Thursday, October 29, 2020

Clear Nights, Full Moon

The full Moon on the 31st is a problem, but the nights are clear and cold. So, I took out my Explore Scientific First Light 102-mm refractor. I also brought my old and overused National Geographic 70-mm refractor. I viewed Jupiter, Saturn, Mars, the Moon, and unsuccessfully chased what appeared to be open clusters near the zenith. I do not know what the atmospheric effect is--and it may be my early cataracts--but I see patches of faint, cloudy light in the open sky. The telescopes do reveal stars there, only not tight groups. 

With the ES-102, the Red Planet was green around white with all oculars. 

Encouraged by a how-to on The Sky Searchers, I tried all of the smaller eyepiece combinations, 17-mm, 13-mm, 8-mm, and 6 alone and with the 2x Barlow lens. The 8-mm alone is the limit and the best views are with the teens through the Barlow. One advantage to the 8-mm over the 17-plus-Barlow is that the 8 alone is just a little clearer because it is just a little less glass for the light to work its way through, but that could just be the result of my expectation.

The Moon was great. I used their 25-mm (with my red filter 15% passage) and my Celestron 32-mm (with Moon filter 14% passage). Almost like being there...

We just had a week of rain and by 11:00 PM stuff was getting wet from condensation. So, I brought everything in. I slept through until 4:30. Tonight I will set an alarm and get up at 01:00 to try the Pleiades.


New Telescope: ES 102 

The Perfect Machine

Seeing in the Dark

Saturday, October 24, 2020

New Telescope: Explore First Light 102 mm Refractor

The problem with consumer goods is that at the designers are not you. Everything is always a matter of trade-offs. The decisions that other people make for you might not be the ones you would make for yourself. 

I bought a new telescope to use in the backyard. As vice president of the Austin Astronomical Society, I invited Scott Roberts, the CEO of Explore Scientific, and Stuart Parkerson, publisher of Astronomy Technology Today, to be our guests for a panel discussion. Ahead of that, I shopped at Explore for my next backyard instrument. They answered three emails and then asked me to call them on the phone before I was a customer. And they talked me out of buying extra oculars until I used the telescope often enough to judge better what would suit my needs. I was impressed. 

The Explore Scientific First Light 102-mm refractor ($279) is a good instrument. Placing aside my cognitive dissonance, I made some minor modifications. 


Because the objective lens is so large and heavy, the telescope does not balance in the center of the dove-tail receptacle. It balances almost full-forward in the grip so that the ocular has more moment arm, like a child on a see-saw balancing a grown-up. 

The objective still has a tendency to dip into the tripod, so I attached two strips of foam under the front. 

The XYZ control is a single lever that I found too short. So, I added 6 inches of plastic tube to bring the control closer to the focus draw adjustment wheels. 

29 October: I removed the extension. It was too much leverage. It is easier to control the alignment by holding the frame. The action is still very tight: won't go--won't go--won't go--too far! I now know that I personally prefer gear-driven tracking. 

The only other payment for the price is that the very artistic mount has the elastic stability of a thin plate. Fortunately, it damps out quickly. 


The optics are good. The 102-mm (4-inch) objective brings in Jupiter, Saturn, and Mars well enough. The 660-mm focal length works best with my 17, 13, and 8 mm oculars. When the weather clears, I will use the Moon to try my 32-mm and the new 25-mm eyepieces. The final test will be the Pleiades, over my neighbor’s treetop after midnight and on the zenith before 03:00. 


I was never satisfied that I had properly collimated my Celestron 130 EQ reflector. After a final round of stargazing and finding Albireo on my own, I put it all back in its shipping cartons and stored it in the garage along with the Meade 10-inch Schmidt-Cassegrain telescope (SCT) that I have on loan from the Austin Astronomical Society. (I took that one out just once; and at 65 lbs to my 68 kg, I found it inconvenient.) I bought a used 8-inch Meade LX Classic SCT from the club. The circa-1995 on-board computer did not work, after being repaired twice. They asked $250 and I countered with $325. It was a nice scope, but the right ascension (XY-left right) locked up and I did not want to take it apart. So, I gave it to the Goodwill. They will fix it, pass it along, and make some money. 


