Getting Astronomy Telescopes For The Backyard Stargazer 

OK lets learn about astronomy telescopes. To begin with have you studied the sky? Can you go out and find five constellations and a few stars and planets?

Great now you should try stargazing through binoculars. Using binoculars will give you some great views of the Moon and get you used to the narrow field of view you get looking through optics instead of naked eye viewing.

Alright fine you feel you're ready for your first telescope, good. First there are things you need to figure out.

Where will the scope be used most often? Do you have dark rural skies or light polluted city or suburban locales?

Do you have a favorite spot? Is your watching place easily accessible? Will you need to load the scope into your car and drive some place and then set it up? Or will you be viewing from the backyard?

Will you be able to mount the scope and keep it ready? Or will you have to remove it from the mount every time for transport and/or storage?

How much weight can you comfortably carry around?

Remember the best astronomy telescope is one that gets used the most. If it's too heavy or too complicated too setup and move to your viewing spot it probably won't get used or enjoyed as much.

MAGNIFICATION

Now it's time to talk about magnification. Most people think, and a lot of sales' copy emphasize, magnification or power as the important factor. It is not.

This is not the place to begin. The most important feature of astronomy telescopes is aperture size. I will repeat that...The Most Important Feature of Astronomy Telescopes is Aperture Size.

A telescope needs to gather light to be effective and the aperture or lens size is how this is done. A larger aperture means more light gathering ability. So... buy the largest aperture size you can afford all things considered.

Power or magnification is determined by the focal length of the telescope tube divided by the focal length of the eyepiece you are using. So if the scope has a focal length of 300mm and the eyepiece has a 4mm focal length then the power is 75 times (300/4=75).

Just remember that as power or magnifying increases, image sharpness and brightness decreases. To increase magnification you take the same amount of light and spread it over a larger area.

Generally at double power the image will be 1/4 as bright and 1/2 as sharp.

Don't let the department store telescopes fool you with claims of 600x power or zoom or whatever they choose to call it in a 2-3in(50-75mm) telescope.

They may give you the eyepiece to magnify that much but you won't be able to see anything worthwhile.

Maximum power should be about 50 times the aperture size in inches or 2 times the aperture in millimeters. This means a 6inch(150mm) aperture should use at most 300 times magnification.

EYEPIECES

Budget in some quality eyepieces as well. You may not want or need them at the time of purchase, but if the hobby catches on and you enjoy it you will want additional eyepieces.

Since eyepieces control magnification, once you know the focal length of the telescope you can figure out what length eyepieces you need for a given magnification.

And since you know the formula for useful magnification you can buy eyepieces that will actually allow you to still see quality images through your astronomy telescope.

Colored filters are also useful to help enhance contrast and color of objects. These can help you see features better. A Moon filter for example can dampen some of the brightness of the Moon and help bring craters and other features on the surface into relief.

SEEING

"Seeing" or atmosphere turbulence will have an effect on how well you can see objects. Turbulence in the air caused by radiating heat as the ground and surrounding areas cool down from the day's Sun can cause a loss of visibility. 

This air turbulence will cause swimming and shimmering of objects as you try to see them. Some nights will be worse than others. You can reduce this distortion effect by using lower magnifications.

Check the "seeing" by looking at the stars, a lot of twinkling means more distortion in the air.

Patience is of value here as the seeing will sometimes clear up for a brief period and you may get a good view of something.

Observe the star Megrez(magnitude 3.4) to see how much can be seen that night. Megrez is the star that connects the handle to the dipper in the Big Dipper asterism in Ursa Major. Any star for which you know the apparent magnitude will do for your local viewing area.

Light pollution is also a factor. Light glow from surrounding cities and towns will be magnified by your telescope, so again lower power may be more beneficial to viewing.

Also when you get to your spot and get set up take about half an hour or so to let your eyes adjust to the darkness.

This will expand the pupils and allow your eyes to gather more light and see better.

The telescope will also need this time to cool down to outside temperature. A scope needs about ½ hour to an hour to cool down. Larger telescopes take longer and the greater the difference in temperature the longer it can take as well.

If you are using star charts or otherwise need light to see, use a red light or a flashlight covered with red cellophane so as not to ruin your night vision. 

BOTTOM LINE

There a three basic types of astronomy telescopes for the backyard stargazer:

Refractor, Reflector, and Cassegrain.

The next question is always..."Which one should I buy?" The answer is “I don't know”.

Only you can answer that question but I have some factors to help you weigh that decision.

Remember though my recommendations are based on my opinions yours will vary.

Take all the info and do your homework then make an informed decision.

Click the links to see some facts about each type of scope and my recommendations.

Refracting telescopes Refractor recommendations

Reflector telescopes Reflector recommendations

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