Thursday, April 28, 2022

Moonrise

 

Many people have little interest in astronomy. Most of them have never given thought, or don't know, for instance, the cause of the Moon's various phases, and its different locations in the sky from day to day.  The picture below was taken through our living room window, the Moon phase shown a day or so after full. The Moon and Earth,  as are all the planets and their moons in our solar system, are illuminated by the Sun. 



The Moon about a day after full.

I expected to see the Moon rise behind the the mountains at about that position and at that time, both from past experience (we've lived in our house for over 50 years), and rough calculations of thumb.

The Moon's speed in its orbit around Earth is such that it moves the distance of its own diameter (about 3500 km) eastward in an hour. That is its real motion in the sky, as is obvious when compared with the position of background stars. The Moon's apparently much larger motion westward is the result of Earth's daily rotation. 

The full Moon is always located in the sky opposite the sun's position in the sky on an imaginary straight  line from the Sun, to the Earth, and then the Moon. For the northern hemisphere in summer, the Sun rises in the northeast, and sets in the northwest. The full Moon on the same day rises in the southeast and sets in the southwest. The winter sunrise and sunset are again opposite each other: Sun southeast rise, southwest set, the full Moon northeast rise, northwest set.

Throughout the year, as the Earth orbits through the four seasons, the rising and setting points for Sun and Moon  change every day; none-the-less, the full Moon is always opposite the Sun. That implies that the position of the Sun in the sky 6 months later will be approximately where the full Moon is today, and the full Moon 6 months later will be approximately where the Sun is today. Opposing positions can also be applied to other phases of the Moon. For instance, first quarter Moon and last quarter are in the same relationship as full Moon and Sun. One difference is that their respective illuminations are opposite. In the northern hemisphere on Earth the first quarter shows the illuminated right side and the third quarter is its illuminated left side, as seen standing up, facing south. In general, all phases of the Moon before full are illuminated on the right side, all phases past full Moon are illuminated on the left side. The opposite is true for the mid-southern hemisphere, where you are looking north to find the Moon. Close to the equator, the Moon moves through the sky overhead, your left/right phase perceptions depend on the direction you're facing. 

An aside: in the northern hemisphere, due to the Earth's daily rotation, Sun, and at night the Moon and astronomical objects move in the sky from left to right, if you are facing south. If you're looking at the North Star, the stars move around it counterclockwise. The North Star is below the horizon for the Southern Hemisphere, there is no South Star. The stars move around the "South Point" clockwise and, facing north, all astronomical objects move from right to left. In the northern hemisphere, you can simulate all these effects by stretching out on the ground. If your head points south, the stars overhead appear to move like they do in the southern hemisphere (right to left); lie down in the southern hemisphere with your head pointing north, they move as they do in the northern hemisphere (left to right). The Cardinal Points North, East, South, and West are never changed. They are the same in both hemispheres. It all boils down to "personal positioning".

The Earth is not flat after all!

The Moon's average apparent diameter, as it appears from Earth, is about half of a degree. Also, the Moon in reality moves eastward about one half of a degree per hour (see above). In a day, that is a distance of about 12 degrees. In a month, Earth, along with the Moon, has moved along the Earth orbit by about 30 degrees. The orbit of the full Moon, say, from today's position with respect to background stars to the next time in the same relative position with the same stars is 27.3 days. That is the sidereal month. At that point the Moon is not full again, because of the 30 degree change in the Earth's orbital position. The Moon has to move about 2.2 days more before full phase occurs. Therefore, the synodic month, from full Moon to full Moon, or any other phase to the same phase again is about 29.5 days.

 The numbers shown here are all general approximations and ignore several other aspects of Earth and Moon orbits. For one thing, the plane of the Moon's orbit differs by 5 degrees from the Earth's orbital plane. The Earth's rotational axis is inclined by 23.5 degrees from the vertical to the Earth's orbital plane. Both Moon and Earth orbits are not circles; that also affects orbital speed and position. The imaginary line I mentioned connecting Sun, Earth, and full Moon is only really straight when the Moon is at the crossover points of Earth's and Moon's orbital planes. When lunar eclipse occurs the Earth is exactly between the Sun and the full Moon. With the new, invisible Moon is exactly between the Sun and Earth, solar eclipses occur. At other times, that line is "slightly bent".

