Observational Parameters by Santosh Takale at MU Astro Basic (11-09-2022).pdf

OBSERVATIONAL PARAMETERS
SANTOSH TAKALE
B. Tech (Mech. Engg.), Scientific Officer,
Bhabha Atomic Research Centre, Mumbai,
09967584554 / santoshatbarc@gmail.com
Free of Cost

This presentation is the compilation of data & details from
Internet as well as few good books. The intent is to spread
the awareness among masses about the facts about ‘Our
Universe & Sky Observation’ and also to eradicate all
myths about the same.
Using similar presentation approximately 2750 nos. of sessions
have been conducted by me, addressing more than 9,00,000
audience, which includes students, teachers & other general
members of public in ALL UT/States of India. All these session
were free of cost with only interest of ‘Science Communication’
& No financial gain in any form has been made by me.
For additional details please refer the mentioned websites or
books.
Dear Participants,
--- Santosh Takale

Astronomy Studies
• Theoretical
• Observational
– Field Observation
• Star Gazing (NESO)
• Telescopic Observation
– Required theoretical Aspects
Santosh Takale (santoshatbarc@gmail.com 9967584554)

Field Observation :
• What we are Looking for ?
– Constellations
– Nakshtras
– Sunsigns
– Planets
– Notable Stars
– Meteor Shower
– Galaxies, Dwarf Galaxies
– Messier Objects, Nebulae, Star Clusters etc.

Constellations :
….. refers constellation with better visibility in normal sky conditions

Andromeda Constellation & Andromeda Galaxy :

Andromeda Constellation :

Ara Constellation :

Camelopardalis Constellation :

Canes Venarici Constellation :

Canis Minor Constellation :

Constellations :

Carina Constellation :

For 11-09-2022 (Starting from West………to East.
&. South to North at 20 Hrs, Panvel, Mumbai. MH, India.
• Centaurus, Virgo, Mercury, Coma Berenices
• Circinus, Lupus, Libra, Bootes, Canes Venatici
• Norma, Scorpius, Ophiuchus, Serpens, Corona Borealis, Ursa Major
• Triangulum Australe, Ara, Scorpius, Serpens, Hercules, Draco, Ursa MI
• Pavo, Telescopium, Corona Australe, Sagittarius, Scutum, Aquila, Lyra,
Draco, Umi
• Indus, Microscopium, Capricornus, Saturn, Equueus, Delphinus,
Vulpecula, Cygnus, Draco, Umi

&. South to North at 00 Hrs, Panvel, Mumbai. MH, India.
• Indus, Microscopium, Capricornus, Saturn, Equueus, Delphinus,
Vulpecula, Cygnus, Draco, Umi
• Tucana, Grus, Piscis Austrinus, Aquarius (Aquariids), Pegasus, Lacerta,
Cepheus, Umi
• Achernar, Phoenix, Sculptor, Cetus, Moon, Jupiter, Pisces, Pegasus,
Andromeda, Lacerta,, Cepheus, Umi
• Hydrus, Reticulum, Horologium, Eridanus, Fornax, Cetus, Uranus, Aries,
Triangulum, Perseus, Cassiopeia, Camelopardalis, Umi

&. South to North at 05.30 Hrs, Panvel, Mumbai. MH, India.
• Hydrus, Reticulum, Horologium, Eridanus, Fornax, Cetus, Uranus, Aries,
Triangulum, Perseus, Cassiopeia, Camelopardalis, Umi
• Mensa, Dorado, Caelum, Eridanus, Taurus, Mars
• Volans, Pictor, Carina, Columba, Lepus, Orion, Auriga, Umi
• Carina, Puppis, Canis Mj, Monoceros, Cmi, Gemini, Lynx, Ursa Major
• Vela, Pyxis, Hydra, Sextans, Venus, Leo, Leo Mi
------- Sun Rise --------
• Crux, Antlia, Hydra, Crater, Corvus, Virgo, Sun, Leo, Canes Venetice, Coma
Berenices, Draco, Umi

