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Observing with the USNA 7.75" Alvan Clark

observing refractor
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#1 John Higbee

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Posted 08 December 2019 - 08:07 AM

We held the latest of our continuing series of USNA Astronomy Nights last night (7 December).  These include an introductory planetarium show at the Academy's Class of 1935 Memorial Planetarium, a GOTO-12 mechanical/optical projector with seating for 110 people, followed by observing time with the Clark (and other more modern telescopes) at the Class of 1941 Memorial Observatory.  (Side note - the "memorial" tag in both cases comes from the particular graduating class funding the acquisition and installation of a new capability for the Academy - usually at the 50 year after graduation point).

 

Last night, the planetarium hosted 90 people for a "stars of winter" presentation by LCDR Kai Seglem...following this, about 60 people visited the Observatory for observations with the Clark, as well as an 8" Celestron SCT from 1976; a 10" Meade LX200 SCT; and a 14" Celestron SCT upgraded with a GOTO GEM.  Attendance was lower at the Observatory due to the cold weather (temperatures falling from the high 30s to the high 20s during the session); but the skies were beautifully clear and seeing was excellent for those who "came out".

 

Specific to the Clark...before the observing session opened, Rich Schmidt from the US Naval Observatory came over - he looks after the Clark 26" and 12", in addition to his observing duties.  He was instrumental in the planning and design of the Class of '41 Observatory, and it had been many years since he had had the opportunity to come over.  In addition to his helping to host the visitors at the 7.75", he schooled us in (very) gently cleaning the outer surface of the 164-year-old objective...which had picked up a thick coating of dust over the last 30 years.  The difference in performance was astounding...the "excellent but slightly soft" images we were used to seeing were replaced by razor-sharp images that resembled etchings (particularly with the Moon and Saturn). 

 

One image in particular stood out...Rich had brought a Pentax 14mm eyepiece, (producing slightly over 200X), and we were using it to observe the Moon.   Looking at Gassendi, there was a sense of complete transparency (as if no objective/eyepiece stood between us and the Moon), and the detail inside Gassendi (the rilles and small details) were awe-inspiring...for the first time, I saw a clarity and  level of detail that resembled the 19th century drawings of the great lunar observers.

 

A great night, with one of the oldest Clarks still in operation - the objective was finished in 1855, and Alvan Clark etched his name and that year on the edge of the objective.

 

John and the USNA Refractor.JPG

 

John


Edited by John Higbee, 08 December 2019 - 03:08 PM.

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#2 rolo

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Posted 08 December 2019 - 08:55 AM

John, thanks for sharing this evening's event with us! Someday I hope I can visit and look through that one of a kind telescope!


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#3 DeWayne

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Posted 08 December 2019 - 09:15 AM

We were able to visit the USNO a few years ago at ALCON and got a great tour including the big Clark refractor.  Thanks for the report.  Great to hear these beautiful instruments are getting used!


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#4 Astroman007

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Posted 08 December 2019 - 09:46 AM

Predates the Civil War...wow. Just amazing to think about all that history that passed that scope by in its lifetime. Way older than the oldest of us, or their grandfathers.

Thank you for sharing this ongoing piece of history with us! It is greatly appreciated. waytogo.gif  like-button.jpg 


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#5 DeWayne

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Posted 08 December 2019 - 12:55 PM

Looking at the picture.  Is the scope painted a dark color, or is it the lighting?  I know the Great Refractors are painted,  but many of the smaller ones I've seen pictures of have a brass finish.   Is this one... black or dark green...or...? Can you post more photos?  Can't see too much of these great works of art....smile.gif



#6 semiosteve

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Posted 08 December 2019 - 01:05 PM

Also would love to know more about what details popped out the most in Gassendi - or if there is a historical drawing from one of the great observers that captures what you saw.

 

Perhaps this one?

 

https://moon.lindahall.org/p27x.html


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#7 highfnum

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Posted 08 December 2019 - 01:25 PM

a real work of art

what F num?


