Solar Filter Recommendations

[BamaDon]

I've been looking into buying a full-aperture solar filter for a C11.

From what I've read, the glass filters are not the best option.

Which filters do you prefer? I've heard the Baader film is good. Thousand Oaks has another. The film-filters are, according to some, optically superior to non-optical grade glass filters.

Baader presents a white image; TO is orange. Also, the TO is not susceptible to scratches, since the filtration is throughout the volume of the filter, not just on the surface.

They are all about the same price: $150 or so for 11" aperture.

What are your opinions on this?

[KathyNS]

I have a Thousand Oaks glass filter for my little C-90. I have been very happy with it. I believe that their filters are optical grade glass.

I would be surprised if the filtration was in the body of the glass. That's the first time I have heard that. Most of the filtration is in the reflective coating, which would be susceptible to scratches. I always carefully wrap mine in bubble wrap before I store it.

[BamaDon]

The glass filters use a reflective coating; some of the film-style filters are dark plastic. if you scratch them, they don't let sunlight through at full intensity.
I was originally planning on a glass filter, but I've heard that optically polished plane parallel glass for a full aperture filter is prohibitively expensive. But if you say they are good, I'll believe you.

I had a SolarSkreen from Tuthill back in the 70's; it was good in my opinion. The sun was transmitted as a light blue color - very pleasing.

I'm really just surveying the options in preparation for the Mercury transit on 11/11/19.

[KathyNS]

Do you even want a full-aperture filter? A C-11 is a big scope, that lets in a lot of photons, especially from the Sun. I would consider a reduced-aperture filter.

[Ozman]

I have both glass filters and film filters (a Thousand Oaks and a Baader). The filter I use the most are the glass filters, and that mostly on the 25x100s. When I use a larger scope (specifically the 8" LX200ACF) I use the smaller Thousand Oaks filter because it fits the off axis mask I have for the larger SCT. I would not want a full aperture filter for the SCT, although if the larger glass filters I have would fit snugly on my mask I would probably use one of them instead of the film filter.

[Lady Fraktor]

The Baader film has the best resolution for white light solar viewing and yes you can scratch a glass filter.
You can do a search online for the resolution/ filtering specifications for these.

This is one of the reasons why you need to visually inspect them before use. I normally use a Herschel wedge now but still have a couple of Baader film filters.
After comparing it to a Thousand Oaks glass filter, as I said to Bryan (Bladekeeper) a short while ago, the TO is a 85€ table coaster.

As the others have stated already, I would not use a full size filter on a 11" SCT either, a off axis filter would still give you a lot of brightness and resolution.

[Lowjiber]

Do you even want a full-aperture filter? A C-11 is a big scope, that lets in a lot of photons, especially from the Sun. I would consider a reduced-aperture filter.

I agree... 100%

[BamaDon]

Thanks, everyone for your thoughts.