Planets & Titius–Bode law :
Planet k
T-B rule
distance
(AU)
Real distance
(AU)
Mercury 0 0.4 0.39
Venus 1 0.7 0.72
Earth 2 1.0 1.00
Mars 4 1.6 1.52
Ceres1 8 2.8 2.77
Jupiter 16 5.2 5.20
Saturn 32 10.0 9.54
Uranus 64 19.6 19.2
Neptune 128 38.8 30.06
Pluto2 256 77.22 39.44

Notable Stars :
Common Name Distance (LY) App Mag Abs Mag Spectral Type
Sun - -26.72 4.8 G2V
Sirius 8.6 -1.46 1.4 A1Vm
Canopus 74 -0.72 -2.5 A9II
Rigil Kentaurus 4.3 -0.27 4.4 G2V + K1V
Arcturus 34 -0.04 0.2 K1.5IIIp
Vega 25 0.03 0.6 A0Va
Capella 41 0.08 0.4 G6III + G2III
Rigel ~1400 0.12 -8.1 B81ae
Procyon 11.4 0.38 2.6 F5IV-V
Achernar 69 0.46 -1.3 B3Vnp
Betelgeuse ~1400 0.50 (var.) -7.2 M2Iab
Hadar 320 0.61 (var.) -4.4 B1III
Acrux 510 0.76 -4.6 B0.5Iv + B1Vn
Altair 16 0.77 2.3 A7Vn
Aldebaran 60 0.85 (var.) -0.3 K5III
Antares ~520 0.96 (var.) -5.2 M1.5Iab
Spica 220 0.98 (var.) -3.2 B1V
Pollux 40 1.14 0.7 K0IIIb
Fomalhaut 22 1.16 2.0 A3Va
Becrux 460 1.25 (var.) -4.7 B0.5III
Deneb 1500 1.25 -7.2 A2Ia
Regulus 69 1.35 -0.3 B7Vn

Field Observation Aspects
• What are the references ?
– Horizon
– Directions
– Pole Star
– Some known objects (constelln)
– Planetary Position
• Aids / Accessories
– Star Maps
– Software : Stellarium, Celestia
– Binocular & Telescopes

• Measuring Sky with Deg, Min & Seconds ?
– Pole Star at 19 degree from horizon (Mum)
– Full Moon /Sun – 0.5 degree (30 min) Link
– M44 ( Beehive cluster) – 90 min
– Smallest constelln (Crux) – 68.45 sq deg
– Biggest Constelln (Hydra) – 1304 sq deg
• Thumb Rules for Degree measurement :
– Fist 10 deg, Raised Thumb 5 deg
– Raised Thumb with little finger & Fist 19 deg
– Mumbai : 19 deg Latt. & 72 deg Long.
– India betn : 68-7’ to 97-25’ & 8-4’ to 37-6’ (Long & Latt)

• Guide lines for Sky observations :
– Wait & Watch (7 to 10 minutes for eyes to acclimatize)
– Initialize sky observation from Home terrace
• A, B, C, S of Sky observations?
– A : Aviation Head lights
– B : Migratory Birds
– C : Clouds
– S : Space awareness

Required Theoretical Aspects
• Distances & Units ?
• Velocities of celestial Objects ?
• Techniques of measurements & Limits ?
• Magnitude, Scales & Calculations ?
• HR, Planck & Wien’s ?
• Colour Index ?
• Standard Candles ?

Distances & Units
• mm, cm, inch, feet, yard, meter, furlong, km, miles .
• AU, LY, Parsec.
• Pico, nano, micro, mili, Kilo, mega, giga, tera.
• Avg. Human Height : 1.5 to 2 meter.
• Plane fly at : 10 kms. (Mt Everest 9 kms)
• India : 3000 EW x 2700 NS (kms x kms)
• Diameter of earth : 12700 kms.
• Dia of Geosta. satellite orbit : 1 00 000 kms.
• Dist to moon from earth : 3 84 000 kms.
• Dia of Sun : 13 92 000 kms
• Distance to sun from earth : 15 00 00 000 kms (ie. 1 AU)
• Distance to sun from Jupiter : 1 00 00 00 000 kms (ie. 7 AU)