As I mentioned in the beginning, past experience and simple calculations give me an approximate idea about the area in the sky where I should find the Moon, the planets or the major constellations and stars. There are much easier ways to do all this, of course. Nowadays, many computer-based highly accurate sky map applications for smart phones, laptops, and desktops are available. I use those quite often, too. What these apps don't do for me is give me a mental perspective of the spacial distribution of the Moon, Earth, Planets, and stars, and the immense time spans and distances in the universe, something like being on a trip in space, or looking at the sky through binoculars and telescopes.  

 You can get an accurate version of the numbers above in the RASC's Observer's Handbook. You can either purchase the book, or have it sent to you without cost if you are a member of RASC Vancouver or other RASC centres.




Thursday, September 30, 2021

My first Astronomy books


A few days ago, I rifled through one of several of our bookshelves in our house. Hidden behind some family pictures I came across two books which I've had since shortly after I first got interested in Astronomy (at the ripe old age of 8 [I'm now 82]). In previous posts I have stated that I was born in Berlin; the books were published in the German language and were first printed in the 1930's. My copies are reprints from the 1940's.They were already well-used books when they were given to me and haven't improved their condition since then. I wrote about what got me started in astronomy in November 2019; the article appeared in the Jan/Feb 2020 Nova newsletter.

The books are written by different authors. The older book, "Von Fernen Welten" (Of Distant Worlds) by Bruno H. Bürgel, was originally published in 1910. The author was a true philosopher; he wrote other books about many aspects of the "human condition". As such, this book was written for the general public and was only meant to be a general look into Astronomy. Nonetheless, it contains a lot of astronomical detail.

The "newer" book, simply named "Astronomie", by Oswald Thomas, was first published in 1933. Thomas was a professional Austrian astronomer and wrote this book for the scientifically interested public and to "fill in" some astronomical themes which were less often addressed in other books on astronomy. It contains a multitude of tables, drawings, information about both the non-rotating and rotating sky, astronomy of the Earth's globe, the solar system, and what was known and unknown of the near and distant universe at the time.   However, it was not annually updated. An enlightened neighbour in the apartment building where we lived gave me this (also used) book in 1953 as a present. 

The battered books

Bruno Bürgel's book gave me more motivation to look at and learn more about the sky. I spent many hours in public libraries. The sky of Berlin in the late 40's and early 50's was far less light-polluted, because many buildings had been bombed into ruins and streets were still sparsely illuminated. We could not afford to buy a pair of binoculars, never mind a small telescope, but I was the proud possessor of a 3X40 Galilean monocular. That monocular was my "telescope" for a number of years. It was an overwhelming feeling for me to find some of the interesting astronomical details mentioned in Bürgel's book. Oswald Thomas's book became my reference book later, and I occasionally still refer to it. Even in this digital age, well-written older books have value. They can last centuries and don't need batteries.

Nowadays, you can get all this information on the internet, and on your smartphone or home computers; at that earlier time the necessary technology did not exist. I've used the two books only occasionally in the last 4 decades. Having been a member of the RASC through all this time I have the advantage of access to up-to-date astronomical information in the annual Observers' Handbook, SkyNews magazine, the RASC Vancouver Centre's library, and the Nova newsletter, all included in membership. The astronomical knowledge and experience of RASC members is freely given to everyone who asks, member or not. 

