"How To..."
Wanna know how to do something in astronomy observing? My simple instructions make it easy for anyone at any skill level to do it!
...Properly Orient Yourself to View the Night Sky
Just go out and start looking? Well... almost.
First, let's get your directions straight. You need to star off looking to the South. Use you smartphone direction finder to point you or 'old skool' it by facing where sunset is in your neighborhood, then make a quarter turn to the left; now you're facing South! North is behind you, east is to your left. Easy, right? Told you it would be...
Now facing South, celestial objects will rise on your left(East) sweep across your forward vision(South), pass by and set on your right(West). With this orientation the sky serves YOU! You look forward, the sky serves it up from the left, slides it past in front of you, then slides it away to your right. All this is caused by the Earth's west-to-east rotation. You just stand and watch!
...Find Your First Constellation
Starting indoors, look at a star map. Doesn't matter if it's digital or paper. Find or set the date and time you're going to observe, then find the one simple star pattern in the center of the sky about half way up from the southern horizon. I'll make it easy by identifying what I call the keystone constellation of each season - the easy star group that is key to locating all the others of the season:
Autumn - Pegasus (a big square)
Winter - Orion (a big rectangle with 3 bright stars across the middle)
Spring - Leo (a reversed question mark and a right triangle pointed East)
Summer - Cygnus (a big cross oriented N-S)
Pick your season, memorize the shape, then go outside and find that one shape. Don't spend more than 10-15 minutes looking on this first try. But here's the most important part: once you find it, immediately go back inside and reward yourself with whatever goodie treat floats your boat! I strongly believe in the 'operant conditioning' method of learning the stars!
On your next observing night(preferably the very next night), before you go out, Pick another star group closely adjacent to your first star group you found the previous night. Memorize the pattern or shape, then go out, find your first star shape and use that to guide you to your next star group. Again, don't spend more than 10-15 minutes and be sure to reward yourself once you've found your second star group.
Follow this pattern for 7-10 days and you will have learned all the brightest constellations of that season! Reinforce your new knowledge with brief observing stints every time the sky is clear. You'll be a master of the night in less than a month!
... Is it a Star or a Planet?
This is an easy one. Just remember: stars twinkle, planets don't.
Why? All the light that comes to us from outer space has to pass through our atmosphere; our turbulent, messy, dynamic atmosphere. Even though it's generally transparent, the fact that it's there affects the light passing through it. The twinkle we see in stars is caused by starlight already compromised by its superlong journey through interstellar space, now passing through different temperature layers in our atmosphere. The different temperature layers have different densities that either slow or speed up the weakened starlight as it passes through. The changing speed slightly bends the white starlight back and forth through the spectrum of colors, resulting in the twinkle we see. Planet light is much less disturbed by the atmosphere because it's had a much easier, less disruptive trip to our eyes here on Earth. So stars twinkle, planets don't. Unless they're down close to the horizon where the thickened atmosphere makes everything twinkle.
Wanna know how to do something in astronomy observing? My simple instructions make it easy for anyone at any skill level to do it!
...Properly Orient Yourself to View the Night Sky
Just go out and start looking? Well... almost.
First, let's get your directions straight. You need to star off looking to the South. Use you smartphone direction finder to point you or 'old skool' it by facing where sunset is in your neighborhood, then make a quarter turn to the left; now you're facing South! North is behind you, east is to your left. Easy, right? Told you it would be...
Now facing South, celestial objects will rise on your left(East) sweep across your forward vision(South), pass by and set on your right(West). With this orientation the sky serves YOU! You look forward, the sky serves it up from the left, slides it past in front of you, then slides it away to your right. All this is caused by the Earth's west-to-east rotation. You just stand and watch!
...Find Your First Constellation
Starting indoors, look at a star map. Doesn't matter if it's digital or paper. Find or set the date and time you're going to observe, then find the one simple star pattern in the center of the sky about half way up from the southern horizon. I'll make it easy by identifying what I call the keystone constellation of each season - the easy star group that is key to locating all the others of the season:
Autumn - Pegasus (a big square)
Winter - Orion (a big rectangle with 3 bright stars across the middle)
Spring - Leo (a reversed question mark and a right triangle pointed East)
Summer - Cygnus (a big cross oriented N-S)
Pick your season, memorize the shape, then go outside and find that one shape. Don't spend more than 10-15 minutes looking on this first try. But here's the most important part: once you find it, immediately go back inside and reward yourself with whatever goodie treat floats your boat! I strongly believe in the 'operant conditioning' method of learning the stars!
