Solar White Light Filters

  • michaeloconnell
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10 years 3 weeks ago - 10 years 3 weeks ago #101046 by michaeloconnell
Solar White Light Filters was created by michaeloconnell
Following on from Solarfest, note some details re solar white light filters and how they differ from camera neutral density filters:

Camera filters
For example nd5 filter transmits 1/5 i.e. 20%

Solar filters:
ND5 means it transmits 1/ (10^5)
i.e. Transmits 0.00001 (fraction) or 0.001%
Always placed at front of scope.

For visual use, a ND5 filter is required.

It is also possible to get a Baader ND3.8 filter (A4sheet) which let's in a bit more light (0.016%). However this is only for photographic purposes! Photographically, it could be combined with a Baader Solar Continuum filter or Baader CaK filter on small scopes where the user needs to push the f/ratio to get a large disc on the chip, thereby resulting in a faint image. That's the only purpose I can think of for the ND3.8 filter. You just need to be careful not to use the ND3.8 filter (A4 sheet) visually - it physically looks identical to the ND5 filter!
I suggest using the ND5 filter first and only the get the ND3.8 if you are having issues with exposure length and know exactly what you are doing. Needless to say, I don't think the photography-grade neutral density filters are appropriate to use.
Last edit: 10 years 3 weeks ago by michaeloconnell.
The following user(s) said Thank You: michael_murphy, KevinSmith

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8 years 7 months ago #105184 by KevinSmith
Replied by KevinSmith on topic Solar White Light Filters
And just to note that there is also a significant difference in the solar film quality by brand (maybe not so much for safety but certainly for optical/photographic quality) I originally had Baader film in my filters but then changed to Seymour Solar and unfortunately had to rip them out of my home made filters as they just did not show much detail - although also ND5 they were almost like X-ray film thickness. I replaced them with the trusted Baader again.

In contrast I have however seen really good reports on the glass Seymour Solar filters.

Another note is that you can get Baader film from Ktec Telescopes at a good price and don't need to order them from Germany.

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