My go-to scope has often been a 70 mm National Geographic refractor that I bought used from some kids down the street. They got it for Christmas and by July had lost the eyepieces, the cellphone adapter, the center plate, and the control rod for altitude (Z-up down). And the dew shield was jammed on backwards. (For all of that, they had never used it outdoors.) But it was a National Geographic brand; and I tested it on the street, and the objective seemed OK. It takes the standard 1.25-inch oculars. And it is an f/10 with a 700 mm focal length, which works well for higher magnifications: 13-mm ocular with 2x Barlow for 108x. So, for what it is, it has served me well in the backyard. But after three years, it is held together with rubber bands. So, I went shopping for a new go-to 'scope. The best thing about the Explore First Light 102 is the word “light.” All together I can carry it with one hand.



Problems with Pop Sci from Sky & Telescope 

Physics for Astronomers: the Works of Steven Weinberg 

The Asteroid Hunters by Carrie Nugent 

Backyard Astronomy (2) 

Backyard Astronomy (1) 


Thursday, October 22, 2020

Galileo and Saturn: Epistemology not Optics

It is commonly claimed that Galileo did not perceive the rings of Saturn because the telescope he was using was not capable of magnifying the image. That is not true. After Galileo, astronomers needed another 50 years to think about the problem and re-imagine it. They needed to ask the right questions. Christiaan Huygens was the first to perceive the structure as a ring. However, it was another 200 years before the ring was understood as a system of particles, rather than a rigid body. The problem was epistemology, not optics.

Galileo’s Images of Saturn 1610 and 1616

    “Galileo Galilei was the first to observe Saturn with a telescope in 1610. Because of the crudeness of his telescope, he couldn't determine what the rings were. He incorrectly guessed that there were two large moons on either side of Saturn. Two years later when he viewed Saturn again, the "moons" had disappeared. We know now this is because Galileo was viewing the rings edge-on so that they were invisible, but at the time it was very confusing to Galileo. After another two years, Galileo viewed Saturn again and found that the "moons" had returned. He concluded that the rings were “arms” of some sort.

            “Many years later, in 1659, a Dutch astronomer named Christiaan Huygens solved the mystery of Saturn's "arms." Because of improved telescope optics, he correctly deduced that the "arms" were actually a ring system. Huygens also discovered Saturn's moon, Titan, and for this reason, the probe exploring Titan is named after him.” 

From NASA’s Cassini-Huygens Mission website (no longer current) here

Galileo’s Sketch of Saturn” 
from Galileo and the Scientific Revolution 
by Laura Fermi and Gilberto Bernardini,
Basic Books, 1961.

“When he turned his telescope on the planet Saturn, he found that this did not always look like a round body but seemed of strangely variable shape. He thought it to be “three-bodied; that is it … was an aggregate of three stars arranged in a straight line parallel to the ecliptic, the central star being much larger than the others.” His telescope was not sufficiently powerful to let him to distinguish the three, possibly four, rings we now know are around Saturn. It was the Dutch astronomer Christian Huygens (1625-1695) who discovered Saturn’s rings.” -- Galileo and the Scientific Revolution by Laura Fermi and Gilberto Bernardini, Basic Books, 1961.


“Galileo continued his telescopic observations from his new home in Florence. Here he discovered that Saturn sports a pair of curious appendages, but his telescope was not powerful enough to reveal their true nature. (They were Saturn’s rings.)” Parallax: the Race to Measure the Cosmsos by Alan Hirshfeld, W. H. Freeman and Company, 2001. 


“1610 - Galileo Galilei becomes the first to observe Saturn's rings with his 20-power telescope. He thought the rings were “handles” or large moons on either side of the planet. He said “I have observed the highest planet [Saturn] to be tripled-bodied. This is to say that to my very great amazement Saturn was seen to me to be not a single star, but three together, which almost touch each other”. 

“1612 - Galileo was astounded when he found that the rings he first observed a couple of years earlier had now disappeared. He wrote "I do not know what to say in a case so surprising, so unlooked for and so novel". The rings were, in fact, edge-on from Earth's perspective. Galileo inadvertently became the first person to observe a Saturn ring plane crossing. 

“1616 - Galileo now observes the rings as two half ellipses. He wrote “The two companions are no longer two small perfectly round globes ... but are present much larger and no longer round ... that is, two half ellipses with two little dark triangles in the middle of the figure and contiguous to the middle globe of Saturn, which is seen, as always, perfectly round.”

