"MALEY, PAUL D. (JSC-DO511) (USA)" wrote: > I propose that there should be a standard rule in daytime satellite > observation that states: "Warning: Observing satellites transiting the sun > SHOULD NEVER BE ATTEMPTED unless the observer utilizes a neutral density 5.0 > filter placed IN FRONT OF the telescope objective." R. Chou's advice (http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/safety2.html) mentions one reason for not using eyepiece filters - that the filter can overheat or crack without warning. Do you think that another reason for this advice could be that any tiny hole in a filter behind the eyepiece could cause damage to points or lines across the retina whereas similar sized holes in a filter in front of the objective will a) be a much smaller proportion of the area of the filter (just because the objective is bigger) and b) have their effect "diluted" across the whole field of view (because the hole would be more out of focus)? R. Chou's advice also mentions use of a particular shade of welder's glass. Anybody know for sure whether welding masks in general are safe to use for solar observation? I've seen people use them for eclipse observation but don't know if they have sufficient IR or UV filtering effect. > There are two other similar safe sun viewing methods that are not > applicable for satellite viewing: 1) pinhole camera; 2) eyepiece projection > onto a white screen. Why are these methods not applicable? I can imagine that a pinhole would have to be pretty carefully set up to get the resolution to see a small dot like a satellite but use of a small lens could work, couldn't it? Perhaps a camera obscura with a CCD camera set for macro focus inside? Maybe even a tiny pinhole "focused" directly onto a CCD - e.g., a Philips web-cam with the lens removed. Ed. ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www.satellite.eu.org/seesat/seesatindex.html
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