NASTRO BINOCULAR 75Introduction NB75 Objects Size,position andmagnitude Objectclasses Recording...

Introduction NB75 Objects Size, position and magnitude Object classes Recording Summary

NASTRO BINOCULAR 75

VISUAL OBSERVING CHALLENGE

Dr Adrian Jannetta MIMA CMath FRASNorthumberland Astronomical Society

NASTRO Binocular 75 1 / 40 Adrian Jannetta


Introduction

• Introduction / motivation• The NB75 objects• Object types• Recording observations• Practice!



Deepsky catalogues: Messier Objects

Charles Messier (1730 – 1817)

Messier compiled a catalogue of109 ’fuzzy’ objects (late 18thcentury).

The purpose was so astronomerscould avoid confusion in searchesfor comets.

Messier’s catalogue contains about40 galaxies, numerous star clusters(e.g. the Pleiades) and gaseousnebulae in the Milky Way (e.g.Orion Nebula).

1 object (M 7) does not rise inNorthumberland; 8 are always< 10◦ above horizon.



Caldwell Objects

Patrick Caldwell Moore (1923 – 2012)

Moore compiled an alternativecatalogue of 109 ’fuzzy’ objects.Caldwell objects are bright deepskyobjects not included among theMessier objects.

Caldwell objects are ordered bydeclination (from north to south inthe sky).

Lots of popular objects: Veil Nebula,Rosette Nebula, ET Cluster and more.

More than 40 objects never riseabove Northumberland horizon.



Other cataloguesThere are lots of existing catalogues and lists for observing challengesalready! In addition to Messier and Caldwell:

• NGC (New General Catalog) published by Dreyer in 1888. Based onearlier catalogues by Herschel. 7,840 objects and ~50% are galaxies.

• IC (Index Catalogue) by Dreyer (1895,1898) added 6,900 objects tothe NGC.

• Melotte – 245 open clusters by British astronomer Philibert Melotte(1915)

• Collinder – 471 open clusters by Swedish astronomer Per Collinder(1931)

Also popular with amateur astronomers: Herschel 400 (a subset of 400objects from NGC) and various lists published by Saguaro AstronomyClub.



Motivation for a new list!

These catalogues are all great places to look for interesting objectsto see! However...

• It isn’t possible to complete observing challenges based onthese because some objects are not visible fromNorthumberland!

• Many objects in the catalogue require a telescope to be seen.Something easier?

• Do beginners get stuck on the same set of objects?(Andromeda Galaxy, Orion Nebula, M 13, etc) Need inspirationto go further??



Devising the NB75After NASTRO was founded – I set myself a challenge to come upwith a list of interesting objects that satisfied the following criteria:

• All objects are visible from Northumberland at some point inthe year.

• Must attain altitude of at least 10◦ above horizon (Declination,δ>−25◦)

• Reasonably bright: must be visible with, at most, a good pair ofbinoculars.

• The objects contain a range of types (stars, star clusters,nebulae, galaxies)

• Assign a level of difficulty (points system!) to each object. Verysubjective!

With these constraints – a couple of hundred objects becamecandidates...



Object typesThe list of candidates was whittled down to 75 to give arepresentative balance of the different object types:

• Open clusters (39 objects)• Globular clusters (11)• Bright nebulae (5)• Dark nebulae (2)• Galaxies (6)• Asterisms and stars (10)• Planetary nebula (1)• Milky Way (1)

These objects are scattered across the sky. Some are always abovethe horizon. Others are have a short window of visibility at certaintimes of the year.


NB75 Objects (October – December)The NB75 list is ordered by Right Ascension so that objects visible at about the same time of the year are grouped.

