[URGENT]How to DIY a proper solar filter?

Discussion in 'Casual Photo Conversations' started by shineofleo, Jul 17, 2009.

  1. I am REALLY in BAD luck! I ordered a solar filter, but the supid seller shipped to a wrong address, and now they are out of stock! (You know people are getting how crazy for this total eclipse)
    I really want to take a photo of the solar eclipse on 22nd, July, and I have camera Nikon D200 and lense 200mm and 1000mm reflex!
    But no solar filter!!!
    I am wondering any alternative solution to do this job? Making a solar filter myself? Or any other ideas?
    Please please please shed a light on me and give some advice. Thank you so much indeed!
  2. It can be done with film... but here are two articles for info...
    Included in the first, is a list of solar filter suppliers...
    Make sure you follow directions to prevent damage to your eyes...
  3. Any welding supply comony will have replacemnt glass filter for welding.
    Ask for a # 12.
  4. In case you're in the path of totality you will definitively want a design you can remove from the lens in a few seconds. Putting back without to much fuss is less time-critical, but also something to consider.
    So depending on time and buying options you have, the material:
    • Cokin, Tiffen, whatever resin filter mount that fits your lenses,
    • welding glass smaller than the filter mount (In case you get one precisely fitting the mount you're even better off, of course),
    • stiff cardboard, thick enough to stay in the mount.
    Then the work:
    • cut cardboard to fit in filter mount,
    • cut hole in cardboard big enough for the welding glass, but leave some border. Dont' worry if this stops down your aperture, that's the least you care about when taking photos of the sun.
    • Then glue welding glass on cardboard.
    There you go.
    For safety try to avoid the viewfinder outside totality, not sure about live view and how solar intensities mact on the sensor. Try to see if you can hold a projection cardboard behind the viewfinder, or tape a piece of paper over the viewfinder and look at that piece of paper indirectly.
    If by doing so you are absolutely sure you will NOT use the viewfinder with your eye, you can also use other materiels with sufficient optical density. However, there is no guarantee that such other materials will block UV and IR sufficiently not to damage your eyes, so be absolutely sure to stay clear of the viewfinder. For the sensor that should be less of a problem (as long as you do not use live-view: to much IR may damage a continuously exposed sensor, while the short exposure times of the real pictures will hardly matter in the heat balance of the sensor).
  5. Best bet for DIY is getting the Badder Astro-Solar Safety Film from Astro-Physics (if you in the USA... I dont know of other distributors.) It costs $40USD, and you have to build a specific "mounting for it for your specific lens, but for white light solar observing, it's the best stuff you can buy.
    http://www.astro-physics.com/index.htm?products/products look under solar accessories.
    That said, I tried that technique of using film awhile ago.. it didn't work out that great for me. Certain grades of mylar are used in white light filters, however, I really dont know much about that anymore.
    That said, I'm thinking the welding glass technique outlined above will probably be the best technique in your current situation.
  6. Thank you guys! So I can do something with it!
    By the way, Badder Astro-Solar Safety Film is the stuff I ordered and got messed up... :S
    What I am thinking is, I can take some picture of the people during the totality or the surroundings, etc. with a wide-angle lens.
    I will let you know how it ends!
  7. Wow Leon that stinks ! I'm sorry you'll have to make due for the eclipse, but still try and get your hands on the Badder Film. It's good stuff. Performed flawless for me with my Astro-Physics 'scope for the Venus Transit in June 2004. Heck, i think I have technical pan negatives of that somewhere... ahh good times!
  8. With a current SLR which has a speed of 1/4000s (or faster), you can shoot the partial phases with an ND 4 or ND 5 filter (though they aren't always in stock either!). You're looking at about 1/4000s at f8 at ISO 100 with an ND 4 filter.
    Note by an ND 4 and 5 I mean filters with an optical density or 4 or 5. An optical density of 4 means that 1/10000th of the light passes through it or an attenuation of 13 stops. An optical density of 5 means that 1/100000th of the light passes through it (just over 16 stops attenuation). Hoya "ND4" filters pass 1/4th of the light which is useless for solar work. Hoya make an NDx400 that passes 1/500th of the light (9 stops attenuation) You could probably use that if you had to and selected your fastest shutter speed, slowest ISO and a small f-stop. B&W make a optical density 4 filter and an optical density 6 filter (20 stops).
    Note that these filters are NOT safe for visual use, only for photography.
    For the total phase, if you are lucky enough to see it, you won't need a filter of course
  9. I would look up those Bader planetarium websites. When I was looking at their solar film (the actual filter material itself) I came across several DIY examples.
    If you are trying to rig up something yourself, maybe it would be a good idea to invest about $20USD in some welder's goggles. I think if you look up the specs on those, some of them may provide suitable protection for eye safety. One of the warnings I came across for the solar telescopy was about instantaneous and permanent damage to the eyes. If you can protect your eyes with a set of welder's goggles from the hardware store, maybe that would safeguard you against a mistake with a DIY rig.
  10. James G. Dainis

    James G. Dainis Moderator

    "Welder's goggles" may be a bit of a misnomer. They are actually just dark sunglasses to remove brightness used with oxy-acetylene burning and brazing and particle protection. No welder would use them when doing arc welding, his eyes would be damaged. Even a few brief flashes of arc can cause eye discomfort later on, like you have sand under your eye lids.

