Galaxy's visible through a telescope

The diameter of the telescope is the most important aspect for a decent Telescope.(not the Magnification)

Just to give an idea,(using the NGC 2000 star Catalog) what is visible through the following size telescopes on a dark clear unpolluted night,(Northern and Southern Hemisphere's)with good eyesight.

Naked eye Magnitude 6 2Galaxy's
50mm Telescope Magnitude 9 36Galaxy's visible
75mm Telescope Magnitude 11 358 Galaxy's visible
100mm Telescope Magnitude12.2  
150mm Telescope Magnitude 13 2175 Galaxy's visible
200mm Telescope Magnitude14.2  
300mm Telescope Magnitude 15 6791 Galaxy's visible
400mm Telescope Magnitude16.1  

This means that you should look for the biggest diameter telescope you can afford with your budget. (not magnification)


Reflecting Telescope

The maximum usable magnification on any reflecting telescope should be 35x every 25mm Diameter of a telescope. A lot of telescopes are sold nowdays to customers with a maximum magnification way out of range. I have seen 50mm refractors been sold, displaying on the box 625x magnification. Yes that telescope might be able to do that magnification, but you would not be able to see any objects with such a magnification through a 50mm telescope. Reflecting telescopes is normaly better value for money and can get any size diameter without glass sging problems..

Telescope diameter
Maximum usable magnification
50mm Telescope
70x Max magnification
75mm Telescope
105x Max magnification
100mm Telescope
140x Max magnification
150mm Telescope
210x Max magnification
200mm Telescope
280x Max magnification
250mm Telescope
350x Max magnification

Refracting Telescope

The maximum usable magnification on any refracting telescope should be 50x every 25mm Diameter of a telescope. The refracting telescope does not have anycentral obstruction like the Reflecting telescopes. ED Aprocromatic refracting telescopes is also about 3x the price of a reflecting telescope but the quality is unmatched and stars is pinpoint. Refracting telescopes won't be bigger than 6" as you will start having problems with saging glass.

Telescope diameter
Maximum usable magnification
50mm Telescope
100x Max magnification
75mm Telescope
150x Max magnification
100mm Telescope
200x Max magnification
150mm Telescope
300x Max magnification
200mm Telescope
400x Max magnification
250mm Telescope
500x Max magnification

Do you know how to make your decision on what Telescope to buy.

Base your decision on the following factors:

1. What you want to do with the telescope.

a. Visual viewing and to learn the sky.

b. Astro photography.

c. Need scope for home or/and traveling.(size of scope)

2. Budget.

Eyepiece Calculator

This Calculator can be used to help you decide on what eyepiece to use for your specific telescope and/or object.

Telescope and diagonal Calculator

Tlar2 Telescope calculator.

Oldham Optical Very nice and easy designing Exel Spreadsheet.


Newtonian CAD program

Why Diagonal Offset is Needed

Notes on Telescope Design (from help files in Newt)


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