ID Name Class Const. R.A. Dec Mag. Size Difficulty

1 M 31 (Andromeda Galaxy) Galaxy And 00h 44m +41◦22′ +4.3 2.6◦ ×1.1◦ 12 NGC 457 (ET Cluster) Open cluster Cas 01h 21m +58◦23′ +5.1 20.0′ 23 M 103 Open cluster Cas 01h 35m +60◦45′ +6.9 5.0′ 34 M 33 (Triangulum Galaxy) Galaxy Tri 01h35m +30◦45′ +6.4 62′ ×36′ 35 NGC 663 Open cluster Cas 01h 47m +61◦20′ +6.4 14.0′ 16 NGC 869/884 (Double Cluster) Open cluster Per 02h 20m +57◦13′ +4.3 18.0′ 17 M 34 Open cluster Per 02h 43m +42◦51′ +5.8 35.0′ 18 β Persei (Algol) Variable star Per 03h 09m +41◦02′ +2.1−3.4 – 39 Cr 39 (Mirfak Cluster) Open cluster Per 03h 26m +49◦56′ +2.3 5.0◦ 110 M 45 (Pleiades) Open cluster Tau 03h 48m +24◦10′ +1.5 2.0◦ 111 Kemble’s Cascade Asterism Cam 03h57m +63◦04′ +6.0 2.5◦ 212 NGC 1528 Open cluster Per 04h 17m +51◦16′ +6.4 16.0′ 213 NGC 1545 Open cluster Per 04h 22m +50◦18′ +4.6 18.0′ 214 Hyades cluster Open cluster Tau 04h 28m +15◦54′ +0.8 5.5◦ 115 θ Tauri Double star Tau 04h 30m +15◦55′ +3.4 – 116 NGC 1647 Open cluster Tau 04h 47m +19◦09′ +6.2 40.0′ 217 NGC 1746 Open cluster Tau 05h 05m +23◦48′ +6.1 42.0′ 218 The Minnow Asterism Aur 05h 19m +33◦23′ +4.0 80′ ×20′ 119 M 38 Open cluster Aur 05h 30m +35◦52′ +6.8 20.0′ 220 NGC 1981 Open cluster Ori 05h 36m −04◦25′ +4.2 28.0′ 221 Cr 69 (Orion’s Head) Open cluster Ori 05h 36m +09◦57′ +2.8 70.0′ 122 M 42/43 (Orion Nebula) Bright nebula Ori 05h 36m −05◦23′ +4.0 40.0′ ×20.0′ 123 Cr 70 (Orion’s Belt) Open cluster Ori 05h 36m −01◦06′ +0.6 2.3◦ 124 M 36 Open cluster Aur 05h 38m +34◦09′ +6.5 10.0′ 225 M 37 Open cluster Aur 05h 54m +32◦33′ +6.2 14.0′ 226 NGC 2169 (37 Cluster) Open cluster Ori 06h09m +13◦58′ +7.0 5.0′ 3

NB75 Objects (January – April)


27 M 35 Open cluster Gem 06h 10m +24◦21′ +5.6 25.0′ 228 NGC 2244 Open cluster Mon 06h 33m +04◦55′ +5.2 29.0′ 329 NGC 2264 (Christmas Tree Cluster) Open cluster Mon 06h 42m +09◦52′ +4.1 39.0′ 230 M 41 Open cluster CMa 06h 47m −20◦47′ +5.0 39.0′ 131 NGC 2301 Open cluster Mon 06h 53m +00◦26′ +6.3 14.0′ 232 M 50 Open cluster Mon 07h 04m −08◦25′ +7.2 14.0′ 333 M 47 Open cluster Pup 07h 37m −14◦32′ +4.3 25.0′ 234 M 46 Open cluster Pup 07h 43m −14◦52′ +6.6 20.0′ 235 M 48 Open cluster Hya 08h 40m −05◦49′ +5.5 30.0′ 236 M 44 (Beehive Cluster) Open cluster Cnc 08h 41m +19◦36′ +3.9 70.0′ 137 M 67 Open cluster Cnc 08h 52m +11◦44′ +7.4 25.0′ 238 M 81 (Bode’s Galaxy) Galaxy UMa 09h 57m +68◦59′ +7.8 21.9′ ×10.5′ 339 M 82 (Cigar Galaxy) Galaxy UMa 09h 57m +69◦35′ +9.0 9.3′ ×4.4′ 440 Cr 256 (Coma Star Cluster) Open cluster Com 12h 26m +26◦00′ +2.9 2◦ 141 Y CVn (La superba) Variable star CVn 12h 46m +45◦20′ +5.3 242 ζ Ursa Majoris (Mizar & Alcor) Double star UMa 13h 25m +54◦49′ +2.1 143 M 51 (Whirlpool Galaxy) Galaxy CVn 13h 31m +47◦06′ +8.7 9.8′ ×7.8′ 444 M 3 Globular cluster CVn 13h 43m +28◦17′ +6.3 18.0′ 245 M 101 (Pinwheel Galaxy) Galaxy UMa 14h 04m +54◦15′ +8.4 22′ ×21′ 446 α Librae (Zuben Elgenubi) Double star Lib 14h 52m −16◦07′ +2.8 147 M 5 Globular cluster Ser 15h 20m +02◦01′ +5.7 23.0′ 2

NB75 Objects (May – September)


