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COUNTING SUNSPOTS WITH A $10 OPTICAL TUBE ASSEMBLY

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#1 retroformat

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Posted 03 July 2022 - 04:16 PM

I encourage anyone with a minimum of technical facility to build their own vintage solar telescope, and join with me on the sunspot counting journey. Next to the study of Earth-grazing asteroids, I can think of no more important branch of astronomy. Aside its obvious ties to climate change science, solar astronomy is extremely important to our understanding of, and ability to predict flares and coronal mass ejections, which have the potential to devastate modern society (google "Carrington Event").

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#2 texcoco

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Posted 10 July 2022 - 11:08 PM

Sir, this is a familiar topic. I have just recently been looking at lenses for building a very similar scope. Can you provide a source or part number for the lens?



#3 lwbehney

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Posted 13 July 2022 - 11:23 AM

This is very cool. I have an old refractor, which has a lens cover with a two inch diameter stop down aperture. I have a mylar sun filter I can put over the lens cover and I could take a photo of the solar surface with my iPhone. If I used an eyepiece with a  magnification of 25X, would that be too much for this purpose?

Thanks for posting this idea.

-Larry



#4 careysub

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Posted 18 July 2022 - 11:34 AM

This lens from Surplus Shed, for $1.50, will do it:

 

https://www.surpluss...tem/L1918D.html

 

50mm x 1000mm

 

I have several of these for making Galileo facsimile scopes.

 

I use 2" cardboard tubes also, they are just right. Galileo used cardboard tubes himself, I'll bet sunspot spotters (sunspotters?) did the same.

 

Maybe not needed for this project, but the inside of the tube is easily blackened by pouring diluted flat black paint through it.



#5 Astrojensen

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Posted 21 July 2022 - 04:06 PM

I also wanted to participate in this project, so I bought some lenses on ebay, identical to the one shown in the article (the box is completely identical), but the optical quality turned out to be so poor, they can barely form a recognizable image. I bought four, and one of them turned out to only have 70cm focal length. The three others are so horribly poor, Jupiter is a giant smear, 1/10 the size of the Moon(!). On either side of focus, Jupiter is drawn out in a long string, almost the width of the Moon... And this is at 25mm aperture. Optically true my butt. Galileo's scope was vastly superior. 

 

 

Clear skies!

Thomas, Denmark 




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