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the sky at night venus transit episode


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Hi all, Pete Lawrence here.

Have just come across this thread so my reply is a bit late - sorry :)

Thanks for all the great comments about the show. I think the producer did a superb job of pulling it all together and recreating the real tension and excitement of our Svalbard transit viewing experience.

Just to clarify a few points. The scope I was using was my trusty FL102S Vixen apo on its original GP-DX mount. I chose this scope because it gives excellent high quality results and is just about portable in normal luggage for a trip like this. Having used it for 14 years or so, I also know the scope extremely well and can break it down into its component parts for transport. In this case, I took the fluorite lens cell and the Solarscope SF-70 hydrogen alpha filter on board the plane in my cabin luggage, just to be safe.

If you were alert during the Horizon programme, you might have seen the self same scope on there too as a background prop!

Weight was an issue and we're always trying to keep costs to a minimum. Consequently, when the scope and mount took up 19kg of my 23kg baggage allowance, I decided that the counter-weight had to stay at home in order for me to take a change of clothes! The alternative was to hang a bag of rocks or bottle of water from the counterweight shaft but the sealed lead-acid battery I was using for power, as luck would have it, wasn't too far off the weight of my original counterweight. I decided to hang this from the c/w shaft and use this to balance the scope.

This has a number of advantages including lifting the battery off the cold, potentially snow covered ground and keeping the cables out of harms way. I chose string as the holder material because it was light and easy to carry lots of spare so alternative cradles could be constructed quickly and easily if the need arose. The string cradle was hung on a metal hook attached to a ring. The ring was held in place on the c/w shaft between two jubilee clips so that it could rotate as the declination axis of the telescope rotated. This is essential to avoid the cradle winding up on the shaft and trying to pull it back round.

I also rather liked the back reference to the way amateur astronomy used to be done (and sometimes still is) - where makeshift solutions often saved the day!

The choice of the Vixen gave me two scopes in one as it works beautifully as a white light solar imaging instrument and, with the Solarscope filter fitted, doubles up for h-alpha use. I also had my trusty calcium-k PST with me to give me the opportunity to capture CaK images.

The use of an alt-az mount wouldn't have been practical on this occasion because before the transit I was trying to capture the full circular atmospheric ring of Venus. A manually positioned alt-az mount would have been dangerous and a nightmare to use. Working that close to the Sun, I needed a system that I trusted and was familiar with. As it happened I did get an image of the ring, so this paid off.

The polar axis on the GP-DX mount doesn't go high enough to satisfy the 78 degree requirement needed for Svalbard so here too some basic DIY needed to be applied to make it work. This involved a well positioned Allen key and plenty of electrical tape! In the end, the mount performed beautifully and allowed me to make the most of the small gaps we had at the start of the transit. The single (7.5Ah) sealed lead-acid battery lasted the entire session. A spare was on hand just in case the cold conditions caused issues though!

The initial finding panic was caused by the total cloud-out suddenly producing the tiniest of gaps. It's tricky to keep composure in front of a camera, talk to your fellow presenters in a calm manner and operate a telescope at the same time but fortunately Chris and Lucie sensed this and let me get on with what had to be done. Pointing the scope was extremely tough at this point. I've been observing the Sun since the mid-70's so I know how to locate it safely and efficiently. On this occasion the cloud was very thick indeed and the gap full of thin cloud moving in different directions to the gap itself. The thin cloud in the gap was enough to dim the brightness of the Sun's disc enough so that it couldn't be seen through my white-light filter. This, of course, added to the stress! :)

Here are some of my image results from the trip...

http://www.digitalsky.org.uk/TOV2012/2012-06-04_15-29-57_atmospheric-ring.jpg

http://www.digitalsky.org.uk/TOV2012/2012-06-06_04-34-41_IR742_3rd-contact.jpg

http://www.digitalsky.org.uk/TOV2012/2012-06-06_04-38-42_Aureole.jpg

http://www.digitalsky.org.uk/TOV2012/2012-06-06_04-54-53_Transit-of-Venus-white-light.jpg

http://www.digitalsky.org.uk/TOV2012/2012-06-06_Full-Disc-h-alpha.jpg

http://www.digitalsky.org.uk/TOV2012/2012-06-06_CaK-fulldisc-flat.jpg

http://www.digitalsky.org.uk/TOV2012/PL-PH-3D_Anaglyph.jpg

The battery arrangement is shown here...

http://www.digitalsky.org.uk/TOV2012/battery-weight_IMG_1508.jpg

The c/w shaft has lost its chrome plating - probably due to being used so much in my home environment which is very close to the sea!

Best regards,

Pete

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Good to see Yeti Monster's photo from the South China Sea on the telly ...........

i have just watched the latest sky at episode on catch up and its not to be missed. i have to say, i can not remember enjoying one episode as much as this one for ages. The Sky at Night team travel to

What a great show; really enjoyed that one and thought all of the presenters did a great job.... sooooo much better than the rather disappointing Horizon special on the transit and a shame that Horizo

Pete that is an excellent report and brilliant astro photos as usual. I really enjoyed this particular episode of the Sky at Night. I was fortunate to see the Transit from San Francisco and the sky was very kind to me.

Like you I only had 23kgs allowance on the plane so because I always went to see the Annular eclipse I was away for 3 weeks. For that reason I took my PST and Canon 50D as hand luggage. I really wish I had been able to take my Astro Tech 4" APO frac but no space.

Mark

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