BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="Binastro" data-source="post: 3175658" data-attributes="member: 111403">. A few further points.If you're using a mirror to project the Crescent Sun onto a white screen or wall it helps if the room into which you are projecting is fairly dark, which enables you to use perhaps a 3 mm mirror rather than 5 mm, for a 5 m projection distance.For a classroom, with a 10 m projection distance, one should try a 6 mm to 10 mm mirror. One should have the lights off in the classroom.One should cover the flat hand mirror with anything, card or even paper.It does not matter what shape the hole is in the card. It can be triangular, square or anything it will still give an image of the Sun on the wall.You should have your back to the Sun when doing mirror projection.Do not shine the beam of light into anybody's eyes.Regarding which binoculars are safe to use for projection.The Royal astronomical Society, which has good information suggests that telescope and binocular eyepieces can be damaged.They make the point of not using unknown apparently dark Materials to view the Sun directly, because of the real dangers of very hot infrared radiation and high energy ultraviolet radiation.However, an optical expert thinks that quality binoculars will be safe. Most eyepieces, he says, have their focal surface ahead of the glassware and are low enough power to have not too much concentration of the beam as it passes through. The antireflection coatings will help to reject heat absorption and the most damage can be done at the exit  pupil which is well out of the way of eye cups; that's the place where a piece of paper can be ignited.The gentleman did get a high quality eyepiece very hot but it survived. Bleaching of colour filters can be rapid and he says that he has badly damaged a polariser that didn't survive a F/15 solar beam.He says that, the exit pupil was where the appalling solar filters were put and the thought of using one is horrible.The Sun can do plenty of damage to telescopes left out under the blue skies. Shrouds burnt, sensors can be destroyed and all manner of expensive smells of burning!So one gets different opinions.Personally, I do not use very good binoculars for projection, particularly I would not leave them set up with the Sun shining through them. I do use the Docter 10x25 for brief projection. But I wouldn't use a good 10x42 or larger binocular.It is up to the individual, to decide which binocular to use for projection.On 2015 March 20 at 0931 UTC in the middle of England the sun's elevation is about 27° and the sun is in the south-east.Projection using a colander is very simple, giving multiple solar images.</blockquote>

Verification