Imaging the Transit of Venus

[Rattler]

I'll be in Turkey for when the Transit of Venus will be taking place so obviously wont be able to do any imaging through my scope. Will it be possible to image it with my DSLR with the 70-300 lens with a solar filter made for it? I'm not sure if this would be a little dot or what but it's something I'd try.

[S.A.M]

The sun is about the same size as the moon (as viewed from Earth), so try you camera out on the moon and see how it goes? You could get a teleconverter for your DSLR which would increase the mag. I have taken pictures of the sun using a Baader paper filter that I made myself with a 70-300mm lens attached to my camera. I am also going to be watching the Transit but not from the UK and I intend taking my 70-300mm lens with me. Venus might be a small spot on the surface but hopefully it will be visible?

Peter

[Gina]

Venus is very small in a webcam with a 600mm scope even with x2 Barlow so with the shorter focal length (effectively a quarter of the scope) and twice the size of pixel, Venus will only be one eighth the size in a DSLR with 300mm fl. You can calculate how many pixels across if you have the size of Venus in arc minutes/seconds but I don't think it will be many.

[Gina]

Here is a screenshot of the graphical calculator showing the size of Venus... I can't see it. TBH I think I shall struggle to see it with my 600mm fl scope even with 2x Barlow which makes the sun's disc almost fill the frame on my 1100D. As I recall, I could barely see Venus as just a tiny dot. The shadow of Venus, although very sharp and black, will be considerably smaller than sunspots.

[Viv]

I've done some with a DSLR, 400mm lens & baader filter (exactly the right fit for my lens hood).

Could be worth looking at a 2 x convertor also - the additional length helps.

Images were ok, not scope quality, but not bad.

[Rattler]

Ok thanks all. I'll look into it.

[ScubaMike]

I thought it was not the size of venus that you need to consider, but the shadow that venus will cast on the earth, which will be far greater than the size of Venus.

Anyway, see Transit of Venus - Wikipedia, the free encyclopedia for example photos of how large Venus will be against the sun.

[pmlogg]

It is not the shadow you are seeing it is the silhouette of Venus against the background of the sun.

The images in that link and others give a good indication of the relative diameters of the Sun and Venus during previous transits. To work our how your own images might look taken at the 2012 Transit various on-line programmes will tell you how far Venus will be away from Earth on 5/6 June (0.28AU from memory). Using that and the diameter of Venus you can estimate what angle it will subtend (i.e. arctan of diameter over distance). Using a calculator such as Starizona's you can get your imager+telescope FOV. The ratio of angle subtended by Venus to your FOV should be the same as the number of pixels taken up by Venus' diameter to the number of pixels across your imager. I took a test shot of the sun today using an FS60C + Canon 450D + Televue 2x powermate. The distance across was around 1263 pixels. My estimate is that Venus would show up as a 39 pixel diameter disk using the same set up.

[Demonperformer]

Definitely possible. The shots I added on http://stargazerslounge.com/imaging-planetary/171997-venus-transit-2004-8-june.html were taken at 300mm.

[Rattler]

Excellent Demonperformer. Will give it a go definitely.