I am about to buy a telescope (within next few days) and have some dumb questions.

My price point is about $700 canadian and I was planning to use it for 60% land viewing and 40% sky viewing.

I was considering buying a SkyWatcher 120mm short tube refractor that I saw advertised for $709. This one actually:

http://www.skywatchertelescope.com/1206.html

The ad reads: 120mm 600mm FL Refractor, EQ3-2 Mount, 25mm,10mm MA Eyepiece., 90° Diagonal., Red-dot Finder $709.95

Is this a good brand of telescope?

Is $709 a good price?

What power magnification does a 25mm and 10mm eyepiece give me on this telescope?

Should I buy a barlow?

Someone told me that 2x the diameter or 240x power is the best I can do with this telescope, so what is the best combination of barlow and eyepiece do I use to achieve the 240x magnification?

Any help you can give me would be appreciated and I apologize in advance for insulting you guys/gals with such dumb questions.

Welcome, BigD! You might want to use the above Search feature, too, as this has come up before. What distances have you in mind for land viewing?

Thanks, I found the power equation Focal Length/diameter of eyepiece:

600/25 = 24x magnification
600/10 = 60x magnification

I live on a hill and the ocean and ships look to be about 3-6 miles away.

Skywatcher telescopes (at least the model you referenced) are made in China by a company called Synta. They're a respectable telescope for the cost. I own one of their Short tube 80's, which is a nice, portable wide field scope. The only real problem with these scopes are that they're 2 element achromat objectives, so you'll get some Chromatic aberation on bright celestial objects. For terrestrial use, they work just fine since chromatic aberation isn't much of an issue.

It's a reasonable price, considering the EQ-3 is part of the deal.

Magnification is equal to the focal length of the objective divided by the focal length of the occular. In this case, 600/25=24x, and 600/10=60x. The scope in question is a wide field, or "rich field" scope. A 2x barlow will double those magnifications to 48x and 120x, about the best you'll be able to do under common skies. Under exceptional skies, you could go higher.

The normal rule is 50-52 times the aperture (in inches), so around 200-240 is correct - but that's under perfect observing conditions, a rarity in most locations. Also, the Ep's that come with the refractor are far from the best, so they will also limit your resolution.

The EQ mount is poor for terrestrial use (and great for astronomy use), but it can be used as a pseudo alt/az mount. Normally, an alt/az mount is used for terrestrial viewing. You'll also want a correct image diagonal (also called an erect image diagonal), otherwise your image will be upside down.

Thank you so much sarongsong and SarahMc for the info, I learned more relevant info from your post than from 3 late nights internet surfing ...

Just a slight correction. . . the formula is focal length of the scope/focal length of the eyepiece (not diameter). Those #'s given on the ep's are indeed the f.l., so your results are correct anyways.

As others have mentioned, your goal every time out should NOT be "maximum magnification", but "how clearly can I see it". Almost always, you're best view of objects will be way below the "accepted" max for your scope. I've got an 8"/F10 scope, but use my 26mm (77x) ep most of the time, while bumping up to my 12.4 (161x) on occasion. I also have 9.6 and 6.4 ep's, but rarely even bother to get them out (unless things look ultra-clear in the 12.4).

Speaking of F10, that's the "focal ratio" of my scope. That's another number you'll hear bantered around when talking about scopes, and generally it is used to describe the "speed" of your scope. You find it by 1) dividing the focal length of the scope by the apeture (making sure you use the same units, of course. . . ), or 2) reading the box/manual, which most times will list the F-ratio somewhere.

The number really doesn't mean much to visual observing, although a scope with a shorter focal length (i.e. a lower f-ratio, or "faster" scope) will require higher powered eyepieces to achieve the same level of magnification as compared to a slower scope (because of the formula you list above, actually). Also, a faster scope will have a wider field of view than a slower scope, all other things being equal.

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