48 M 4 Globular cluster Sco 16h 25m −26◦34′ +5.4 36.0′ 349 M 13 (Great Hercules Cluster) Globular cluster Her 16h 42m +36◦25′ +5.8 20.0′ 150 M 12 Globular cluster Oph 16h 48m −01◦59′ +6.1 16.0′ 351 M 10 Globular cluster Oph 16h 58m −04◦08′ +6.6 20.0′ 352 M 92 Globular cluster Her 17h 18m +43◦07′ +6.5 14.0′ 253 IC 4665 Open cluster Oph 17h 47m +05◦43′ +5.3 70.0′ 254 M 23 Open cluster Sgr 17h 58m −18◦59′ +5.9 29.0′ 255 Cr 359 Open cluster Oph 18h 02m +02◦54′ +3.0 4.0◦ 156 M 20 (Trifid Nebula) Bright nebula Sgr 18h 04m −22◦59′ +6.3 16′ ×9′ 257 M 8 (Lagoon Nebula) Bright nebula Sgr 18h 05m −24◦23′ +5.0 17′ ×15′ 258 Sagittarius Star Cloud Milky Way Sgr 18h 20m −18◦24′ +2.0 90′ 159 M 16 (Eagle Nebula) Bright nebula Ser 18h 20m −13◦49′ +6.0 9.0′ ×4.0′ 360 M 17 (Omega Nebula) Bright nebula Sgr 18h 22m −16◦10′ +6.0 11.0′ 361 M 25 Open cluster Sgr 18h 33m −19◦06′ +6.2 29.0′ 262 M 22 Globular cluster Sgr 18h 38m −23◦53′ +5.2 32.0′ 363 ϵ Lyrae (The Double Double) Double star Lyr 18h 45m +39◦41′ +4.7 264 M 11 (Wild Duck Cluster) Open cluster Sct 18h 52m −06◦15′ +6.1 32.0′ 165 Cr 399 (The Coathanger) Asterism Vul 19h 26m +20◦13′ +4.8 89.0′ 166 M 71 Globular cluster Sge 19h 55m +18◦50′ +8.4 4.0′ 367 M 27 (Dumbbell nebula) Planetary nebula Vul 20h 00m +22◦46′ +7.3 8.0′ 468 Northern Coalsack Dark Nebula Cyg 20h 45m +40◦00′ – 7◦ 169 Funnel Cloud Dark Nebula Cyg 21h 15m +48◦00′ – 15◦ ×5◦ 170 M 15 Globular cluster Peg 21h 31m +12◦15′ +6.3 18.0′ 271 M 39 Open cluster Cyg 21h 32m +48◦31′ +5.3 29.0′ 272 M 2 Globular cluster Aqr 21h 34m −00◦44′ +6.6 16.0′ 373 µ Cephei (Garnet Star) Variable star Cep 21h 44m +58◦52′ +4.3 274 M 52 Open cluster Cas 23h 26m +61◦42′ +8.2 15.0′ 275 NGC 7789 (Caroline’s Rose) Open cluster Cas 23h 58m +56◦49′ +7.5 25.0′ 3

Visibility of objects at this time of year is complicated by twilight in Northumberland...


Day, night and twilight0h

0h

6h

6h

12h

12h

18h

18h

24h

24h

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

DaylightCiviltwilight

Nauticaltwilight

Astronomicaltwilight

Fulldark

Astronomy in Northumberlandcan be frustrating! Between earlyMay and early August – there isno full dark during the night.

During this period – the objectslisted can be viewed against darkskies either:

• Late (after midnight) inApril/May

• Early (before midnight) inJuly/August.

Many brighter objects are visiblethrough the summer.



Excel SpreadsheetAll 75 objects are listed in a spreadsheet along with position, size,magnitude and other information.

The spreadsheet can be downloaded at www.nastro.org.uk/nb75.html.


www.nastro.org.uk/nb75.html


Differentiated difficulty

Difficulty rating (points!) assigned based on “best visibility”.

1 Easy! (24 objects)

2 Moderate (31)

3 Difficult (16)

4 Very challenging (4)

A little bit subjective... A nice round total of 150 points for allobjects!



Angles in astronomyAstronomers often need to give the positions of objects in the sky or ‘distances’from one part of the sky to another.

Angles are an appropriate way to do this. For example:

• The distance between the horizon and zenith is 90◦.• On 11-Sep-2014 the Moon was 142◦ west of the Sun.• On 11-Sep-2014 Comet Jacques was moving across the sky at 0.08◦ per hour.

The apparent sizes of celestial objects can also expressed using an angle.



Estimating angular sizes

With your hand at arms length, this shape makes an angle of 15◦, whichencompasses the brightest stars of Cassiopeia.




With your hand at arms length, this shape makes an angle of 10◦. This is about thedistance between Betelgeuse and the three Belt Stars in Orion.




