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  1. #11
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    I am no expert on welding glasses however I would be nervous about using them for something they were not designed to be used for. My sight is far too valuable to take that kind of risk with.

    As far as the specifications that have been mentioned, I can not find the complete ANSI Standard Z87.1-2010 specification online without paying for it. If someone would like to link to a source I would love to read it.

    What I have found is that the specification allows for varying degrees of protection for many types of light including the W# for welding up to #14, and then goes on to have seperate specifications for UV protection (U# up to U6), and IR light (R# up to R10).

    It also seems clear that there are items that fit specifications for ANSI Standard Z87.1 (1968 edition), ANSI Standard Z87.1-2003 and ANSI Standard Z87.1-2010 so buying something used or that was just laying around in the garage may conform to an older specification which may, or may not, provide reasonable protection even if you assume the latest version is safe for solar viewing.

    So I guess it all comes down to what are you willing to risk on the assumption that your welding glass will do something it was not designed to do?

    Allan

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  3. #12
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    This seems like the perfect thread to hop onto for my question.

    My 8" Sky-watcher dob conveniently comes with a cover that has a 2" aperture built-in, which is great for this situation.

    The Baader film is quite expensive here(Montreal), $40-$45, and I unfortunately could not find #14 welders glass, only #10. But I seem to understand that if layered, each pane doubles the strength of the glass, so 2 #10 would be #11, 3 would be #12 and 4 would be equivalent to #13.


    Assuming this is the case, I took 4 panes of #10 glass, taped them together(quite securely in my opinion) and fitted it on top of the opening.

    So 2 questions, is my assumption correct? and secondly will my slip-shod(but very sturdy actually) attachment method affect the image? I think not, since its so far out of focus. But I have a couple other ideas that are not in the way of the optical path if necessary.



    Last edited by gelu88; 06-01-2012 at 09:11 PM.

  4. #13
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    I would also STRONGLY recommend that you do NOT use welders shades in this way. You cannot be sure it will work, and you will only need to be wrong once to cause lasting damage or blindness.

    If you cannot get proper solar filter in time for the transit, it would be safer to project the image of the Sun onto a sheet of white paper or card, than to take a chance on the welders shade.
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  5. #14
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    You seriously cannot want to see a transit so bad that you would risk damaging or permanently disabling your vision, can you ?
    Please pony up and buy the right material, even if that means missing a transit. Everyone knows that its expensive, but vision is priceless !

  6. #15
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    It'll probably degrade the image, somewhat - especially stacked - since it's more like window glass than perfect optical glass. There doesn't seem to be a lot of obvious info on the web comparing strengths of the different types of welders glass - and what I have seen doesn't appear to follow your 'adding a layer adds one to the strength' idea. In the absence of solid, reliable data, I'd be tempted to look at an alternative - like using the 2" aperture and a cheap eyepiece to project an image of the sun - rather than taking a chance with your sight. If you fry an eyepiece, you can replace it. Not so with your eyes "probably ok" isn't something I'd want to risk...

  7. #16
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    I've been told repeatedly that stacking welder's glass does not make it equivalent to the glass you really wanted.

    Yes, people use welder's glass all day long and do quite nicely. They are designed very well to block harmful radiation at that intensity.

    But you've got some problems matching welder's glass to your telescope.

    The first thing I'd worry about is getting the intensity correct. The ETX-90 is not a light bucket, but it will collect an awful lot more sunlight in all aspects of the spectrum than would your eye. If you get enough welder's glass between the Sun and your objective that might be safe - but I don't think anyone has ever tested this and I wouldn't risk it.

    Your views are likely to be rather poor. Welder's glass is built for welding. This is not optically wonderful glass and you are likely to end up with distortions of the image. Stacking the welder's glass is likely to make this worse.

    One other thing. One of the problems we try to solve when doing solar observing is heat build-up. So if you are doing solar projection with even a fairly small scope (refractors and catadioptrics especially) it's not recommended that you aim your scope at the Sun for more than about one minute. The eyepieces are especially prone to damage so they recommend you not pull out your better eyepieces for this duty. . . In your current proposal I contend that we don't know if you are going to have heat build-up issues. If you do have heat build-up I don't know how long you can view before you are going to have an issue. Since you should have decent IR blocking it may not be an issue at all.

    Personally, I value my eyes a lot and don't intend to use anything which has not been properly tested and found to be safe. We might get by doing other stuff, but I'll give up watching each and every viewing of a transit, eclipse, or whatever in order to make sure I can see my wife, kids, grandkids - and other essential sights.

    What's more, if you get it wrong on just one transit or eclipse - you may not get to see another astronomical sight.

    Call me paranoid about this - and I won't mind at all.

    Months ago I decided to do it right. So I've obtained solar filters for two telescopes and I have one of Ed Jones's solar projectors as well as a bunch of eclipse glasses. It cost me advance planning and some money, but I'm not going to take chances with my eyesight.

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  8. #17
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    The simple answer is that NONE OF US really know if it is safe. Personally I would just buy a normal solar filter from a reputable supplier and not try to use something that is really NOT tested as a telescope filter.

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  10. #18
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    I do quite a bit of welding around the house. Have made many safety rails, repaired numerous objects for the neighbors, etc. My welding hood was great for watching an eclipse we had here several years ago. However, I would not even consider using welder's glass for a solar filter on a telescope.

    Approach this problem from the back door. Remember the primary purpose of a telescope is to concentrate light and welder's glass is designed for usage where light is not concentrated. The image you will see through a telescope screened by welder's glass will be far brighter than the one you see with the glass without a telescope. The image produced by a focused telescope eyepiece is approximately 1/4 inch in diameter. A 90 mm telescope has a diameter of 3.54 inches. Do the arithmetic. A 90mm telescope will collect about 200 times more light than the welder's lens was designed to screen. While there may be a safety factor of 2 or 3 with welder's glass, I seriously doubt that there is one of a factor of 200.
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  12. #19
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    At this late date, you are unlikely to find a suitable filter. However, you can try this:

    Take a sheet of cardboard and cut a hole in the centre.
    Tape a piece of aluminum foil over the hole in the cardboard.
    With a fine sewing needle, poke a small hole in the centre of the aluminum foil.

    You can use this apparatus as a pinhole projector. In the shadow of the cardboard, you will see the image of the Sun. The image of Venus crossing the Sun's disk should be easily visible with this setup.

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  13. #20
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    Well, there seems to be a fair amount of conjecture in the replies generated by my question and some that seem to have not actually read past the first line of my post... I appreciate the reasoned and considered responses, thank you. I have decided to use my ETX 70 instead and have built a sun funnel for it. It seems to work pretty well, now just hoping for clear skies on Tuesday.

 

 
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