FAQ


Buy Telescope India
About Telescope - You Should Know
What is AstroPhotography?
How can I make video of what I see in the Sky?
What are the Imagers, their types and uses?
What are the Deep Sky Imagers?
What is Camera and Tripod Photography?
What is Prime Focus Photography?
What is Afocal Photography?
What Softwares are used for stacking Photographs their usages?
What attachments are used for Prime Focus Photography?
What attachments are used for Afocal Photography?
How many types of Telescopes?
What are the Various Combinations of Mounts, Tripods and OTA?
What is Polar Alignment and why it is required? What kind of a Mount is required to achieve it?
Which Books i can use to understand basic and advanced Astronomy?
What are Star Charts? How are they useful? From Where i can buy it?
What is OTA?
How should i invest in equipment so that it can be upgraded and re-used?
What is Eye Piece?
What is Astronomica?
What is Collimation?
Which devices are used for Collimation?
What is a laser Pointer and how it is used?
what is Spotting Scope and where it is used?
 
 
Q - About Telescope - You Should Know
Ans - The best way to choose your telescope, is to first attend a star party or an event or Join Astronomica where there are a few telescopes showcased. That will give you an idea of what a telescopes capabilities are and how binoculars compare with telescopes, or which is the best telescope to buy. In this article, we have tried to present some theoretical parameters that characterize a telescope, and a good understanding of these parameters will help you choose the right telescope for you.

There are quite a few important factors that determine the capabilities of a telescope:

Telescope Parameters

  • Telescope type
  • Aperture
  • Focal Length 
  • Type of mount
  • Motorization / Computer Control or GOTO
  • Compatibility with standard eyepieces
  • Cost


We shall now see how each parameter affects the capabilities of a telescope.

Telescope Type

There are many types of telescope which are classified as per the optics uesd. Telescope can be broadly classified as:

  • Refracting telescopes or Refractors
  • Reflecting telescopes or Reflectors
  • Catadioptric telescopes


Refractors use lenses to create an image of the faint / distant object. Reflectors use mirrors to focus an image of the object. Catadioptric telescopes use a combination of mirrors and lenses to create an image.

What are the pros and cons of each type? We will discuss refracting and reflecting telescopes as they are popular.

Refracting Telescopes

Refractor Telescopes use lenses to have image of the Object. Combination of lenses gives you required mangnification (hyp). Refractors are usually expensive because a well-engineered combination of several lenses is required to create a good image. Creation of Lenses are expensive because it consumes time and also requires a lot of engineering.

Refractors suffer from a defect called “Chromatic Abbaration”. This defect can be minimised by using special techniques to manufacture lenses and this results in “Achromatic Lenses” which again makes it expensive. But to remove chromatic abbaration so that the image is more crisp , Other techniques are used to create more error free lenses. Thus, there are two types of popular refractors:

  • Achromatic Refractors
  • Apochromatic Refractors or ED Scopes


An achromatic refractor will gives you  a quality image. Apochromatic lenses produce the most crisp images, and are ideal for photography of celestial objects. Apochromats are more expensive than Achromats.

Refractors are  not preferred for visual observations because as the aperture increases the cost increases exponentially, so only small aperture telescopes are used for visual observation to view planetary objects and close by objects.

Pros:

  • Very crisp image
  • Are usually portable
  • Ideal for astrophotography because the light gathered is more as compared to  Reflectors.


Cons:

  • Good apochromatic refractors are of huge cost.
  •  Small aperture Refractors can view only planets and bright celestial objects only.
  • They are expensive


Reflecting Telescopes

Reflecting telescopes produce an image by using combination of mirrors.

  • Newtonian reflector


Newtonian reflectors are the most popular for visual observing of distant celestial objects.

Newtonian Reflectors

This is the most popular design for visual observing. Newtonian reflectors have two mirrors - a "primary" concave (actually parabolic) mirror and a "secondary" flat mirror. The primary mirror gathers the light from the celestial object and focusses it. The secondary mirror only changes the direction of the light, so that it is suitable for viewing. Big Aperture Mirrors are economical as compared to big aperture Lenses and the cost reduces heavily. Newtonian reflectors are the most suitable for visual observing and can also be used for Photography.

Pros:

  • They are cheaper
  • They come in a large range of apertures, starting from small 3-inch apertures to more than 30-inch aperture.
  • They are ideal for visual observing
  • They can also be used for Astro Photography.
  • Desired Magnifications can be obtained by using various focal lengths.