In early 1950, I joined an astronomy club called the BAV (Berlin Association [workgroup] for Variable stars) which had access to the what was then a temporarily located Wilhelm Foerster observatory (see note). It had a seven inch refractor, exposed to the weather (no domed building). The telescope had been built by dedicated amateur astronomers with salvaged parts from the bomb-damaged Urania observatory in Berlin. We were an enthusiastic group of people of various age and, beside variable stars, observed everything else, too, along with setting up and showing people the view through the telescope on public astronomy nights. Our variable star observational results were mailed to the AAVSO in the U.S. and I hand-copied their reference maps by tracing them on transparent paper (AAVSO's star maps are now accessible on-line). I still regard my participation in our RASC's in-person public astronomy nights as my most rewarding of astronomical activity. Covid-19 has put a damper on this in the last couple of years, but I'm hopeful about doing so again soon (subject to Covid-related rules at this time).


 The "temporary" Wilhelm Foerster Observatory, about 1950

Note: The new Wilhelm Foerster observatory is now located on top of the only "mountain" in Berlin worth that designation (in my opinion); the mountain consists of thousands of tons of broken bricks and cobblestones, and other detritus collected from the war's ruins when rebuilding of the city was underway after the war. Trees and other plants have turned it into a beautiful park. The 3-dome Wilhelm Foerster observatory is now a totally up-to-date public institution connected to a Zeiss planetarium.

Sunday, August 8, 2021

Radio Station Andromeda ?



 (whimsical) 

Radio Andromeda

  

I take a daily half-hour walk, sometimes inside our house, or the back yard, or around several blocks in our neighbourhood. While doing that, most of the time I listen to the radio or music library on my cell phone. I've set the music to be played in random sequence. It seems to make the time go faster.


One of the tracks is called "Radio Andromeda" (electronic music by Michael Walthius). 7 minutes long, it has just the right tempo for a good walk. The other day, walking, and fantasizing that this melody was actually a transmission sent by a civilization living somewhere in the Andromeda Galaxy, and imagening my receiving it just now on my radio. It would imply a much advanced intelligence but with a technology in some way compatible with ours. 


We know of nothing in our physical world that can move faster than the speed of light. The interesting aspect of my fantasy would be that this music would have had to be transmitted about 2,400,000 years ago, since the Andromeda Galaxy is 2.4 million light years distant. It also means that these "Andromedans" will have had 2,400,000 years to evolve since then (approximately the time it has taken for humans to evolve from  Australopithecus to Homo sapiens). If they exist, would we even be able to recognize them? 


There is another field of physics, the mathematical and observational basis of how the world around us works: it is called Quantum Mechanics. Personally, I find it difficult to wrap my mind around many of the concepts of this discipline. Perhaps the "Andromedans" have mastered the art of making use of its quantum entanglement and superposition effects, and have somehow circumvented its no-communication theorem. That might give them the ability to be aware of who we are and what we do in "real time", even from a distance as far away as the Andromeda Galaxy. (NO, I don't take "social" drugs, or smoke anything. I do have the occasional glass of red wine, though not before my daily walk). 


This fantasizing is, of course, just my brain freewheeling. Quite aside from that, I look at the Andromeda Galaxy through binoculars often, preferably  from an area with no or little light pollution. It looks nothing like its long-exposure, colourful photos. Our visual perception of it is colourless. The light emitted from all the stars in that galaxy is too faint to stimulate the colour receptors in our eyes. 


As an example, look at our own galaxy, the Milky Way. We can't see it in our light-polluted cities at all; in dark areas it just appears to be, well, faintly "milky" - no colour. Consider that we actually live inside our galaxy, in comparison, at its distance, it's no wonder the Andromeda Galaxy appears so faint. And yet, it is larger than our Milky Way and bright enough under a clear, dark sky to be visible with the naked eye as a grey patch. The best view I've had of the Andromeda Galaxy was in 1993 under a very dark sky at Crater Lake, Oregon.



This image approximates how the Andromeda Galaxy shows in binoculars under a dark sky. 


I've written in earlier posts how useful binoculars are in astronomy; if you know the sky reasonably well, a whole evening can pass looking at or searching for many objects, using only binoculars. Interesting views of those, i.e. the Orion Nebula, M13 (the global cluster in the constellation Hercules), the Milky Way in our southern sky with several gaseous nebulae and star clusters, and numerous stars; several nebulae in the Cygnus area overhead; all are bright enough to be visible at this time of year. The wide field of view in binoculars make them ideal for objects that cover a wider area in the sky. Stars bright enough to actually show some colour are also enhanced when looking at them through binoculars. 