On your next observing night(preferably the very next night), before you go out, Pick another star group closely adjacent to your first star group you found the previous night. Memorize the pattern or shape, then go out, find your first star shape and use that to guide you to your next star group. Again, don't spend more than 10-15 minutes and be sure to reward yourself once you've found your second star group.
Follow this pattern for 7-10 days and you will have learned all the brightest constellations of that season! Reinforce your new knowledge with brief observing stints every time the sky is clear. You'll be a master of the night in less than a month!
... Is it a Star or a Planet?
This is an easy one. Just remember: stars twinkle, planets don't.
Why? All the light that comes to us from outer space has to pass through our atmosphere; our turbulent, messy, dynamic atmosphere. Even though it's generally transparent, the fact that it's there affects the light passing through it. The twinkle we see in stars is caused by starlight already compromised by its superlong journey through interstellar space, now passing through different temperature layers in our atmosphere. The different temperature layers have different densities that either slow or speed up the weakened starlight as it passes through. The changing speed slightly bends the white starlight back and forth through the spectrum of colors, resulting in the twinkle we see. Planet light is much less disturbed by the atmosphere because it's had a much easier, less disruptive trip to our eyes here on Earth. So stars twinkle, planets don't. Unless they're down close to the horizon where the thickened atmosphere makes everything twinkle.
Want to Buy a Telescope?
Making the right purchase need not be a daunting task if you're armed with a few simple guidelines. There are several different types of telescopes on the market and the first place to start in choosing one is to decide what you want to do and how much you want to spend.
If you're a beginner or a casual observer, this guide's for you. You'd probably like to see the moon up close, observe the planets or get a good look at a passing comet, but you're not ready or interested in spending the time or money to do astrophotography just yet. You might also like the telescope to have some portability so you can take it to dark sky locations or with you on vacation without much trouble.
Part I - Binoculars
The best way to start is with a pair of binoculars. Binoculars have several advantages. They're lightweight, portable, easy to aim, have low powers of magnification and a wide field of view. Just in case you lose interest, they can be used for other observing pursuits. Also, they tend to be less expensive than a telescope and you might have a pair already.
Binoculars are typically rated by their power of magnification and the size or aperture of the front lens. This information is contained in those cryptic numbers on the eyepiece end of the binoculars. They read as 7X35, 7X50 or some combination of numbers on either side of an 'X'. To define the numbers, let's start with the 'X'. It stands for the binoculars' power of magnification. So in 7x35 we have 7-power magnification. Typically, binocular power is usually 7, 8 or 10. The higher numbers like, 10, 15 and the occasional 25-power are rarer and usually quite expensive. They're also impractical for casual observing because you'll need a tripod to hold them without jiggling at 10-power and higher.
The other number is the diameter measurement of the front lenses in millimeters. This number can range from 35 to 70 and higher. As with the magnifications though, the higher the number, the more expensive and more difficult they are to handle. This brings us to our first tenet of buying binoculars or telescopes: Always buy the biggest aperture you can afford. Reason? The bigger the lens or mirror in your optics, the more light you can gather. The primary misunderstanding about telescopes and binoculars is that magnification is your ultimate goal. While magnification is nice, you can't magnify what you can't see. In other words, if you aren't gathering enough light from an object to make it visible, what's the use of magnification? With binoculars purchased for bird-watching or enhancing the view of the game from the nosebleed section, you can also do some casual skygazing. Ordinary binocs will give excellent views of the moon and greatly improved views of Jupiter, Saturn, and comets. Good binocs start at around $65 and go up from there. Check to make sure they're built well and test them by looking at something with lots of vertical lines. You want to make sure that the lines don't curve near the edges of the field and that they have a hard, sharp focus. Did you know that most comet discoveries are made by amateurs with binoculars? Or that those old binocs you have in the drawer at home are more powerful than Galileo's first telescope? Try them. They might just be the best way for you to begin.
