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Thread: TOTAL ECLIPSE

  1. #1
    George Papantoniou's Avatar
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    TOTAL ECLIPSE

    On Wednesday at 12:30 local time (GR), the sun will be totally eclipsed by the moon. The phenomenon will be visible from some greek regions, notably the island of Kastellorizon (100%) and the Heraklion (home of APUGGER Aristoteles Grammatikakis) city (94%).

    I will try to be in Heraklion (cannot make it to Kastellorizon) for a job on Wednesday and, in this way, be able to view the eclipse (although it will not be a total eclispe for me).

    I have a few questions:

    Has anyone photographed the sun and a total eclipse, and if yes, how?

    Will my B&W infrared 093 filter permit me to view the phenomenon with safety (for my eyes) ? Would a pair of solder's protective glasses be better ?

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    arigram's Avatar
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    If in Kastellorizo its 100%, would it be also in Asia Minor in Turkey?
    I guess I'll have to live with the 94%...
    Too bad I don't have any special glasses.
    aristotelis grammatikakis
    www.arigram.gr
    Real photographs, created in camera, 100% organic,
    no digital additives and shit




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    Hi

    Do NOT use the infrared filter to view the partial phase of the eclipse, as you very likely will damage your eyes.There is a lot of IR-radiation in sunlight, but as your eyes (retina) is not sensitive to pain, you will end up with damaging your eyes, without knowing it, until it is too late.

    For visual observation of the sun astronomer normally use a special filter which allows only 1/100.000 of the solar radiation (UV, visual and IR radiation) to pass.
    Instead of this special filter you can use protective glasses for arcwelders, normally referede to as No. 14 (Very dense filter).
    The glasses for solder's are not dense enought, only no. 8 or so.

    I have photographed a solar eclipse (back i 1999) and for the patial phases I used a solarfilter (Astro Solar TM Sonnenfilterfolie D=5) from this firm
    http://www.baader-planetarium.de/zub...lar.htm#asolar
    The price for the filtermaterial in A4-size is reasonable and it one of the best filtermaterials you can get at the moment.

    If you plan just to observe the partial phase visually, try to get hold of some Eclipseglasses, they are normally made of the same filtermaterial that I referede to above, mounted in a primitive cardboardframe, the price is about 3-4 Euro (in Denmark). The Eclipseglasses is normally sold through opticians or the local planetarium.

    Photographing the total phase (whitout the solarfilter in front of the lens) is "easy" as any exposure between 1/1000 and 1 sec. through a telelens at f:5.6 and a 100 iso film, will reveal some of the suns corona. For "landscape" photos including the eclipsed sun, start out with what the automatic suggest as exposure and then make a lot of bracketing over and under this value.

    My best advice for you, is just to forget the photography and sit back, relax and enjoy the show (with a proper pair of eclipseglasses). It is an experience you will never forget, as the "world" turns dark and the birds starts to sing and the cockcrows in the middel of the day.

    Tom

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    George Papantoniou's Avatar
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    Quote Originally Posted by arigram
    If in Kastellorizo its 100%, would it be also in Asia Minor in Turkey?
    I guess I'll have to live with the 94%...
    Too bad I don't have any special glasses.
    Ari, I've got arcwelder's masks and I will carry one or two with me if I make it to Heraklion. You can pm me with your cell phone number and I'll give you a call in the morning so that we meet for the time of the eclipse. I hope I'll have the time to do the pictures of kitchen tops I have to do :-)

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    George Papantoniou's Avatar
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    Thanks for the advice, Tom. I guess that I won't have the time to find the special filter you're talking about. And the opticians will be selling the eyeglasses but at 10x their normal price (as always in Greece, when they find an opportunity to make some quick extra money, they jump on it)... but I'll give it a try...

    What about a ND6.0 (20 stops -) PLUS the IR filter ? In fact, I made a trial looking at the sun (just for a second) through the IR filter and it looked dim (but I guess that since I cannot see the IR radiation, it was there and it's still dangerous to the retina)... Maybe I'll stick to the arcwelders mask...

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    Lee L's Avatar
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    Quote Originally Posted by George Papantoniou
    What about a ND6.0 (20 stops -) PLUS the IR filter ? In fact, I made a trial looking at the sun (just for a second) through the IR filter and it looked dim (but I guess that since I cannot see the IR radiation, it was there and it's still dangerous to the retina)... Maybe I'll stick to the arcwelders mask...
    Many ND filters are "leaky" at IR, as it's presumed that they'll be used for films with limited IR sensitivity. So you can't be sure you're getting the true specified density in IR. You may remember that Galileo went blind. He observed the sun through carbon deposited on glass from a candle flame, which cut the sun's intensity enough for comfort, but still passed longer wavelengths and so he burned his retinas out in comfort.

    The AstroBaader and other filters made for safe visual observing of the sun are typically metal film deposits on a plastic substrate, and some are thick deposits of other materials in a thick polymer film. The "glasses" mentioned in the earlier posting are these same materials in cardboard frames, and are often sold for anywhere from US$1 to about US$12 or so as fundraisers and/or a service to the public to promote safe viewing by local astronomy clubs or observatories.

    Dont view without the proper protection. The #14 welding filter is safe, but will give you a green cast. The other filters mentioned will give color casts in the blue-neutral or yellow-orange range.

    You can also make a pinhole and safely watch the projected image on a shaded white card. See: http://www.mreclipse.com/Totality/TotalityCh11.html for good advice on viewing an eclipse.

