Solar filter

[spendrey]

In preparation for viewing (and hopefully imaging) the transit of venus on June the 8th, do you think I should purchase a solar filter for my 8" reflector that will cover the entire aperture or would I better off going for an off-axis filter cell?
Has anyone had experience with these and if so what are the pros and cons?
I've been looking at the Kendrick solar filters, are they any good?

[Ian]

I have a solar filter made out of Baader Solar film. I made it as big as possible which since it's an A4 sheet, is a little less that full aperture on an 8". The reason being was that I wanted to preserve the resolution of the scope. I can mask it down if I want to reduce the brightness. In any case it would have cost the same for either type. If I was going to buy a glass solar filter, the cost would probably mean I would look at a stopped down one. Paul has a Thousand Oaks filter if I recall, so he'll have an alternate view.

[Whitters]

The advantage with the thousand oaks is that the filter is made of optical flat glass, the metalic film is sandwiched between the glass and therefore, unless you drop it, indestructible, It also gives a yellow rather than blue sun. But it costs more, £110 when I bought it five years ago.

[Rick]

Go for full aperature if you can afford it...

[spendrey]

Hi guys, it's a been a while since I originaly posted this and I'm afraid I'm still no nearer to getting myself a solar filter in preparation for the venus transit in a few weeks time.

I do like the look of the glass ones that I've seen because of the yellow images that are visible but I have not had a lot of luck finding many places in the UK that sell anything other than the usual baader filters.
Does anyone have any ideas as to where I could try looking?

Many thanks.

[Rick]

Assuming you've tried Telescope House on Farringdon Road, your best bet is to look hard at the adverts in Astronomy Now. Trouble is, time's getting a bit short, and the demand for equipmant for solar observing is at a peak. I've had a filter on order for a couple of months, and it's not turned up yet....

[spendrey]

Yes I was worried that I'd left it a bit late. I think I may have to settle with a Kendrick solar filter for now as it seems that it may be all I can get in the time available. I've noticed however that there are 2 different types of baader paper that these filters seem to be made with, one of which is called photographic. Does anyone know if they are both...
a) Safe for visual observations?
b) Usable for webcam imaging?

Thanks.

[Ian]

I believe that the photographic ones have a higher transmission, so are not suitable for visual unless expressly noted. I've used my webcam to image through the baader film (visual use) and there is no problem. I've also used it over a camera lens, and although the image is bright, stopping the lens down brought it to a level that exposed properly.

[spendrey]

Thanks Ian,

I've noticed that David Hinds sells a ready made baader filter for a Celestron C8.

http://www.dhinds.co.uk/pages/fullProd.php?id=187

The C8 has the same diameter as my Skywatcher Explorer (200mm) and I was thinking of getting this for mine. I phoned to ask how it is attached to the scope though and was told that it just pushes on so now I'm not so sure. If it was the type that has the 3 screws on the outer ring to hold it in place I would be more confident about it being compatible.

SCS Astro seem to do these (with the 3 screw attachment)...

http://www.scsastro.co.uk/it220006.htm

but even after phoning them I'm still unsure as to which one to go for. They told me just choose one that will fit my scope but there appears to be more than one!

[Whitters]

The mirror size of the C8 and Skywatcher are the same, but it will be the outer tube diameter that will be the critical measurement.

[ This Message was edited by: Whitters on 2004-05-15 00:01 ]