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Gallileian Renaissance

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#26 Vesper818

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Posted 20 February 2019 - 02:52 PM

I'm painting the inside of the tubes with black hole paint today:
https://www.amazon.c...=gateway&sr=8-3
Yes, it will be decorated similar to Galileo s beauty, in a simpler manner.
Will post pics with when there's visible progress.
C
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#27 Vesper818

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Posted 22 February 2019 - 08:06 PM

Today, the objective and eyepiece ends were sanded down and given a coat of satin black paint as a base.
The experimental covering for the main tube was started, part of it glued on. I think it will work. Far cheaper and easier to work with than Cordovan leather.
Nothin' fancy.....yet.
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#28 sarastro

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Posted 23 February 2019 - 08:00 PM

I found a very interesting and detailed paper by Harold R. Suiter: http://www.bay-astro...ELESCOPES_6.pdf

 

I wish I had seen this before I picked up a Zeiss Ikon 1.0 diopter  and a Nikon Nikkor 0.7 diopter close up lenses. They weren't very expensive and maybe they will test better. I also ordered ten 38mm x 1000mm DCX lenses from Surplus Shed yesterday for a whopping $5. Hopefully one will test well enough.


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#29 Vesper818

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Posted 23 February 2019 - 08:31 PM

That's wonderful. I also have a 38 diopter set ordered on eBay that has the +1 for 1000mm fl. Looking forward to whichever gives the better view
.
Please, if anyone else has made, or is thinking of making a Galileian scope,or any other retro-experiments, please add your remarks here!
And pics of your scope!
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#30 DMala

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Posted 23 February 2019 - 11:17 PM

I'm painting the inside of the tubes with black hole paint today:
(...)  
C

Aha! Let us know if you also think that such product is a pretty good flat dark black.

 

Only now I realize that you opened a specific thread on the topic, after your inquiry I was still waiting for your posts on the other thread! Keep sending out updates pls..... it sounds like you are having a good time.


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#31 Vesper818

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Posted 23 February 2019 - 11:27 PM

Yes, I think the Stuart Semplr flat black is ideal for scopes. I don't see 5hat it's much blacker than the ultra flat spray paint. But the inside of a scope is a 'low wear" protected area. The acrylic is thick, with a high ratio of pigment. I taped a small soft brush to a chop stick and applied inside the 1.23" tube from both ends. No fumes, easy clean up and quick drying. This jar will go a long way.

I would recommend it! 


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#32 Astrojensen

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Posted 24 February 2019 - 03:00 AM

I found a very interesting and detailed paper by Harold R. Suiter: http://www.bay-astro...ELESCOPES_6.pdf

 

I wish I had seen this before I picked up a Zeiss Ikon 1.0 diopter  and a Nikon Nikkor 0.7 diopter close up lenses. They weren't very expensive and maybe they will test better. I also ordered ten 38mm x 1000mm DCX lenses from Surplus Shed yesterday for a whopping $5. Hopefully one will test well enough.

After reading Suiter's most interesting paper, I realized even more how unfortunate it is that Galileo never tried a Keplerian eyepiece. Compared to the Galileian eyepiece, the Keplerian is orders of magnitude easier to use on long focal length instruments, as the field doesn't depend on the f/ratio of the objective and has a real exit pupil, which makes for a much better defined field stop. This makes it vastly easier to use higher magnifications and also easier to install baffles in the telescope tube. The apparent field is around 15°. I encourage everyone that makes a copy of one of Galileo's telescopes, to also make some Keplerian eyepieces for it. 

 

 

Clear skies!
Thomas, Denmark


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#33 careysub

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Posted 24 February 2019 - 04:25 PM

Suiter_Galileo.jpg From Suiter's paper there is the following table about the specifications of Galileo's surviving instruments.

 

It lists the following objectives:

51mm full diameter, but 26mm aperture, 1330mm FL

37mm full diameter, but 16mm aperture, 980mm FL

58mm full diameter, but 38mm aperture, 1710mm FL

 

The eyepieces are:

26mm full diameter, but 11mm aperture, -94mm FL

51.5mm full diameter, but 16mm aperture, -47.5mm FL objective

 

Suiter argues in the paper that the breakthrough making telescopes possible, and suddenly widespread was the aperture stop that converted the bad optics of the day into serviceable ones. Galileo's were definitely aperture stopped at both ends, by this table.

 

So in recreating Galileo's instruments it seems like you should be aperture stopping them similarly, or make that optional to show what he had to work with vs our lenses. And it shows that, yes, our lenses are vastly better than what Galileo could make.

 

The SurplusShed offering most like these objectives are:

EDUCATIONAL DCX 50MM X 1000MM

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

 

and

EDUCATIONAL DCX 38MM X 1000MM

https://www.surpluss...tem/L1908D.html


Edited by careysub, 24 February 2019 - 04:26 PM.

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#34 Ken Launie

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Posted 24 February 2019 - 05:58 PM

For further information on the topic of the earliest telescopes I recommend reading "The Long Route to the Invention of the Telescope" by Rolf Willach, American Philosophical Society, 2008. Living in Switzerland, he spent a number of years testing early spectacle lenses in monasteries, museums and private collections all over Europe, and his book describes the progression of spectacle lens fabrication techniques used over the centuries leading up to the sudden emerging of the telescope virtually overnight. The key was the aperture stop. So easy to see, it didn't remain a secret very long. I believe that Willach is the first to speculate that the real "invention" was the aperture stop, and in a talk of his in the Netherlands at a conference in 2008, he set up 16th/17th century spectacle lenses in a Galilean arrangement on an optical bench looking at a target across the room. Attendees would look through initially at a quite distorted full-aperture view that sharpened dramatically when a stop was pivoted into position. Pretty convincing demonstration.

