Most people get to this site because they have a specific question. Sometimes they find it right away, and sometimes they don't. But many of these questions are common, recurring ones. So I thought I would save everyone some time and compile some Frequently Asked Questions (FAQ's) and their answers. I hope you find what you are looking for here. And if not, feel free to contact me and I will see if I can find an answer to your question.
How many planets can you see?
The short answer is "all of them", but let me elaborate.
As of 2006, there are officially 8 true planets in our solar system. Closest to the sun is Mercury, which is a tiny bright speck that is visible to the naked eye or binoculars, but only when it at it's greatest distance from the sun (as viewed from Earth). But Mercury's maximum elongation from the sun is only 23 degrees - enough to place it low over the horizon when the sky is dim enough to see it. I find that when it is visible in the morning sky it tends to be easier to spot it. A few years ago it was easily visible on Christmas morning, which was very memorable.
Venus is the brightest object in the night sky, and again may be visible either in the morning or evening, depending on where it is in its orbit. Really, when it is high, you can't miss it. Venus is bright enough that you can see it easily even in the daytime - as long as you know where to look!
Earth - look down, and cross one planet off your list.
Mars and Earth come into close proximity every 26 months or so, and at these times Mars is quite bright and a ruddy reddish colour. when it is more distant in its orbit, it can still be seen naked eye or with binoculars, but you have to know where you are looking.
Jupiter is bright any time it is up in the sky, and is an easy naked-eye target, outshining all of the visible stars.
Saturn is as bright as many of the brighter stars, so it is visible to the naked eye, but you have to know which of those points of light it is.
Uranus is at the very limit of naked eye visibility - so a keen observer from a very, very dark site might catch a glimpse of it. But it is quite visible in binoculars.
And finally, Neptune is too faint to see naked eye, but can be found in binoculars or a telescope - though it only reveals itself as a planet a very high powers, as the disk of the planet is so small as seen from Earth.
Pluto, the dwarf planet, pushes the limit of most amateur scopes. At this point a 10" aperture at least is required to see it.
Can you see Saturn's rings?
In a good pair of 10x binoculars, held very steady, the planet is distinctly oval in shape. Through a scope at moderate powers the rings are visible, but at high powers - 150 to 200x - the rings are dazzling. Unlike the rings of Jupiter, that can only be seen with special IR imaging systems on satellites, the rings really are as bright as they appear in pictures.
Can you see Jupiter's Red Spot?
Yes. But it requires a magnification of 100x or greater, and clear, steady air. The Great Red Spot (GRS) lies in a hollow in the South Equatorial Belt (SEB), and often appears tan or slightly salmon coloured compared to the surrounding creamy clouds. If the seeing is poor, it may be hard to distinguish it from the SEB, which is also darker in colour. It should be noted that the GRS makes a complete rotation around the planet in just under 10 hours, so it is only visible when it is facing us.
Can you see Jupiter's Moons?
Absolutely. The four main moons, Calisto, Ganymede, Europa and Io were discovered by Galileo using a telescope with a small aperture, just over an inch. These "galilean" moons are easily visible even in small binoculars, such as 6x30. The two inner moons, Io and Europa, have orbital periods of 1.7 and 3.5 days, respectively, so the motions of these moons can be easily seen as their relative positions change night to night, and can even be seen over a few hours.
Can you see Galaxies with a telescope?
Absolutely. There are dozens of galaxies easily visible in even moderate sized amateur telescopes, and hundreds visible to dedicated observers with larger scopes. Many galaxies are bright enough to be seen even from suburban skies. The closest galaxies to the Milky way are dwarf galaxies called the Magellanic clouds. These are bright naked-eye objects in the southern hemisphere. The closest large galaxy is the spiral Andromeda Galaxy. This large, fuzzy oval in the constellation of Andromeda (hence the name) is easily visible in binoculars, and even visible to the naked eye in dark, rural skies. Although the core of the galaxy is what is easily visible, the entire galaxy appears several times the width of the moon!
Can you see the milky way?
Yes, and no. The milky way is, as the name implies, a pathway across the sky that, from a rural site, is bright and indeed milky or smoky looking. In the (northern) summer sky it passes through Sagitarius in the south, to Cygnus overhead, to Casseiopea and Perseus in the Northern sky. In winter it can be seen again through Casseiopea, and through Sirius, but it is faint overhead. Of course, what we are seeing, is the Miky Way Galaxy from the inside. Or solar system is in a spiral arm, about 2/3 of the way from the central bulge to the outer rim of the galaxy. We can't see the whole galaxy, of course, because we are inside it, and we can't see the far side because the centre is in the way. The summer Milky is brightest around Sagittarius, because that is towards the central bulge of our galaxy, and dimmest out toward the rim, in the opposite direction (around Orion and Taurus).
From a moderately dark site, the naked eye view of the milky summer Milky Way is quite exquisite, though it takes some practice to tease out the details. With Binoculars or a small scope it just explodes with stars!
Can you see the hubble telescope?