Part II - Telescopes
Telescopes come in two basic types - refractors and reflectors. Refractors use lenses to gather light from dim objects while reflectors use a mirror. Refractors are the long narrow tubes with the eyepiece at the back end. Reflectors are usually shorter, fatter and open at the top. In most styles of reflector, the eyepiece is placed near the top. Refractors provide good, sharp images and are good for observing pinpoint light sources such as stars and planets, but tend to be on the expensive side. Reflectors are good for observing more diffuse light sources such as galaxies and star clouds. They also provide good, sharp images but they are much less expensive because reflectors reflect the gathered starlight from just one surface. In refractors, the light has to pass through two lenses and the surfaces of both (four altogether) have to be polished as close to perfectly as possible. This is both time-consuming and labor- intensive. Going by our first tenet of "Always buy the biggest aperture you can afford", you can almost always purchase a much larger reflecting telescope for what you'd spend on a smaller refractor.
In many stores telescopes are sold by their power of magnification. It actually has very little importance in purchasing a telescope because of the second tenet, "You can't magnify what you can't see". : as magnification increases, resolution decreases. The rule of thumb for magnification limit in telescopes is 50 power per 25 millimeters(25mm = 1 inch). It works like this: the main lens or mirror of a telescope gathers light from an object and forms a small image near the eyepiece. The eyepiece magnifies the small image. Different eyepieces have different magnifications. The numbers on the eyepiece refer to their focal length. If you divide the focal length of the main lens by the focal length of the eyepiece, the resulting number is the magnification you'll get with that particular eyepiece. For example: 900 mm focal length divided by 25 mm focal length = 36 power magnification.
The lower the eyepiece numbers, the higher the magnification. Remember: the rule of magnification is 50 power per 25 mm of aperture. In a 60 mm scope, the best you can do is 100 power. In a 100 mm scope, 200 power and so on. If the advertised magnification is 500 power, the scope size HAS to be 250 mm(10 inches!) or more of aperture, otherwise the loss in resolution will degrade the image dramatically. It's also just plain better to begin with low powers anyway. Telescopes have high magnification and a small field of view - just the opposite of binoculars. Using lower powers of magnification in a telescope make it easier to find and keep track of the objects in view.
Your telescope must have a finderscope - a smaller telescope mounted adjacent to the eyepiece. The finder, with much lower power and much wider field makes object location much easier.
For casual observing, motors to drive the telescope for tracking objects aren't really necessary. After just a little practice you'll find that guiding a telescope by hand as you observe is quite easy, especially at low powers of magnification. Motors are important if you're planning to do astrophotography or perhaps if you plan to show an object to a multitude of people in a short amount of time. For beginners, complication of operation and price are reduced if you don't have a motor drive - save it for your next, larger telescope.
Computerized ‘Robotic’ Telescopes
The wonders of the digital age have now made it possible for anyone to own what used to be professional observatory-grade optics and, more specifically, highly accurate tracking systems. Most telescopes now have a computerized guiding system that uses an on-board database of hundreds of thousands of objects. The database provides the locations of the objects and the microprocessor control systems run the telescope across the sky to the desired object at the push of a button. Ah, bliss! No longer does the operator have to know where anything is in the sky, the computer will do it all for you, right? Wrong! Even with GPS positioning capability, the operator still should know the night sky well enough to realize whether or not the guidance system knows what its doing. So you the operator DOES have to know what’s up there to confirm that the scope is pointing accurately, even and especially at start-up. Otherwise, the scope will just point to where it thinks the object is – oblivious to whether or not an object actually is there. Remember: it’s just a machine and not a very smart one at that. So don’t expect one of these scopes to do it all for you. They do have advantages but those only become obvious once you really learn how to use the instrument.
The mount or tripod of the telescope should be firm and steady. The more massive the tripod is, the less prone the telescope will be to fall over or to wind vibration. The simplest telescope to set up and use is the Dobsonian reflector. The optic tube just sits in a giant "lazy-susan" type mount. It's very easy to operate and is often the best value for your dollar. But you’ll have to at least know the bright stars and planets to use this scope effectively. You'll find very good star maps online or in the periodicals Astronomy or Sky and Telescope.