Distances & Units
• Distance to sun from pluto : 40 AU.
• Distance to sun from kupier belt : 700 AU.
• Oort’s cloud is up to : 20000 AU
• One Light year (1 Ly) : 63271 AU = 1 x 1016 mts
• One parsec (Pc) : 3.26 Ly = 206265 AU
• The nearest star to us : 4.3 Ly
• 10 Parsec : 32.6 Ly = 3.26 x 1017 mts
• Center of galaxy from us : 8.5 kpc
(beyond reach of parallax method)
• Dia of Milky way : 1 Lac Ly = 30 kpc = 1021mts
• Dia of Andromeda : 1.8 Lac Ly
• Dist betn Andromeda & MW : 22 Lac Ly
• Dia of Local Cluster of galaxy : 1 Mpc
• Span of Universe : 15 billion Ly = 1.5 x 1023 kms

Distances & Units
• Age & Span/Size of Universe :
– 1919 : Age: Infinite / Size: 300,000 Light Years
– 1929 : Age: 2 Billion Years / Size: 280 Million Light Years
– 1955 : Age: 6 Billion Years / Size: 4 Billion Light Years
– 1965 : Age: 10-25 Billion Years / Size: 25 Billion Light Years
– 1993 : Age: 12-20 Billion Years / Size: 30 Billion Light Years
– 2006 : Age: 13.7 Billion Years / Size: 94 Billion Light Years
– https://imagine.gsfc.nasa.gov/educators/programs/cosmictimes/educators/guide/age_size.html

• Point on Earth Surface :
• Velocity (kms/ hr) = Dist / Time = 12700 x 3.142 / 24
• Velocity (kms/ sec) = 12700 x 3.142 / (24 x 3600) = 0.5 kms / sec
• Point on Sun Surface :
• Velocity (kms/ hr) = Dist / Time = 13 92 000 x 3.142 / (25 x 24)
• Velocity (kms/ sec) = 13 92 000 x 3.142 / (25 x 24 x 3600) = 2.2 kms / sec
• Point on Altair Surface :
• Velocity (kms/ hr) = Dist / Time = 1.5 x 13 92 000 x 3.142 / (6.5)
• Velocity (kms/ sec) = 1.5 x 13 92 000 x 3.142 / (6.5 x 3600) = 280 kms / sec
• Earth around Sun :
• Velocity (kms/ hr) = Dist / Time = 2 x 15 x 107 x 3.142 / (365 x 24)
• Velocity (kms/ sec) = 2 x 15 x 107 x 3.142 / (365 x 24 x 3600) = 30 kms / sec
• Sun in Milky way :
• Orbit dia = 30000 Ly, Period is 240 million Yr.
• Velocity : 486000 miles / hr
: 220 Kms / Sec
Velocity Calculations

Convenient Units in Astronomy
• Astronomical Unit (A.U.)
– The average distance between the sun and the Earth
– 150 million km  1.5 x 108 km
– Useful for planetary distances
• Light Year
– The distance covered by light in 1 year
– Approximately 1013km = 1016m
• Parsec
– The distance at which 1A.U. subtends parallax of 1 arc second

Distance to nearest stars
Name
Distance
(LY)
Spectral
Type
R.A. Dec.
Luminosity
(Solar Units)
Proxima Centauri 4.2 M5V 14 30 -62 41 6 x 10-6
Alpha Centauri A 4.3 G2V 14 33 -60 50 1.5
Alpha Centauri B 4.3 K0V 14 33 -60 50 0.5
Barnard's Star 6.0 M4V 17 57 +04 33 4 x 10-4
Wolf 359 (Gliese 406) 7.8 M6V 10 56 +07 03 2 x 10-5
Lalande 21185 (HD 95735) 8.2 M2V 11 04 +36 02 5 x 10-3
Luyten 726-8 A 8.6 M5V 01 38 -17 58 6 x 10-5
Luyten 726-8 B (UV Ceti) 8.6 M6V 01 38 -17 58 4 x 10-5
Sirius A 8.6 A1V 06 45 -16 43 24
Sirius B 8.6 WD 06 45 -16 43 3 x 10-3
Ross 154 (Gliese 729) 9.6 M4V 18 50 -23 49 5 x 10-4
Ross 248 (Gliese 905) 10.3 M6V 23 42 +44 12 1 x 10-4
Epsilon Eridani 10.7 K2V 03 33 -09 27 0.3