Cons:

  • Image quality usually not as good as apochromatic reflectors
  • Are usually designed to produce inverted images
  • Collimation is not easy, which requires skill and technique to learn, but it is not that problametic, it can be learned easily. Various collimating tools are available to help in collimation.


Catadioptric Telescopes

This design is usually preferred for astrophotography of small celestial objects. This design accomodates long focal lengths in a shorter tube length, making it less bulky. A favourite amongst astrophotographers.

To summarize:Schmidt Cassegrains are suitable when you want large magnifications, especially for photography.

Pros:

  • Large magnifications with small sizes
  • Ideal for photographing small objects.


Cons:
  • Expensive than Reflectors


Aperture

The clear aperture of a telescope is the diameter of the objective lens or primary mirror specified in either inches or millimeters (mm). The larger the aperture, the more light it collects and the brighter (and better) the image will be. Greater detail and image clarity will be apparent as aperture increases. In astronomical telescopes, the light-gathering power is more important than magnification.

The light-gathering ability of a telescope varies as the square of the diameter of its aperture. Which means that a 8" telescope is 4 times more powerful than a 4" telescope, which in turn is 4 times more powerful than a 2" telescope.

To summarize: Larger aperture helps you view objects more clearer by gathering more light from teh object.

Pros:

  • Larger aperture show more detail
  • Larger aperture increases contrast
  • Larger aperture shows fainter objects, more distant galaxies
  • Large aperture is ideal for deep-sky observing (seeing galaxies, nebulae, star clusters etc.)


Cons:

  • Larger aperture costs more
  • Larger aperture makes telescopes bulky


Focal Length

Focal length, usually measured in mm, refers to the focal length of the primary optical element (objective lens in refractors, primary mirror in reflectors). Larger focal length gives more magnification with the same eyepiece. Smaller focal length gives more field-of-view with the same eyepiece, but less magnification.

To observe planets in great detail, an objective with a long focal length and high optical quality is preferred. To observe deep-sky objects, an objective with a short focal length is preferred.

Most telescope users would like to see both planets and deep-sky objects, so intermediate focal lengths are preferred. A focal length of anywhere between 40" (about 1000mm) and 64" (about 1600mm) is preferrable. Magnification (HYP) can always be increased or decreased by changing the eyepiece.

Astrophotographers who want to photograph small objects will prefer long focal lengths and go in for Schmidt Cassegrain telescopes to reduce the bulkiness of the telescopes.

Pros:

  • Long focal length will increase magnification
  • Long focal length will reduce optical defects (abberations) like Coma
  • Long focal lengths are easier to make and usually reduce cost


Cons:

  • Longer focal lengths cause telescopes to be bulky (unless they are Cassegrains)
  • Longer focal lengths expose defects in the objective element
  • Longer focal lengths limit the field of view


Type of Mount

There are two basic classes of telescope mounts:

  • Equatorial Mounts
  • Altazimuth Mounts


Equatorial mounts are required for photographing celestial objects, and for tracking objects as they drift across the sky.

Altazimuth mounts are ideal for observing as they are simple to operate. A type of Altazimuth mount called the 'Dobsonian Mount' is very popular for visual observing. Most large Newtonian Reflectors use Dobsonian mounts.

Pros of Equatorial Mount

  • Tracking of sky objects is possible
  • Astrophotography is possible


Cons of Equatorial Mount

  • Expensive
  • Heavy
  • Cumbersome to use for visual observing


Pros of Altazimuth Mount

  • Cheaper
  • Easy to operate
  • Ideal for visual observing


Cons of Altazimuth Mount

  • Cannot track, and hence unsuitable for astrophotography


Motorization / Computer Control

Motorization is usually required for astrophotography setups, except when doing wide-field astrophotography. Computer control is hardly ever required, unless you want to slew to objects automatically, rather than finding them manually.

To summarize:

Motorization is required for astrophotography, except for wide-field astrophotography.

Compatibility with Standard Eyepieces

Eyepieces come with two standard outer diameters: 1.25" and 2". Telescopes with focussers 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.
Buying a Telescope – Recommendations


For Visual Observing

It is ideal that a beginner should not focus on planetary observing unless he is planning to do research on them. The planets, and bright "stellar" planetary nebulae are limited in number and hence only few objects can be studied with a planetary (long-focal-length) telescope.