 

--Ken


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#35 clamchip

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Posted 24 February 2019 - 09:23 PM

I was looking for something else and stumbled on this:

https://lib.ugent.be...010_0001_AC.pdf

what I am looking for is a Galileo telescope resolution test done in a Italian

school yard, I'll keep looking...

 

Robert


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#36 Vesper818

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Posted 24 February 2019 - 09:44 PM

Thank you you Roger ,Ken, Carey and Robert for the great resourses! I downloaded the articles and will be reading them between bouts of ATM. The scope construction is coming along nicely, and I will post a pic or two when the covering is finished gluing onto the aluminum tubes. It's an engaging adventure over many areas. All the timings were just right for a brilliant man to make what he needed to open up new worlds.
Ciao
Carol
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#37 clamchip

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Posted 24 February 2019 - 09:58 PM

I feel a tractor beam reeling me in, Oh no I have too many irons in the fire.

This is very  interesting subject.

 

Robert


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#38 terraclarke

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Posted 25 February 2019 - 08:54 AM

There was a Galileo-type telescope set up on the Hartness House lawn doing solar projection at Stellafane a couple of years ago. It was pretty cool.
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#39 Vesper818

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Posted 25 February 2019 - 06:23 PM

I feel a tractor beam reeling me in, Oh no I have too many irons in the fire.
This is very interesting subject.

Robert

Aw, it doesn't have to be iron, Robert! Give a couple pvc or aluminum tubes, some plumbing bits, and SS lenses to your assistants, and they'll have one together in no time. My bet is you could find the optics you need in your Edmund stash!
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#40 clamchip

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Posted 25 February 2019 - 09:22 PM

My assistants are willing and able, and just as perky as me about Galileo.

It's fascinating how much information is out there about Galileo and his telescopes.

I want to get involved, and so do my assistants Frenchie and nurse Mendy, they

are excited about a new project.

Robert

 

post-50896-0-27212100-1520809126_thumb.jpg


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#41 clamchip

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Posted 26 February 2019 - 09:07 PM

My last venture way back back back is this 3 inch f/25 non-achromatic singlet which I still

haven't finished! bad Robert!

https://www.cloudyni...ical-telescope/

I can't seem to get Galileo out of my mind and I keep coming up with excuses not to pursue...

Robert

 

post-50896-14073295569166_thumb.jpg


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#42 Vesper818

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Posted 26 February 2019 - 10:18 PM

I have an extra 38mmx1000mm pcx objective. Would that help?
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#43 Vesper818

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Posted 27 February 2019 - 12:09 PM

Yesterday, I puttered inside with painting the ota, reading, and sorting lenses. A fun way to while away a rainy afternoon.
Another article, sent from a friend in the 60mm Telescope Club:
http://martins-artic...th-century.html
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#44 clamchip

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Posted 27 February 2019 - 12:12 PM

I'm going to wait until I have fewer pots on the stove, it's crazy around here.

I love it when it's crazy though, I get scared when I flounder.

I need a steady flow.

 

Robert


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#45 bremms

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Posted 27 February 2019 - 02:20 PM

I will post a picture of my Gallileian scope replica later tonight.


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#46 Vesper818

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Posted 27 February 2019 - 02:49 PM

Cool!😊👍

#47 careysub

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Posted 27 February 2019 - 03:15 PM

My last venture way back back back is this 3 inch f/25 non-achromatic singlet which I still

haven't finished! bad Robert!

https://www.cloudyni...ical-telescope/

I can't seem to get Galileo out of my mind and I keep coming up with excuses not to pursue...

Robert

 

attachicon.gif post-50896-14073295569166_thumb.jpg

Looks finished to me, if it works.

 

Oh you mean to pretty it up?

 

Pshah, you mainly use it in the dark.


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#48 clamchip

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Posted 27 February 2019 - 05:29 PM

Looks finished to me, if it works.

 

Oh you mean to pretty it up?

 

Pshah, you mainly use it in the dark.

Yes I thought I'd varnish it with a clear marine varnish.

And line the bores of the focuser boards with Teflon or felt because after I varnish I'm sure

the focus will be sticky.

I don't think I mentioned this singlet is pretty good on celestial objects, not so hot for

daytime terrestrial which I did note in my link provided earlier.

Robert

 

post-50896-14073295267337_thumb.jpg


Edited by clamchip, 27 February 2019 - 05:32 PM.

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#49 Vesper818

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Posted 02 March 2019 - 06:06 PM

Spent a bit of time on the OTA yesterday, having much fun with the trompe l'oeil process. With all our rain and clouds, the decoration gives me something to do while waiting first light.
I did find a 1330 lens for a companion scope ( in the plain brown wrapper).
We shall see!
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#50 droid

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Posted 02 March 2019 - 08:44 PM

Yes I thought I'd varnish it with a clear marine varnish.

And line the bores of the focuser boards with Teflon or felt because after I varnish I'm sure

the focus will be sticky.

I don't think I mentioned this singlet is pretty good on celestial objects, not so hot for

daytime terrestrial which I did note in my link provided earlier.

Robert

 

attachicon.gif post-50896-14073295267337_thumb.jpg

looks like a motor tube and centering rings in any one of my high power rockets. 

 

Maybe check out a local hobby lobby for the focuser?


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