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Rob

Primer - Choosing a Telescope

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Selina    10

thank you for this, great info as just about to buy my first telescope.

sorry for the silly question but what does d=114m f=900m mean - does that mean it is a good telescope?

thanks, Selina

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mikeyrea    69

Thanks for this advice Rob - I'm saving up for a scope and it's all food for thought!

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Mr Q    258

Here are two links for those thinking about getting a telescope. The first is about choosing what type/size while the second is about what you can expect to see with each type/size.

CHOOSING

WHAT TO EXPECT

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Aenima    387

msg-18772-0-52482300-1342389156_thumb.jpgHere are soome size comparison pics showing the 130p explorer next to the 200p explorer. I tried to include mounts/tripods but compromised due to space issues.

Hope this helps.

msg-18772-0-59679200-1342388038_thumb.jpgmsg-18772-0-91956600-1342388210_thumb.jpgmsg-18772-0-55897900-1342388522_thumb.jpg

Regards

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Philjer    0

Hi Rob,

I just ordered a Celestron NexStar 4SE for my very first telescope, UPS sa'sy it will be delivered to day. "GREAT" wating , waiting and still waiting

Regards

Philjer

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sodejm    2

Just started looking into an actual telescope to go along with my binos and this information actually is really helpful at clearing up some questions i had so thank you very much

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Rob1956    2

Thanks for the info Rob, and Aenima thanks for the comparison pictures.

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Watchman    64

Good post thanks, taking in as much as I can before I buy something

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worthy52    1

Hello, I am extremely new to this--just purchased a Meade ETX-80--Telescope came with lenses of 26mm and 9.7mm--Could not see Moon in the magnification I thought I would be able to--What type of lenses would  y'all recommend---Thanks, Steven--Please do not get too detailed.

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drguybs    0

Choosing a Telescope

1: Avoid buying a low cost "beginners", or "starter" type telescopes from high street stores / tv shopping channels. You will almost certainly be disappointed and discouraged. Most of these inexpensive telescopes have poor optics, with flimsy mounts that will be of no use and provide you with shaky images.

A good start telescope range such as the Skywatcher / Celestron will give the amateur astronomer a great start in the hobby. As with binoculars, the most important factor is the light gathering power of the telescope, this of course depends on the lens / mirror diameter, known as aperture. The bigger the aperture, the more light is gathered by the telescope.

2: When buying a telescope, you need to consider portability.

A 16" Dobsonian or (light bucket as some may say) might be appealing if you're interested in deep space observing, but not if you live in a flat on the 4th floor!!. Carrying around a telescope of that weight 80 kilos (176 lbs) which could be around 67 inches long, can be daunting + put you off the hobby in one easy step! (oh yes, it can also put your back out!). So match your ambitions to your main observing site. Its easy to get aperture fever!. Don't overdo size, weight, or price. Choose a telescope you can carry and set up by yourself, just in case a family member or friend can't or won't go with you.

3: What kind of telescope?

Many telescopes are capable, with varying degrees of success of showing you virtually everything in the night sky. But no one telescope does it all perfectly. This is the hardest part of telescope selection. Every telescope excels in particular areas, and others where it's only adequate. Refractors, for example, are usually better at high power lunar and planetary observing than they are at finding faint fuzzy nebulae and galaxies. Reflectors are the reverse.

4: What magnification should you use?

Any telescope can magnify to any extent, however, the highest useful power of a telescope under ideal seeing conditions is only 50 to 60 times per inch (25mm) of aperture. Under average seeing conditions, atmospheric turbulence limits the highest useful magnification to 25 to 30 times per inch (25mm) of aperture.

So, how much power do you really need? High magnifications are OK when viewing the solar system, as there is plenty of light available, although you don't always need to use high magnification as there is plenty of lunar and planetary detail to see at 50 to 100 times.

Except for resolving close binary stars and globular clusters, very high magnifications are not usually needed outside the solar system either as stars always look like points of light, no matter what the magnification. Many planetary nebulae, like the Ring, Nebula, M57, look great at 100 times, but are too dim to see well if you increase the magnification. The Andromeda Galaxy is over 3° across, or six times the diameter of the moon. You don't need high magnification to see something that big!

Clear Skies

Rob

Source: R.M. Clarke. The salopain web - edited by R Hughes. 2005

Thank you. The nebulae vs Moon observing analogy is very helpful.

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