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The 550D CR2 raw format is indeed 14-bits per pixel (i.e. 0 – 16384) but the processing for extracting the green channel from the two green pixels of Bayer colour array adds an arbitrary scaling probably due to the interpolation required. A simple scaling doesn’t really matter since you do the photometric calibration after extracting the green channel.
Most of the non-Canon software in use uses functions based on dcraw to do this coversion so you can have a look at the source code if you are interested!
Nice image. It just goes to show that there is always something interesting going on in H-alpha even when there are no white-light spots.
Thanks Dominic for doing this so quickly and thanks to everyone who provided material. The video thumbnail shows a frame from one of Mattias Malmer’s amazing 67P shape model videos. There are a lot more examples on his home page here.
Glad you enjoyed the meeting and the pub afterwards. For people who couldn’t make it we’ve recorded the projector video stream courtesy of a box that Dominic Ford found so we should be able to get it up on the site more quickly than before.
James, Looks like you had a really good view from the north of Scotland. This 1700 UTC Eumetsat image just shows how much of a north-south divide there was.
That’s really nice David. I had wondered about the plot on Xavier’s page. Great to see that it really was like that!
Thanks for all the images. It’s good to see that the transit was well seen around the country. I’ll be using these in my Sky Notes at the BAA meeting on the 25th.
I’ve made a small composite of frames I shot at ingress. These were the best single frames that I could find in a video which redefines the term “atrocious seeing!”.
Nick.
That’s a really nice timelapse James. I’m doing the Sky Notes at the next BAA London meeting and would like to show the final version when you have it. I hope you get clear weather through to the end.
I wonder what people would have thought back in 2003 when we had the last transit of Mercury if you had told them that in 2016 we’d be taking pictures like this with a mobile phone!
After a lovely clear morning cloud came across just as Mercury moved onto the disk. Here’s some video I shot but the seeing is awful and the clouds were a real pain. This is a single frame from the video near the time of internal contact.
Many congratulations Bill but you are currently unobservable near conjunction at about mag 21.6 in Pisces. You do get “easier” at the end of the the year as you brighten to mag 20 approaching opposition in Taurus. Harold is a bit easier since he is mag 20.5 in Leo at the moment.
That’s a really nice image. You obviously had very good skies there. The startrails software is very good and saves a lot of time when making pictures such as this.
Martin/James,
I’ve just watched this all the way through and it was great fun. Thanks very much for posting it. It gives a really good impression of the trip and shows how very different things were back then. It’s also great to see so many old BAA stalwarts at their prime.
Nick.
Yes, really bad news and another good reason why we should try to get as many plate archives scanned as soon as possible. There is a huge amount of historical data in those archives. The DASCH project is a really good example of this (see here) and I hope that they can recover from this disaster.
I think the reason for the difference is that the two values of JD that you calculated are in different timescales. I assume that the BAA calculator calculates HJD in the UTC timescale whereas the Ohio site calculates it in TDB. At present TDB is around 68.2s ahead of UTC so a BJD(TDB) will be around 68s later than HJD(UTC). When talking about JD it is important to specify the timescale used. The difference between the Ohio and BAA times is 68.44s which agrees well.
