White light Solar Film

[evltoy (Wayne)]

Hi All,

I notice baader have 2 grades of solar film available

OD 3.8 "Photo" Film
OD 5.0 "Safety: Film

I suspect the cheaper OD 5.0 Safety film is used in most solar filter caps labeled baader film.

Has anyone had any experience with the two types of film for both visual and imaging? Is there a noticeable difference when imaging between the two?

Cheers
Wayne

[John W (John Wilkinson)]

Hi Wayne,
The OD number refers to the optical density of the film. OD 3.8 is not intended to be used for visual viewing. You would normally use OD 5.0 as it is safer and darker to use for visual viewing and photography. There is a difference between the two - if you use it on a telescope then it must go on the front of the objective. If 5.0 is a bit dark when taking photos then increase your exposure. Make sure the film has no pin holes in it.

Cheers, John W.

[evltoy (Wayne)]

Thanks John for the quick reply. So other then the density there is no colour or clarity difference?

I expect I would be mostly using the film for imaging, but now and then will do some visual.

and yes, the film will always be upfront over the objective.

[John K]

Originally Posted by evltoy

Hi All,

I notice baader have 2 grades of solar film available

OD 3.8 "Photo" Film
OD 5.0 "Safety: Film

I suspect the cheaper OD 5.0 Safety film is used in most solar filter caps labeled baader film.

Has anyone had any experience with the two types of film for both visual and imaging? Is there a noticeable difference when imaging between the two?

Cheers
Wayne

Hi Wayne,

I use both - the 5.0 visual stepped down with a mask to about 3" and the 3.8 full aperture for imaging on a 12.5" f/5 reflector.

I already had the 5.0 and for visual stuff it's fine stepped down.

The 3.8 clearly has a higher transmission and the reason I use it for imaging at full aperture.

Without knowing your telescope, I guess you can go full aperture 5.0 which gives you more light overall in any case.

Hope it helps.

John K.

[evltoy (Wayne)]

Originally Posted by John K

Without knowing your telescope, I guess you can go full aperture 5.0 which gives you more light overall in any case.

That is very good information!

I have a SW ED80 and ED120

I have a full aperture filter cap that I can use on both scopes - Thinking to replace the film with OD 5.0 film.

The dust caps on both scopes allows me to place film inside them to have an aperture of 50mm - Thinking to put the OD 3.8 film in these.

Native
ED80 FL600 @F/7.5
ED120 FL 900 @F/7.5

With the 50mm Aperture
ED80 FL600 @F/12. with reducer F/10.2
ED120 FL 900 @F/18 with reducer F/15.3

Camera's will be a mix bag. ASI294, ASI462 or Nikon D600 (APS-C)

[John K]

Originally Posted by evltoy

That is very good information!

I have a SW ED80 and ED120

I have a full aperture filter cap that I can use on both scopes - Thinking to replace the film with OD 5.0 film.

The dust caps on both scopes allows me to place film inside them to have an aperture of 50mm - Thinking to put the OD 3.8 film in these.

Native
ED80 FL600 @F/7.5
ED120 FL 900 @F/7.5

With the 50mm Aperture
ED80 FL600 @F/12. with reducer F/10.2
ED120 FL 900 @F/18 with reducer F/15.3

Camera's will be a mix bag. ASI294, ASI462 or Nikon D600 (APS-C)

You might find 50mm a bit small?

It's quite easy to make full aperture or filter caps of any aperture really with cardboard that can slide over your telescope.

[OzEclipse (Joe Cali)]

I have used Baader Astrosolar film extensively over the past 20 years. The optical quality of both types are identical and excellent.

Although Baader say that only the V5 is safe for visual, Ralph Chou, eclipse chaser and professor of ophthalmology has tested both types and determined that both are safe for visual. You will find the 3.8 really uncomfortably bright for visual but while uncomfortable and impractically bright, you won't get eye damage. I find the V5 too bright for comfortable extended visual work through an ED 80 or 4" Mak. Don't get the V3.8, get the V5.

The 3.8 is intended to provide sufficient transmission to give fast shutter speeds when used in high focal ratio projection systems f25-f45. When used at prime focus f ratios, the requisite shutter speed is too fast for most cameras, faster than 1/10000 second.

I have some filters made from ND 3.8 made specifically for photographing low altitude solar eclipses where atmospheric extinction comes into play.

The V5 is perfect for visual and photographic with f4-f22 systems
@ ISO 100
.......f............Tv
.......4..........1/2000
......5.6........1/1000
.......8..........1/500
......11.........1/250
......16.........1/125
......22.........1/60

The material is 10 microns thick and optically excellent, neutral maybe slight purple tinge easily colour corrected. To preserve the optical wavefront, the material must not be stretched or stressed. Attach the reflective film loosely to the front of the optics. I produced a detailed description on how to make holders for this type of film that are optimised for solar eclipse viewing. The holders are securely attached so that they can't blow off in strong winds and then easily and quickly removed and reattached before and after totality. The thin material does not affect focus and so during a solar eclipse, the camera can be focussed on the partial phase. Thick glass and black polymer filters can alter focus and so the system needs to be refocussed after the filter is removed.

https://joe-cali.com/eclipses/EQUIPM...arfilters.html

I have used these filters without any mishaps at 14 total, partial and annular eclipses since 2002. If you make the recessed holders as I've described on the web page, they are very resistant to scratches and damage and I have travelled all over the world with the same filters for almost 20 years.

Experienced eclipse chasers have agreed this is a good system and many simply link to my web site for filter construction recommendations rather than write their own.

Joe

[evltoy (Wayne)]

Joe,

Thank you so much for the detailed information. I just checked out your site and its

I pulled the trigger on a sheet of OD3.8 & 5. My understanding by what you say on your site is that the 3.8 can be used on small aperture/long FL (f15-f40)... So my ED120 & ED80 with an aperture of 50mm will be suited for the 3.8

"ND3.8 (6300 times light reduction) is designed for telescope eyepiece projection photography where effective focal ratios of f15-f40 are typical."

I can use the OD5 on a full aperture setup and on my finder scopes (ST80 and 60mm).

[kencas (Ken)]

Thanks Joe! Your web page is a wealth of information. I had been scratching my head to get around the OD ratings and how they apply (coming from a purely photography background), so while they are similar the scale isn't!