14 replies to this topic

[grif 678]

Has anyone here seen any photos of Jupiter through the 40 inch Yerkes 40 inch refractor. I would like to be able to look through that scope at the planets, should be unbelievable detail.

[Astrojensen]

 

Has anyone here seen any photos of Jupiter through the 40 inch Yerkes 40 inch refractor.

Oddly, no. I've been looking for photos or videos of the planets or the Moon through some of the large refractors for a while, and there doesn't seem to be any, or at least nothing that is easy to find. I found some from the 28" in Vienna, but it turned out to be heavily edited images, so they don't say anything about the visual sharpness or the amount of false color. 

 

Why hasn't anyone put a smartphone to the eyepiece and grabbed a shot? 

 

Some years ago, I found a visual description in a German forum from someone who had observed Jupiter with a 25" Zeiss in Germany (either Berlin or Hamburg) and he said it was far better than what the theory would lead you to believe. Even at moderate magnification, 2-300x, the view was staggeringly much sharper than in smaller scopes and the planet filled with an overwhelming amount of details. He said it was much sharper and steadier than you'd expect from such a large scope in a large city. The false color was much less of an issue than he had anticipated, though it was certainly visible. 

 

 

Clear skies!

Thomas, Denmark 

[Dave Mitsky]

Many years ago, I saw Saturn through the 24" f/18 Brashear refractor at the Sproul Observatory.  The telescope is now at another location.
 

https://en.wikipedia...oul_Observatory

 

https://www.science....aas_sproul.html

[SpitzA3P]

You might try looking at some older text books.

 

I visited Yerkes in 1980, but since it was not officially open , I was only able to wait outside in the cold of January.  There were students inside who saw me and when I ventured around the corner, one quickly slipped out so as not to have me intercept them.  That's the closest I got to the big one.

 

I have seen Jupiter from the observatories at UVa , and Swarthmore college and it was quite a sight ! (Both refractors)

[RedLionNJ]

Geoff Chester (when he still worked there) used to take the occasional planetary image (definitely including Jupiter) through the 12" refractor at the USNO in Washington, DC. I'm not sure if it was a mis-matched focal ratio to pixel size issue, or just poor seeing, but they rarely seemed to live up to expectation.

 

The problem with most of the larger instruments found around the country is that the 'business end' doesn't easily lend itself to inserting a modern planetary cam in a secure manner. Typically the eyepiece holders are 3 to 4 inches across (inside diameter) and were meant to be used with very specific eyepieces.

 

Of course, in these days of easy 3D printing, you'd think somebody could print something up to convert from the eyepiece holder diameter to the standard 1.25" camera nosepiece.

[Eikonal]

There were some beautiful planetary images taken by Felix Langgassner, student of the Ludwigs-Maximilians-University in Munich, through the 285 mm Fraunhofer refractor from 1835, still preserved at Munich-Bogenhausen:

​https://www.usm.uni-...ktuelles_en.php

 

Here is one night's worth of Jupiter images, from 2022:
https://www.usm.uni-...Langgassner.mp4

And here is a Mars image taken six days after the Maras opposition in 2020:

https://www.usm.uni-...fraktor_USM.jpg

The information is there. The trouble for the visual appearance starts when the aperture is larger than the average diameter of the turbulence cells of the ground boundary layer of the lower atmosphere, i.e. larger than 30-50 cm.
So, the 285 mm (10 1/2 Parisian inches) refractor, is just below this size, and, therefore, quite all right as far as turbulence goes.

Edited by Eikonal, 15 February 2025 - 10:39 AM.

[Eikonal]

Erratum: the Jupiter rotation sequence was taken on five separate nights and processed acoordingly. Sorry for that: my bad.

Here is one night's worth of Jupiter images, from 2022:

https://www.usm.uni-...Langgassner.mp4

[Mcloud]

In God awful Pittsburgh my brother once asked me why Jupiter looked better in my 4 inch refractor than the clubs monster 11 incher & I think it really came down to seeing conditions which are noticeable more amplified in larger instruments. When I went to have a look Jupiter was a colorful bloated boiling orb with perhaps a cloud band or 2 barely discernable. Back to the 4 inch refractor, reasonably sharp clear well defined cloud bands some festoons 3 of the 4 moons pinpoint and bright as well as the GRS. I think that for lunar and planetary work large telescopes can work against you in terrible seeing. As a matter of fact when I upgraded from an 8 to 10 inch Dob I was surprised to say that the 8 incher was clearly the better planetary telescope. I wouldn't consider anything over 8 inches here if planets are your thing as that since that time I've seen this same phenomenon play out over and over again. Deep sky is another story of course. What I'd really love to see is the planets through a very large Obsession or the likes Dob under highly regarded seeing condition skies. Ive been told that once you get up to 20 inches and over that on good nights insanely high power can be used and that the views can compare to some of the very best photos I've seen. And I too have wondered about the views through a mammoth observatory telescope in a good sky but haven't been able to find much online...

