Here's a great first telescope

Sometimes it's cost that keeps us from getting started on a new journey. Here's a scope anyone can afford. If you can't afford it now just do a little recycling and you'll afford it soon enough. It's great for learning about telescopes, too. Read the text below the image for a little basic learning about telescopes.

This is a 42x scope and for the beginning explorer or for the professional wanting a great little instrument to keep in your car or truck.



This is the "spec sheet" on this telescope. Spec is short for specifications. The spec sheet tells you about focal lengththe F#, eyepiece diameter, etc. So, since this may be your first look at a telescope technical data specification sheet take a look and then we'll examine each line indivually.

Design: Newtonian Reflector
Diameter: 80mm
Focal Length: 550mm
F/#: 7
Eyepiece: 13mm
Magnification: 42x
FOV: 10
Length: 14 inches
Weight: 5 lbs.

Newtonian Reflector - this tells us that this a telescope which makes use of lenses and mirrors instead of just lenses. In another posting I said my first telescope was a refractor scope. That scope used only two lenses, one small to look through called the eyepiece and the other larger called the objective lense. This telescope uses an eyepiece to look through but everything else is handled by curved mirrors. The refractor telescope was invented by a Dutch eyeglass maker named Hans Lippershey in 1608. It was Isaac Newton who used mirrors to perfect the image. Reflector scopes give a clearer image because of the way they handle the light. More on that elswhere. Another type of scope popularized recently may be the Dobsonian named after a still living American from California by the name of John Dobson. More on Dobson elsewhere.

Diameter 80mm - this tells use the diameter of the primary mirror in this case. In some cases is gives the diameter of the primary mirror or the objective lense. In any case this refers to the largest optical compenent of these telescopes which are, in actuality, called the arpeture. There are two mirrors in this telescope: the primary mirror which we mentioned already is at the "bottom" of the tube and the secondary mirror which is mounted on the "spider" in front of the eyepiece. The secondary mirror aims the image into the eyepiece. (80MM is nearly 3.15 inches. There are 25.4 millimeters in 1 inch.)

Focal Length - is both simple and mildly complex. In it's simplest form it is the distance from the optical device (lense or mirror) to the point where the image is in focus. Anyone who has used a simple magnifying glass has dealt with focal length. In that case it is the distance from your eye to the lense where the object you are viewing appears to be in focus. The focal length of this scope is given as 550mm. Using the numbers we learned above we can determine that length in inches by dividing 550 by the number of mm per inch. So 550 / 25.4 = 21.654 inches. (Anytime you want to convert mm to inches just divide the number of mm by 25.4 - to convert from inches to millimeters multiply the number of inches by 25.4)

F# - shouldn't frighten or puzzle you like it did me because I'll teach you the simple definition! In fact it just uses the two numbers above to calculate. Simply divide the focal length by the arpeture. For this little telescope that would be 550 / 80 = 6.875 and rounded up to the nearest whole number would be 7. This is also referred to as the F/Stop or a focal ratio. The focal ratio is a more important number when it comes to photography. Specifically because the lower the F# the more light (or the lighter the image) is apparent in the image.

Eyepiece 13mm - describes the part you actually look into. On this telescope it is the part sticking out of the side of the tube near the large opening at the top. The eyepiece has a great deal of control over the field of view (FOV described below) and magnification. The field of view is simply how much you can see. For example with your eyes wide open and nothing interfering (obstructing) your sight your field of view is about 165 degrees more or less. If you put your hands on the side of your face to block what you can see you narrow (decrease or diminish) your field of view to about 50 degrees. The smaller the opening in the eyepiece the higher the magnification and the smaller the field of view. Using a smaller opening eyepiece such as a 10mm would increase the magnification and decrease the field of view.

Magnification 42x - is how many times larger the object appears through the telescope compared to just looking at it with your naked eyes (naked eyes means no help from a magnifying device). It is written as a number followed by a small x which is the international mathematic symbol for times (as in multiplication).

FOV 10 - tells us that the field of view we learned about above is 10 degrees. That means that what you see through the telescope is about 10 degrees of what you see with your naked eyes. 10 degrees is equal to about one width of your fist held at arm's length (with your arm fully extended). The moon, for example, is about .5 degrees (one half [1/2] of a degree) across as seen with your naked eyes. This means with this telescope in it's default (the way it comes) setup you would be able to see all of the moon with plenty to spare through the viewer.

Length 14 inches - is usally the length of the tube.

Weight 5lbs - us how force is required to keep the telescope off the ground ... but that's a physics lesson in the waiting.

If this explanation is still too difficult for you please feel free to post your questions and I or some real professional will answer as quickly as possible.