    Lee

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    Forget the IR-filter! It just gives a false sense of security.

    The ND6.0 filter will do - if it blocks for IR-radiation. I don't know how effectiv the ND-filters are, on heliopans webside they show the transmissioncurves for a few ND-filter, but only till 800nm and there is a lot more IR-radiation beyond the 800 nm.

    In the good old days (back when all people used film ), it was not unusual to make a makeshift solarfilter from a piece of exposed B&W-film, which is just as safe as the expensive but optical better solarfilters.

    To make a makeshift filter, take a b&w-film (preferably 120-format, big is better) with a lot of silver in it, Tri-X or Pan F. Roll the film out and expose it to daylight for a minut or more (every grain of silver has to be exposed). Then develop it as normal. It can all be done in daylight

    Mount a double layer (one layer is not enough) of this film in a cardboardframe, with the emulsionsides facing each other, to avoide scratches in the emulsion, and you will have a safe solarfilter.

    The safety in this filter relays on the metallic silver and therefore it is not possible to use film which are processed in C-41 or E6, as they don't contain any silver.

    Because the silvergrains scatters the light, the filter is not good for photography (use the ND6.0 filter on your camera instead, if you still have the intend to photograph the eclipse), but the filmfilter is okay for visual use.

    Tom

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    Sparky's Avatar
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    I would think welding goggles (glasses) would do the trick nicely - and be cheap and easy to find.

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    Quote Originally Posted by Tom A
    Forget the IR-filter! It just gives a false sense of security.

    The ND6.0 filter will do - if it blocks for IR-radiation. I don't know how effectiv the ND-filters are, on heliopans webside they show the transmissioncurves for a few ND-filter, but only till 800nm and there is a lot more IR-radiation beyond the 800 nm.

    In the good old days (back when all people used film ), it was not unusual to make a makeshift solarfilter from a piece of exposed B&W-film, which is just as safe as the expensive but optical better solarfilters.

    To make a makeshift filter, take a b&w-film (preferably 120-format, big is better) with a lot of silver in it, Tri-X or Pan F. Roll the film out and expose it to daylight for a minut or more (every grain of silver has to be exposed). Then develop it as normal. It can all be done in daylight

    Mount a double layer (one layer is not enough) of this film in a cardboardframe, with the emulsionsides facing each other, to avoide scratches in the emulsion, and you will have a safe solarfilter.

    The safety in this filter relays on the metallic silver and therefore it is not possible to use film which are processed in C-41 or E6, as they don't contain any silver.

    Because the silvergrains scatters the light, the filter is not good for photography (use the ND6.0 filter on your camera instead, if you still have the intend to photograph the eclipse), but the filmfilter is okay for visual use.

    Tom
    I'd strongly avise against the developed film method because of the danger of not developing to completion and the variable quantities of silver and grain distribution in modern films. If done by someone with insufficient experience by which to judge the end product it's a huge risk, and not worth it when high quality, safe filters are readily available. I would never do it myself, and I have 40 years of photographic experience. I also work in an observatory and teach college astronomy labs, including safe solar viewing. You don't have nerve endings in your retina that will tell you when you're burning them, and you can blind yourself without knowing it. At lower, but lethal exposure levels it can take hours or days for your retinal cells to die.

    The ND 6.0 filter may work for film, but I'd never view through one designed for photography. Photographic ND filters are on NASA's UNSAFE visual filter list. See below. If you use one on an SLR, you're still looking at possibly damaging IR getting to your eye while framing or focusing.

    Lee

    From NASA:
    http://sunearth.gsfc.nasa.gov/eclips...lp/safety.html
    Quote Originally Posted by NASA
    The Sun can be viewed directly only when using filters specifically designed for this purpose. Such filters usually have a thin layer of aluminum, chromium or silver deposited on their surfaces that attenuates ultraviolet, visible, and infrared energy. One of the most widely available filters for safe solar viewing is a number 14 welder's glass, available through welding supply outlets. More recently, aluminized mylar has become a popular, inexpensive alternative. Mylar can easily be cut with scissors and adapted to any kind of box or viewing device. A number of sources for solar filters are listed below. No filter is safe to use with any optical device (i.e. - telescope, binoculars, etc.) unless it has been specifically designed for that purpose. Experienced amateur and professional astronomers may also use one or two layers of completely exposed and fully developed black-and-white film, provided the film contains a silver emulsion. Since all developed color films lack silver, they are always unsafe for use in solar viewing.

    Unsafe filters include color film, some non-silver black and white film, medical x-ray films with images on them, smoked glass, photographic neutral density filters and polarizing filters. Solar filters designed to thread into eyepieces which are often sold with inexpensive telescopes are also dangerous. They should not be used for viewing the Sun at any time since they often crack from overheating. Do not experiment with other filters unless you are certain that they are safe. Damage to the eyes comes predominantly from invisible infrared wavelengths. The fact that the Sun appears dark in a filter or that you feel no discomfort does not guarantee that your eyes are safe. Avoid all unnecessary risks. Your local planetarium or amateur astronomy club is a good source for additional information.

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    Quote Originally Posted by arigram
    If in Kastellorizo its 100%, would it be also in Asia Minor in Turkey?
    I guess I'll have to live with the 94%...
    Too bad I don't have any special glasses.
    Yes - lots of people into amateur astronomy (well, I guess not just them) are heading to Turkey to see it.

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