It's trashscope season again - don't be fooled

Even if I don't pay attention to anything else, I'll always know that the holidays are around the corner when the trashscopes come out.

• What's a trashscope? It's a mass market telescope that over promises and under delivers.
• How to recognize one? If you walk into a store that normally doesn't sell telescopes and there's one on display it's probably junk. That includes big box stores, camera stores, educational stores, drug stores, and department stores.

But what can you get for that budding young stargazer? How will you know what to buy? Here's some guidance:

• Consider a good pair of binoculars and a companion book on stargazing. Your first telescope provides some guidance here. The right kind of binoculars will have a lot to offer including portability, ease of use, wide field of view, and they can be used for far more than just stargazing.
• If you have your heart set on seeing the rings of Saturn you'll need a telescope. But before you buy take some time to learn about telescopes. Read Avoiding the Christmas trash-Telescope Blues or check out this series of short videos over at the One Minute Astronomer on How to Choose a Telescope.
  

Why do people buy trashscopes? Basically it comes down to the fact that most people aren't familiar with telescopes. Things about telescopes that you might think are important aren't and get over sold. As a result people can be easily mislead. High magnification, large numbers of eyepieces, large and beautiful pictures of galaxies and planets on the box are the hallmarks of this deception.

When it comes to the familiar people are more apt to spot things that look too good to be true. Consider buying a car. If you were to walk into a store and saw a car that promised to carry 10 people, out accelerate a dragster, out maneuver a Ferrari, use less gas than a hybrid, and cost only a bit more than a bicycle - you wouldn't be fooled. So the way to get a scope that you will enjoy is to learn a few basics and to remember that a telescope is no different than any other hobby item. You get what you pay for.

Please take a few moments read the articles and check out the the videos above. And when you're done visit a telescope store or find a star party and talk to the people there.

If you are looking for an inexpensive starter scope, consider the modest Celestron First Scope. It costs less than a typical trashscope and will perform much better. And if you do get the astronomy bug, remember it's called the First Scope for a reason - there will be a second once you know what you want. And if you don't get the bug, it will provide hours of casual stargazing fun.

Easy "Red Eye" Exit Pupil Method

Astronomers talk about the "Exit Pupil" of their optical systems. Most commonly it's used with binoculars but it also applies to telescopes. It's used in two ways, (1) to find the best match between the lowest power of your system and your eye's pupils, and (2) in binoculars which have a fixed magnification to get the maximum light available into your eye.

The rule of thumb used is that the exit pupil should be 7 mm. In binoculars, a 7x50 (7 power x 50 mm lens) is considered a near perfect fit for star gazing because it matches the exit pupil. A 10x70 would also be an excellent fit, but an 8x25 wouldn't provide enough light.

For more on this see Visual Astronomy on The Effects of Exit Pupil.

My son recently completed a Science Fair project on night vision which looked at pupil size and age. To get enough data he needed a quick, easy, and reliable method of measuring pupil size in the dark. They couldn't take everyone to an eye doctor and the "slit" method was neither easy nor quick.

What he came up with was the "red eye" method. By taking a flash photo with a digital camera after about a minute of darkness you can then use software like Photoshop or GIMP to measure the diameter of the red eye in pixels. The only other thing you need is an object of known size to find the number of pixels per mm. For this he used a dime (18 mm) on a Popsicle stick.

The photo above shows a 7 year old with an amazing 9mm pupil!

Later, I'll provide more about pupil size and age.

Related Articles

• Your first telescope ...
• Binocular Astronomy
• Avoiding the Christmas trash-Telescope Blues

Binocular Astronomy

One of the best things a budding astronomer can do is not buy a telescope!

Instead, buy two!! Quite simply, a good set of binoculars is a better way to start off. For more information on why this is true, see "Your first telescope".

Update: There is a caveat I should mention, handheld binoculars will be unlikely to give you a good view of Saturn's rings. I'll write more about beginner telecsopes before Christmas.

Choosing Binoculars

If you are looking for binoculars that you can use to look at the stars, I recommend you read Binoculars for Astronomy over at The Universe Today. Tammy Plotner, a professional astronomer and frequent writer on binocular astronomy, covers size, weight, portability, magnification, size of the objective lens (large end), and exit pupil (small end), tripod adapters, and what types are suited to children versus adults.

Because they are so versatile, many astronomers have several pairs. For example, I have have a compact 8x21, mid-size 10x50, and a large 11x70. The first pair doesn't really gather enough light but makes up for it in portability. The last pair is near the limit of being hand holdable. Anything larger are considered giants.

Giant binoculars require tripods (some have seats) and are used by comet hunters amongst others. They come in sizes like 15x80, 25x100, 30x90, 25x125.

Some astronomers so enjoy using both eyes they get binocular eyepiece mounts for normal telescopes.

One of the most advanced telescopes in the world, called the large binocular telescope uses two scopes with 8.4 meter diameter mirrors!

Things to see with binoculars

Below I've summarized some of Tammy's articles and given viewing dates assuming evening viewing around 9pm.

• Get Sirius! (March 2008) - describes how to use Sirius to find the open clusters M41, M47, and M50 [January-April]. I wrote on this article before, here.
  
