Posts Tagged ‘Safe viewing’

DIY solar filters for camera

20 July, 2009

From our earlier post on the topic, here is how we made our solar filter holders for some of our cameras.

Plastic bottleFirst we got plastic soya sauce or pepper bottles from the local sundries store. The kind you find in kopitiams or the local coffee shops.

They’re made of soft plastic, so they’re easy to cut up with scissors.

To start, we cut a hole in the bottom, and cut off the edge of the top as well.

For our filters, we exposed a roll of black-and-white film to light and got that developed it. The silver nitrates in the film will serve as the protective filter for the camera.

Cut two layers of the developed film together and glue them down to the plastic holder.

And voilà — protective filters for your camera.

Secure this to your camera with tape. Works great for digital cameras and handicams.

filters

Protection for your camera

17 July, 2009

If you are going to photograph the eclipse, here’s one way to fashion some protection for your camera.

(It’s not advisable to point your camera directly at the Sun, you might damage the photosensors.)

Get some black-and-white film that has been fully exposed to light, and have it developed to maximum density. This method relies on the metallic silver contained in the film emulsion as the protective filter.

Self-made optical filter (Photo: Kalan)

Collect the roll later… Voilà!

You can get creative with how you affix the filter to your camera.

Use the universal answer to everything, i.e. duct tape. Build a holder out of string and toothpicks (like the picture on the right). Or build some sort of holder for the filter (like cut a plastic bottle up and paste the filter at the hole at the bottom… which is what we plan to do).

That’s for your camera.

Now, about your eyes.

If you really have to look at the Sun with a self-made filter, and you’ve heard your science teacher mention this technique in the past, please note that these days, some films use dyes instead of silver.

This makes them unsafe for blocking out the Sun properly. So when purchasing the film, make sure to ask the staff at the film shop and that you get the right type of black-and-white film.

We’re making our plastic-bottle-filter-holder right now. I’ll post the results once we’re done. This is so fun.

Solar eclipse viewing safety II

16 July, 2009

More ways to view a solar eclipse safely.

SOLAR FILTERS

Specially designed solar filters also allow you to observe the solar eclipse safely.

However, beware of fashioning a filter on your own. In the past, many have used one or two layers of black-and-white film that has been fully exposed to light and developed to maximum density, relying on the metallic silver contained in the film emulsion as the protective filter. However, these days, some films use dyes instead, making them unsafe.

If you have to fashion your own filter, make sure that you’re using the right film with the silver in it, and not one that has dyes. We used B/W film and asked the guy at the photo shop just to be sure…

Blackened X-Ray film may not be completely safe either, and self-made objects like a floppy dish removed from its case or the black colour slide film should be avoided.

Photo: Guy LebègueSource: Eclipse Viewer

 

WELDER’S GOGGLES

One of the most widely available filters for safe solar viewing is a piece of No. 14  welder’s glasses, available from welding supply stores.

Do not use sunglasses. No matter how expensive they are, they are not suitable for looking at the Sun.

Ævar Arnfjörð Bjarmason

 

For a more detailed explanation of observing eclipses safely, you might want to check out these websites:
NASA’s Eye Safety During Solar Eclipses
MrEclipse.com

Solar eclipse viewing safety

16 July, 2009

Okay, now we’re really feeling like naggy mothers, but here’s a reminder again:

Do not look at the Sun or a solar eclipse with your naked eyes. 

Looking at the Sun without proper solar filters or other such protection, even briefly, could hurt your eyes, and possible cause blindness.

This applies to looking at partial solar eclipses too. Even if 99% of the Sun was covered, the 1% that is still visible is still 10,000 times brighter than the full Moon.

We listed out good ways to catch a solar eclipse in a couple of earlier posts (part 1 and 2), but this topic bears a second mention.

 

Good ways of catch a solar eclipse are:

THE PINHOLE METHOD

The safest way to view the Sun’s disc is by indirect projection, such as the pinhole projection method, or a pinhole camera.

First, poke a small hole (about 1 mm in diameter) through a piece of paper or cardboard.

Let sunlight go through that hole onto a second piece of paper, cardboard or clean surface which serves as a screen. Practically any plain surface will do, like the paper plate in the picture below.

An inverted image of the Sun will be projected.

Let the pinhole be small, about 1 mm in diameter. If the pinhole is too wide, it will just be a shaft of light passing through the hole.

To make the image larger, move the pinhole away from the screen.

Photo: Mila ZinkovaEclipse-assiette

By the way, it’s exciting and all, and the projection may not look that bright, but do not look through the pinhole at the Sun.

 

PROJECTION WITH BINOCULARS OR TELESCOPE

An adaptation of the Pinhole Projection Method of viewing a solar eclipse — projection using binoculars or a telescope.

Point a pair of binoculars (with one of the lenses covered) or a telescope towards the Sun and hold a white piece of paper behind the eyepiece.

An image of the sun will come out the eyepiece and shine onto the paper, like an overhead projector would shine onto a screen. As the eclipse happens, you can see it in the image of the Sun on the paper.

The projection can be made small, or onto a big plain surface for many to enjoy.

Here are some examples of the setup:

Photo: Luis Fernández GarcíaPhoto: Luis Fernández GarcíaPhoto: Kasos fr

Erm, again, do not look through the telescope or binoculars at the Sun.

Protect yourself – a reminder in viewing safety

22 June, 2009

Photo: LykaestriaA gentle reminder to all again, if you are gonna catch the upcoming solar eclipse, or any future solar eclipses, please take proper precautions to view it safely.