Looking for a bargain? Consider a used telescope but caveat emptor - let the buyer beware! You really have to know your stuff to buy used equipment or have someone knowledgeable do it for you. On-line you can check out www.skyandtelescope.com/marketplace or www.Astromart.com. You'll find their listings of equipment for sale under the ‘Classifieds’ tab.
Looking for local resources to help you find a telescope or learn the sky? There’s an astronomy club near you where enthusiastic amateur astronomers will gladly share their knowledge and experience about telescopes.
On-line Resources:
www.telescope.com- Orion Telescopes and Binoculars; good primers on what to look for in a scope.
www.skiesunlimited.net- Skies Unlimited – local guys!
www.meade.com/- a ‘big gun’
www.celestron.com - the other ‘big gun’
www.astromart.com- the ‘craigslist’ of amateur astronomy sales.
Astro Magazines: all available at your local bookstore; all have websites. Be sure to see their special editions.
Sky and Telescope - a more technical periodical for a more advanced amateur observer.
Astronomy – the magazine for all the rest of us. Great articles, prettier pictures.
Basic Telescope Formulae:
Mag = fL(o)/ fL(e)
fL = dist from objective to focal point
Pitts’ Power Law - 50x/in(ap)
Price x Weight = Immovability
U(scope) is inversely proportional to M
Making the right purchase need not be a daunting task if you're armed with a few simple guidelines. There are several different types of telescopes on the market and the first place to start in choosing one is to decide what you want to do and how much you want to spend.
If you're a beginner or a casual observer, this guide's for you. You'd probably like to see the moon up close, observe the planets or get a good look at a passing comet, but you're not ready or interested in spending the time or money to do astrophotography just yet. You might also like the telescope to have some portability so you can take it to dark sky locations or with you on vacation without much trouble.
Part I - Binoculars
The best way to start is with a pair of binoculars. Binoculars have several advantages. They're lightweight, portable, easy to aim, have low powers of magnification and a wide field of view. Just in case you lose interest, they can be used for other observing pursuits. Also, they tend to be less expensive than a telescope and you might have a pair already.
Binoculars are typically rated by their power of magnification and the size or aperture of the front lens. This information is contained in those cryptic numbers on the eyepiece end of the binoculars. They read as 7X35, 7X50 or some combination of numbers on either side of an 'X'. To define the numbers, let's start with the 'X'. It stands for the binoculars' power of magnification. So in 7x35 we have 7-power magnification. Typically, binocular power is usually 7, 8 or 10. The higher numbers like, 10, 15 and the occasional 25-power are rarer and usually quite expensive. They're also impractical for casual observing because you'll need a tripod to hold them without jiggling at 10-power and higher.
The other number is the diameter measurement of the front lenses in millimeters. This number can range from 35 to 70 and higher. As with the magnifications though, the higher the number, the more expensive and more difficult they are to handle. This brings us to our first tenet of buying binoculars or telescopes: Always buy the biggest aperture you can afford. Reason? The bigger the lens or mirror in your optics, the more light you can gather. The primary misunderstanding about telescopes and binoculars is that magnification is your ultimate goal. While magnification is nice, you can't magnify what you can't see. In other words, if you aren't gathering enough light from an object to make it visible, what's the use of magnification? With binoculars purchased for bird-watching or enhancing the view of the game from the nosebleed section, you can also do some casual skygazing. Ordinary binocs will give excellent views of the moon and greatly improved views of Jupiter, Saturn, and comets. Good binocs start at around $65 and go up from there. Check to make sure they're built well and test them by looking at something with lots of vertical lines. You want to make sure that the lines don't curve near the edges of the field and that they have a hard, sharp focus. Did you know that most comet discoveries are made by amateurs with binoculars? Or that those old binocs you have in the drawer at home are more powerful than Galileo's first telescope? Try them. They might just be the best way for you to begin.
