Telescope Optical

How should I select a telescope

The telescopes are categorized in three categories depending upon the optics used.

 

1. 1. Refractors use lenses as optics at both the ends of the tube to achieve Magnification. Galileo used a Refractor telescope around 400 years back. They are easy to use and require less maintenance, but on the other hand they are costly. The cost of the refractor rises exponentially as the size of the aperture(main lens) increases. Refractors are used for both planetary observations and
2. 2. Reflectors use primary and secondary mirror as main optics. Reflectors are economical as compared to Refractor telescopes. Reflectors are majorly used when big aperture is required to view deep sky objects due to its economical value. Reflectors are also used for Astro Photography.
3. 3. They are easy to use, compact and are power packed. They have large focal lengths to have better depth of the object, and the size of the tube is reduced drastically, thus it can be transported easily. It is also majorly used for Deep Sky Photography as well as Deep sky Visual Observation.
4. 4. A Dobsonian telescope is variation of an alt-azimuth mounted reflector telescope. Dobsonian telescopes are simple and easy to use. They are compact, rugged and portable and are great for deep sky viewing.

 

Q. What Is a Telescope Mount? Which one should I buy?

the base on which OTA (Optical tube assembly) is fixed. Fundamentally there are two types of Mounts

1. Equatorial
2. Altazimuth

 

Dobsonian mount is basically an Altazimuth mount.

GoTo or Computerised can be both Altazimuth and Equatorial.

 

All the above mounts can be controlled manually called Manual Mounts, through motor called Motorised Mounts and computerised called GoTo Mounts.

 

1. Manual: The movements are controlled manually. There are two types of movement which are called RA and DEC. RA movement is for achieving Azimuth movements or horizontal movements and DEC movements is for achieving altitude movements or vertical movements. But the movements are relative to the polar movement. It moves relative to polar axis movements.

 

1. Motorised: The movements are controlled by the help of gears which can be moved electronically to track the desired heavenly object.

 

1. GO TO: This is an automatic motorised machine which can point and track any object in the sky automatically with the help of a pre-fed database in its system. Hence the name GoTo. There are around 40,000 objects database normally fed in the system. The machine has to be initialised first by telling the co-ordinates (longitude and latitude) , local time and Altitude of North pole, where it is placed.  There are various other techniques to initialize the machine.

 

Q. What are Tripods?

 

Tripods: Tripods are stands on which the mounts are placed. Thus a Tripod supports a mount and the telescope/OTA. Tripods are of various types. Light or heavy, Aluminum or Stainless Steel.

 

Q. How do I configure/buy the right combination?

 

There are four basic elements of a telescope:

 

 

OTA: OTA is called Optical Tube Assembly and it contains the Optics part of the telscopes. It is the main part though which you observe the heavenly objects. It is recommended to have Small Refractor OTA's and have 6-8" Reflector OTA depending upon your budget. You can fit these OTA on your Mount with the help of Tube Rings and dovetail Plate. Refractors can be used for Planetary observation and Astrophotography and can also be used as a guide scope which doing Astrophotography.

 

 

Mount: A mount is the part of the telescope which holds the OTA and the tube is attached to the Mount, so that the desired movements can be achieved. Selecting your Mount is very important. An Altazimuth mount cannot be used for tracking and astrophotography, so it is recommended to choose an Equatorial Mount , then depending upon your budget go for Manual Tracking, Motorised Tracking or GoTo tracking. Atleast Motorised Tracking Mounts are recommended for AstroPhotography.

 

Eye Pieces: Eyepieces are the optical instrument which is used to view the Objects far in space. It provides Magnification depending upon the focal Length of the OTA. Plossal Eyepieces of all the ranges are recommended. The Eyepieces are available from 4mm, 6mm, 10mm, 12mm, 15mm, 20mm, 25mm, 30mm, and 40mm. Other wise a moderate range can be procured.Eyepieces come with two standard outer diameters: 1.25" and 2". Telescopes with focusers that do not comply with these sizes should be avoided, because you might not be able to buy separate eyepieces that are compatible with your telescope.

 

Q. Which devices are used for collimation?

 

Collimation is the adjustment of the position and orientation of optical elements within a telescope to achieve optimum performance. Poor collimation is the number one killer of telescope performance. Many people are intimidated by the prospect of collimating their telescopes and consequently will not attempt it. As a result many telescopes, with otherwise good optics, are left operating below their true optical capability. A laser collimator is by far the easiest technique and tool to collimate a telescope using red laser.

 

Eye Piece:

 

This collimating eyepiece is a combination of a sighting tube and Cheshire eyepiece. The sighting tube's narrow field of view and crosshairs provide a centering reference for the telescope's optical elements. The Cheshire eyepiece has a means of providing illumination to a target face (set at 45 degrees to the illuminating hole) that will be used to collimate the primary mirror.

 

Q. What is a laser Pointer and how it is used.

A is most commonly used to project a point of light to highlight items of interest during a presentation. Most laser pointers have low enough power that the projected beam presents a minimal hazard to eyes for incidental exposure. A beam of light is not in itself visible from the side, but only by light scattered by dust particles; the small width of the beam and low power of typical laser pointers makes the beam itself invisible in a reasonably clean atmosphere, showing a point of light when impinging on an opaque surface

What is Spotting Scope and where it is used.

 

Q. I am a beginner. How can I learn astronomy?

 

It is always suggested to join an Amateur Astronomy group in your area, where you can go and learn basics of Astronomy. For this reason we had initiated Astronomica, You can join Astronomica and be exposed to various kinds of equipments and meet people like you who are new to astronomy along with trained Astronomers.

About the Author

My name is sarvesh kumar. i am working as business developer E. Marketing in space group. we having deal as branded products of astronomy like telescopes, binoculars and all accessories of photography. space is a hub of astronomy products in Delhi India.

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