A comfortable reclining chair greatly enhances an experience similar to actually being "in space". You may even want to listen to a  radio while you're exploring the sky, perhaps looking at the Andromeda Galaxy. Who knows what you might hear... ?



Monday, May 31, 2021

An interesting pair

Lately, there have been several missions to Mars; a number more to the Moon and the "rocky" planets in our solar system are planned. Among these, NASA and JPL are working on two missions to Venus, the planet physically very similar to Earth, but, environmentally speaking, very different.

Venus and Earth.
(image credit NASA/JPL)

Venus' orbit is closer to the Sun. It is also the closest planet to us, its distance from the Sun is 72% of Earth's distance. This implies that Venus may have had a climate similar to Earth's in the earlier years of its existence. It makes sense that a closer distance to the Sun would result in a higher, but still tolerable average surface temperature there. Venus orbits within the "Goldilocks" zone, nearer the inner limit. Mars orbits inside the outer limit. Water can exist in a liquid state in that zone. However, at the present time, Venus' surface temperature is about 460[!] degrees Celsius. In addition, the atmospheric pressure is about 90 times that of our home planet; the composition of its atmosphere is also very different from ours. The reason for this extreme climate change is unknown, a greenhouse gas effect, perhaps? The rotational axis of Venus is only 2.3 degrees off its orbital plane and Venus rotates "retrograde" once in 243 days; could this have contributed to the current situation? Finding a possible cause is also a purpose of the two missions. 

As usual, NASA's planned Venus missions are named to have some clever, and purpose-implying acronyms. VERITAS (Venus Emissivity, Radio science, InSAR [Interferometric Synthetic Aperture Radar], Topography, Spectroscopy) will orbit Venus with the purpose of obtaining surface and interior gravitational details. Perhaps there are formations (i.e. possible traces of lake beds or river valleys) that indicate the presence of water at an earlier time. There will also be an effort to determine whether there is evidence of tectonic plates and activity in the past, or even now. 

The other orbiter, DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, Imaging Plus) consists of an orbiter and a lander. The lander is designed to settle on the surface of Venus, to measure atmospheric details on the way down, and surface characteristics as well. Both orbiters will probably act as communications relays. Lately, there have been some reports of detecting phosphine gas in the atmosphere, maybe indicating some form of airborne life. Others disagree. After a number of years of lax interest, Venus has come to the forefront of scientific investigation again.

To withstand the current temperatures on Venus, a lander will have to have especially well designed heat protection. Russia sent the world's first-ever lander to Venus (Venera 9) in 1975; it sent signals for a little more than 50 minutes, after which contact was lost. There have been a number of landers by both Russia and NASA since then. I think that the super-hot environment likely gets the better of most of them.

Venus' atmosphere now is mostly carbon dioxide, with sulfur dioxide clouds and sulfuric-acid rain drops. Life on Earth (you and I are included) also generates carbon dioxide all the time, much of which, via a series of chemical actions, is converted back to oxygen by plankton in the oceans, and our plants and trees. But our industrial and agricultural activities are releasing large amounts of methane (20x more efficient at trapping heat than CO2) and other pollutants, some of which also trap heat. Recent climate changes hint that global warming is happening now. 

Venus and Earth are an interesting, at first glance very similar pair of planets next to each other, yet they have such amazingly different surface environments.

Are we looking at a future on Earth similar to the present conditions on Venus ?  Are we smart and nimble enough to head off such future ?

If you're interested in seeing both of the other two planets sharing the Goldilocks zone, in the western sky on July 12, 2021, around 9:30 pm and later, you can see both Mars and Venus close together (and the Moon a bit farther away). Be careful if you look for Venus before sunset. It is fairly close to the Sun - the standard warning is: don't damage your eyesight, never look at the Sun with the naked eye, binoculars, or telescopes. Proper solar filters are necessary for that. After sunset, Venus, Mars, and the Moon are all close to the West North Western horizon; at that point binoculars are helpful. An unobstructed western horizon is best.





