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Larger Solar Spot...
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Richard Taylor send an eMail to RASC members stating that the large
sunspot he observed recently (I observed it as well and posted here), is now near the middle of the sun and is large enough to be seen using just your eyes (through an appropriate solar filter of course). Now's the time, if you have solar filter! Solar max is active again but it won't last forever! ;-) Photons Rule! Rol |
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Bruce McGlashan
I checked it out this afternoon, with the #14 welder's glass I picked up for
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the Christmas eclipse. Neat! To my bleery eyes (too much programming this afternoon), it looked like a vertically-oblong spot. For anyone with some power, is that what it looked like on closer inspection? {Geez, I should have picked up a solar filter with my new scope.} My wife suggested I haul the finderscope off the scope and look at the sun through it and the welder's glass (glass in front). I didn't try it, because I wasn't sure that's a safe thing to do. Anybody know? BTW, I'm pretty sure that was the first sunspot I've personally observed since 1972, when I was using my department-store 60mm scope and eyepiece sun filter (yes, I dodged that bullet, countless times). That's about all that scope was good for - sunspots and exploring the moon. -----Original Message-----
From: r.prevost@... <r.prevost@...> To: OAFs@... <OAFs@...> Date: March 28, 2001 16:39 Subject: [OAFs] Larger Solar Spot... Richard Taylor send an eMail to RASC members stating that the large |
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--- In OAFs@y..., "Bruce McGlashan" <mcglashanb2@h...> wrote:
To my bleery eyes (too much programming this afternoon), it looked >I sketched it a few days ago. At that time, the spot seemed horizontally oblong if you included the greyish area around the main black spot itself. There are a number of smaller sunspots as well. The E-W size was about 120" whereas the N-S was only 80". However, if you looked only at the largest dark spot, through the scope, that was oblong in a vertical direction, as you describe it now. I wonder if it has changed much in the last few days? My wife suggested I haul the finderscope off the scope and look atA finderscope concentrates the light maybe 7X. Welder's glass is said to protect unaided eyes. I don't know with certainty, but common sense says "don't do it!" Good call, I'd say. If we go observing soon to a place where I bring my scope, I'd gladly bring my solar filter so you can catch a few glimpses. We'd have to go just a bit earlier.do some solar observing/sketching, then observe the evening & night stuff. Soon, the sun will still be high enough at 6pm to do a bit of solar observing. The Photon Hound |
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Wagner,Rick [CIS-ADS]
Sure it's safe. I have a 2x4" welder's glass which I use in front of my
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9x21 binos for quick checks of the sun. A telescope/binocular can't concentrate the light to any greater intensity than that which is coming into the objective. Therefore anything which is safe to look through with the naked eye is also safe in front of the objective. BUT, make sure you fasten it on well and make sure that it covers the whole objective. The optical quality of the filters isn't great but at 9 or 10x it's fine. Rick -----Original Message-----
From: Bruce McGlashan [mailto:mcglashanb2@...] Sent: Wednesday, 28 March 2001 18:33 To: OAFs@... Subject: Re: [OAFs] Larger Solar Spot... snip My wife suggested I haul the finderscope off the scope and look at the sun through it and the welder's glass (glass in front). I didn't try it, because I wasn't sure that's a safe thing to do. Anybody know? snip |
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--- In OAFs@y..., "Wagner,Rick [CIS-ADS]" <rick.wagner@e...> wrote:
Sure it's safe. I have a 2x4" welder's glass which I use in frontI'm glad to know that. Better safe than sorry. You explanation makes sense -- the light is already at a safe level before entering your binoculars. Thanks Rick! Where does on get welder's glass anyway? Rol |
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Bruce McGlashan
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-----Original Message-----
From: r.prevost@... <r.prevost@...> To: OAFs@... <OAFs@...> Date: March 29, 2001 17:48 Subject: [OAFs] Re: Larger Solar Spot... [snip]
I bought mine at Messer at 1750 Woodward Drive. It was #14, and it measures about 4x6". |
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Bruce McGlashan
Thanks. I was not really concerned with the visible light, but with the UV.
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I guess what I was concerned about was whether the glass is as efficient at blocking UV as it is at blocking visible light. It could be minimally acceptable in the UV band for naked-eye observation, but magnification would put it over the safe limit. See what I mean? {pardon the pun} -----Original Message-----
From: Wagner,Rick [CIS-ADS] <rick.wagner@...> To: 'OAFs@...' <OAFs@...> Date: March 29, 2001 08:35 Subject: RE: [OAFs] Larger Solar Spot... Sure it's safe. I have a 2x4" welder's glass which I use in front of my |
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Richard Harding
Hi Bruce!
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I have read many threads about people using welder's glass in the front of binoculars for viewing solar events. I have often heard the warning to make sure that the glass is SECURELY fastened to prevent it falling off or shifting to let some light in. However, I have never heard of a UV danger (ie. a concentration of UV light). I suggest that if you are concerned, that you buy a piece of Bader filter material (quite cheap I think) and use that with your finder scope and binos. This is obviously safe, as people are spending hours at the eyepiece of telescopes with Bader filters looking at the sun at far higher magnifications than you are talking about, without reported problems. Just my two cents worth! Richard Return-Path: <sentto-2911285-245-985922045-rharding=iosphere.net@...> |
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Wagner,Rick [CIS-ADS]
Well, I got mine in a little welding supply shop in Cold Lake Alberta but
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I'm sure there are closer places than that. It was actually a nation-wide chain called Acklands and I believe they are in Ottawa as well. Rick -----Original Message-----
From: r.prevost@... [mailto:r.prevost@...] Sent: Thursday, 29 March 2001 17:48 To: OAFs@... Subject: [OAFs] Re: Larger Solar Spot... --- In OAFs@y..., "Wagner,Rick [CIS-ADS]" <rick.wagner@e...> wrote: Sure it's safe. I have a 2x4" welder's glass which I use in frontI'm glad to know that. Better safe than sorry. You explanation makes sense -- the light is already at a safe level before entering your binoculars. Thanks Rick! Where does on get welder's glass anyway? Rol Your use of Yahoo! Groups is subject to |
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Wagner,Rick [CIS-ADS]
Light from the sun works the same way as light from a nebula - it just
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happens to be at the other extreme of the range of brightness we astronomers have to deal with. Let's compare a 6x30 finder with naked eye - let's assume a 5mm pupil (the solar astronomer's will be smaller than this, the stellar astronomer's probably larger). The 30mm aperture of the finder is 6 times larger in diameter or 36 times the area of the naked eye pupil. It therefore accepts 36 times as much light. However, when using the telescope the image of the sun on the retina will also be 6 times larger in diameter or 36 times the area of the image when observing naked eye. So 36 times as much light spread over 36 times as much area gives the same intensity per unit area. What if we reduce the magnification of the scope to say 3x? Then the exit pupil of the scope will be 10mm so 1/4 of the light coming from the scope will be blocked from entering the eye by the pupil and we end up with the same intensity. Finally - the welding filters are designed for use with arc-welding which generates copious amounts of UV and IR. They are guaranteed safe naked eye. And, of course, the UV and IR are both affected the same way as visual light as far as aperture and magnification goes. Therefore if a filter is safe for naked eye viewing it will also be safe in front of any scope. Note that all this works the same for nebulae. A nebula can never have a higher intensity of light on the retina than when observing naked eye. So why does the telescope help? By increasing the size of the nebula at the same intensity the eye/brain combo is able to better detect the photons arriving over a larger area - they don't ignore it as noise. For more detail check out, for example, Mel Bartel's web pages on optimal visual magnification - . All this doesn't work for stars though. A star is essentially a point object so it doesn't look any bigger in a 60x300 telescope than a 6x30 so it does get much brighter in the larger scope. Rick -----Original Message-----
From: Bruce McGlashan [mailto:mcglashanb2@...] Sent: Thursday, 29 March 2001 22:13 To: OAFs@... Subject: Re: [OAFs] Larger Solar Spot... Thanks. I was not really concerned with the visible light, but with the UV. I guess what I was concerned about was whether the glass is as efficient at blocking UV as it is at blocking visible light. It could be minimally acceptable in the UV band for naked-eye observation, but magnification would put it over the safe limit. See what I mean? {pardon the pun} |
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