 From Views of the Solar System Copyright © 1995-2015 by Calvin J. Hamilton.


Museo Galileo, Florence

“In some observations conducted in 1610, Galileo (1564-1642) saw Saturn as tricorporeo [three-bodied], i.e.,composed of a central body and two lateral bulges, which he mistakenly thought to be satellites. In 1655, Christiaan Huygens (1629-1695), thanks to a more powerful telescope, observed Saturn's rings for the first time. He described them accurately in Systema Saturni (The Hague, 1659). The Accademia del Cimento was concurrently investigating the nature of the rings. Between 1671 and 1684, Giovanni Domenico Cassini (1625-1712) discovered four satellites of Saturn, in addition to the one previously found by Huygens. Cassini also observed and studied the divisions between the rings. Recently, the Voyager space probes have revealed that the many concentric rings are thin bands consisting of countless rock and ice fragments that orbit the planet and reflect sunlight.”

© 2018 - 2020 Museo Galileo - Istituto e Museo di Storia della Scienza

“Telescopic studies of Saturn, its ring system, and its satellites from 1610 to about 1900 are surveyed. Early observations of the Saturn system and changing beliefs about the constitution of the rings are covered, showing that what an observer sees in the heavens depends not only on the quality of his instruments, but also on what he expects to see. The first observations of the Saturn system by Galileo, the development of the ring theory by Huygens, and the replacement of Herschel's and Laplace's solid ring theories by Maxwell's particle ring theory are recounted.” 

Saturn Gehrels, Tom; Matthews, Mildred Shapley (Editors). Tucson, University of Arizona Press, 1984, p. 23-43.


Introduction to Objectivist Epistemology
by Ayn Rand (2nd. edition)

In Introduction to Objectivist Epistemology, Ayn Rand asserted that a sensation must be identified to become a percept. A set of percepts, identified and integrated by common attribute becomes a perception. A set of perceptions integrated by their common characteristics are given a name and thereby made into a concept. Concepts are further abstracted by their essential distinguishing characteristics, according to objective context, into wider (and more powerful) ideas. Without identification, a sensation alone is meaningless. Not knowing what to expect, Galileo could not perceive the rings of Saturn correctly.

Just as it took time for the nature of Saturn’s rings to be teased out from the observations, so, too, did someone 400 years after Galileo finally put 2 and 2 together. In 2005, the science of epistemology informed astronomy.

“Saturn was first seen through the telescope by Galileo in the summer of 1610. In the ensuing half century, Saturn's strange appearances became a celebrated puzzle. The problem was often not the poor quality of telescopes: a number of observers drew images that we would interpret as showing a ring around the planet. It was also a problem of concepts because for several decades observers had the wrong model in mind when they observed the planet. Thus we could say that their telescopes could show them the ring, but their preconceptions did not allow them to see it. The manner in which Christiaan Huygens arrived at the solution, in the winter of 1655-56, shows that more than good telescopes were necessary, although for rhetorical reasons Huygens maintained the opposite. And Huygens's ring-theory, [elegant] as it was, had several shortcomings that were slowly fixed--often by others.” --  “Saturn through the Telescope: The First Century” by Albert Van Helden. American Astronomical Society, DPS meeting #37, Bulletin of the American Astronomical Society, Vol. 37, p.620. Pub Date: August 2005


Explore Scientific First Light 102
660 mm focal length

Last night, I went out with my telescope to see what Galileo could or could not have perceived, had he held the identifying concept. Admittedly, the 102 mm objective of my Explore Scientific refractor has 16 times the area of his. However, I am inside a city, a mile from a major shopping center. He was in Florence, a city with smoke, perhaps, but no arc vapor street lights. 

I tested three magnifications: 20.8x (32 mm), 26.4x (25 mm) and 38x (17 mm). At 21 power, it was a strong “maybe” given Galileo's patience. At 26.4 power the rings were discernable without question, and at 38x, they were undeniable. Although his 20x telescope was his primary instrument, it was not his only telescope. He had made a 30-power at the same time, but gave it to Cosimo Medici. I believe that Galileo’s instruments were good enough, but understanding of the taxonomy of the solar system required a conceptual leap that would have to wait for later astronomers.



The Scientific Method 

Feynman's Rainbow 

Harriman's Logical Leap

Cosmos: a Spacetime Travesty