Somewhere quite some time ago I saw an advertisement for the sale of an ND filter for photographing the sun. It had a very high ND number to it (for good reason). Anybody know where this filter can be found?
A simple explanation -- A ND filter is a Neutral Density item, that is, it does not affect the color of the photograph, just reduces the amount of light transmitted to the film.
Filters used for photographing sun events are special type, such that one cannot become blinded. Or without a filter, the image must be viewed as a reflection and not directly through the viewfinder of the camera.
Yes, I have an understanding of a neutral density filter. I know about the various methods of viewing the sun (such as the method people use - like me - of making a pin hole in a box lid and then letting the suns rays pass through that onto another surface). And you won't catch me looking directly at the sun with welders masks or various sunglasses. There are different types of radiation being emitted by that big ball of fire that our human eyes don't register but believe you me they are there and welders masks, etc do not filter out those nasty wave lengths.
There are ND filters for photographing the sun. I will have a look at the link you provided and see if it mentions those filters specifically for photography. Thank you.
Edit: I just had a look-see at the article you pointed out to me and they have the right idea but didn't provide a source for the filter. Oh, well, that's a step in the right direction.
For amateur astronomers, there are, in fact, four different types of solar filters. Each effectively blinds the viewer unless the scope is pointed directly at the sun. The filter blocks all light except that from the solar disc itself. The differences in the four types result in different colors to the eye and the camera, from a blue image to a deep yellow-orange.
These can be located from among the many advertisers found in the pages of two magazines, "Astronomy" and "Sky & Telescope."
The filter blocks all light except that from the solar disc itself. The differences in the four types result in different colors to the eye and the camera, from a blue image to a deep yellow-orange.
These can be located from among the many advertisers found in the pages of two magazines, 'Astronomy' and 'Sky & Telescope.'
That's what I was thinking about, Landscaper. I will have to look those magazines up. I know I have seen "Sky + Telescope" on the magazine racks and I think perhaps the other as well. Maybe they have their own web sites. Thanks for pointing that out.
Edit: Sky and Telescope was a good reference. I came across this:
Solar filters are more than ND filters, they also block IR and UV better than standard photographic ND filters. This is critical for visual use. BTW, photographically, my solar filter (see below) is ND5.
Another thing to keep in mind is that the different solar filters on the market render the Sun in different colors. Several years ago, Sky & Telescope (or maybe it was Astronomy) ran a detailed article about solar filters. Depending on the filter, your Sun could be yellow, orange, blue, or white. The article was timely for me because I had just started to research solar filters for my 5" telescope. I choose a Baader AstroSolar film filter, which gives a white image. The Baader film provides slightly sharper images than mylar, polymer, or glass. The Baader film is also more economical. You can buy individual sheets and make your own filters. I think an 8"x10" sheet is less than $20.
The common solar filters cover the visible light spectrum and are designed to show sun spots and some granulation. You will not see solar prominences and flares--they are too faint. For that you need a specialty filter such as hydrogen alpha. If you are interested in a different view of the sun in Ha or CaK, check out http://www.coronadofilters.com/. Coronado makes specialty solar filters as well as small specialty solar telescopes (40 mm - 140 mm aperture) and binoculars. I've got the PST (about $500) on my "to buy" list.
From my experience with Celestron, a full aperture telescope filter must have a density of 5.0 or a bit over 16 fstops. Furthermore we always coated the filters with water white plate glass and it was coated on both sides with inconel. Both sides are coated in case there are pin holes in the coating. Looking at a telescope without such a device can instantly blind you, and possibly kill you.
It has been a long time since I did sales and marketing for Celestron, maybe 33 years.