http://m.snapdeal.com/product/celestron-astromaster-70az-telescope/1178699
How's this one? It refractor telescope too and 70 mm. What's basic things we need to look out for in a telescope?
This is another variant of the 70AZ Altaz mount that I had suggested earler (bare boned version) & which was a lot cheaper ~ 5199. The one you picked has an Pan handle Alt-Az control with clutch and a better mount/tripod.
WHAT BASIC THINGS TO LOOK/KNOW FOR IN A TELESCOPE
Based on my personal experience - these are some of the things in brief.
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Refractor (this is the only type which can also be used for terrestrial viewing as the image viewed is upright); needs least maintenance. No need for collimation (periodic lens adjustment/alignment); gets more expensive as the aperture (diameter of the mirror) increases. The larger aperture scopes are more expensive than reflector or catadiopteric scopes. Contrast is better than reflector scopes. Cassegrain scopes. Bright images may cause chromatic aberrations (faint fringes of color around say moon or jupiter).
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Reflector - less expensive than above; needs periodic colimation (especially if you move/transport/bump it around a lot; Dobsonian; Newtonian etc designs. Has better light gathering capacity than a refractor - so good for viewing distant objects in the sky.
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Catadioptric or Compound - A mixture of the above two containing both refractor & reflector elements. Schmidt-Cassegrain and Maksutov-Cassegrain designs; needs periodic colimation
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Mount - The most important thing. It should be stable; sturdy; smooth. Do not ever use a DSLR camera tripod for a telescope. Cheap scopes have cheap mounts. Sometimes manufacturers charge as much as 40-50% of the cost just for the mount. An unsteady scope will cause viewing problems in moderate wind also - so as you keep focussing the image will keep bouncing
- even if there is no wind
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Overall weight - very important consideration as it affects portability. Check out videos of the specific model you wish to buy to find out how to mount/unmount/assemble your scope. If you have an SUV and travel a lot, then no harm in going in for the largest aperture scope (even if it's heavy)
A small scope you can transport will probably see a lot more use than a larger one you don’t feel like hauling around.
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Eyepiece - Your new scope should have at least 1 eyepiece, and often 2 or 3. An eyepiece is rated by millimeters (mm), with smaller numbers indicating higher magnification. A 25mm eyepiece is common and appropriate for most beginners. While a higher magnification eyepiece may provide more details, it may be harder to keep an object in view, unless you are using a motorized mount. They also require the scope to gather more light to provide a clearer image.
A lower power eyepiece makes it easier to find objects and keep them in view. Lower magnification eyepieces require less light, so viewing dimmer objects is easier. You may keep adding eyepieces as they are not very expensive.
Lastly
Why are Images mostly upside-down in most scopes (except in Refractor scopes) -
One of the most surprising discoveries first-time telescope owners will find is that images may appear upside-down or backwards depending on the type of telescope. The first thought is the telescope is broken - when in fact it is working perfectly normal. Depending on the type of telescope images may appear correct, upside-down, rotated, or inversed from left to right.
Why is this? Why would I want to see everything incorrectly? For astronomical viewing, it is not important whether an object is shown correctly. In space there is no up or down. Besides, Saturn is not something you see everyday and you would not know if it was upside-down or not. A Tree, Building, Person or an Automobile for example would be important to see correctly. When you view an automobile upside-down, you recognize that this is not correct. Lets talk about the different types of telescopes and how the orientation of the image is observed through them and what you can do to correct it for land use.
Refractor and Cassegrain telescopes will produce an image that is upside down when used without a diagonal. When a diagonal is used the image will be corrected right side up, but backwards from left to right. It will look like trying to read a sign in a mirror. There are special diagonals called Erect Image Prism diagonals that can correct the backwards image for land use.
Newtonian Reflectors will produce an image that is upside down and are not recommended for land use. There are no ways to correct this with a Newtonian Reflector.
- http://www.telescopes.com/telescopes/imageorientationwhyiseverythingupsidedownarticle.cfm
And check out these excellent articles for further details:
http://media.skyandtelescope.com/documents/AboutScopes.pdf - Highly recommended to read
http://www.skyandtelescope.com/equipment/basics/12511616.html
What Kind of Telescope should I buy
http://www.astronomy.com/Equipment/How-To/2004/07/Buying a telescope.aspx
http://space.about.com/od/telescopesandoptics/p/6scopepoints.htm
http://space.about.com/od/telescopesandoptics/ht/telescopehowto.htm
http://www.telescopes.com/telescopes/howtoselectyourfirsttelescopearticle.cfm - Highly recommended
Happy Viewing
Terry
. Trust me ... the farther away (sky objects) we wish to point our scope - the tougher is it to get it stable on the viewfinder. But with patience - loads of it, you will be rewarded.