With your hand at arms length, this shape makes an angle of 5◦. This is about thedistance between the pointer stars (Dubhe and Merak) in The Plough.




With your hand at arms length, this shape makes an angle of 12◦

. This is diameterof the lunar disk. Some other objects of comparable size are also shown.



Small angles

• 1◦ = 60′ (1 degree equals 60 arcminutes).• 1′ = 60′′ (1 arcminute equals 60 arcseconds).

Picture: Venus and the moon (02-Jan-2014). Venus (50 arcseconds) and moon(about 30 arcminutes).



Very small angles



Equatorial coordinates

Every point on the sky can be specified by two numbers:

Declination an angle measured north or south of the celestialequator. The North Celestial Pole is at +90◦ and theSouth Celestial Pole at −90◦.

Right Ascension an angle measured from a zero line (the FirstPoint of Aries) to the object line. The RA of an object isusually expressed as the time period between the zeroline being on the local meridian to the object being onthe meridian.

The RA and Dec of stars doesn’t change much over human lifetimes- almost constant.

Equatorial mounts of telescopes are designed to follow this system.



Right Ascension and Declination simulation

(0,0) circle (0.4);

Courtesy of UNL Astronomy Education



Equatorial and Horizon coordinates

(0,0) circle (0.4);

Courtesy of UNL Astronomy Education



Star magnitudes

The magnitude scale of brightness is based on a simple six pointscale devised by Hipparchus (c.190BC — c. 120 BC).

• Brightest stars — magnitude 1• Faintest stars — magnitude 6



Magnitude scale for brightness

• The definition was put on a more precise footing in the 19thcentury (by N R Pogson).

• Difference of 5 magnitudes corresponds with exactly 100 timesdifference in the amount of light.

• Logarithmic scale; One magnitude difference is 5p100 ≈ 2.51times brightness difference.

• The star Vega was chosen to be magnitude 0.• Scale extended to include brighter and fainter objects than the

scale was designed to include.



Magnitudes of some common objectsThe following scale shows how the magnitude scale quantifies the brightness ofsome objects in the night sky visible without optical aid.

-2 -1 0 1 2 3 4 5 6 7

Nakedeye

limitUranus

AndromedaGalaxy(M31)Spica PolarisVegaSirius

The magnitude scale must be extended to include brighter objects than the starsand fainter objects than those visible with the naked eye.

-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30

HSTvis-iblelightlimit

Pluto’ssmallermoons

Pluto

Nakedeye

limitSirius M31

Venus

BrightIridium

flare

Full moonSun



Integrated magnitudeExtended objects (nebulae, galaxies, etc) are assigned an integrated magnitude.

• Integrated magnitude is the magnitude the object would have if all the lightwere compressed to a single point (i.e. an equivalent magnitude star)

• Magnitudes of NB75 objects are integrated magnitudes! Need to beconsidered along with angular size (area) in terms of how easy to see anobject might be.



How deep can you see?The magnitude limits for some binoculars and telescopes are given below.

Instrument Magnitude limit

Naked eye +6.5Binoculars, 8×30 +9.2Binoculars, 7×50 +9.6

Binoculars, 10×50 +10.0Telescope, 80mm (3 inch) +12.3

Telescope, 150mm (6 inch) +13.7Telescope, 200mm (8 inch) +14.5

Telescope, 350mm (14 inch) +15.1

These values are approximate; local observing conditions, health, age andexperience will influence them to some extent.

These values don’t apply to imaging – only visual observing. Moonlightand sky transparency will act to reduce limiting magnitude (more difficultto see fainter objects).


Moon phase calendar (2019)

January1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

February1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

March1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

April1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

May1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

June1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

July1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

August1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

September1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

October1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

November1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

December1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Darkest evenings are when the moon is below horizon. The 7-10days around full moon add a lot of light to the sky making it hard tosee the fainter objects.


Open clusters

M 39 in Cygnus (#71 on NB75)

Open clusters contain typically containseveral tens to several thousand stars.They tend to have an irregular shape.

The stars in a cluster form at roughly thesame time from a giant cloud of gas anddust within the disk of the Galaxy

Since the stars all formed at the sametime it is possible to date the age of acluster by the age of the most massivestar left in the cluster (because thelifetime of a star depends on its mass!)

Open clusters were traditionally classedby how densely packed the starsappeared to be (Trumpler, 1930)



Stars

Some of the NB75 objects are stars: either variable or double stars. Thechallenge for double stars is to split the components. For variable stars – itis to see the brightness changes over a period of time.