West North West

Simulated image from SkySafari 4 Plus

(References and credits: RASC Observer's Handbook, Scientific American, Wikipedia, NASA/JPL, The Planetary Report)

Friday, April 30, 2021

In thin air


 

In my previous post, I alluded to the immense engineering resources needed for the very demanding, highly successful landing of a very complex rover vehicle (named Perseverance) on Mars.  

The Perseverance rover on Mars had, as part of the payload, a small, specially designed helicopter to test the possibility of flying in the very thin Martian atmosphere. Ingenuity, the name of  this helicopter, has now flown several times on Mars and met and exceeded all goals set for it, including flying far enough to be almost out of sight of the cameras on Perseverance. By necessity, both Perseverance and Ingenuity have to be autonomous; at this time any control signal from Earth would take about 16 and a half minutes to reach both Ingenuity and Perseverance. Information from NASA/JPL regarding Ingenuity says that this little helicopter exceeded the test performance well beyond expectations.

 

(Online readers click on image for larger image)

          This is a picture of Ingenuity flying in the distance (label) imaged from the Perseverance rover (Image from NASA and JPL.) 

NASA News indicates an expanded demonstration phase is going to start a couple of weeks from the time of writing (April 30). Ingenuity has proven that its communications, navigation, imaging and other functions are working well, and expanded operations will be initiated. In future, other Mars helicopters will play an ever-expanding role in getting to know far more Mars details. One of the main efforts is to find out whether traces of past or present extraterrestrial life exist now. There are many interesting topological formations on Mars which may be suitable;  an area on Mars in which traces of life (as we know it) could possibly be found: under the icecaps. Martian seasons are similar to Earth, but last about twice as long. Mars is farther away from the Sun, and takes about twice as much time to complete one orbit. 

Below are some of pictures showing the edges of Martian ice caps. The ice caps contain water ice for the most part and are usually covered by CO2 ice (dry ice) during the Martian "winter". The caps melt and rebuild much like on Earth over the span of the Martian "year". Wikipedia contains details regarding Martian polar ice caps.

 

(Online readers click on image for larger scale)

(Credit for above images: NASA/JPL, Caltech, University of Arizona)

It seems that this rough terrain would be problematic for any rover, but could much more easily be explored by drone-like "Ingenuity" helicopters. 

There is a iGadgetPro YouTube entry showing ice and dust avalanches at the edge of the North Polar ice cap. The images were obtained by NASA's Reconnaissance orbiter's HIRISE camera.




(Online readers click on image for larger scale)

(Credit for above images: NASA/JPL, Caltech, University of Arizona)

When the Sun shines on the layers of the ice caps edges, the warmth makes the ice unstable. Blocks of rock and ice can break off and fall down the about 500m tall edges to create ice and dust clouds when they hit bottom. The colours vary depending on the proportions of dust and ice mixed in these avalanches. 

It always amazes me to see dense clouds of dust in such a thin atmosphere in pictures transmitted from Mars. Well, it made the idea to try flying aircraft on Mars plausible. 



Monday, March 1, 2021

Life on Mars?


The recent landing of the newest Martian Rover (named Perseverance) on February 18, 2021 is truly amazing. The engineering resources deployed to reach this highly difficult goal are overwhelming. Perseverance has as one of its main tasks the finding possible traces of past or present life on Mars. There are several new and proven sensing, imaging, and analyzing devices on board, in addition to others of Mars-proven technologies. Congratulations to everyone who is involved with and contributes to this astounding feat. 

The picture shows a bleak, dry, and waterless landscape, unlikely to be very hospitable to life. But we have images of what appear to be momentary water flows on some Martian crater slopes. We know from past rovers that, in some areas, water ice is present close to the surface. That is a driving reason behind the plans to land people on Mars in future.

