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The Discoveries of Galileo – Part 3: The Moon

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#1 E-Ray

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Posted 01 March 2021 - 07:14 AM

In the fall of 1609 Galileo began studying the Moon with his spyglass and he would sketch the features he saw. We need to understand that the magnification of his spyglass by this time was around 21x and it had a very narrow field of view such that he could only see about half the width of the Moon. His telescope was also rather long at about a meter (39.4”) so it must have been very difficult for Galileo to track the Moon with his makeshift tripod.

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#2 LU1AR

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Posted 01 March 2021 - 07:53 AM

Excellent article. There should be links for part 1 and 2 of the note.
Edgardo


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#3 E-Ray

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Posted 01 March 2021 - 10:27 AM

Hi LU1AR, 

Thanks for the comment. Parts 1 & 2 are still on the main CN Articles & Reviews page. I will however look into including links in Parts 4 & 5 coming out in April and May.

Regards, Ed 

Excellent article. There should be links for part 1 and 2 of the note.
Edgardo


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#4 Tyson80s

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Posted 01 March 2021 - 08:58 PM

Just fascinating.


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#5 Special Ed

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Posted 02 March 2021 - 03:20 PM

E-Ray,

 

I enjoyed reading your third installment.  waytogo.gif   I am always impressed by the thought process Galileo used when coming up with explanations for the unprecedented things he was observing, e.g. why Earthshine had to be sunlight reflected from Earth to Luna.

 

As a sketcher, I'm also impressed with the quality of Galileo's moon sketches--especially his sepia watercolors.  They are beautiful and beautifully done.

 

With only a quarter degree FOV, he was really at a disadvantage when producing his lunar sketches yet did excellent and accurate work.  My Galileoscope has about a one degree field and better optics than he had.  I made this approximation of the Moon in his honor.

 

https://www.cloudyni...ope-20110211v1/


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#6 E-Ray

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Posted 03 March 2021 - 07:45 PM

E-Ray,

 

I enjoyed reading your third installment.  waytogo.gif   I am always impressed by the thought process Galileo used when coming up with explanations for the unprecedented things he was observing, e.g. why Earthshine had to be sunlight reflected from Earth to Luna.

 

As a sketcher, I'm also impressed with the quality of Galileo's moon sketches--especially his sepia watercolors.  They are beautiful and beautifully done.

 

With only a quarter degree FOV, he was really at a disadvantage when producing his lunar sketches yet did excellent and accurate work.  My Galileoscope has about a one degree field and better optics than he had.  I made this approximation of the Moon in his honor.

 

https://www.cloudyni...ope-20110211v1/

Hi Special Ed,

Thanks for the comment. I've only recently taken up astro sketching as a way to increase my appreciation of astronomy. That was a very nice drawing that you linked. I'm amazed too at how well Galileo was able to make many of his sketching using such a narrow FOV. He probably had a fairly sturdy tripod but it must have been a challenge to draw by a torchlight! :-)

 

You've probably heard of the old saying, "Two Ed's are better than one!"

 

Regards, Ed aka E-Ray.


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#7 GeoNole94

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Posted 05 March 2021 - 02:56 PM

Thanks for this third installment, a great series!


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#8 oldmanastro

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Posted 06 March 2021 - 10:09 AM

Excellent articles. The series should be posted permanently on CN. Galileo's work with his first telescope is alway fascinating. What he was able to observe with that telescope was truly outstanding. The limitations imposed by the chromatic aberration, less than perfect lenses and diminutive field of view just have made his first attempts at observing quite challenging.

 

A few years ago I built a Galileo-like telescope from a kit offered on this website:

 

http://www.telescope...m/Telescope.htm

 

It is almost equal to Galileo's telescope in terms of lenses, focal length, field of view and magnification. My appreciation for Galileo's work with his telescope increased many times over when I first tried to look at the moon with this telescope. He must have been a keen, careful and very perseverant observer. Observing the moon with this Galilean telescope replica places into perspective the difficulties that he must have encountered during his first trials with the instrument.

 

Thank you for this article, those before and future ones.

 

Guido


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#9 gwd

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Posted 06 March 2021 - 02:10 PM

"So, Galileo used geometry to calculate the height of many of the mountains on the Moon based on the shadows cast by them."

I don't remember seeing these geometrical constructions in  Sidereus Nuncius, nor do I recall him giving a numerical estimate for the heights of any features.   Even if I've forgotten, he did not consider alternate explanations for his observations.  One alternative explanation is that a perfectly spherical, translucent moon could be non-homogenous with respect to its transparency and index of refraction.   Galileo could bolster his argument but not entirely refute this "translucent, non- homogenous perfect sphere" theory by observing a grazing lunar occultation of a star.  


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#10 gwd

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Posted 07 March 2021 - 08:46 AM

I must have hit the underline button on my previous post.  I downloaded a translation of the starry messenger from project Gutenberg and see that I did forget that Galileo did make an estimate of the heights of the moon's mountains.   He also gives two explanations as to why he didn't perceive the outline of the moon as jagged.   


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#11 E-Ray

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Posted 08 March 2021 - 12:26 AM

Excellent articles. The series should be posted permanently on CN. Galileo's work with his first telescope is alway fascinating. What he was able to observe with that telescope was truly outstanding. The limitations imposed by the chromatic aberration, less than perfect lenses and diminutive field of view just have made his first attempts at observing quite challenging.

 

A few years ago I built a Galileo-like telescope from a kit offered on this website:

 

http://www.telescope...m/Telescope.htm

 

It is almost equal to Galileo's telescope in terms of lenses, focal length, field of view and magnification. My appreciation for Galileo's work with his telescope increased many times over when I first tried to look at the moon with this telescope. He must have been a keen, careful and very perseverant observer. Observing the moon with this Galilean telescope replica places into perspective the difficulties that he must have encountered during his first trials with the instrument.

 

Thank you for this article, those before and future ones.

 

Guido

Thanks Guido! One of my projects for the next year will be to construct a Galileo type refractor telescope similar to what you have listed on your link. I've been having a hard time finding the telescoping shipping tube of the correct dimensions. Are the kits mentioned in the link still available?

 

Regards, Ed



#12 rodney j johnson jr

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Posted 11 March 2021 - 12:29 AM

i'm not sure i can take much more fresh air!


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#13 spmbrown

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Posted 05 April 2021 - 03:51 PM

Please remember to mention that Galileo wasn't the first. Thomas Harriot deserves his credit.


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