• What to Look at With Binoculars - describes how to find the open clusters M44 (The Beehive), and M67 [December-June]; the globular cluster M3 [June-September]; the open cluster Melotte 111 [February-August]; the galaxies M65, M66, NGC 3628 [February-July]; and M105, and M96 [June-July].

Tammy has a series of articles called "What's Up" at the Universe Today as well she has written a book " The Night Sky Companion 2008-2009". The What's Up articles cover what can be seen with binoculars, scopes, and the naked eye on specific dates and may require staying up late or rising early. Many of these take into account the brightness of the moon, as well as the position of planets and asteroids that will vary from year to year.

Update:

I forgot to include a few objects on my list:

• M45 (Seven Sisters), the famous open cluster in Taurus [October-April]
• M42 and M43, in the sword of Orion Nebula [November-April]
• The Double-Double, a multiple star, in Lyra [May-December]
• Alberio, a multi-coloured double star in Cygnus [May-December]
  

Also, the May/June 2008 issue of "Sky News Canada" has an article titled "Welcome To The Binocular Universe" ... "These double-barrelled optical wonders will enhance your exploration of the night sky." written by Gary Seronik.

Update: David Hofland of the North-East Alabama Astronomical League sent me a copy of his NEAAL article describing how to make a liquid filled stabilizer for binoculars using PVC, contact cement, and bungees. Granted it looks a bit odd, but it should have some advantages over a camera tripod when looking way up. I've reprinted it here with permission.

Feedback

I'd love to hear from anyone with ideas about good targets for hand held binoculars. I'd also like to hear from people with binocular experience south of the equator. Please comment or respond via the guestbook or email form on the sidebar. Thanks.

Astronomy Sale ....

Khan's Scopes on Dufferin (east side, south of Yorkdale) have a twice yearly tent sale. The spring installment is this Saturday. If you're in the area, it's worth checking out. Their web site is here.

If you see Ray, tell him George :), David, Mang says hi.

Article on Binocular Astronomy

A while back I wrote that your first telescope should be a good pair of binoculars. This morning I came across an article on things to look at with those binoculars using Sirius as a reference star. You can find the article at Universe Today. From Sirius you should be able to find two or three Messier Objects even in the city.

Cubs working on their astronomy badge should recall that Sirius is easy to find. It's the very bright star, trailing Orion slightly to the south and east. From Etobicoke we can see down to magnitude 4 on a good night.

And if you want to look at more, there's always the wonders in Orion!

Your first telescope ...

I frequently hear from people wanting to get a telescope as a Christmas or a birthday present for someone who is just getting interested in astronomy. Even if they want one, resist. The best advice of experts is don't start with a telescope.

Update: If you really want to start with a telescope you should read Avoiding the Christmas trash-Telescope Blues.

Most inexpensive telescopes are very poor instruments that will be difficult to use and lead to frustration. Poor quality eye pieces, useless finder scopes, terrible tripod mounts, and advertised high magnifications that are unusable. Terrence Dickinson, a respected astronomy author coined the term "Trash Scope Blues" for these disappointments.

Different types of telescopes suit different purposes, requiring the buyer to consider trade-offs. Leave these decisions until you're more certain of what you need.

So what to get your budding astronomer? A good pair of binoculars, and a beginners' book on astronomy!

• Dickinson's, "Night Watch" (4th ed.) is a good beginners book that I recommend. It contains lots of useful information, including discussions of telescopes for when you're ready to move up.
  
• Binoculars for astronomy need to be able to gather a lot of light, so 8x50's are better than 8x25's (the 8 is the magnification and the 50 is the diameter of the lens in mm). You may want to read Tips for Store-Testing Binoculars. A rule of thumb is that the second number should be 6 to 7 times the first, hence 7x50's or 8x50's are good for astronomy. Of course, the larger the optics the heavier the instrument. While I have an excellent pair of 11x70's, they are simply too big for children unless mounted on a tripod. Also, look for binoculars that can take a standard (camera) tripod adapter.
  

Another good thing, is a Planisphere or star wheel. In a future post about the astronomy badge, I'll include some do-it-yourself templates for a simple one.

And if you really want to investigate telescopes, there are three two specialty stores in the Toronto area: Khan's and Efston Science are located near Yorkdale. Kendrick's is located near Dundas and Keele. no longer selling telescopes but still make good accessories.

Updates:

1. For a great example of where binoculars are better, consider our look at Comet Holmes. Also, I missed opportunities to see two magnificent comets, Hyakutake and Hale-Bopp, in part because I had no telescope at the time and didn't consider binoculars.
2. A useful chart on binocular size can be found here.
3. If you're looking for a simple free starter planisphere, look here.
4. If you are considering a telescope instead of binoculars you may want to read a good article about the different types of telescopes. It covers reflectors, refractors, and compound designs. I'd also suggest talking to serious amateur astronomers about the pros and cons of each. BTW. Binoculars are refractors.

Update and important CAVEAT: If you want to see the rings of Saturn then hand held binoculars will not cut it. You probably need at least 20x magnification and that means a telescope!