Part II - Telescopes
Telescopes come in two basic types - refractors and reflectors. Refractors use lenses to gather light from dim objects while reflectors use a mirror. Refractors are the long narrow tubes with the eyepiece at the back end. Reflectors are usually shorter, fatter and open at the top. In most styles of reflector, the eyepiece is placed near the top. Refractors provide good, sharp images and are good for observing pinpoint light sources such as stars and planets, but tend to be on the expensive side. Reflectors are good for observing more diffuse light sources such as galaxies and star clouds. They also provide good, sharp images but they are much less expensive because reflectors reflect the gathered starlight from just one surface. In refractors, the light has to pass through two lenses and the surfaces of both (four altogether) have to be polished as close to perfectly as possible. This is both time-consuming and labor- intensive. Going by our first tenet of "Always buy the biggest aperture you can afford", you can almost always purchase a much larger reflecting telescope for what you'd spend on a smaller refractor.
In many stores telescopes are sold by their power of magnification. It actually has very little importance in purchasing a telescope because of the second tenet, "You can't magnify what you can't see". : as magnification increases, resolution decreases. The rule of thumb for magnification limit in telescopes is 50 power per 25 millimeters(25mm = 1 inch). It works like this: the main lens or mirror of a telescope gathers light from an object and forms a small image near the eyepiece. The eyepiece magnifies the small image. Different eyepieces have different magnifications. The numbers on the eyepiece refer to their focal length. If you divide the focal length of the main lens by the focal length of the eyepiece, the resulting number is the magnification you'll get with that particular eyepiece. For example: 900 mm focal length divided by 25 mm focal length = 36 power magnification.
The lower the eyepiece numbers, the higher the magnification. Remember: the rule of magnification is 50 power per 25 mm of aperture. In a 60 mm scope, the best you can do is 100 power. In a 100 mm scope, 200 power and so on. If the advertised magnification is 500 power, the scope size HAS to be 250 mm(10 inches!) or more of aperture, otherwise the loss in resolution will degrade the image dramatically. It's also just plain better to begin with low powers anyway. Telescopes have high magnification and a small field of view - just the opposite of binoculars. Using lower powers of magnification in a telescope make it easier to find and keep track of the objects in view.
Your telescope must have a finderscope - a smaller telescope mounted adjacent to the eyepiece. The finder, with much lower power and much wider field makes object location much easier.
For casual observing, motors to drive the telescope for tracking objects aren't really necessary. After just a little practice you'll find that guiding a telescope by hand as you observe is quite easy, especially at low powers of magnification. Motors are important if you're planning to do astrophotography or perhaps if you plan to show an object to a multitude of people in a short amount of time. For beginners, complication of operation and price are reduced if you don't have a motor drive - save it for your next, larger telescope.
Computerized ‘Robotic’ Telescopes
The wonders of the digital age have now made it possible for anyone to own what used to be professional observatory-grade optics and, more specifically, highly accurate tracking systems. Most telescopes now have a computerized guiding system that uses an on-board database of hundreds of thousands of objects. The database provides the locations of the objects and the microprocessor control systems run the telescope across the sky to the desired object at the push of a button. Ah, bliss! No longer does the operator have to know where anything is in the sky, the computer will do it all for you, right? Wrong! Even with GPS positioning capability, the operator still should know the night sky well enough to realize whether or not the guidance system knows what its doing. So you the operator DOES have to know what’s up there to confirm that the scope is pointing accurately, even and especially at start-up. Otherwise, the scope will just point to where it thinks the object is – oblivious to whether or not an object actually is there. Remember: it’s just a machine and not a very smart one at that. So don’t expect one of these scopes to do it all for you. They do have advantages but those only become obvious once you really learn how to use the instrument.
The mount or tripod of the telescope should be firm and steady. The more massive the tripod is, the less prone the telescope will be to fall over or to wind vibration. The simplest telescope to set up and use is the Dobsonian reflector. The optic tube just sits in a giant "lazy-susan" type mount. It's very easy to operate and is often the best value for your dollar. But you’ll have to at least know the bright stars and planets to use this scope effectively. You'll find very good star maps online or in the periodicals Astronomy or Sky and Telescope.
Looking for a bargain? Consider a used telescope but caveat emptor - let the buyer beware! You really have to know your stuff to buy used equipment or have someone knowledgeable do it for you. On-line you can check out www.skyandtelescope.com/marketplace or www.Astromart.com. You'll find their listings of equipment for sale under the ‘Classifieds’ tab.
Looking for local resources to help you find a telescope or learn the sky? There’s an astronomy club near you where enthusiastic amateur astronomers will gladly share their knowledge and experience about telescopes.
