This document discusses telescope operation and design. It covers different types of telescope mounts including equatorial mounts, which allow viewing both celestial poles. It then describes the steps to set up a telescope mount and balance the telescope. Various techniques for observing the sky such as polar alignment and choosing observation times are explained. Details are provided on telescope components like eyepieces, objectives lenses, and hand controllers. Basic refracting telescope designs using PVC pipes are outlined. Key eyepiece specifications like apparent field of view, eye relief, and exit pupil are defined.

1. Telescope operation and
design
Antilen Jacob G
Project fellow, DST-SERB
Department of physics

2. Telescope mount
• A telescope mount is a mechanical structure which supports a
telescope, they design to support the mass and track the fixed stars.
• Fixed mounts, Fixed altitude mounts, Transit mounts, Altazimuth
mounts, Alt-alt (altitude-altitude) mounts, Equatorial mounts, Hexapod
mounts William Herschel's 49-inch (1,200 mm)
40-foot telescope on an altazimuth
mount.
Equatorial mount Dobsonian mount
Hexapod mount

3. Equatorial mount EQ6
• Payload Capacity 20 kg.
• Motor Drive 1.8° stepper motors .
• Slewing Speed up to 3.4°/sec (800X).

4. Steps before mounting telescope
• TRIPOD SET UP
• Place the tripod facing towards North
• Place a carpenter's level or bubble level
on the top of the tripod legs. Adjust the
height of each tripod leg until the tripod
head is properly leveled
• Slide the accessory tray along the
primary locking shaft until it pushes
against the tripod legs

5. Installing the Counterweights
• Loosen the counterweight rod lock knob and gently pull out the
counterweight rod. Re-tighten the lock knob to secure the
counterweight rod in place
• Locate the counterweights and slide them halfway along the
counterweight rod. Tighten the counterweight thumb screws to
secure.
Telescope Assembly
ATTACHING THE MOUNTING PLATE
ATTACHING THE TUBE RINGS
ATTACHING THE TELESCOPE MAIN TUBE TO THE
TUBE RINGS
ATTACHING THE FINDERSCOPE
BRACKET

6. Alignments
• Telescope weight balance, R.A. Balancing, Dec.
Balancing
• Polar Alignment
• Step 1: Orienting the Polar Scope Reticule
• Step 2: Aligning the Polar Scope Reticule
• Finder scope and telescope point

7. Pointing your telescope
• An Equatorial mount has an adjustment, sometimes called a
wedge, which tilts the mount's polar axis so that it points at
the appropriate Celestial Pole (NCP or SCP
• Do not reposition the mount base or change the latitude
setting you can skew the optical tube around the polar (R.A.)
and declination axes.
• Pointing to the NCP
• Pointing toward the western or eastern horizon

8. OBSERVING THE SKY
• Sky conditions
• seeing, or the steadiness of the air,
• and transparency
• Selecting an observing site
• away from city lights, and upwind from any source of air pollution. Always choose as high an
elevation as possible.
• Don’t try to observe any object when the light path passes near any protrusion on the ground
• Choosing the best time to observe
• Some of the best observing time is often in the early morning hours
• Cooling the telescope
• heat wave distortion inside telescope tube (tube currents), A rule of thumb is to allow 5
minutes per inch of aperture
• Adapting your eyes
• Do not expose your eyes to anything except red light for 30 minutes prior to observing, It is
important to observe with both eyes open. This avoids fatigue at the eyelens, The center of
your eye is the least sensitive to low light levels

9. hand controller
• The SynScan Hand Control also has the ability to connect to a
computer via an RS-232 cable
• Positioning Accuracy up to 1 arc minute. Accuracy enhanced
by software collimation error (mount mechanical error)
compensation
• Auto Guider Interface for astrophotography.
• Object database containing complete Messier, NGC, and IC
catalogue
• automatic slewing to 42900+ objects. Even an inexperienced
astronomer can master its variety of features in a few
observing sessions
• Stepper motors with 1.8° step angle and 64 micro steps
driven.

