Sun Funnel for Transit of Venus - projector screen material?

[orfeo]

Hi Guys/Gals,

I'm wanting to build a sun funnel for the transit of Venus and i was planning to follow the simple instructions found here http://www.transitofvenus.org/june2012/eye-safety/293-build-a-sun-funnel-for-group-viewing-with-a-telescope

however i can't find the Da-Lite High Contrast Da-Tex (Rear) - Cut-to-Size Screen Material - 95774 in a store that ships to Australia.

Does anyone know where this screen material (or something of similar application) is available in Australia?

Many thanks
orfeo

[Tinderboxsky]

Hi Orfeo,

I've been thinking about exactly the same thing this week, having recently read the article re the sun funnel. Having not had much luck either, my attention has turned to businesses that use and/or repair rear projection screens. For example a big user of the material is the national firm Staging Connections. They have a branch here in Hobart and I was intending to talk to them next week, hoping to get lucky and find they have off-cuts available. I'll let you know if I have anything to report. Perhaps this might give you some ideas.

Cheers

Steve

[ZeroID]

Get an old computer LCD screen, disassemble. Inside you will find a few matt surfaced plastic screens ( light spreaders ) that are perfectly flat and make excellent back projection screens. I've been playing with one for a transit scope idea and it works a treat.
Not sure how big you want it but plenty of 15"-17" screens being chucked as people upsize and I got a 19" where the cold cathode tube had failed. Wasn't worth the cost of repair at work so out it went.
I know there are at least three of them out on the rubbish trolley at work right now.

EDIT: Just read the instructions and the stuff they are using is a flexible material. So you might have to cut a circle of LCD plastic to make it similar to theirs. Same result. Edge duct tape it on with the magic go fast hold anything stuff. I love DIY

[orfeo]

Thanks for the tips, i'm surprised that there isn't an australian solution. I think i'll just order it to a friend in america and get them to post it on.

[tboyer]

I made a screen assembly using the LCD panel filters mounted in an old CD container (100 CD-R spindle) and a 40mm PVC waste outlet. PCV waste outlet fits neatly over eyepiece and diagonal, cut out groove to pass over eyepiece fixing screw. blacken all internal surfaces. Provides for an image up to 110mm using 12mm eyepiece or smaller clearer image with 20mm eyepiece. Works a treat on my 80mm refractor and/or 114 mm reflector stopped down to 50mm appature.

[koputai]

I just pulled apart an HP 17" LCD monitor. In it I found three plastic diffusers. They are rather floppy, rather like thick overhead projector transparencies, and will need some supporting framework to keep them flat and the projected image in focus.

The ones in this machine work much better one way around than the other. You need the dull surface towards the telescope eyepiece, and the shiny side towards your eye.

Cheers,
Jason.

[Tinderboxsky]

I made a sun funnel a week or so ago. I too, dismantled an LCD computer monitor and used one of the diffuser sheets. As per Koputai's suggestions you get best results with the shiny surface towards the sun and the mat surface towards the viewer.

The attached photo shows my sun funnel. A simple larger diameter short tube sitting inside the funnel supports the screen. The darkest flat paint I had left over was some blue which I painted on all interior surfaces. This helps to improve the image and the viewing experience. Mine is set up on my Carl Zeiss 85TFL. The image is bright and reasonably crisp. The active sun spots were quite visible, so Venus will be easily seen. I have simple hand guiding on the Vixen Porta Mount making this a very relaxed way for a couple of people to watch the transit.

I am also experimenting with hand holding my 6 year old simple Nikon Coolpix P2 to get snapshots of the event. My best endeavor to date is attached. The three sun spots at the time are just visible, so I am thinking I will be able to get a photographic record of the event.

It is my first ever astro photo with the simplest of gear!

Cheers

Steve.

[jasongrover]

Great job , Steve.The pictures are actually amazing. I was trying with my camera to get some snapshots of the occasion as well but it was not as beautiful as this.
...................................
projection screen materials (http://www.buildyourownprojectionscreen.co m/projection_screen_material.html)