1942 replies to this topic

[tim53]

This is interesting!

 

https://www.yahoo.co...-162654511.html

Indeed it is.  But so is the untruth.

[deSitter]

Ed Ting's buddy has never bought a large commercial scope. Telescope tinkerer's paradise!

 

https://youtu.be/YMiaqNYiGzo

 

-drl

[deSitter]

Electrons can make images too - a guy restores a donated electron microscope.

 

https://youtu.be/Kqx9blbYDB0

 

-drl

[deSitter]

Spectacular re-entry of a polar orbiting satellite in Missouri. In the first images, Vega is on the right and Polaris above the center. The lozenge of Draco is near Vega. The satellite passed nearly overhead. In other views, it is fairly easy to recognize the constellations. The trail shining in the moonlight must have been a sight!

 

https://youtu.be/0NTTnnhg1jQ

 

-drl

Edited by deSitter, 06 April 2025 - 12:01 AM.

[deSitter]

Semiconductor lithography depends on optics which are vastly more accurate than telescope optics demand - not only in figure, but in smoothness - they are designed to focus images in the extreme ultraviolet, about 14 nm wavelength (compare to green light at 550 nm), so they must be ridiculously smooth.

 

https://youtu.be/QdESABi1Avk

 

-drl

[clamchip]

Characteristics of Early Questar Telescopes: 

https://www.gregoryg...acteristics.php

 

Robert

[RichA]

Electrons can make images too - a guy restores a donated electron microscope.

 

https://youtu.be/Kqx9blbYDB0

 

-drl

TEMs are a nightmare, which is why they sell pretty cheap (old ones) on Ebay whereas SEMs sell for big money because they are so much easier to get working.  But, keep your eyes open, you can nab a AFM for around $2k if you want to go down to the atomic level.  

[deSitter]

You think telescopes are 'spensive?

 

Try $19,000 for a single microscope objective.

 

I saw a UV APO objective for $27,000.

 

-drl

Attached Thumbnails

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Edited by deSitter, 15 April 2025 - 12:12 AM.

[deSitter]

Characteristics of Early Questar Telescopes: 

https://www.gregoryg...acteristics.php

 

Robert

 

"With its resolution exceeding the Dawes limit for a telescope its size, it performed at least as good as a four-inch refractor."

 

Hmmm... laws of physics etc. etc. obstruction hrmpf cough light loss on two mirrors ahem cough..

 

Still an interesting article. Cave couldn't make a decent Cassegrain but they made some Questar optics - who knew!

 

-drl

[DAVIDG]

Still an interesting article. Cave couldn't make a decent Cassegrain but they made some Questar optics - who knew!

 

      Cave didn't make the optics for their Cassegrains. Companies like 3B and Mars made the optics for their Cassegrains.

 

                 - Dave 

[tim53]

Still an interesting article. Cave couldn't make a decent Cassegrain but they made some Questar optics - who knew!

 

      Cave didn't make the optics for their Cassegrains. Companies like 3B and Mars made the optics for their Cassegrains.

 

                 - Dave 

...and Tinsley!  One of my 10" f/16 DK Caves has mirrors etched with TLI on them.

 

Primary:

 

Secondary:

[tim53]

Whole scope with Tinsley mirrors:

 

My other 10" DK doesn't have any markings on the mirrors, and no means to date the scope, except that it has the short saddle and otherwise looks "early 60s".  The mirrors are pristine, however, making me wonder if it was recoated or refigured at some point.  It's missing the focuser.

[DAVIDG]

 Tim,

    Tinsley was known for of Dall Kirkham optics. Their smaller cassegrains were of the DK design. There is Dec 1974 Sky and Tel article were Tinsley had  an  ATM class on making DK cassegrains and offered the use of the testing equipment and casting for the mirror cells and other parts.

 

                - Dave 

[cavecollector]

OMG, wow, seriously gorgeous scopes! You lucky dog!

 

FYI, Cave only made the optics for the first batch of Questar Field models - the ones in the rather rough looking tube assemblies.  All future Field models after this - the ones in the much improved tube assemblies that actually looked like Questars (just having been removed from the fork mounts) had optics made by another company). This is from what looks like a rough draft of a book on Questar that came with some Questar  equipment I purchased (possibly the one by Stew Squires?)

 

At any rate, it claims the optics in this initial batch of Questar Field models were of extremely poor quality which was why Questar did not continue using Cave for optical sets. Still, I would love to have a Cave Questar,  what a cool find that would be! I don't  care how bad the optics were or how poor the initial tube assembly might have been, that would be one massively cool instrument (historically speaking).

[Bomber Bob]

Your odds of nabbing a Cave / Questar are pretty good.  Jim @ Q told me that Cave supplied the first 200 optic sets.  Serial Numbers 201 & above are Cumberland Optics -- he assured me that my '58 Standard #259 had the better optics.

 

IDK much about the first Questars, but sounds like some interesting astro history...

 

(I wonder how many of that 200 are in closets, attics, or basements - hopefully still in their cases?)

Edited by Bomber Bob, 15 April 2025 - 12:09 PM.

[CHASLX200]

Whole scope with Tinsley mirrors:

 

Is the scope sharp?

[98105dude]

In the interest of accuracy - the first Questar (De Luxe) produced was assigned serial number #50 and not #1.

[tim53]

Is the scope sharp?

Not as sharp as the 10" f/6 that I made with Dave Groski's help at the Delmarva mirror making class.  I've been meaning to DPAC test the Caves, but have been distracted by other issues for quite some time now.  Hope to get back to telescopes soon, though.