BANGKOK DEEP-SKY OBJECTS OBSERVING

OBSERVING TIPs:

Basic knowledge
Refer to Observation records, they contain many technical terms and/or short descriptions. The basic definition & meaning list here may be useful.
  • Object type:
  • Open cluster: the cluster of stars form as irregular shape normally they are young stars condensed from surrounding dust & gas , the open clusters may consist of nebulosity when the surrounding gas release or reflect photon caused by high energy young stars in the cluster. M6 or butterfly cluster is my favorite open cluster without nebulosity. M8 or lagoon nebula is the finest example for open cluster with nebulosity.
  • Globular cluster:
    • the cluster of stars form as sphere shape ,they are consist of very old stars. They located around the center of galaxy. Redshift, show that they are formed at the same time with galaxy. The big globular clusters such as M13 consist of 30,000 stars. NGC 5139 The Omega centauri is the finest one contains over a million stars.
  • Nebulae:
    • The Bright Nebulae (or Diffuse Nebulae) are the glowing gas around star(s) or star cluster, There are two type:
    1) Emission nebulae, the atom of gas release photon when receive energy from star(s). The most is hydrogen gas, which emission photon in red color band. M16 is an example of emission nebula.
    2) Reflection nebulae, contains dust that does not shine by itself but simply reflects the light from stars nearby such as M78.
    The Great Orion Nebula or M42 is not pure emission but have some effect of reflection as well.
    Dark nebulae: the dark gas & dust that block light of background star field. The Horsehead Nebula or B33 is spectacular dark nebula. For visual observing, it needs more than 12" aparture and very dark skies.
  • Planetary Nebulae:
    • The remnant of dead stars. Occur when fuel for nuclear fusion are run out, star will explode due to unbalance of gravity force and internal pressure. For big stars, the explosions will extremely strong that called novae or supernovae. For smaller stars the explosions not so strong like novae then the stars shell will be symmetrically run away from star center. At the center will be white dwarf star. M57 or Ring Nebula is the finest sample. the central star is mag15.2
    Super Nova Remnant: as the result from supernova, the well known is M1 or crab nebula. The central star is neutral star or pulsar.
  • Galaxies:
    • The primary unit of universe contains billions stars. Their diameters range from a few thousand of light years up to about 100,000 ly.
    Hubble Classes of Galaxies :
    E Class: Elliptical, E0=nearly round, E7=highly flattened
    S Class: Spiral, S0=lenticular form, Sa (b,c,d or m)=simple nucleus, SBa (b,c,d or m)=include bright central bar. The lowercase letter a,b,c,d or m show the sequence begins with galaxies having a very prominent bulge and tightly coiled spiral arms, and it ends with those showing hardly any nucleus at all and very loose, open arms.
    Irr Class: Irregular shape galaxies
    M31 or Andromeda is Sb class but edge on toward us. M51 is face on class Sc, well known as Whirlpool Galaxy.
  • Magnitude:

    • The brightness scale of objects e.g. sun = -26.8, Sirius = -1.5, Antares = 0.9, the faintest star for naked eye = 6 but for galaxies & nebulea the brightness are spread out in wide area the the term of surface bright (SB) uses to consider how hard or ease for observing rather than their total brightness. Surface Brightness uses for calculating SB of large objects. The faintest star for my observing site with my telescope is about 10 th-magnitude. Magnitude Calculation can be down loaded for more study & fun.
  • Diameter:

    • Diameter of objects are apparent angular size e.g. sun = 0.5 degree or 30 arcminute or 1,800 arcsecond; cassini division is about 0.7 arcminute; M4 diameter 35 arcminute or nearly equal full moon. The relation of angular size (a), object size (D) and distant (d) are:

    a = 206265 D/d
    a = Apparent Angular size of objects in arcsecond
    D = Actual size of objects in km, mile or light year..
    d = Distant form observer to Objects in the same unit as D
    It fun to prove where 206265 come form
    Let try Angular Size Calculation
  • Distance:

    • Distant unit is Light Year (ly), the distance that light traveled in one year:
    1 Astronomical unit (AU) = 93 million miles
    1 ly = 63,240 AU
    1 ly = 5.88 trillion miles
    1 ly = 0.307 parsecs
    1 parsecs = 3.26 ly or 206,000 AU
    M31 or Andromeda galaxy is 2.3 million ly away from us. The light we see today traveled form its source 2.3 million years ago!
  • Constellations:

    • The imaginary pattern of bright stars, such as Orion, Scorpion, Big dipper..etc. The modern Constellations are consisted of 88 standard configurations. The brightest star is called Alpha e.g. Alpha-Scorpii, the order of Greek alphabet are applied to lesser brightness stars e.g. Beta, Gamma, Delta.. Flamsteed star number are no limit when 24 Greek letters can be run out. Sometime I refer to both in my hopping session.
  • Date/Time/Place:

    • Date & Time is local Thailand time which is UT(Universal Time)+7. Bangkok located on central of Thailand at Latitude 13 degree 44 lipda (arcminute) North, Longitude 100 degree 34 lipda East.
  • Transparency:

    • The clearness of sky, roughly classified into 3 levels:
    Good = very clear sky; no cloud, smog & hazy
    Fair = some cloud, slightly hazy
    Poor = more cloud, more hazy
  • Seeing:

    • The Atmosphere turbulent condition, also classified into 3 levels:
    Good = no or little stars twinkle
    Fair = more stars twinkle
    Poor = high stars twinkle
  • Light polluted:

    • The interference sky glow, classified same as both conditions:
    Good = no or little sky glow around zenith area
    Fair = More sky glow at high altitude (or Moderate/Medium)
    Poor = Highly sky glow up to zenith area
  • Telescope:

    • There are classified into two major type:
    1) Refractor : consists of object lens & eyepiece, Galileo Used 1" refractor telescope.
    2) Reflector : uses Primary Mirror instead of object lens. Newtonian, , schmidt-Cassegrain & Maksutov-Cassegrain are popular for this kind of telescope.
    For more information, please take a look on Orion learning center which have precise & concise information.
  • Eyepiece/Power:

    • Eyepiece is highly influence to image quality. There are four key parameters involved as following:
    1) Power or Magnification = Focal length of objective / Focal length of eyepiece
    2) Field Of View (FOV) = Apparent field of view / Magnification
    3) Eye relief: distant from eye to lens that can see full FOV. If too short, it hard to see especially with glasses.
    4) Exit pupil: select to match observing objects.
    Please see Telescope & Eyepiece combination performance and try to match for your needs.
  • Sky atlas:

    • I've used Sky atlas 2000.0 which have total 26 charts ,contained 2,700 deep sky objects, showing 81,312 stars down to mag8.5
  • Sketched image:

    • Orientation: West direction was marked at eyepiece, by observing stars drift.
    Field Of View: The object size may be larger or smaller than apparent size in eyepiece, in order to keep hi-light features and sometimes reference nearby stars for comparing with text books & Programs.
    Negative image: for deep sky objects the bright area will be black
    Positive image: for moon the bright area will be left white. but for planets, sometime mixed both negative & positive.
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