Perseverance on Mars (from Space.com)

This landing achievement, the activities planned for this most complex of Martian rovers, and the recent close opposition of Mars in our sky, made me think of a book my mother gave me in 1953, knowing my interest in astronomy. The book's contents address the idea that life of some kind exists everywhere in the universe. Its title is (translated from German) "What lives on the stars"; in it, the author Desiderius Papp describes the intense human fascination with extraterrestrial life during the period in the late 1920s. I had a look into that book again while writing this.

Humanity has for ages "populated" Mars (and the other planets, and some of their moons) with some type of life, usually at least equal, if not superior to us. In the later part of the 1920s a lot of people again speculated about the existence of extraterrestrial life on the planets of our solar system. The beginning of this period seems to have been based on the Mars drawings by the astronomer Giovanni Schiaparelli, who observed Mars for many years in the 1870's and beyond. Some of these drawings show thin lines, which he labelled "canali" (channels), later translated by others as "canals". 

Schiaparelli's visual images were produced using a modest telescope (by today's standards) at an Observatory in northern Italy, working near the limits of its capabilities. As a conscientious observer, he must have had some doubts about the lines he saw, asking himself whether they were optical illusions or real. Many other astronomers of renown never saw these channels. In the 1920's, on and after the 50th anniversary of Schiaparelli's publication of his drawings, the general public got excited over the idea that these supposed canals were the product of highly intelligent and accomplished beings, trying to save their existence by collecting the meltwater from Mars' icecaps; realizing that their planet was rapidly losing its water. 



One of Giovanni Schiaparelli's Mars maps (scienceclarified.com)

It seems that Schiaparelli never promoted those ideas himself (he died in 1910).  However, there were numerous people who expanded this concept, well-known scientists, poets, researchers, and authors of phantasy literature, comics etc., all contributed. One popular astronomer (Camille Flammarion) had no compunctions about stating that these canals were, without a doubt, the result of beings with immensely superior logic and capabilities. Flammarion and other people produced amazingly detailed maps of Mars and the canals, the location of supposedly large cities, possible transportation methods, plant life, many of these ideas amazingly anthropological. One well-known explorer of Mars (Percival Lowell, business man, mathematician, astronomer, author) used his own fortune to build a then state-of-the-art observatory in 1893-1894 at Flagstaff, Arizona, dedicated to the exploration of Mars. He died in 1916, but the Lowell Observatory is still in use today. The observatory's telescope was later used by Asaph Hall, in 1933, to find the then outermost planet in the solar system, Pluto. Hall was also the astronomer who found the two moons of Mars, Phobos and Deimos, in 1877, before the existence of the Lowell Observatory. 

We now know the topology of the Martian surface in reasonable detail. The landscape is indeed complex in many areas, and a number of hints point to the existence of rivers and lakes in the early history of Mars, with canyons and valleys in existence which, however, show no hint of artificial creation. Perhaps Schiaparelli got the first glimpses of something that looked a little like his canali, but we have seen no water canals built by some intelligent and logical beings.

I think that the events referred to above contributed to the path that lead to the efforts referenced at the beginning of this article. We are still looking for life forms that will confirm that we (that is, all life on Earth) are not alone in the universe. From the past and present data sent back by many of the orbiting Mars satellites, on-the-surface moving rovers, and fixed sensing stations, a life as fantasized above is not very likely. At the moment, though, we still cannot answer the questions: is there now or was there ever any life as we know it on Mars? Perhaps any life as we DON'T know it?






 



Sunday, December 27, 2020

A Great "Get-together"

 

One of the rare events in the sky is a conjunction of the two largest planets in our solar system.

I logged into Slooh.com on December 21 to watch their live presentation as this conjunction was in progress. There was also a link to the International Astronomical Center in Abu Dhabi, U.A.E.  The image below originated there; it was shown during the presentation, Saturn at the upper left, Jupiter lower right. 