On-line Resources:
www.telescope.com- Orion Telescopes and Binoculars; good primers on what to look for in a scope.
www.skiesunlimited.net- Skies Unlimited – local guys!
www.meade.com/- a ‘big gun’
www.celestron.com - the other ‘big gun’
www.astromart.com- the ‘craigslist’ of amateur astronomy sales.
Astro Magazines: all available at your local bookstore; all have websites. Be sure to see their special editions.
Sky and Telescope - a more technical periodical for a more advanced amateur observer.
Astronomy – the magazine for all the rest of us. Great articles, prettier pictures.
Basic Telescope Formulae:
Mag = fL(o)/ fL(e)
fL = dist from objective to focal point
Pitts’ Power Law - 50x/in(ap)
Price x Weight = Immovability
U(scope) is inversely proportional to M
Star Maps
Star maps allow us to locate or identify celestial objects. The maps are laid out either by time or by celestial latitude and longitude. The primary difference between maps is how many stars are shown. Maps meant to be used under urban night skies may have fewer stars per page. Maps meant for use under the darkest skies have hundreds to thousands of stars per page. Maps to be used under darker skies will also show the locations of star clusters, nebulae and galaxies, objects visible only under the darkest sky conditions.
Until recently, maps were books, pamphlets, foldouts, or indexed wheels. These items have mostly been replaced by apps on digital devices. Here are some examples of live, online digital star maps:
There are many different star map apps for smartphones that all do the same thing. Some are more elaborate than others and cost a few dollars while freeware may be less ornate, but it is no less accurate. Here are a few examples of smartphone starmap apps:
Star maps allow us to locate or identify celestial objects. The maps are laid out either by time or by celestial latitude and longitude. The primary difference between maps is how many stars are shown. Maps meant to be used under urban night skies may have fewer stars per page. Maps meant for use under the darkest skies have hundreds to thousands of stars per page. Maps to be used under darker skies will also show the locations of star clusters, nebulae and galaxies, objects visible only under the darkest sky conditions.
Until recently, maps were books, pamphlets, foldouts, or indexed wheels. These items have mostly been replaced by apps on digital devices. Here are some examples of live, online digital star maps:
- stellarium-web.org/
- theskylive.com/planetarium
- skyandtelescope.org/observing/interactive-sky-chart/
- www.google.com/sky/
There are many different star map apps for smartphones that all do the same thing. Some are more elaborate than others and cost a few dollars while freeware may be less ornate, but it is no less accurate. Here are a few examples of smartphone starmap apps:
- Stellarium
- Sky Safari Plus
- Orbitrack
- Pocket Universe
Websites
There may be a million astronomy related websites - or more! So there's no point in listing many here, you'll just have to explore on your own, according to your interests. But I can at least point you in the right direction for the most reliable and trustworthy information source - NASA.gov. Every NASA mission has it's own website - from Mercury to Artemis; every planetary mission from Mercury to Pluto has its own website with complete information about the target location; every space telescope from Orbiting Astronomical Observatory to James Webb Space Telescope has its own website with every image ever taken available for view. Here are a few examples:
There may be a million astronomy related websites - or more! So there's no point in listing many here, you'll just have to explore on your own, according to your interests. But I can at least point you in the right direction for the most reliable and trustworthy information source - NASA.gov. Every NASA mission has it's own website - from Mercury to Artemis; every planetary mission from Mercury to Pluto has its own website with complete information about the target location; every space telescope from Orbiting Astronomical Observatory to James Webb Space Telescope has its own website with every image ever taken available for view. Here are a few examples:
- www.nasa.gov/mission_pages/juno/main/index.html
- www.nasa.gov/jupiter
- webb.nasa.gov/
- www.nasa.gov/specials/artemis/
Books
These are my recommended reads for understanding the night sky:
These are my recommended reads for understanding the night sky:
- 365 Starry Nights by Chet Raymo
- Burnham's Celestial Handbook, Vols. 1, 2, 3 by Robert Burnham, Jr. ; Dover Publications, Inc. NY, NY
- Little Book of Stars, Jim Kaler, Copernicus Books, 2001
- The Astronomical Companion, Guy Ottewell, Universal Workshop