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Beginners Telescope

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#26 beanerds

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Posted 23 November 2013 - 07:28 AM

:cool: Good selection Joe , even tho these are way above the budget here they are better options and will keep you happy for years .
My personal choice here would be the 90mm refractor on the AZ3 mount , great scope .
Brian.

heres a few link that show better scope altho more than a $100 these can last a lot longer and make his viewing better much better.

http://www.khanscope...?productID=4384

http://www.khanscope...?productID=2146

http://www.khanscope...?productID=2212

http://www.khanscope...?productID=4389



#27 scopeboy42

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Posted 23 November 2013 - 09:57 AM

Why not buy a telescope made in India.

See:

http://www.sharpvisi...ia.com/prod.htm

Based on online currency converter $100 USD = Rs 6,270.

The Astro View model will be closest to your budget at Rs 6,000 (+500 p/f).

Hope this helps.

#28 JustaBoy

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Posted 23 November 2013 - 10:02 PM

I think one of those Sharp Vision scopes might keep someone happy for the time it takes to set it up, then...Not so much.

A real waste of money to buy a small aperture reflector like that when for around the same money you can get a refractor.

Please understand that the Obstructed Newtonian design does not scale well to very small apertures - You should consider a 3.5" to 4" Newtonian to be the minimum. - How do I know?...I've owned a 2.5", but more importantly have built many of various sizes. - Just to illuminate the field stop of a very modest 20mm eyepiece, the central obstruction must be an appreciable percentage of the primary's diameter in these very small sizes. - Not good.

I still say this one:

http://www.ebay.in/i...321346145?pt...

Good luck,

-Chuck

#29 SpooPoker

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Posted 24 November 2013 - 12:26 AM

The obstruction of the diagonal is one of the most overemphasized aspects of reflector type telescopes and one that yields itself more to myth than reality. Increasing a diagonal (relative to the primary) does not necessarily translate to a poorer image that is obvious through the eyepiece. To talk of the obstruction creating a large enough amount of shadowing on the primary and interference that would severely affect the quality of the image, one would be looking at obstruction ratio's over 0.4. Few if any companies routinely design telescopes with such a large diagonal relative to the primary mirror. Most of the time, the obstruction ratio for most designs is between 0.15 and 0.3. Both are entirely acceptable, and it would take a keen eyed observer to notice much of a difference. John Isaacs, a long time and prominent visual astronomer here uses predominantly fairly low focal ratio telescopes (and thus with so called large secondaries/diagonals) for all kinds of observations and I have never heard him complain his 12" f/4.5 is throwing up a poor image!

The most important aspect of the secondary size is that it is not too small, i.e. effectively stopping down the telescope aperture. Using some very simple design rules, it is possible to avoid this completely. Too large a diagonal can affect the image contrast and slightly dim the object, a conservative approach aiming to fully illuminate a .5" diameter field nearly always results in a very good all round telescope. Most, if not all, major brands/makers hit the .5" - 1" mark and this nearly always results in an aesthetically pleasing image.

A 3" f/10 Newt can be designed to accommodate a .75" diagonal, yielding an obstruction ratio of 0.25, which is respectable and would compare very well with a 70mm f/10 achromat. The refractor in this case would not give a major improvement in image quality or contrast (a slight improvement noticeable in the eyepiece perhaps to a keen eyed observer, but certainly not major). There is no particular advantage of the newtonian over the achromat, although an achromat could potentially throw up some false color on bright targets.

I personally would go with the 70mm achromat for a beginner scope. It will come on an easy to use ALT AZ mount and will be good to go out of the box.

#30 Arpita

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Posted 02 December 2013 - 11:50 AM

Hey thank you all for your replies...Atlast I have purchased Celestron Astromaster 70EQ for my husband :)






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