Newtonian Reflector telescopes on Dobsonian or other Altazimuth mounts are ideal for visual observing.
For Planetary Observing

A telescope with very high optical quality and long focal length with moderate apertures is ideal to study planets and planetary nebulae in great detail.

For General Purpose Observing

Choose an aperture as large as your budget can accomodate. Choose reasonable optical quality upto 6" of aperture, good optical quality for upto 12" and very high optical quality for larger telescopes. Buy an eyepiece of very short focal length (4.8mm), of a very good design (Nagler / Panoptic / Ethos) if your budget permits. For lower budgets, cheaper Barlow lenses and low-grade eyepieces can help instead. Focal length could be in the range of 1000mm to 2000mm.

Beginner's Telescope

Choose an aperture of 4" - 8", unless you plan to observe faint objects, or your budget can fit in more. Choose a moderate focal length. A focal length that is 8 to 10 times the aperture diameter should do. Ensure that the focusser is either 1.25" or 2" in barrel diameter.

For Astrophotography

A normal Refractor, Achromat or  apochromatic refractor and/or a Schmidt Cassegrain telescope of high optical quality, with Motorized/GoTo equatorial mount are ideal for astrophotography. For Schmidt Cassegrains, choose an optimum aperture and high optical quality.
 
Q - What is AstroPhotography?
Ans - Astrophotography is a specialized type of photography that involves making photographs of astronomical objects in the sky such as the Moon, Sun, planets, stars, and deep sky objects such as star clusters and galaxies. Astrophotography ranges from simple images of bright objects like sun/moon to very complex exposures designed to reveal objects that are too faint to observe with the naked eye e.g. faint nebulosity . With only a few exceptions, almost all astrophotography employs long exposures since both film and digital cameras can accumulate and sum light photons over long periods of time. This is just one of many distinct aspects of astrophotography that sets it apart from conventional photography.

Astrophotography poses challenges that are distinct from normal photography, because most subjects are usually quite faint, and are often small in angular size so the astrophotographer requires skills far more than what is required in normal photography.
 
Q - How can I make video of what I see in the Sky?
Ans - As the objects to be clicked are very faint, one cannot make the videos of these objects like we do in normal photography where one can throw light on the subject while making a video. Light levels are too low in the skies so different techniques are used to shoot the objects barring the bright objects like Sun and moon which have got much light. There are other ways to make astronomy videos by stacking the still images to make animations also.
 
Q - What are the Imagers, their types and uses?
Ans - Imagers are devices which capture the faint light from heavens (skies). These can be camera, web camera or any other device which converts light into information.
 
Q - What are the Deep Sky Imagers?
Ans - Deep sky imagers are special ccd devices which allow one to capture deep sky objects as galaxies, nebulae, star clusters, comets etc on the chip and convert the light in to digital information which then can be processed in different photo processing softwares.
 
Q - What is Camera and Tripod Photography?
Ans - This is the simplest form of astrophotography in which one makes use of the camera and a mount. As we require exposures of longer duration in astrophotography, we cannot just simply use the camera in hand as it will introduce shake in the image. Generally any exposure of less than 1/30th of a second requires a mount on which camera can be put and the image can be taken without the shake. To take longer exposure like star trails one need to put it on mount (tripod). Various interesting astophotos can be clicked using this method as seen in following images.
 
Q - What is Prime Focus Photography?
Ans - Next step in astrophotography is Prime focus photography where the camera (with its mail lens removed) is attached to the telescope and use the lens or mirror of the telescope as the main lens. So a SLR camera is a must for this type of photography. For "prime focus" photography you remove the camera lens and the telescope eyepiece and mechanically couple the camera body to the telescope. Usually a "T" ring and "T" ring adapter is used to attach the camera to the telescope focuser. One can shoot the whole moon in one frame for most of the available focal lengths in the telescopes. E.g. a 1000mm focal length lens will give an image of full Moon of 9mm dia on the film frame and of 23mm on DSLR.
 
Q - What is Afocal Photography?
Ans - Afocal projection is a method that uses both the camera lens and the telescope eyepiece. The camera is focused on infinity and merely held up to the eyepiece. This can be a wonderful way to take pictures of the moon and sun with film or with that new digital camera that you just bought. If you are taking pictures of the sun you must use a full aperture solar filter or you could ruin your camera, your telescope or your eyes. This method is very easy and is especially applicable to those of you who have a Dobsonian mount telescope. The exposures of the moon and sun are short so no tracking is necessary.
 
