What did I do wrong?

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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brebisson
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What did I do wrong?

Post by brebisson » Tue Jan 17, 2017 11:52 am

Hello,

I am new to this forum and new to solar astronomy. I tried to make a cheap solar telescope, but I am assuming that I messed up something (it woudl be unlikely for a beginner like me no to!). So please do not hesitate to point my errors!

I used a 76 f 700 spherical mirrors sets available on ebay (telescope warehouse) for $12 and a $6 focusser that I had lying around. This was basically my total $ investment in the project!

After de-aluminizing the mirror with feric acid (lefovers from my electronic days), I mounted the mirrors in a 100mm PVC tube lying around using a simple wood block (and 3 silicone dabs) as a mirror cell. The spider is a bent piece of metal holding the secondary. Bend it to colimate!

The final piece of the puzzle is a bit of welder's glass (N11 from memory) just bellow the EP in the focuser. This makes the sun viewable and cuts UV light.

"good" enough safety, I hope, (in case the welder's glass goes away) is provided by the fact that the small mirror is de-aluminized.
This means that even if the filter goes way, the light is roughly equivalent to looking at the sun with your naked eye, and this spread over a large area of the retina (due to the zoom), which you can do for a second or 2 without burning your retina. Giving you enough of time to close your eye or look away.
Furthermore, the low reflexivity of the glass means that there is no heat build up on/in the filter, thus avoiding heat related shattering.

Of course, you can only see the photosphere with it, and the sun does not have a lot of sun spots at the moment... but still fun!

De-aluminized mirror glued to cell + secondary gluing also..
IMG_0053 - Copy.JPG
IMG_0053 - Copy.JPG (67.67 KiB) Viewed 980 times
Welder's glass in drawtube
IMG_0058.JPG
IMG_0058.JPG (75.03 KiB) Viewed 980 times
OTA + spider
IMG_0054 - Copy.JPG
IMG_0054 - Copy.JPG (67.58 KiB) Viewed 980 times
IMG_0059 - Copy.JPG
IMG_0059 - Copy.JPG (81.53 KiB) Viewed 980 times
scope (using the dob base of my daughter's 76mm scope)
DSC_6483 - Copy.JPG
DSC_6483 - Copy.JPG (142.03 KiB) Viewed 980 times
cyrille

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marktownley
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Re: What did I do wrong?

Post by marktownley » Wed Jan 18, 2017 7:11 am

Welcome to the forum Cyrille. Nice project! The only thing that makes me nervous is that welders glass. With a spotless sun you should get some nice views of granulation if you use some Baader film on those reflectors you have in the background of image 4.
Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!

brebisson
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Re: What did I do wrong?

Post by brebisson » Wed Jan 18, 2017 7:31 pm

Hello,

"The only thing that makes me nervous is that welders glass"

Could you expand on this? Why is it making you nervous? Note that I am not asking to be a contrarian, but because I am truly attempting to find a good system/solution.

Cyrille

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