Double stars Many stars are gravitationally bound to another star (abinary system). Sometimes a chance alignment can maketwo unrelated stars appear close together (an opticaldouble). Separation of the primary (brightest) from thesecondary (fainter) is usually measured in arcseconds.

Variable stars are stars which change their brightness over time. Thismay occur because the star itself is pulsating or changingin lumosity (intrinsic variable) or because of externalfactors such as a companion eclipsing it (extrinsicvariable). There are further sub-classes of each type!



Globular clusters

M 13 in Hercules (#49 on NB75)

Globular clusters contain typicallycontain tens of thousands to morethan a million stars. They tend to bespherical and much more denselypacked than open clusters.

Globular clusters are old – the mostmassive stars have long since diedand the remaining population tendto be low mass, yellow dwarf stars.

Globular clusters orbit the Milky ineccentric orbits which take them farout of the disk and into the halo ofthe Galaxy.



Bright nebulae

M 8 (bottom) and M 20 (top) in Sagittarius (#57,#56 on NB75)

Bright nebulae are also known as HIIregions. They are clouds of hydrogenand helium heated by stars to the pointthey glow. In photos the red light ofhydrogen is prominent but visually theylook somewhat gray.

Nebulae like these are associated withstar formation; the nebula may fragmentand collapse into clusters.

It is not unusual to find young openclusters still enveloped in the glowinghydrogen gas.



Asterisms

Kemble’s Cascade (#11 on NB75)

Asterisms are unrelated stars which form a striking pattern to the eye.They are not usually open clusters and the stars may be very differentdistances from us.

Examples of asterisms include The Plough, the Square of Pegasus, theCoathanger. There are many more!



Planetary nebulae

The Dumbbell nebula (M 27). Planetary nebula inVulepecula (#67 on NB75).

Low mass stars (such as the Sun) expeltheir atmospheres in a brief, final phaseknown as a planetary nebula.

Prior to this phase hydrogen burning inthe core ended and the star swelled tobecome a red giant. The outer layers ofthe star become enriched with carbon,nitrogen and oxygen – dredged up fromthe core by convection.

The hot, inert core of the star remains. Itheats the expanding nebula making itglow. This hot core at the centre is awhite dwarf star.

The expanding nebulae eventuallydissapates and contributes to the dustcontent of the Milky Way and to futuregenerations of stars and planets.



Star clouds and dark nebulae

Funnel Cloud and Northern Coalsack: darknebulae in Cygnus (#69, #68 on NB75).

The Milky Way is the disk of star towhich the Sun belongs. Our view ofthe central regions is obscured bydust clouds (dark nebulae).

Dust comes from stars which ejectedtheir carbon-rich atmospheresduring the later stages of their lives.

The absence of dust in somedirections allows deep views into theMilky Way – these windows areknown as star clouds.

The image shows the Cygnus Rift tothe south of Deneb in Cygnus. TheNorthern Coalsack and FunnelNebula lie close to Deneb.



Galaxies

M 82 (left) and M 81 (right) in Ursa Major (#39,#38 on NB75).

A number of galaxies are visible tothe naked eye or binoculars. Thebrightest galaxy on the NB75 is theAndromeda Galaxy (M 31) which isvisible to the naked eye.

Galaxies are islands of starscontaining many tens or hundreds ofbillions of stars.

A major discovery of the 20thcentury was that stars represent atiny proportion of the total mass.Another component – dark matter –is thought to be the majorconstituent. The precise nature ofdark matter is largely unknown.



Keeping a recordAstronomical observations record information related to the observingsession along with your impressions / observations of each obejct. Detailsto include:

• Observer name and location• Date and time• Air transparency (Clear sky or cloud cover? Mist / haze / high cloud?)• Instruments used (naked eye, binoculars, telescopes, eyepieces,

filters)

• Object details and impressions. Helpful to estimate the altitudeabove horizon (can be calculated by software/apps later).

• Sketch or drawing?

Sample observing form at www.nastro.org.uk/nb75.html.


www.nastro.org.uk/nb75.html


Summary

• NASTRO Binocular 75 is an observing challenge!• 75 objects visible from Northumberland with, at most,

binoculars.• Aims / motivation:

• A list of objects which can be completed by observers inNorthumberland

• To develop skills associated with searching and visualobserving.

• A range of objects which might inspire the observer to find outmore

• Consider the NB75 as a way of extending the objects youusually observe!

• ...and as a stepping stone to tracking down fainter objects inthe sky with your telescope.


IntroductionNB75 ObjectsSize, position and magnitudeObject classesRecordingSummary

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NASTRO BINOCULAR 75Introduction NB75 Objects Size,position andmagnitude Objectclasses Recording...

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