Q - What Softwares are used for stacking Photographs their usages?
Ans - Once the images are taken and stored in a DSLR or incase of a film camera, images are printed and scanned, any number of post-processing operations may be performed on them. In astrophotography, much liberty is taken with the enhancement of images, including noise reduction (by "stacking" several similar images), and contrast and saturation enhancement. Several software packages exist specifically for this purpose. Registax, Deepsky stacker, startrails are few of these.
 
Q - What attachments are used for Prime Focus Photography?
Ans - One needs T adaptors and T rings for their particular SLR cameras.
 
Q - What attachments are used for Afocal Photography?
Ans - You need afocal adaptor for the camera and telescope for the acfocal photography.
 
Q - How many types of Telescopes?
Ans - The telescopes are categorized in three categories depending upon the optics used.

1. Refractor : Refractors are made of lenses to achieve Magnification. Refractors are easy to use and requires less maintenance on the other hand they are costly. The cost of the refractor rises exponentially as the aperture increases. It is recommended to have planetary observation , use refractor and for Photography Refractors are used. Please Visit Knowledge Base for more details.

2. Reflector: Reflectors use Primary and Secondary Mirror as main Optics. Reflectors are economical as compared to refractors. Reflectors are majorly used when big aperture is required to view deep sky objects due to its economical value. Reflectors are also used for Photography. Please Visit Knowledge Base for more details.

3. Catadioptric: are easy to use , compact but are power packed, they have good 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 Visual Observation. Please Visit Knowledge Base for more details.
 
Q - What are the Various Combinations of Mounts, Tripods and OTA?
Ans - 1. MOUNT : This is the base on which Optical tube assembly (OTA) is fixed. there are various kinds of mounts. There are two types of Mounts

  1. Equatorial
  2. Altazimuth
  3. Dobsonian are basically Altazimuth mounts
  4. GoTo or Computerised can be both Altazimuth and Equitorial

All the above mounts can be controlled Manually, through Motor (Motorised) and Computerised (GoTo).

a) Manual : The movements are controlled manually. There are two types of Movement which are callled RA and DEC. RA movement is for achieving Azimuth movemts 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.

EQ5 Mount Photograph  

b) Motorised:
The movements are controlled by the help of Gears which can be moved Electronically to track the desired heavenly object.  GE Mount Photograph

c) GO TO: This is automatic motorised machine which points to and tracks any object in the sky automatically, because the location is already fed in the system. there are around 40,000 objects database normally fed in the system. these systems are called the go to system because you simply order the  machine to GOTO  a planet or a nebulae and it automatically points there. Of course the machine has to be initialised first by telling the co-ordinates where it is placed or there are various techniques to initialize the machine. GOTO MOUNT PHotograph

d) Tripods : Stands are of various types Wooden, Aluminium, Stainless Steel Tube Pipe etc. Mounts are placed on Stands also called a Tripod.


2. OTA : Optical Tube Assembly, is the telescope tube which contains Optics and can be mounted on a stand and mount. There is one universal formula that the bigger the diameter of the optics the better is the result. The dia is measured in Millimeters (mm) or inches . There are around 25 mm in one inch. so if we say 100mm telescope it is equivalent to 4 " dia.
 
Q - What is Polar Alignment and why it is required? What kind of a Mount is required to achieve it?
Ans - Polar alignment is the act of aligning the rotational axis of a telescope's equatorial mount in parallel with that of the Earth . The polar axis of the telescope must be made parallel to the Earth's axis of rotation, called the North Celestial Pole (NCP) for Northern Hemisphere. When this is accomplished, the sky's motion can be cancelled out simply by turning the axis (either by hand or with a motor drive) at the same rate as the rotation of the Earth, but in the opposite direction. Although residents of the northern hemisphere are convenienced with a bright star (Polaris) less than a degree from Earth's rotational axis, the NCP can still be a somewhat elusive place to locate.

The North Celestial Pole (NCP) is the point in the sky around which all the stars appear to rotate. The star Polaris lies less than a degree from the NCP and it can be used to roughly polar align a telescope. However, for accurate polar alignment, the polar axis of the telescope's mount needs to be aligned to the true NCP.
 