[quilty]

Erratum: the Jupiter rotation sequence was taken on five separate nights and processed acoordingly. Sorry for that: my bad.

this is the coolest capture of Jupe I've ever seen.

[12BH7]

Geoff Chester (when he still worked there) used to take the occasional planetary image (definitely including Jupiter) through the 12" refractor at the USNO in Washington, DC. I'm not sure if it was a mis-matched focal ratio to pixel size issue, or just poor seeing, but they rarely seemed to live up to expectation.

 

The problem with most of the larger instruments found around the country is that the 'business end' doesn't easily lend itself to inserting a modern planetary cam in a secure manner. Typically the eyepiece holders are 3 to 4 inches across (inside diameter) and were meant to be used with very specific eyepieces.

 

Of course, in these days of easy 3D printing, you'd think somebody could print something up to convert from the eyepiece holder diameter to the standard 1.25" camera nosepiece.

The Lowell Observatory had an 8" refractor specially built for plantary work. The docent said that it was a hugh mistake and now the scope is more of a show piece than oberving tool. 

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[Tyson M]

The Lowell Observatory had an 8" refractor specially built for plantary work. The docent said that it was a hugh mistake and now the scope is more of a show piece than oberving tool. 

I wonder why he would say that? That is a stunning scope and 8" of refractor goodness would excel at planets

[quilty]

I think he said so because no one dared to use or move the monster.
And indeed, in here from the save distance it looks nice.

[12BH7]

I wonder why he would say that? That is a stunning scope and 8" of refractor goodness would excel at planets

The docent said that basically the two million dollar Planewaves and the 14" and 16" SCT's were much better. 

[CrazyPanda]

Oddly, no. I've been looking for photos or videos of the planets or the Moon through some of the large refractors for a while, and there doesn't seem to be any, or at least nothing that is easy to find. I found some from the 28" in Vienna, but it turned out to be heavily edited images, so they don't say anything about the visual sharpness or the amount of false color. 

 

Why hasn't anyone put a smartphone to the eyepiece and grabbed a shot? 

 

Some years ago, I found a visual description in a German forum from someone who had observed Jupiter with a 25" Zeiss in Germany (either Berlin or Hamburg) and he said it was far better than what the theory would lead you to believe. Even at moderate magnification, 2-300x, the view was staggeringly much sharper than in smaller scopes and the planet filled with an overwhelming amount of details. He said it was much sharper and steadier than you'd expect from such a large scope in a large city. The false color was much less of an issue than he had anticipated, though it was certainly visible. 

 

 

Clear skies!

Thomas, Denmark 

I mean that makes sense. 300x in a 25" is over a 2mm exit pupil. Every single time I observe the planets in a 2mm exit pupil in my 14.7", I get the same impression in steady seeing. The contrast and detail delivered to the eye at a 2mm exit pupil that neither taxes the telescope's optics, or taxes your vision, is hard to beat. I know the usual advice is 1mm-1.5mm exit pupil, but 2mm delivers such a rich, vibrant, satisfying view it's hard to want to go any higher even if the seeing supports it.

 

But 2mm exit pupil in my scope is a measly 185x. 300x @ a 2mm exit pupil in good seeing would be a dream.
 

Edited by CrazyPanda, 11 March 2025 - 12:22 AM.

[Jon Isaacs]

I mean that makes sense. 300x in a 25" is over a 2mm exit pupil. Every single time I observe the planets in a 2mm exit pupil in my 14.7", I get the same impression in steady seeing. The contrast and detail delivered to the eye at a 2mm exit pupil that neither taxes the telescope's optics, or taxes your vision, is hard to beat. I know the usual advice is 1mm-1.5mm exit pupil, but 2mm delivers such a rich, vibrant, satisfying view it's hard to want to go any higher even if the seeing supports it.

 

But 2mm exit pupil in my scope is a measly 185x. 300x @ a 2mm exit pupil in good seeing would be a dream.
 

 

A 2mm exit pupil in my 22 inch is 280x.  Indeed, they are amazing, when the seeing is stable. That is no so common in the high desert.

 

I remember Roland Christen writing that in the Yerkes 40 inch, the colors came to focus about 1/4 inch apart.  Vlad of Telescope-optic.net said this regarding the 40 inch Yerkes refractor:

 

"It may be "diffraction limited" in the optimized wavelength, but its polychromatic Strehl (photopic) is 0.36, with near perfect central line correction. If central line correction is, say, 0.80 in the central line, it drops to 0.29. This is still much better than what its nominal secondary spectrum implies, but polychromatic Strehl in achromats changes with the square root (closely) of the nominal secondary spectrum, not with it."

 

To view the planets, it would seem a filter just might be helpful.

 

https://www.cloudyni...s/#entry9666282

 

Jon

Edited by Jon Isaacs, 11 March 2025 - 06:42 AM.