Here are Frequently Asked Questions about Solar Eclipse.

Here are few frequently asked questions about solar eclipse viewing. I have tried my best to answer them.

What is solar eclipse?

It is when the moon comes in between the sun and the earth to block the sun rays on a new moon's day.

What time does it start and end on June 21 (Asar 7)?

Sunday, the solar eclipse will start at 10:53AM

blocks 99.4% of sun  at 12:41PM

and ends at 2:24PM

and do you know June 21 or Asar 7 is the longest day of the year, which is also called summer solstice. 

What type of eclipse is it?

It is annular solar eclipse, but Kathmandu will not witness the annulus. So, for Nepal it will be partial solar eclipse that will block 99.4% of the sun for a maximum of 38 seconds.

Can I watch the eclipse?

No, without any proper protection it is not advisable to watch the solar eclipse.

Shall I have to wear the protection for watching the lunar eclipse too?

No. You can watch the lunar eclipse directly without any protection because you will not be exposed with the direct solar radiation. In lunar eclipse, we are watching just the shadows of our earth.

What are the organs that are much affected by viewing solar eclipse?

First, the eyes and then the skin.

How does eclipse affect the skin?

Longer exposure to the skin maybe carcinogenic, so while going outdoors in the time of eclipse, don't forget to wear full clothes.

What damage can watching a solar eclipse do to the eyes?

Solar eclipse affects the central portion of retina if viewed without protective wears. The central portion is called macula and heat-mediated photochemical reactions like photo-oxidation and photo-coagulation causes delayed scarring of the macula. The pathologic condition of formation of this kind of scars is called solar maculopathy. Some people call it, less specifically, solar retinopathy. The resulting condition of reduced visual functioning is called eclipse blindness. It is, however, not a total blindness and is just the reduction of central visual acuity (acumen of seeing sharply).

In certain conditions, the outer layers or epithelium of cornea (outermost transparent portion of eyes) might peel off due to longer solar exposure which later heals by itself without any residual effects. It, however, causes pain until complete recovery.

Is there a point when we can watch solar eclipse with naked eyes?

Yes. Total solar eclipse, which can last up to few minutes, can be watched with naked eyes safely because at the time of total blockade solar radiation cannot reach to your eyes. But it is risky because you don't know when a small portion of sun will be suddenly visible and harshly damage your eyes unprecedented. Partial and annular solar eclipses are, hoewever, never safe to watch at any point.

How long can a total solar eclipse last?

In a totally extreme case, total solar eclipse can last up to 7 minutes and 31 seconds.

Is the effect of solar eclipse to your eyes is immediate?

It is, oftentimes, not immediate. You won't feel that your vision is affected during the time of watching. The visual reduction may ensues in 12- 48 hours or so.

What procedures do clinicians use to diagnose the effects of solar eclipse to your eyes?

According to your history of recent solar eclipse exposure, they will have a dilated fundus evaluation (they use eye drop that dilates your pupil and scope the back of the eye or retina with high plus lenses in a slit lamp or indirect ophthalmoscope). They can also advise you for an OCT (optical Coherence Tomography) scan that pictorially depicts layer-wise differentiation of lesions in the retina.

So, how can we watch the eclipse safely?

There are two methods to watch solar eclipse safely.

First: projection method which has two sub-types. 1) pinhole projection: make a small hole in a cardboard and let the sun-rays pass through the pinhole to cast a circle of rays that will have shadows of eclipse. 2) In optical projection, the image of the eclipse will be projected at a screen or paperboard after the eclipse rays pass through optical instruments like astronomical telescope. This method, can however, damage the lenses of the instruments due to extensively concentrated UV rays. Both the projection methods are applicable only when there is a partial solar eclipse. Why? Use your brain.

Second method is use of the protective eye shields, solar shades or eclipse filters. Various online markets offer these eclipse filters. For example: American Paper Optics. In Nepal, the price ranges of these filters falls in Rs. 1000 to Rs. 2000.

Once your eyes are damaged by the eclipse viewing, will it recover?

In many case, most of the effect will heal by a few months but some of the visual functioning like contrast sensitivity might be permanently impaired. Up to few months people may experience central black spots in the visual field which later on subsides.

Are medical x-ray films and polarized sunglasses are safe to watch eclipses?

No. s-ray films and polarized glasses are not safe to watch solar eclipses. Watching water reflections and mirror reflections are too hazardous.

Is eating during the eclipse harmful?

Many cultures and religion prohibits eating during and right after the eclipses. Hindu culture also proclaims not to eat during eclipses and throw the food or water touched by the solar eclipse. They also say that to sanctify the food one can use Tulsi patta (ocimum leaves), which have a purifying, antibacterial properties. 

Since generally, the daytime temperature of earth falls due to eclipses, and religions seem to stand to the point that it arouses the abundance of harmful organisms (mainly bacteria). However, this is quite contradictory to the scientific evidences because the concentrated UV and near UV rays would instead kill the bacteria.

Science also has proven that eclipses harm human health if they eat during or around the occlusion because many harmful elements fall on the earth at that time. Among them is Radon, which is more prone to be stored in wet substances like food and water. Radon is harmful to human body.

For a more detailed information please watch the video: 

Please turn the subtitles (closed captions) on by going to the YouTube if you are a Non-Nepali speaker.

References:

1. Pasachoff JM. Observing Solar Eclipse in the developing world.

2. Banerjee Sk & Chaterjee SN. Killing of bacteria in solar eclipse and its biological implications.

3. Chou BR. Eye safety during solar eclipses: Myths and realities.

4. Solar eclipses. timeanddate.com

5. Pasachoff Jm. Solar eclipse as an astrophysical laboratory.

6. Mark Littman, Fred Espenak, and Ken Wilcox. Totality: Eclipses of the sun.