Q - Which Books i can use to understand basic and advanced Astronomy?
Ans - 1. Norotn Sky Atlas
2. Pocket Sky Atlas by Roger Sinnot Sky
3. Atlas 2000 by Wiltirion Night Sky Atlas- Philips company
4. Collins Star Atlas/guide Book
5. UranoMetria
6. Astrophotography Manuals
7. Collimation Treatise
8. Hatfield Lunar Atlas-cook
9. Celestial sites celestial splendour-Burlillier
10. Voyages through Universe-Wolff
11. Seeing Stars-Forrest
12. Cambridge Guide to Stars and Planets-Patrick Moore
13. Beginner Giude To Universe-Coleman
14. Cosmic Perfection-voit
15. Stargazing-Patrick moore
16. Universe-Kuffman

Name Author Publisher
Universe Gribbin, John PENGUIN GROUP (UK)
The Stargazer's Handbook Sparrow, Giles Penguin Books India
Pocket Nature - Night Sky   Penguin Group (UK)/Dorling Kindersley
Encyclopaedia Of Astronomy And Space Science Bhardwaj, Anandi Anmol Publications pvt. ltd.
Space : Our Final Frontier Gribbin, John BBC
Stargazing Harper collins  
The Early Universe facts and fiction Borner,Gerhard Springer-verlag
Atlas of the Universe Moore Cambridge University Press
The Heavens on fire - The Great Leonid Meteor Storms Littmann, Mark Cambridge University Press
Exploring the Moon - The Apollo Expeditions Harland Springer-verlag
 
Q - What are Star Charts? How are they useful? From Where i can buy it?
Ans - Just like the map of any city, country or earth helps us to find a location correctly similarly we require the star charts to find objects in the skies. Akin to longitude and latitude on earth which helps us to find the location, RA and declination are used to pinpoint an object in the skies. These star charts let us find the heavenly bodies in the skies.
 
Q - What is OTA?
Ans - Optical Tube Assembly, is the telescope tube which contains Optics and can be mounted on a stand and mount. There is one universal formula that the bigger the diameter of the optics the better is the result. The dia is measured in Millimeters (mm) or inches . There are around 25 mm in one inch. so if we say 100mm telescope it is equivalent to 4 " dia.
 
Q - How should i invest in equipment so that it can be upgraded and re-used?
Ans - There basic elements of a telescope are:

1. Mount & Tripod

2. OTA

Mount: Select your Mount first. An altazimuth mount cannot be used for tracking and astrophotography, so it is recommended to choose an Equitorial Mount , then depending upon your budget go for Manual Tracking, Motorised Tracking or GoTo tracking. It is recommended to selected Motorised Tracking Mounts.

OTA: It is recommened 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.
 
Q - What is Eye Piece?
Ans - Plossal Eyepiece of all the ranges are recommended to have. The Eyepieces are available from 4mm, 6mm, 10mm, 12mm, 15mm, 20mm, 25mm, 30mm, 40mm. Other wise a moderate range can be procured.

Eyepieces come with two standard outer diameters: 1.25" and 2". Telescopes with focussers 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 - What is Astronomica?
Ans - Our co. has introduced a unique concept of Providing a Astronomy club membership free with purchase of any telescope which is unmatched and unparallel. This club caters to a group of amateur astronomers by facilitating them to visit dark skies and arrange a meet with our team of professional astronomers and astro photographers, where they can learn concepts of astronomy and enhance their skills about photography. Not only that they get a regular email alerts about the latest happening in the feild of Astronomy. They can take part in a formal chat group Provided by our initiative called "Astronomica". We provide them a platform where they can take part in all National and International Events, conferences and can be a part in the scientific experiments whenever solar and Luncar Eclipses takes place in any part of the world. Please visit www.astronomica.in for more details.
 
Q - What is Collimation?
Ans - The proper alignment of the optical elements in a telescope is called collimation. Collimation is critical for achieving optimum results. Poor collimation will result in optical aberrations and distorted images. Not only is the alignment of the optical elements important but even more important is the alignment of the optics with the mechanical tube-this is called opto/mechanical alignment. Please visit http://web.telia.com/~u41105032/kolli/kolli.html for more details.
 
Q - Which devices are used for Collimation?
Ans - Laser Collimator : 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.

Cheshire collimation 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?
Ans - A laser pointer 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
 
Q - What is Spotting Scope and where it is used?
Ans - I am a Novice . 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. Please visit www.astronomica.in for more details.
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