Venus transit 6th June 2012

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Unlike the last Venus transit in 2004, tomorrow's transit will be almost over by the time the Sun rises here in Denmark. I shall have to set the alarm clock for 4am and drive to a local hill with all my equipment. This is the only place nearby, in our rolling landscape, where a clear view is possible of the North-East horizon. Where the sun will (hopefully) rise into a clear sky with the transit already well under way. The weather forecast is for high cloud. Thickest where I live!  

I decided not to bother using the Universal Digiscoping Adapter. While it has obvious potential, it is just too fiddly and prone to misalignment.

I knew I would want to use my no-name 20mm Plossl. This eyepiece focal length provides the ideal image size when used with a simple P&S digital camera in extra-focal mode. The rubber eye-shield cracked off soon after purchase. Leaving a nice, smooth rubber barrel.

Now I had to find a simple tube into which the eyepiece could slip. No plumbing or drainage tube matched my needs. Fortunately my wife had a collection of plastic ready for the recycling centre. Amongst her horde I found a measuring cap from a detergent bottle. It was thin, tough and a funny shape where it screwed onto the bottle neck. The eyepiece fitted perfectly and stopped naturally. Precisely where I needed it to.

I cut off the outer screwed section in the lathe. Using a craft knife with only a tiny bit of blade showing. Then I smoothed the remains to produce a neat flange for a little more strength and rigidity in use. Though it's probably more decorative than anything else.

Now all I needed was to make a suitable section of tube for the camera nose to slide into without effort. First I had to cut off the closed, top end of the cap. This section had to be smooth and soft to avoid damage to the camera finish. So I used sportsman's injury binding tape to reduce and adapt the end of the tube to the size of the telescoping, camera lens barrel.

After some fiddling, with small pieces of tape, I found it much easier to just wrap it over the edge. Half inside and half out. The sticky tape is thin, fine cloth and matt black into the bargain. Absolutely Ideal! There was no need for internal blackening to reduce stray light reflection. The lens is very close to the black top of the eyepiece. I suppose I could have made the binding tape a bit neater but nobody else is going to see it. ;-)

Here is the blue, bottle-top adapter, 20mm eyepiece, Baader "Fringe Killer" filter and the simple P&S digital camera. Note the small camera lens aperture and short zoom are ideal for this purpose. The eyepiece fits in the far end of the blue adaptor. The camera into the soft, black taped end. The length of the adaptor is made to just bring the camera lens very close to the eye lens of the eyepiece without touching. Producing a smooth edged stop, central in the camera viewing screen. Though only at widest angle setting. Any zooming produces a clear field to the edge of the image frame.

Here, the eyepiece is inserted, friction tight, to very near the end of its rubber sleeve. The eyepiece barrel will be inserted and stop just as normal in the telescope focuser. 

The filter has been screwed to the eyepiece barrel. While the camera lens housing has been slid gently into the other end of the adapter. Perfect alignment is achieved without any effort or adjustment required.

The camera will not stay in place of its own accord unless pointing downwards. Particularly as there is always the risk of lens retraction. Though the lens will be deliberately set in the camera menus not to retract. Battery energy saving will also be cancelled. This should avoid auto shut-down.

When attached to a star diagonal the camera will rest naturally (nose down) on the adaptor. It is a snug fit but not remotely tight. One must avoid physical damage and fault reporting by the camera. The camera senses when it has been overloaded on the end of the lens barrel. It will report this fact then withdraw the lens and close down for a reset to avoid damage.

I will set the camera to focus on infinity in the Program menu. This is important. As I have discovered that on 'Auto' it will cycle between Normal distance and Macro. My first pictures of the Sun were actually Macro shots of the illuminated, eyepiece field lens. Ugly and worthless. Except to point out that I really ought to clean the lens properly before use! The distance between the top of the adapter and the eyepiece is just over 20mm. i.e. the length of the camera lens nose plus a little clearance. 

There is still the risk of camera movement when releasing the shutter. I can't take my massive stands and Fullerscopes mountings with me in the car. So inevitably the Vixen 90mm f:11 telescope will not be supported as well as usual.

I have a choice between the Bogen video tripod with heavy duty, pan and tilt head. Or the Bresser 70mm refractor mounting.  I shall probably use the Bogen with the Vixen dovetail screwed to the Bogen's quick release plate. This worked well for the partial solar eclipse which was also a low altitude, dawn event.

Wish me luck with the weather! If it is clouded over at 4am I shall still have to go in case it clears. At least I can sit in the car. The narrow lane goes right over the top of the hill I have chosen as my observing site. Traffic is almost non-existent at any time of day. The chances of anybody else choosing that hill are as remote as the hill itself. My partial solar eclipse on a popular hill was spoilt by noisy smokers!

THE BIG DAY:

I awoke naturally at 3.30am to find the sky clear except for a plate of cloud in the North-East. Precisely where I don't want any! The horizon is bloody red with dark clouds above very slowly moving away. The moon is low in the South. Rising so early allowed a leisurely bowl of muesli and a cup of coffee before setting off. With luck I shan't forget anything. The blackbirds have started singing (loudly) already. It was lucky my wife reminded me to charge the camera batteries last night! 

Click on any image for an enlargement.

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