Christmas is coming and my spouse is thinking that I need a solar filter for my telescope--he's been listening to all the stories on solar activity on the radio. Naturally, I'm not averse to this idea, but I have some questions. The filter made by the manufacturer for my scope is relatively pricey, and I don't want him to spend that kind of money unless it's worth it. I'm using an 8" Newtonian, F5, equatorial mount. It's been great for "faint fuzzies" and o.k. for planetary viewing, which is what I expected. So how does solar viewing fit in here? Do aperture and focal length have a great effect on solar viewing? Or is the sun so big and close that it doesn't matter? Any other advice on solar viewing would be appreciated.

I have a mylar filter for my 8" Celestron. It was about $100.00, I haven't priced any lately. It gives a visible light view of the sun, but the sun is blue in my filter. Hydrogen alpha filters, are the ones you need to see solar flares and prominences, but last time I checked they were around $2000.00, so unless you are really serious about looking at the sun, that is a bit much. What ever you do, DON'T by those cheap filters that screw into the eyepiece. They have been known to break while observing and cause severe eye damage. The sun is large enough that any type of scope will do a good job. Refractors are the best, but your newtonian should do fine.

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Thanks Walter. That's pretty much what I was wondering. My scope is an Orion, and they make a solar filter that runs around $100 to fit it. Thinking maybe we'll go for it.

The Apollo 12 astronauts returned a tv camera from the Surveyor 3 probe that had been on the moon for about 3 years. Bacteria inside the camera was still alive after that time. So contamination is a real possibility. There has already been enough cross contamination from asteroid impacts over the last few billion years, that I think any contamination from a space craft wouldn't make much difference now.

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Whatever filter you eventually obtain, be sure to cover up your finderscope's objective when you view the sun. Besides the possibility of someone peaking through it while it's aimed at the sun and cooking their retina is the risk of damage to the finder itself. I once forgot to do this and the low quality 20mm finder on my ETX melted its own crosshairs.

The good thing was that I ended up making my own replacement cross hairs for it out of spider's silk. It was tedious, but they are far superior to the one's the manufacturer provided!

That post about Mars life was supposed to go under the Japanese contaminating Mars thread. How it got here, I haven't a clue.

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http://www.rrac.org

You also might consider making your own with Baader solar filter material, available from Astrophysics. $30 for a 200mm x290mm (8" x 11 1/2") sheet or $70 for a 500mm x 1000mm (20 x 40in.) sheet (enough for several scopes + binoculars).

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A good idea. I used that material for an off axis filter for my SCT. The Baader material gives you a whitish image, as opposed to some of the others (blue or yellow). With an 8" newtonian, you don't need a full aperture solar filter, so look for one that uses a smaller, off-axis aperture. The images you get will be just fine, in fact, you won't have the central obstruction there.

The material is nice for another reason - you'll have enough left over for your finder, a pair of binoculars, and even a camera filter if you plan ahead with the A size (smaller) sheet.

Oh, and you can order it from Adirondack Astro as well, about the same price.

Thousand Oaks also sells solar filters and their own brand of film. I have one of their "glass" filters for one of my refractors. It gives a "yellow/orange" image. I think the Baader film is much better, but that's just my opinion. Other people feel differently. You might want to see if anyone in your local astronomy group has some solar filters from different brands you can take a peek through.

Whatever you get, make sure it fits snugly on the objective. I ended up getting a mylar filter for my Meade 8", but it was originally made for the Celestron. It fit a little loose, and I was paranoid that a gust of wind would be all it'd take to blind me. Got some stick-on velcro, and used the fuzzy part to add more friction when the filter was on the scope. No worries now!

ps. I'd love to have a Hydrogen Alpha filter! That may be my next major purchase in a few years.

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Thanks again, everyone.
SarahMc: Particular thanks. Checked out the Thousand Oaks link and found an off aperture that might do the trick. I wouldn't have known the off aperture was a possibility without your expert advice.
I love this board. =D>

Edited to add: I'd sure love to try making a filter, but, I'm a bit too intimidated by the prospect. I can make beer, I can sew, I can cook. I stay away from really hard stuff.