in the Earth’s shadow but the second stage motor will still be burning at that point (SECO is around T+ 590s). It will be over 500km up when it crosses over LP. It might be visible coming up in your north but I have no idea how bright the exhaust plume would be at that range and you have a bright Moon to contend with as well.
Attachments:
Yes, the spaceports in the Highlands and islands will be for vertical launches unlike the air launch approach adopted by Virgin Orbit. They are all currently aiming for 300 kg or so to polar LEO. You can do a lot with that mass these days. They are also looking at being able to insert small payloads into heliocentric orbit so missions to the Moon and other planets are possible with these small launchers. You only need really big stuff for people!
For the UK vertical launch vehicles have a look at Skyrora and Orbex:
https://www.skyrora.com/
https://orbex.space/Skyrora in particular are using a very British set of propellants (Hydrogen Peroxide and RP-1 kerosene). These were used in the Black Arrow launch of Prospero 50 years ago.
It is not just careers and training, it is a potentially huge and very lucrative business.
Regarding range safety the mission planning ensures that there is a very low probability of debris hitting anyone. The CAA wouldn’t licensed the launches otherwise.
The attached plot should allow you to determine the visibility at your location. Use the ground track and launch profile plots to determine the altitude and great circle distance from your observing site and the curves show how far above the horizon the launcher will be. For example if it is 1000 km away and 150 km in altitude it will be around 4 degrees above your horizon.
First stage burnout (MECO) is at around 180s and occurs at an altitude of around 75km. For the far southwest tip of Cornwall the ground track shows a great circle distance of around 450km. This corresponds to an elevation of around 10 deg above the horizon so the first stage should be visible from Cornwall if the weather cooperates. The visibility from SW Ireland is similar.
If anyone gets any video or images please send them to me. I can include them in the Sky Notes at the next meeting.
Attachments:
