Solar observation via projection

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SkyBrowser
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Solar observation via projection

Post by SkyBrowser »

Is anybody looking at the Sun via projection? If so, could you see "spot" 12793 today?

I'm projecting with a 60mm refractor (of 1960s vintage) and I couldn't see hide nor hair of it.
RMSteele
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Re: Solar observation via projection

Post by RMSteele »

Hello Skybrowser, I project the Sun with a 90mm refractor stopped down to 60mm at F15. Please excuse my lack of certainty (I’m not into the technicalities of sunspot identification - I just record what I see) but I did project the Sun yesterday and recorded a group of 4 spots amid faculae near the following limb. I suspect this was the (altered) group you were seeking today. I couldn’t get a glimpse today, so I can’t be sure. They weren’t easy to see yesterday because the seeing is not great now the Sun is quite low and it makes the smaller spots easy to overlook with a 60mm. That said a 60mm is a good aperture to use for solar projection because, particularly with a focal ratio of f12 or above, it gives great images with no excessive heat that can damage eyepieces and plastic bits at the eyepiece end of the scope.
Kind thoughts, Bob
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Re: Solar observation via projection

Post by SkyBrowser »

I guess you've got a better 60mm refractor than me! I do have difficulty getting a sharp focus - the eyepiece is one of those small ones, and it's non-removable and zoom, so not ideal. I'm pondering another 'scope for solar work, but the current one, on a photographic tripod, is so quick and easy to bring into action I do wonder if it's worth it.
RMSteele
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Re: Solar observation via projection

Post by RMSteele »

These 60s Japanese refractors usually have decent objectives, though the eyepieces are tiny and basic by today's standards aren't they? At any rate I am not surprised an old zoom ocular doesn't give a sharp projected image. But before you set it aside, consider that the Sun is low at this time of year (at least it is from my latitude of 54 North) and unsteady seeing is usually enough to blur the kind of small spots we are talking about anyway: so, they are very hard to see unless you have a well-shaded projection box (you can see how mine shades the solar image in the "Sunspots" photos in the Gallery thread dated 26 Nov). Moving the telescope back and forth in RA or azimuth might help reveal them on the projection card. I couldn't see the two small spots today, even though the card was well shaded, until I looked very closely. One of them was dark against the solar surface when the seeing steadied but the other was much smaller and fainter, visible only at intervals. I hesitate to recommend butchering a vintage 'scope but is there any chance you could replace the whole focuser with a cheap 1.25 inch rack and pinion? You can get 'em for about 20-odd quid plus p&p of course. Bob
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Re: Solar observation via projection

Post by SkyBrowser »

Well, a rack and pinion and real eyepieces would be nice, but I'm not sure I could find a focuser that I could fit to the tube. But I'll bear it in mind, thanks.

Current plan is to look out for a short tube 80mmm 'scope since 80mm seems to be what a lot of people use for solar observation. I need to check what focal ratio my current 'scope is and try to find something similar. Long (F12 or more) would be good for the image, but awkward to store and move when the Sun comes out so I may have to risk a faster 'scope.
michael feist
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Re: Solar observation via projection

Post by michael feist »

Sunspot, 23rd December MMXX, NOON. Cobbled together a sunspot projector using a spare objective and eyepiece, bits of cardboard to make a tube,, and some black tape. Rested the resulting rather crude device on my shoulder, and against window frame, and projected solar image onto the wall. Good view of that sunspot. regards maf.
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Re: Solar observation via projection

Post by SkyBrowser »

Nice one! Could you post a picture of your new telecope?
michael feist
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Re: Solar observation via projection

Post by michael feist »

Unfortunately I cannot post a photograph here...why not, you may ask. Well, I am pretty hopeless at computer usage. However it is nothing special. The object-glass was from a disassembled spotting scope [65mm diameter] , the eye-piece a 25mm standard eyepiece, the tube was from a cardboard box that I removed from our recycling bin, rolled into a tube and taped together. Focus is by simply sliding the added smaller tube, also from the recycling bin, back and forth. Really just cobbled together from spare bits and pieces to hand. Took half-an-hour to put together and at not at all elegant. But shows sunspots! regards maf
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Re: Solar observation via projection

Post by brian livesey »

The smallest 'scope I have is a 40mm/f.12 refractor. The eyepiece tube was a sliding one with different magnifications marked on it. I replaced the tube with a little rack-and-pinion focuser that takes Continental 24.5mm eyepieces. Then, a small, taping, plywood solar projection box was made to suit. With this modest arrangement I get decent views of sunspots.
brian
RMSteele
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Re: Solar observation via projection

Post by RMSteele »

Mike I am nominating you for the 2020 Percy Verance award. Bob
SkyBrowser
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Re: Solar observation via projection

Post by SkyBrowser »

I think it should be a Blue Peter Gold Badge :)
michael feist
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Re: Solar observation via projection

Post by michael feist »

The 'Blue Peter Badge' I understand but who was Percy Verance? ... Aaargh, yes, I see it now... ! Thank you chaps! regards maf.
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Re: Solar observation via projection

Post by SkyBrowser »

Finally, it stops raining! The Sun is a bit spottier today after many days of "no" spots.
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