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PostPosted: Fri Oct 04, 2019 8:46 am 

Joined: Fri Dec 10, 2004 10:34 pm
Posts: 370
Location: Surrey
The next transit of Mercury will be on 11th November 2019 and the first half will be visible from the UK weather permitting though you will need a good southern and particually SW horizon due to the low altitude of the Sun.

Robin will tell us more at the October London meeting but the timings are available at The Sun will set from the UK at about the time of greatest transit.

The May 2003 transit was better as the Sun was high in the sky, I have some images from that transit on my website at [url] ... index.html[/url].

As well as a solar filter you will need a lens with a long focal length or a telescope to get the image of the Sun and Mercury to a size where it can be seen. I used a 300mm f/l ( 473 mm on full frame sensor) lens in 2016 and Mercury is only just visible ( see image) . One tip is to avoid over exposing the Sun which automated exposure systems are likley to do as Mercury will disappear in the glare. The best way is either to use spot metering if you camera supports this or else use manual exposure as well as bracketing the exposures.

I have left the image the same size as it was on the camera to show just how small Mercury is - the best lens / telescope focal length with a DSLR is around 1000 to 2000mm.

I have just looked up the relative apparent sizes of the Sun & Mercury on the 11th November the Sun's apparent diameter is 1938.5 arc seconds and Mercury is 9.9 Arc Seconds so roughly 1/200th of the Sun diameter. As a guide if your setup shows the Moon full frame the magnification should be Ok for the ToM though you will need to add a solar filter of course.

Here is hoping for clear sky.


File comment: 2016 ToM Mercury is at about 9 o'clock on the image if you have trouble finding it - this is with a 300mm fl lens
20160509-123609-small.jpg [ 41.33 KiB | Viewed 587 times ]

Engineer @ Work - Astronomer @ Play
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PostPosted: Fri Oct 04, 2019 9:56 am 

Joined: Mon Jan 09, 2006 11:05 am
Posts: 5361
Location: Lancashire
I imaged the 2003 Mercury transit in the PST. The image included two small prominences and lots of filaments. Some regard H-a more interesting than white light observations for transits.


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PostPosted: Fri Oct 04, 2019 2:47 pm 

Joined: Sun May 11, 2008 6:11 pm
Posts: 3303
Location: Portslade, Sussex Lat 50deg 51min Long 0deg 13mins West
The 9/5/2016, Mercury Transit was very frustrating due to cloud, although we did manage a couple of glimpses in cloudgaps from Foredown Tower at 1214 & 1344 BST using PST scopes.
The 7/5/2003 Mercury Transit was wonderful, and was followed from start (0627 BST) to finish (1132 BST), first using the 12" camera obscura + high power viewer and later with projection using 30x75 spotting scope.
The 11/11/2019 Mercury Transit should be well placed for viewing at the FT as we have a clear south to southwest sea horizon , right around to Worthing and even sometimes the IOW! Weather permitting, will try various methods again. Regards maf

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PostPosted: Sat Oct 05, 2019 7:54 am 

Joined: Sat Jan 26, 2008 4:03 pm
Posts: 564
Location: Galloway, SW Scotland
Ooh, thanks for the tip-off, John. I observed one a few years ago, and it was well worth it.

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