Distances measurement of Celestial bodies :
• Radar - measuring distances in our solar system
• Parallax - measuring distances to nearby stars
• Cepheids - measuring distances in our Galaxy and to
nearby galaxies
• Supernovae - measuring distances to other galaxies
• Hubble's Law - measuring distances to objects far away

What is parallax? arcsec
p
Dpc
1

Techniques of measurements

• Basics of Parallax :
• Arc (S ) = radii (r) x angle (p) …{ angle is physically measured, Arc is dist
bet S & E, radii is dist bet Earth & star }
• r = S/p x 360/(2 x pi) in degrees ... { 1 deg = 3600 sec}
• r = S/p x 3600 x 360 /(2 x pi) … { p is in arcsec}
• r = 206265 x S/p … { p is in arcsec}
• r = 206265 AU / p (arcsec)
• r = 1 parsec = 206265 x 15,00,00,000 kms = r / 9.46 x 1012 Ly = 3.26 Ly
• Distance in parsec Dpc = 1/p (arc sec)
• 1pc = 3.26ly = 206265 A.U.
b
Techniques of measurements
• For stars having co-latitude b :
Measured change = True change / cos b
• Parallax method is reliable up to about 1kpc

• Magnitude scale – Originally by Hipparchus :
– After the sunset the first set of stars to be seen were 1st magnitude
stars, then 2nd, 3rd, … magnitude stars are visible.
– Hence the brightest stars are 1st magnitude while the faintest stars are
6th magnitude stars.
• When quantitative studies was done with the visual
appearance and the amount of light received from the
stars it was observed that the magnitudes are
logarithmically related to the flux of light emitted by the
stars.
Magnitude, Scales & Calculations

• The flux l is defined as the amount of energy received per
unit area per unit time. e.g. we receive solar flux of 1400 W/m2.
• The flux received is inversely proportional to the square of
the distance.
• If the two stars emit flux l1 and l2, then their magnitudes
m1 and m2 respectively are related by the formula:
m2 – m1 = - 2.5 log(l2/l1)
• The 6th magnitude star is 100 times fainter than the 1st
magnitude star. One magnitude = 2.512 times brighter

What’s Ref :
• A survey of hundred 6th magnitude (visually the faintest) stars
around the pole star was done. The average flux of these 100
‘north polar sequence’ stars was taken as the flux for the 6th
magnitude star.
• From that, for m = 0, the flux is 2.48 x 10–8 W/m2
• Once the fixed point of magnitude scale was defined this way,
the brightest star have magnitude even negative. E.g. the
Sirius has magnitude of –1.47, Venus can have magnitude
of – 4.4

Magnitude scale :

Apparent/Visual and Absolute magnitudes
• In order to compare the real brightness of stars, one uses
absolute magnitude (M) - It is the apparent magnitude of an
object when it is placed at a distance of 10pc.
• The sun’s apparent magnitude is – 26.8, while its
absolute magnitude is 4.5
• A star might look brighter than another star
– Either, it is actually brighter
– Or, it is closer to us than the other star

Relation between m and M :
• M = m – 5 log Dpc + 5
• Canopus (the second brightest star in the
night sky) has apparent magnitude of -0.72,
while the absolute magnitude is -2.5
• Estimate its distance.
• Sirius has m = - 1.46 and M = 1.41
• Estimate the distance of Sirius.

Distance Estimation using HR diagram
• Knowing the spectral class of
stars one can determine its
absolute magnitude
• Knowing the apparent
magnitude we can determine
its distance
• All O class stars have same
brightness. Hence by finding
O type star in distant cluster –
one can determine cluster
distance

Sun – A perfectly black body!