Edited by highfnum, 08 December 2019 - 01:26 PM.


#8 John Higbee

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Posted 08 December 2019 - 03:00 PM

Looking at the picture.  Is the scope painted a dark color, or is it the lighting?  I know the Great Refractors are painted,  but many of the smaller ones I've seen pictures of have a brass finish.   Is this one... black or dark green...or...? Can you post more photos?  Can't see too much of these great works of art....smile.gif

It's a combination of the lighting and the finish...the scope, mount and pier are painted a dark blue, with brass highlights.  I'll provide several more pictures later today.  John


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#9 John Higbee

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Posted 08 December 2019 - 03:03 PM

Also would love to know more about what details popped out the most in Gassendi - or if there is a historical drawing from one of the great observers that captures what you saw.

 

Perhaps this one?

 

https://moon.lindahall.org/p27x.html

Steve - this drawing is very similar, except the light was coming from the opposite direction (waxing vice waning). 

 

Besides the rilles, the light was coming in at a low angle, and the unevenness of the surface inside the walls was visible in high relief.  John


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#10 John Higbee

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Posted 08 December 2019 - 03:05 PM

a real work of art

what F num?

f 14.2 - approximately 110 inches.  John


Edited by John Higbee, 08 December 2019 - 03:09 PM.

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#11 Astroman007

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Posted 08 December 2019 - 03:24 PM

Also would love to know more about what details popped out the most in Gassendi - or if there is a historical drawing from one of the great observers that captures what you saw.

 

Perhaps this one?

 

https://moon.lindahall.org/p27x.html

Oh, wow!



#12 grif 678

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Posted 08 December 2019 - 04:37 PM

Do you know what kind of solution and procedures they used to clean the lens.



#13 Carl N

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Posted 08 December 2019 - 07:11 PM

Beat Navy!

#14 BFaucett

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Posted 08 December 2019 - 08:43 PM

John,

 

Thank you for sharing your report and photo with us! waytogo.gif   I truly enjoyed reading it. I'm looking forward to any additional photos. 

 

Cheers!  Bob F. smile.gif



#15 John Higbee

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Posted 09 December 2019 - 03:10 AM

Additional photos:

 

Jeff and John USNA Observatory.jpg

 

20180718_221014.jpg

 

20180718_212445.jpg


Edited by John Higbee, 09 December 2019 - 03:11 AM.

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#16 John Higbee

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Posted 09 December 2019 - 03:31 AM

and more...

 

the Clark from the floor.jpg

 

 


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#17 John Higbee

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Posted 09 December 2019 - 03:51 AM

Beat Navy!

we shall see...smile.gif



#18 semiosteve

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Posted 09 December 2019 - 09:18 AM

Steve - this drawing is very similar, except the light was coming from the opposite direction (waxing vice waning). 

 

Besides the rilles, the light was coming in at a low angle, and the unevenness of the surface inside the walls was visible in high relief.  John

For many of us, these old lunar and planetary drawing are what drew us into the hobby.. My 7" AP Starfire does a nice job of coming close - but I would love to have been with you at the USNO.

 

Isn't this also the Vice President's official DC residence?

 

sv


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#19 jcruse64

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Posted 09 December 2019 - 11:16 AM

That is a beauty!



#20 John Higbee

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Posted 09 December 2019 - 07:13 PM

For many of us, these old lunar and planetary drawing are what drew us into the hobby.. My 7" AP Starfire does a nice job of coming close - but I would love to have been with you at the USNO.

 

Isn't this also the Vice President's official DC residence?

 

sv

The United States Naval Observatory is in Washington DC...it has Clark 26" and 12" refractors.  The house for the Director, USNO was converted into the Vice President's official residence in the mid 1970s.  First VP in residence was Nelson Rockefeller.

 

The Clark 7.75" is at the United States Naval Academy, in Annapolis.

 

John 


Edited by John Higbee, 09 December 2019 - 07:15 PM.

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