One day later, the Simon Fraser University's Trottier Observatory did the same thing through its telescope on line, with assistance by the RASC. I also watched that well done presentation via YouTube.

Jupiter/Saturn conjunction (International Astronomical Center)

This conjunction was the result of a particular positioning of Jupiter, Saturn, and Earth in their respective orbits. At the time pictured, the visual separation in the sky of Jupiter and Saturn was about six arc minutes, which is about one fifth of the apparent diameter of our Moon as we see it from Earth. That essentially "united" the two planets into one brighter "star" when looking with our unaided eyes. In reality, Saturn is about 700 million kilometres "behind" Jupiter from Earth's point of view. For perspective, Jupiter is approximately five times Earth's distance from the Sun, Saturn almost twice as far.

The large planets in our solar system orbit the Sun in approximately the same plane; Earth's orbital plane is taken as the reference. As a result, the sun 's annual apparent motion across the sky from Earth appears to be the same from year to year with very small changes over time. This path is called the Ecliptic. The larger planets have orbital planes which are close to the ecliptic, but deviate from it to varying degrees. From our Earth-bound point of view, therefore, for them to appear very close together, such as the Jupiter-Saturn conjunction, happens only now and then. Jupiter can even cover (occult) Saturn, but that is a very rare occurrence. It would require that the centres of Earth, Jupiter, and Saturn be exactly on one specific line. The latest Jupiter-Saturn conjunction came very close to that possibility.

The two planets move quite slowly. Jupiter takes about 3 hours for a distance equal to its own diameter, Saturn is even slower. Both move in the same direction. That means the they will be visible in a pair of binoculars at the same time for a number of days. Standard binoculars have fields of view in the order of 5 to 7 degrees. On January 1, 2021, Saturn and Jupiter are about 2 degrees apart, easily within the same  binocular field of view. Unfortunately they are positioned so close to the sun at this time that they will set closer to sunset every day, so following both planets is going to get more difficult. For this purpose, use your binoculars only after the sun sets. Never look at the sun directly through binoculars, or even with your unprotected eyes only; permanent eye damage may be the result!

Covid-19 is forcing us to keep separate for the time being, it was a good thing to see at least one "heavenly" get-together.
 


Monday, November 30, 2020

An old Workhorse


Since the invention of the telescope and its use for astronomical purposes, the exploration of the universe has progressed at first slowly, and then much faster. That also included advancement in the performance of telescopes themselves. The two main types of telescopes, refractors and reflectors have been around for about 350 years.

Among both types of telescopes, I own one that is my particular favourite. It's a 75mm refractor, purchased used in 1964; its true age I don't know. Here is a picture:


This 75mm, f16 refractor came with a solid wooden equatorial mount tripod (hand-driven tracking). 
The telescope is now mounted on an used EQ5 tripod, purchased about three years ago. 
Right-ascension-tracking and declination motors are powered by a D-battery power pack (not shown).

The telescope has the brand name "Polaris", and someone told me that it is the European version of the "Unitron" brand which was very popular here in North America in the middle of the last century. It has an achromatic objective - chromatic aberration is almost unnoticeable because of the large f-ratio. The telescope produces beautiful views of the major planets, the moon, and open star clusters, but is just on the borderline of dissolving globular clusters into individual stars (i.e. M 13). It's also pretty good at showing the brighter nebulae (Orion nebula, Dumbbell, etc.) and double stars (Mizar, Alcor, the "double double" Epsilon Lyra when pushed to 130 times magnification power, and much more). It's my preferred telescope for Public Astronomy Nights.

In previous centuries, instruments of this size and performance (3", 4", and somewhat larger telescopes) were used to do serious scientific work. For instance, Johann Heinrich von Mädler and Wilhelm Beer produced a highly accurate atlas of the Moon (in four volumes fro 1834 to 1836). It was used by astronomers for over a century.  Mädler  and Beer also produced the first reliable Mars maps and were instrumental (pun intended) in assigning Sinus Meridiani as the Prime Meridian on Mars. Photography was not yet available, so all maps were hand-drawn. Here's an example:  

A part of the "Mappa Selenographica" by Mädler and Beer.