Wien’s displacement Law
• maxT = 0.29 cm-K
• Larger the surface temperature, the star peaks at smaller wavelength

Colour Index
• Magnitude gives only information about the flux, while
the colour index gives information about the colour of
the star, which might be useful to know the structure of
the star/ its position in HR diagram.
• To find the colour index, typically three different filters
are used. U, B, V
• B: Blue filter has central wavelength of 440nm
• V: Visual filter has central wavelength of 568nm

• The apparent magnitudes using these filters are found.
• Then B-V colour index is calculated.
– For bluish star, magnitude using B filter is smaller than that
using V filter. Hence B-V number is negative.
– Similarly B-V number positive means the stars are reddish in
colour.
– E.g. Betelguese has colour index B–V = 1.50 while Rigel has
colour index = –0.03

Standard Candles :
• If we had standard light bulbs around the
universe, we could have found distance from
the source by measuring the intensity of light
from that source alone.
• Such sources are called “standard candles”.
• They are:
– Cepheid Variables
– Supernovae

Variable Stars
• Some stars are found to have variable magnitudes.
• Their magnitudes increase and decrease over the period.
• The first such star was observed in 1596 by Fabricius.
– It was o-Ceti or Mira.
– Its period is 11 months (332 days)
– Its magnitude varies between 3.5 to 9
• In 1784,  Cephei, a yellow supergiant star was found to
be variable : Its period is 5d 8h 37m

Cepheid Variables
• Stars having similar light
variation as  Cephei are
called Cepheid variables.
• Cepheid variables are
supergiant stars and can be
seen at distances out to about
10-20 Mpc.
• One needs a distance
measurement from some
other method for at least one
Cepheid – parallax for delta
Cephei or distance to SMC.
 American astronomer
Henrietta Leavitt looked at
many Cepheid variables in
SMC.
 She found the period
luminosity relation (reported
in 1912).

Period – Luminosity relation

Types of spectra
• Hot solid bodies show continuous spectra
• Atomic gases show line spectra

Supernovae
• Constant absolute magnitude of
-19.6
• Type I – no hydrogen line in
spectrum, shows Si emission
• From white dwarfs or stars
close to the Chandrasekhar limit
• Very bright initially, and slow
decay in brightness due to
cobalt  iron conversion
• Brightness estimated, hence
standard candle.

Doppler Effect
• Approaching vehicle’s
whistle blows with higher
pitch.
• The receding vehicle’s
whistle has lower pitch.
• The frequency of the
whistle is the same.
• We hear different notes
because of the motion.

Determining Stellar distance
from Doppler Shift
• Comparing wavelengths
of the absorption lines of
stars with those in the
laboratory frame, we can
find whether the star is
approaching us or
receding from us.
• Entire pattern needs to
be compared for this.

Hubble’s Law
• Edwin Hubble in 30’s found that all the far off galaxies show red shift
indicating that they all are receding away from us.
• Farther the galaxy, they recede faster.
Distance
D
km/s/Mpc)
(73
Constant
Hubble
H
velocity
l
recessiona
v
D
v



 H

Various Methods to measure distances

References & Thanks to :
• Prof. Mahesh Shetti’s notes.
• Shri. Mohan Apte sir’s book ‘Astronomical Calculation’.
• Marathi website : www. Avakashvedh.com by ‘ Sachin Pilankar
• Wikipedia website : http://en.wikipedia.org

Details of Additional free Lectures delivered by Santosh Takale :
(Few lectures will be with Slide shows. Duration is 45 to 75 minutes)
• Understanding the Universe ( ivaSvaacao AMtrMga).
• Career Guidance ( kiryar maaga-dSa-na).
• Snakes- Myths & Facts. ( saap : samaja - gaOrsamaja).
• Sky Observation with naked eye & Telescope ( AakaSa inarIxaNa).
• Communication skills & PD, Time Mgt (saMBaaYaNa klaa va vya@tIma%va ivakasa).
• Manufacturing Technology : Welding & NDT for Students & Professionals.
How you can Help…………. Organise Free of cost Online/Offline Lectures.

Self Funded Social Activities by Santosh Takale :

Social Activities by Santosh Takale :

Contacts Us :
Santosh Takale
Ph : 9967584554 / 8451963305
santoshatbarc@gmail.com
Address :
House-470, At & Post Shirdhon
Tal : Panvel, Dist : Raigad
Maharashtra – 410221, India.

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