10. Simple Refractor telescope from pvc pipes
• Assemble Materials (PVC, Lens, Lens holder,
Couplers and reducer)
• Determine the focal length of lens
• Cutting the PVC pipes in proper dimension
• Sliding mechanism for adjusting the focal point

11. Choosing objective lens
• achromatic doublet lens for objective and eyepiece
• Typically, one element is a negative (concave) element made
out of flint glass such as F2, which has relatively high
dispersion, and the other is a positive (convex) element made of
crown glass such as BK7, which has lower dispersion.
• Best Galiloscope can go Max magnification of 40X.
J. Arthur Wetenkamp’s construction

12. Choosing eyepiece lens
• The eyepiece is of two lenses or lens combinations, of which
the one closer to the eye is termed the eye lens, while the other,
closer to the primary image formed by the objective, is termed
the field lens.
• The combination of the field lens and the eye lens is designed
so as to minimize or reduce the aberrations
• The function of the field lens is to bend the rays forming the
primary image, so that their divergence from the axis is
reduced, and to produce the first stage of magnification
• the eye is to be placed at the exit pupil of the eyepiece so as to
capture all the rays coming out of the latter
• Two forms of the eyepiece that were in common use in the
early days 1) Ramsden and 2) Huygens eyepieces
The Ramsden eyepiece The Huygens eyepiece
Kellner, Plössl, Orthoscopic,
Monocentric, Erfle, König,
RKE, Nagler

13. FIELD OF VIEW: APPARENT AND TRUE
• An eyepiece's Apparent Field of View (AFOV) is expressed in degrees (°). It is
how much of the sky is seen edge-to-edge through the eyepiece alone. AFOV's
range from narrow (25° - 30°) to an extra-wide angle (80° or more).
• An eyepiece's true field of view is the angle of sky seen through the eyepiece
when it's attached to the telescope
• 𝑇𝑟𝑢𝑒 𝑓𝑖𝑒𝑙𝑑 𝑓𝑜 𝑣𝑖𝑒𝑤 =
𝐴𝐹𝑂𝑉
𝑀
• For example, 2000 mm focal length and a 20 mm eyepiece with a 50° apparent
field. The magnification would be 2000 mm / 20 mm = 100x. The true field
would be 50100 or 0.5°

14. EYE RELIEF AND CORRECTIVE LENSES
• Eye Relief refers to the distance between your eye and
the eyepiece lens when the image is in focus
• Typically 18mm (varies from 14-20 mm)
• The shorter the focal length, the shorter the eye relief
• However, some of the more modern eyepiece designs
provide long-eye relief regardless of focal length, which
is especially beneficial to those who wear glasses
• the eye relief of an eyepiece is an important
specification to consider
Sufficient eye relief
Insufficient eye relief

15. EXIT PUPIL
• Exit pupil refers to the size of the bundle of light rays
coming out of the eyepiece
𝐸𝑥𝑖𝑡 𝑝𝑢𝑝𝑖𝑙 =
𝐴𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒
𝑀𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑖𝑡𝑜𝑛
• In order for all the light rays to enter your pupil, the exit
pupil must be smaller than the pupil of your eye
• A young person's fully dark-adapted eyes may have 7
mm-wide pupils. As you age, the maximum pupil diameter
decreases
• magnifications that yield an exit pupil in the range of 0.5
mm to 1.0 mm, empty magnification begins to set in, this
much magnification starts to degrade the image you see

16. Focal Length
• The purpose of an eyepiece is to magnify the image projected by the objective lens or mirror of a
telescope
• Magnification = Focal Length of Telescope / Focal Length of Eyepiece
• For example, a telescope with a focal length of 1200mm and an eyepiece of 12mm has a
magnification of 100x. With an eyepiece of 6mm focal length, it has a magnification of 200x.

17. Thank You