(from planetologia.elte.hu)

Mädler and Beer were also able to determine the rotation period of Mars to within 1.1 seconds. It is highly admirable that astronomers made such demanding observations with telescopes of really moderate size. Even today, refractors built many years ago are still in use for scientific research. 

Photography through my 75mm (3") telescope is also possible. With today's digital cameras and technology it's much easier to take some good pictures. Below is an image of the southern part of the Moon, taken with a handheld Samsung smartphone.  



Handheld smartphone photography through a telescope held against the telescope's eyepiece is difficult, because precisely aligning the optical axes of the smartphone with that of the telescope is mostly a matter of luck. Smartphone holders which attach to a telescope and position the camera lens of a smartphone precisely in line with the telescope eyepiece are available. 

You can see that even old and relatively small telescopes are really useful for getting involved with Astronomy. One additional requirement is a sturdy tripod on which to mount the telescope. It should be included in any telescope purchasing budget. Nothing spoils the performance of telescopes more than a wobbly tripod.

Old workhorses indeed.










Saturday, October 3, 2020

An old Standby

 
In these days of Covid-19, getting together with others to have a look at the night sky is an exercise of don'ts: don't get too close to each other, don't touch or look through the telescope, don't come without a mask, etc. On-line meetings are substituting for the in-person ones. My wife and I are practicing voluntary self-isolation (we are old enough to make this necessary). That means that I'm confined to observing the sky from our home. 
 
We live in a highly light-polluted and horizon-limited area. The smoke from the wildfires in the U.S. has added to the lack of visibility of the stars. There were just a couple of acceptable evenings which led me to look for one of my favorite objects in the sky: The Whirlpool Galaxy not far from the end of the Big Dipper's handle. In a dark sky, M51 can be seen in larger binoculars as a small, diffuse patch of light.

I used my 15x50 Canon stabilized binoculars to try and see it. I did not detect it at all. The gray sky here made it an impossibility.  In earlier years M51 was easy to see from our house; high-rises, new and under construction, now limit our horizon and add much light pollution.

I decided to get my "M51 fix" by posting an image I took a couple of years ago by connecting my computer to Slooh.com to use one of their remotely accessible telescopes and take a picture; below is the result:
 

 Messier 51 
Image taken through the wide-field, 17 inch remote-control Slooh.com telescope located at the Institute of Astrophysics of the Canary Islands. 


 Some history (from Wikipedia):

"What later became known as the Whirlpool Galaxy was discovered on October 13, 1773, by Charles Messier while hunting for objects that could confuse comet hunters, and was designated in Messier's catalogue as M51. Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain, although it was not known whether it was interacting or merely another galaxy passing at a distance. In 1845, William Parsons, 3rd Earl of Rosse, employing a 72-inch (1.8 m) reflecting telescope at Birr Castle, Ireland, found that the Whirlpool possessed a spiral structure, the first "nebula" to be known to have one. These "spiral nebulae" were not recognized as galaxies until Edwin Hubble was able to observe Cepheid variables in some of these spiral nebulae, which provided evidence that they were so far away that they must be entirely separate galaxies even though they are seen close together. The advent of radio astronomy and subsequent radio images of M51 unequivocally demonstrated that the Whirlpool and its companion galaxy are indeed interacting."

There are still some uncertainties regarding M 51. For instance, the distance of it is variously quoted as 31 million light years (NASA), Wikipedia says about 23 million, universetoday.com states 19 to 27 million light years. A location chart is shown above. A dark sky will allow for M 51 to be seen in 10x50 binoculars as a faint patch of light. An 8" (200mm) telescope will begin to show its spiral structure.

Messier 51 is circumpolar, so it is accessible for most of the year. At this time of year, the Big Dipper skirts the northern horizon through the night. M51 is therefore moves along above the northern horizon as well. Give it a try under a dark sky anyway. Its position will improve as we progress through winter and into next year.