The Hubble Space Telescope, or HST, is in orbit at a height of approximately 565km. It is large enough and close enough to be naked-eye visible, typically about as bright as a star in the Big Dipper. However, Its orbit is inclined by 28.5 degrees, meaning it never moves north or south of the equator by more than 28.5 degrees. As a result, it will not pass overhead if your lattitude is above 28.5 or below -28.5, and barely rises above the horizon from mid-northern (or mid-southern) lattitudes. Predictions for passes of the HST and other sattelites can be found on heavens-above.com
How many stars can you see in the pleiades?
The pleiades open star cluster, also known as M45, actually contains over a hundred stars, but only the brightest of these are visible, as the group is approximately 425 light years away. Typically, one can see five or six stars in the cluster with the naked eye, forming a shape similar to the Big Dipper - only much smaller. Under ideal conditions, I have seen eight stars, but I have heard of more experienced observers spotting 10 or even 11 stars - which is truly exceptional.
With binoculars, two to three dozen stars are visible in the cluster. It is a very "showy" cluster, and one of my favourite binocular targets.
Can you see colour in galaxies or nebulae?
This question is tricky to answer. In Galaxies, no, they appear in "monochrome". In theory, nebulae too should appear only in shades of grey, because they are not really bright enough in most scopes to trigger colour vision. Some nebulae, however, such as the Orion Nebula (M42), appear to have some colour in mid or large sized scopes (8" or larger). Reported colours vary from greenish to hints of purple. Whether this is true colour vision or your eyes (or brain) playing tricks I don't know for certain - so let us say that under ideal conditions, with a good aperture, you can perceive some colour.
How far can you see with a telescope?
I get this question frequently. Far is not the issue. Brightness is the issue. There are objects that are relatively close (Pluto, for instance, or many asteroids) that I have not seen, because they are too faint for me to see with my scopes. On the other hand, galaxies that may be several million light years away are easily visible, because they shine with the combined light of billions of stars. But since the question was asked, the farthest object I have seen in a telescope is the quasar 3C273, in the constellation of Virgo. This quasar is most likely the result of high energy radiation being emitted from an accretion disk around a supermassive black hole in the centre of a galaxy. But this object is about 2.44 billion light years away. Yes, billion. Whatever it really is, it shines about 100 times brighter than an entire galaxy full of stars.
What is the best first telescope to buy?
For a longer discussion, see the section on choosing a telescope. People have different needs and desires, so there may not be one correct answer. However, in my opinion (having gone through this myself), as a first telescope I would say that the best bang for your buck is an 8" Newtonian on a Dobsonian mount. These can be purchased now for under $400, they are easy to set up and use, and they work well as both deep sky and planetary scopes. An aperture of 8" is an ideal size. You can get 6" scopes, but they are not much smaller, or 10" scopes, which are significantly heavier and more expensive. One thing I have learned over the years is that as you get used to observing with your scope, you are able to see more and more, so in effect the aperture seems to get larger the more you use it.
What can you see with binoculars / 3" / 6" / 10" Telescope?
I get these kinds of questions frequently, and the answer is not always simple - but I will try to keep it concise. Technically, the limit of what can bee seen with a given aperture is frequently given using a mathematical formula - but this is only a guideline, and refers to stars. With extended objects, such as galaxies and nebula, it is the surface brightness, rather than the total magnitude, that determines how visible an object is. But there are other factors as well, including how dark your skies are, the contrast of the object, the magnification used, how good your eyesight is, how much experience you have as an observer, the location of the object in the sky, the quality of the optics, etc.
Rather than extolling on the physics and physiology of observing, let me provide an idea of some of the things you can see in different instruments.
Binoculars (40-50mm, 8-10x) - the low magnification of binoculars limits their use for detailed observing of small objects, such as planets and galaxies. The wide field of view, however, lets them excel at observing bright open clusters (Coma Berenices, Pleiades, Hyades), scanning the milky way, observing fainter constellations (Delphinus), and spotting bright DSO's such as the Orion Nebula, Andromeda Galaxy, Wild Duck cluster, Lagoon Nebula, Sagittarius Star Cloud, and glubulars such as M22 and M13. Binoculars of this size also give great views of the moon, and can easily locate the four galilean moons of Jupiter.
Small telescope (70-100mm) - these instruments have the benefit of a stable mount and adjustable magnification. At low powers, they can be used for the same targets as binoculars. At higher powers, they can also be used to see markings on Jupiter, see the rings of saturn, and see moderately close double stars. As well, some of the brighter galaxies, such as M81 and M82, can be seen quite well, and the brighter nebulas (Orion, Ring, Dumbell, Swan, Lagoon, Triffid...) can be seen in considerable detail at moderate to high magnification. An experience observer should be able to see all of the Messier objects in a a scope this size (from a dark location), though an inexperienced user would likely have difficulty.
Mid sized scopes (150-200mm/6-8") - These scopes can see everything visible in the smaller scopes, except for very large objects. These scopes have a longer focal length, and as a result an intrinsically narrower field of view. Targets such as the Pleiades Coma Berenices are much nicer in binoculars or wide field scopes. Scopes in the 6-8" range can easily be used for all of the Messier objects. some details in galaxies and nebulas with contrast (eg dust lanes) can be discerned.
Large scopes (over 250mm/10") - In the larger aperture scopes, both the increased resolution and light gathering make it possible to tease out more detail, more easily, than in smaller scopes. In the 14"-20" range, the images can be truly breathtaking.
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