The safest viewing technique is the pinhole projection method or to use a pinhole camera. Otherwise make sure you use proper solar filters.

Do not look at the Sun or a solar eclipse with your naked eyes.

(And yes, we can just hear you go “Yes, Mum.”)

Looking directly at the Sun, even briefly, can cause temporary blindness, possibly even permanent blindness.

The Sun delivers 4 milliwatts of sunlight to the retina, slightly heating it and potentially causing damage as our eyes cannot respond to the brightness. You could even suffer permanent blindness. Let’s not forget that the Sun is 1.3 million times the size of Earth, and made up of burning nuclear fusion energy.

Photo: NASAThe Sun also exposes us to UV rays. In our eyes, the UV rays yellows the lens and over a period of years cause cataracts. That’s why protective sunglasses are a good investment.

UV rays from the Sun are also what gives us sunburn; the rays reach the layer just under the skin’s surface, damaging the cells there and causing the “burn”. Over time, this could lead to higher risk of skin cancer.

The Sun may be magnificent and necessary for life, but it’s still a powerful force to watch out for.

Viewing a solar eclipse safely, Part II

31 May, 2009

Here are more ways you can try to observe a solar eclipse.

Photo: Nils ÖlmedalPROJECTION WITH BINOCULARS OR TELESCOPE

An adaptation of the Pinhole Projection Method of viewing a solar eclipse — projection using binoculars or a telescope.

Point a pair of binoculars (with one of the lenses covered) or a telescope towards the Sun and hold a white piece of paper behind the eyepiece. An image of the sun will come out the eyepiece and shine onto the paper, like an overhead projector would shine onto a screen.

Adjust the focus on the binoculars or telescope until the image of the sun has a sharp and not blurry edge. You can also adjust the distance of the paper from the eyepiece.

sunspotsFor best effect, the lens should be stable, e.g. place the binoculars a tripod. This technique can also be used to observe sunspots.

Warning: Do not look at the sun through the binoculars without proper protective filters.

Which leads us nicely to…

CAMERA AND TELESCOPE SOLAR FILTERS

Many telescope and camera companies provide metal-coated filters that are safe for viewing the Sun. They are more expensive than common Mylar, but expert observers generally like them better because they are available in various colours, such as a chromium filter through which the Sun looks orange. Through aluminized Mylar, the Sun is blue-gray. As with the Mylar, you can look directly at the Sun through these filters.

However, do not confuse these filters, which are designed to fit over the lens of a camera or the aperture of a telescope, with a so-called solar eyepiece for a telescope. Solar eyepieces are still sometimes sold with small amateur telescopes. They are not safe because of their tendency to absorb heat and crack, allowing the sunlight concentrated by the telescope’s full aperture to enter your eye.

Viewing the Sun’s disc on a video display screen (provided by a video camera or digital camera) is safe, although the camera itself may be damaged by direct exposure to the Sun. 

via: www.space.com and www.mreclipse.com

Viewing a solar eclipse safely, Part I

30 May, 2009

WARNING: Do not look directly at the sun with the naked eye.

Your mother, your teachers, have all told you this. And this rule still applies when it comes to solar eclipses.

800px-EclipsbrilletjeDo not look at the Sun without adequate eye protection, not even during a partial or annular eclipse, not even if you glance at it for a few seconds, because permanent damage to the retina of the eye can result due to the intense visible and invisible radiation that the photosphere of the Sun emits.

Furthermore, the retina has no sensitivity to pain and the effects of retinal damage may not appear immediately so there is no warning that injury is occurring.

Even if only 1% of the Sun’s surface is still visible, it is still 10,000 times brighter than the full Moon. And is still intense enough to cause retinal burn, even though illumination levels of your surroundings are comparable to twilight.

Sunglasses, however expensive or high quality they are, do not work and you will damage your eyes permanently. Only properly designed and certified solar filters should ever be used. 

The only time when it is safe to view the Sun with the naked eye is during a total eclipse, when the Moon completely covers the disc of the Sun. In fact, it is one of the most spectacular sights in nature.

Otherwise, here are a few good ways to 

THE PINHOLE CAMERA

The safest way to view the Sun’s disc is by indirect projection, such as the pinhole projection method, or a pinhole camera. First, poke a small hole (about 1 mm in diameter) through a piece of paper or cardboard. Let sunlight go through that hole onto a second piece of paper, cardboard or clean surface which serves as a screen. An inverted image of the Sun will be projected.

projection methodLet the pinhole be small, about 1 mm in diameter. If the pinhole is too wide, it will just be a shaft of light passing through the hole. To make the image larger, move the pinhole away from the screen.

You can make more complex versions of a pinhole camera using cardboard boxes, which are easily found on the Internet, such as this one. By the way, do not look through the pinhole at the Sun.

SOLAR FILTERS

Specially designed solar filters also allow you to observe the solar eclipse safely.

However, beware of fashioning a filter on your own. In the past, many have used one or two layers of black-and-white film that has been fully exposed to light and developed to maximum density, relying on the metallic silver contained in the film emulsion as the protective filter. However, these days, some films use dyes instead, making them unsafe.

Blackened X-Ray film may not be completely safe either, and self-made objects like a floppy dish removed from its case or the black colour slide film should be avoided.

WELDER’S GOGGLES

One of the most widely available filters for safe solar viewing is a piece of No. 14  welder’s glasses, available from welding supply stores.
 

For a more detailed explanation of observing eclipses safely, you might want to check out these websites:
NASA’s Eye Safety During Solar Eclipses
MrEclipse.com
Viewing eclipses on Wikipedia