    A #12 welding filter would protect your eyes, but I don't know if there would be any distortion from the glass held in front of the lens . A heavy ND, neutral density, filter or two might be a good bet for your camera.
  11. Please be very careful here. A welding filter (even a #14) may not be enough to protect your eyes, especially for extended viewing of the sun. Damage could be done that might be permanent. It's just not worth the risk. Unless you have a filter specifically designated for visual service, indirect viewing of an eclipse is the only safe option (a cardboard box with a pinhole in one end and a blank sheet of paper at the other will work).
    During totality, although the sun's brightness dims, damaging rays (IR, UV, and others) are still present in amounts that can be very dangerous to human eyesight. This can result in short-term retinal burns (possibly severe), and long-term or long-latency vision problems like cataracts and retinal/macular degeneration.
    I know of where I speak - my day job for the past 17 years is as a Safety, Health, and Environmental manager on field projects for a very large world-class global heavy industrial construction company. I also have several years 'under the hood' as a welder in construction and fabrication shops, so I know a little something about welding, arc rays, and their implications for eyesight.
    From B+W's handbook (my bold and italics):
    ND#113 "With its light reducing capability of 13 f-stops, this B+W Neutral Density Filter is used in astronomy for photographs of the sun and for recording the relative movements of heavenly bodies as light traces in extremely
    long exposure times. For photographs of the sun, this filter must be positioned in front of the lens and under no circumstances should it be located near the primary focus in front of, or behind the eyepiece because of the intense heat at those locations.
    It must not be used for observation of the sun (danger of blindness!) due to its greater transmission in the infrared range. The filter factor is 10000x."
    ND #120 "With its light reduction capability of 20 f-stops, this B+W ND Filter is used for the same astro-photographic
    applications as ND filter 113 when an even greater light attenuation is required. In spite of its much higher density, this filter too, must not be used for visual observation because of its transmission in the infrared range. The filter factor is 1000000x."
    IMO, if B+W (Schneider Optics) says it isn't good enough, then it isn't good enough! Better to miss an eclipse than take a chance with your eyesight.
  12. Two things:
    The filters are to be used with a camera and a sensor, I completely agree that you should stay clear of direct sight through the viewfinder by all means.
    However, and I say this as a professional astronomer with eclipses under the belt, there is no IR or UV in dangerous amounts during totality. The sun is not dimmed, it is completely covered by the moon, thousands of kilometers of solid silicates between you and the glowing ball. The main radiation during this phase is the pinkish hydrogen emission in the solar flares (prominences), and the scattered light of the corona.
    BUT accidents do happen when peop le overestimate the remaining time to the end of totality. Know how long totality is at your spot, make sure you know when it is going to end with a safety margin.
    For an exhaustive overview what is and what is not safe, see http://eclipse.gsfc.nasa.gov/SEhelp/safety2.html
  13. The above link explains my concerns exactly. The actual track of a true total eclipse (as opposed to an annular or partial eclipse) is quite narrow (http://eclipse.gsfc.nasa.gov/SEmono/TSE2009/TSE2009.html), and actual totality occurs for a relatively short time period.
    While it is safe to view a genuine total eclipse during totality, laymen (like myself or the OP) probably can't reliably determine safe viewing conditions with certainty . As much as we might not want to admit it, we'd be guessing (an educated guess is still a guess). As the article noted, even 99% coverage of the sun is dangerous to the eyes, and most laymen (especially within the mass media) use the term 'total eclipse' to include annular eclipses and near-total partial eclipses. Hazy or slightly overcast conditions could exacerbate the temptation for unsafe viewing. Taken together, that's just too big of a risk for me to chance it, but YMMV. I've watched several total and annular eclipses indirectly, and would realy love to observe one in person through a properly equipped telescope, especially a large one in an observatory. Failing that, I'll pass on direct observation.
    The reason I recommend against the idea of using a welder's filter plate is that reflective-coated plastic ones are prevalent these days (ADFs - automatic darkening filters - are rare to unavailable in #14 shade) and I've seen a few arc burn cases in welders that were due to small scratches and/or pits on the reflective coating. From personal experience, I know the surface of these filters to be delicate, and disliked using them for that reason, even though the glass ones get hotter in service and are harder to see the weld with.
    A solid, 'green glass' one, #14 shade (or darker), is indeed ok, but they're very uncommon and the temptation might be to use an older or 'found' one that may have defects (scratches, pitting), or use a lesser filter shade value. The filter shade value should be etched near an edge of the glass (where a frame would cover the marking while in service). Checking for defects in the filter plate is critical - unless the filter has no flaws, full protection is unavailable. I've seen a couple of serious cases of arc burn from cracked glass filter plates (#10 and #11). An ocular burn from a cracked or weakened #14 filter plate could be very serious.
    Sorry if I seem like I'm belaboring this y'all, but when I saw the original post, I just couldn't sit by and say nothing...I truly mean well. Eyesight is precious. Please don't take chances - be certain your eyes are protected.
  14. Updates:
    Thank you so much guys giving me lots of information!
    I am getting Lucky because the seller was able to re-ship the Badder film to me! And I got it seconds ago! :D
    The film is very nice and it block almost everything, except the sun!
    So, do you have any sugguestions on the Aperture/Shuttle speed settings with the film on when taking picutre of sun eclipse?
    The normal solar photography can be straightforward, but I think when the entire sun is behind the moon ,the settings must be different and the Badder film has to be taken off. What is the settings now?
    Any comment is appreciated!

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