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Here’s the latest uncompressed FITS from the STEREO HI. This is from Oct 5th at 23:28. Lots of nice tail detail visible.
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60s exposure in grotty, hazy conditions from Chelmsford tonight (Oct 4) shows it around mag 13.2 unfiltered vs Gaia G.
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It is continuing to fade. For photometry it is worth checking that you don’t include the 15th mag star just west. There are also a few 17th and 18th mag stars within a few arcsec that will come into play as it fades. Attached image taken earlier this evening as it got dark.
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Last night (July 14/15) was clear here in Chelmsford. This asteroid is now 12 million km away and is around 19.3 at its brightest. It varied quite a bit over my 20x60s subs and, at its faintest is probably mag 20 or so.
https://britastro.org/observations/observation.php?id=20240715_211942_4a7a99b2a55cc815
Giovanni – The Nikon D3000 shouldn’t do anything with the pixel data in raw mode so none of the setting that change JPEGs should do anything. I think the CMOS sensor in the D3000 is 12-bit native. Could you put some of your raw images online somewhere so that I can download them and have a look?
Dave Coffin’s dcraw is the basis of most, non-proprietary, raw converters out there:
https://en.wikipedia.org/wiki/Dcraw
It is open source and converts from pretty much any raw format to start TIFFs. It can do this without applying any modification to the data. I believe that there are Windows versions out there.
A nice application which uses dcraw is rawtran. This converts raw files to pseudo photometric band FITS files:
2024 MK was still a fairly easy target this morning (July 7) at a range of 6 million km. Magnitude was around 18.6 at brightest.
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The Goldstone SSR did some bistatic Doppler radar imaging of 2024 MK using DSS-14 (transmit) and DSS-13 (receive) at around 2m resolution. The images show that the asteroid is around 150m across:
https://echo.jpl.nasa.gov/asteroids/june2024.goldstone.planning.html
Petr Pravec had already determined that it was a non-principle axis (aka tumbling) rotator from optical observations showing multiple rotation periods from just over an hour down to around 20 minutes.
That looks very impressive!
This article on the silvering of the 100-inch Hooker mirror is on a slightly bigger scale:
https://articles.adsabs.harvard.edu//full/1933ASPL….2….5E/0000005.000.html
It’s clear in Chelmsford at the moment. Here is the asteroid.
https://britastro.org/observations/observation.php?id=20240629_223859_f40c4f01458212ac
This is pretty old news. Here is some background: https://www.iau.org/static/science/scientific_bodies/commissions/c3/c3-annual-report-2022-2023.pdf
A key comment is that “The OC is worried that a new nomenclature might be simply ignored by most astronomers”. Indeed it might.
The early explorers were clearly not “nice” people as currently defined but who of us today will pass muster when compared to the moral standards of people 500 years in the future?
And here’s a colour wide-field image from tonight (Jun 24/25). The bright star at the top is epsilon CrB which is mag 4.2. T CrB should be brighter than this when it goes off.
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I’d forgotten about this. I’ve just had a look and Pallas has just sneaked in to my 30s patrol image from last night.
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As you say, the first opportunity to get this object from the UK is as it gets dark on June 29, around 8 hrs after close approach. It is then moving rapidly north through Pegasus. It is then visible throughout the short night moving rapidly but quite bright (fading from 11.3 to 11.7). By the following night it is well-placed in Andromeda and moving much more slowly but it will have faded to below 14. It then stays in Andromeda as it moves away from us and fades to around mag 18 by the night of July 5/6.
I had a go at imaging Capella this afternoon in a clear, transparent sky after I’d finished with the Sun. I took 1000 frames with an exposure 879 us and gain set to minimum on an ASI1600 using a 90mm, f/6 refr and then took the same number of dark frames with the same exposure. Capella was quite close to the Sun so there is a lot of forward scatter from drifting pollen but, after calibration, and taking the V mag of Capella as 0.08 I get a sky brightness of 2.6 mag/arcsec^2. Remarkably close to what I expected. A video of the calibrated light frames is here:
The Meinel plot approximates the response of the human eye which is what I think Grant was interested in. Clearly things would be different if you used filters etc.
What’s a summer blue daytime sky?
Anyway, interesting calculation. The wonderful book “Sunsets, twilights and evening skies” by Aden and Marjorie Meinel contains the attached plot. It indicates a factor of 70 million between a perfect night sky and the noon zenith sky. That is 2.5 * log10(70E6) = 19.6 mags. Assuming a perfect night sky to be 22 mags per square arcsec that would put the noon daytime sky at about 2.4 mags per square arcsec so a bit brighter than you calculated.
The surface brightness of the Full Moon is around 3.4 mags per arcsec so that would imply that it is about 40% the surface brightness of the daytime sky which would be easily detectable with the naked eye. That is something you should be able to demonstrate easily by taking an image and measuring it.
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