Viewing the Sun with Welding Glasses

-- Joel | August 4, 2023

Question:

Hello…I’m a retired 60 year old living in Ohio and I’m spending my time learning all I can that I didn’t learn in school. I have a sunspotter telescope which I love; this has lead me to buying a #12 welding glass to view the sun without the “glare”.

Here’s my question: How is the sun measured from earth? I’ve read where, by coincidence, the sun and moon appear the same size due to their relative size and distance from each other, but that supposes one measures the suns “glare” as well or otherwise the sun is much smaller than the moon in the sky. Is viewing the sun through this #12 welding glass a fair approximation of the sun’s size or is something else going on? If this is a “fair” viewing option, what describes the “glare” we see of the sun on a typical day?

Thank you for this great service and I look forward to hearing from you. Joel H., Ohio

-- Joel

Answer:

First of all, it is important to note that you should only use glasses made with lens material rated for solar observations. This includes shade 14 glasses and glasses compliant with all ISO 12312-2:2015 transmission requirements. The Phillips Safety Products web site provides further information. The size of the Sun as viewed through proper solar observation glasses is the same as its visible size. That size is also the same as the visible size of the Moon, as you note. The “glare” that you are referring to might be solar coronal emission, which do extend beyond the visible surface of the Sun but are in general much fainter than the disk of the Sun at visible wavelengths.

-- Jeff Mangum

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