Bader film vs polymer vs type 2 glass filters

[SmokeyJoe]

I would like to dip my toe in solar observation/imaging.   So far I have come across three different types of 'clip on' filters with very little explanation of the difference between them.  They are

Bader Solar film

Black polymer solar filter

Type 2 glass solar filter

Can anybody provide a simple explation of the differences. 

I'm using a 4" frac if it makes any difference.

[johninderby]

Baader solar film is the best and will give sharper more contrasy views than the others. Next best thing to a Herschel wedge. 👍🏻👍🏻👍🏻

Black polymer filter is no where near as good as the Baader. Lacks sharpness and contrast in comparison to the Baader. 👎🏽👎🏽👎🏽

Glass filters aren’t that good as the price of optically flat glaas is so expensive it’s simply not used any more in solar filters. The cheap glass used in the commonly available filters simply isn’t optically flat unlike the Baader film. 👎🏽👎🏽

The old Zeiss glass solar filters were exceptional but if you could find one nowadays it would probably cost over a thousand quid. 🙀

 

So I would recommend the Baader film if you are on a budget or a Herschel wedge. Wedges are only for use on refractors. 

This is what I use now. I do use a Baader filter on the RACI finder though.

Edited December 31, 2020 by johninderby

[Alien 13]

Interesting, had always thought of Baader film as being as flat as the ocean in a gale, odd that my ND/UV/Polarizing camera lens filters etc are as flat as a flat thing.

Alan

[SmokeyJoe]

Thank you so much for your clear explanation johninderby.  Been mulling over these for a couple of months and getting nowhere.   Now just got to find one in stock. 

[johninderby]

Baader film should be loose fitted and not pulled flat. Many have trouble getting their heads round the fact that the film can be optically flat even though it isn't physically flat.

Edited December 31, 2020 by johninderby

[Peter Drew]

The "secret" of Baader type film is it's thinness.  It's so thin that it has no optical effect even when in a relaxed undulating state.  Pulling the material taut in order to make it look flat stretches the material and causes distortions.    🙂 

[johninderby]

Would love to try one of these glass solar filters. 🙂

 

Edited December 31, 2020 by johninderby

[Peter Drew]

I have a couple of vintage full aperture glass filters for 8" SCT's.  They give an excellent performance but cost over £200 each back in the 1970's.     🙂