On viewing the Sun in the early 19th century

[Hans]

Hello a question for you very smart guys:

What did they use to view the Sun in the 1830's and not get blinded? What technology existed to allow an amateur to see sun spots or an inferior conjunction of Venus? I read once they used 'smoked' glass but can anyone suggest a name/description of that type of device?

Thanks

[Noclevername]

Camera Obscura. A pinhole projects an inverted image on a background.

[grant hutchison]

Smoked glass is just a sheet of glass held over a smoky flame until it is blackened with fine soot. Bit of trial and error involved, but eventually you get an even black layer that is dense enough to allow comfortable viewing of the sun.

ETA: Not a good idea, by the way - you've no way of knowing how much UV or IR is getting to your eye.

Grant Hutchison

[01101001]

Don't assume sun observers always put safety above all.

Galileo, solar observing, and eye safety

I hasten to add that I do NOT recommend trying this yourself! Nevertheless, it is certainly experimental confirmation of the conclusion by White et al. that the heating of the direct solar image “can be safely tolerated” — at least for a few minutes.

[grant hutchison]

BTW, I've seen a sunspot (or rather, a giant sunspot complex) with the naked eye. It was easily visible at sunset (a very red sun in a dusty part of the world), and I could track its movement over the course of a week. We've got records of apparent sunspot observations going back to the Ancient Greeks, if not earlier.

Grant HUtchison

[Hans]

Thanks all for the replies and information

[ngc3314]

Also, Galileo may have the first to note that a telescope can be focused to project the Sun on some sort of screen. (It took me a minute to realize this is about as easy for a Galilean design as it is for a Keplerian refractor, as long as the tube has enough focus travel). Weasel wording because we know others were, for example, mapping the Moon earlier, and Christoph Scheiner was all about sunspots near the time Galileo was working on them. This let Galileo record sunspot positions quite faithful and demonstrate that they were on the solar surface rather than in some sort of orbit well above it.

[plphy]

The "Herschel wedge" was invented in the 1830s: Before being viewed, the light is reflected from a glass surface in the eyepiece so that only about 5 % of the original intensity are left. The other 95 % are safely disposed of.

See the Wikipedia article: Herschel wedge (the article notes that a neutral density filter is still needed).

Bye,
Thomas

[AGN Fuel]

BTW, I've seen a sunspot (or rather, a giant sunspot complex) with the naked eye. It was easily visible at sunset (a very red sun in a dusty part of the world), and I could track its movement over the course of a week. We've got records of apparent sunspot observations going back to the Ancient Greeks, if not earlier.

Grant HUtchison

Yes, similar story - I once saw (naked eye) a sunspot complex on the setting sun when there had been bushfires in the region and the sun was shining through a significant depth of smoke. I was actually just admiring the extraordinary colour of the sun when I noticed the spots and a check of the SOHO image when I got home confirmed that's what they were.

[DaveC426913]

When I was young, I used to stare directly at the sun for as long as I could. I was too dumb to realize it could be very damaging.
But, I'm not blind - fingers crossed.

[Solfe]

One weird gizmo from the 19th century was the Claude glass or black mirror. While it was meant of observation while painting, the use of it requires the sun to be at one's back and very often the sun would be reflected to the viewer. It isn't remotely an astronomical device, it was a mirror that soften the reflected image. I would imagine that a lot of people would have looked at the sun in the reflection. It doesn't magnify directly, but it does distort.

[grapes]

When I was young, I used to stare directly at the sun for as long as I could. I was too dumb to realize it could be very damaging.
But, I'm not blind - fingers crossed.

Same, fifty years on. There were a lot of things we did that *should* have left us blind/deaf/disfigured/bereft.

[George]

When I was young, I used to stare directly at the sun for as long as I could. I was too dumb to realize it could be very damaging.
But, I'm not blind - fingers crossed.

After learning that no aperture increase can increase surface brightness, though it can greatly increase total flux, I used binocs on a soft setting Sun with no problems. Ironically, it may be safer to use binoculars since the glass helps block the IR that has little attenuation due to our atmosphere alone. [There is a NASA site warning of IR risks.]

Caution must be exercised, nevertheless, as there is some risk in doing this. I had a mylar filter crack suddenly in half just as I was perhaps an inch away from viewing the Sun. The solar intensity was concentrated at this filter which was overcome with heat. I could have lost what is now my good eye.

[wd40]

If the medievals had the Sunstone to locate the Sun through cloud, could the ancients have had a canny way of viewing the Sun that we don't know about?

[antoniseb]

If the medievals had the Sunstone to locate the Sun through cloud, could the ancients have had a canny way of viewing the Sun that we don't know about?

Odd, I was just trying to use a Sunstone on Saturday... I wasn't terribly convinced that they are easy or reliable, but the concept is pretty cool. Still, I don't see how the existence of Sunstones (Iceland Spar) would suggest in any way that there was some unknown way of observing the disk of the Sun. As noted above Camera Obscura is a well documented method of doing the same (see the work of Levi Ben Gerson (1288-1344 CE) on this topic for example). Pinhole cameras are perfect for seeing the Sun.