If you are into astronomy, chances are you already know the purpose of a generic astronomical telescope.
Astronomical telescopes are telescopes best used for viewing planets and galaxy to locate celestial objects. The terrestrial telescope is used for viewing objects on the surface of the earth.
Reflector telescopes are major improvements upon the refractor telescope which reflected light instead of refracting it. This was because Reflector Telescopes used curved mirrors to capture an image as opposed to the Refractor Telescopes which used lenses. Reflector telescopes were considered to be superior to the refractor telescope design because of the enhanced chromatic quality and potential for an enlarged viewing diameter.
In terms of value for money, reflector telescopes cost you less for all the same benefits and features you get through other telescopes. Reflector telescopes are also known for being the perfect astrophotography tools.
Amateur and professional astronomers that are looking for large-aperture telescopes to capture deep-sky objects lean towards reflector telescopes to do the job.
There are two types of telescope curve mirrors.
- Concave Mirror
- Convex Mirror
A concave mirror is capable of forming the image of an object placed in front of its reflecting surface, and the image is either a real image or an inverted image.
A convex mirror is capable of forming a virtual, erect and diminished image of an object placed in front of the reflecting surface of the mirror. This is always so, no matter where the object is placed in front of the reflecting surface of the mirror.
Images through Double Convex Lenses in Telescopes
Double convex lenses are designed to have two focal points, one on either side of the lens. If a double convex lens is being used, one must remember to place objects at twice the focal length in order for them to be reflected. Therefore, the points F and 2F along the principal axis are considered as placement points for subjects under view.
When we are using mirrors, we must trace the rays falling on the lens to figure out what the final image will look like. These rays refract when they enter the lens, and hence the point where they converge is the actual point of image formation. In the figure below, we can see that the 1st ray approaches the lens parallel to the principal axis and gets refracted through the focal point. The 2nd ray also travels through the focal point and is then refracted parallel to the principal axis. The inverted image then forms on the right side of the lens.
The diagram above shows the situation when the object is outside 2F. In this situation, the image will be between F and 2F on the other side and will be inverted, diminished, and real. A real image is formed through convergence of rays that can be projected on a screen. That is, if you placed a sheet of paper at the image position, the image would actually appear on the paper.
If your subject of choice is placed between points F and 2F, the image will form past the point 2F on the other side of the lens. This image will be categorized as a real image because it will also be enlarged and inverted. You can do a ray-tracing like the one shown to demonstrate this is true.
If your subject is placed between F and the lens, an image will form on the same side of the lens as the placement of the object. This image will be categorized as a virtual image and it will be enlarged and upright.
For the secondary lens, make sure you have a 10 to 25 mm wide convex lens with a focal length of 70 mm highest.
Step 2: Prepare the Telescope Body
Get two corrugated paper sheets and make two cylinders with those sheets. But keep the radius different. Just make sure that one cylinder can slide inside another cylinder.
Use tape while building those cylinders.
An easy way to build the telescope body is by making the paper cylinders by wrapping around the lenses. Just put one lens on the paper sheet and start rolling it around the lens. Once the paper wraps your lens completely cut the rest of the paper. Or you could measure the circumference of the lens and prepare a paper sheet of that width.
After making the cylinders, comes the hard part. Now you have to insert the lenses into the cylinders. Cut a section of your cylinder and insert your lens through the cylinder.
Now you’ve got two cylinders with two lenses on those.
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