1 Introduction to Observation 2 Telescope 3 Observatory and Telescope
Telescope
Yudhiakto Pramudya, Ph.D Astronomy 2014
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3 Dark adaptation 1 2 the pupils will dilate so allowing more light to enter the eye the dark adaptation mechanism takes about 20 minutes to come into effect.
Without high light levels reaching the retina, vitamin A is converted first to retine and then into rhodopsin that significantly improves sensitivity of the rods and cones which are the light sensitive receptors in the retina of the eye. Strong white light can quickly reverse this change. That’s why we will use RED light.
Equipments
Software : Stellarium, Celestia, Starry Night, Your Sky Weather : BMKG, cleardarksky Compass, Star Map, Flash Light Log Book : observation report Light pollution : lightpollutionmap.info
But...
Miscell : insect repeller, tea, coffee, cookies, blanket, jacket
Report : 1 Time 2 Date 3 Location 4 Telescope type, focal length, focal ratio, eyepiece, magnification, etc 5 Your target, may include sketch or image 6 note of local weather 7 thoughts about the equipment, the sky, etc 8 Misc : anything happen during an observation
A telescope is used to do three things: 1 To collect more light so that fainter obejects can be seen beter than 2 with unaided eye. 3 To enable us to see greater detail in a distant object. to gain resolution Besides telescope, we can use binocular to aid us to observe the night sky.
The considerations to choose telescope : Aperture Portable Optical Quality Versatile Durability Upgradeable Serviceable
Telescope classes : 1 2 Refractors, which use lenses to gather light 3 Reflectors, which use mirros Catadioptric system, which use a combination of lens and mirror The Objective : the main light-gathering component.
The greater its area, the greater the amount of light received. f-ratio : the ratio of its focal length (F) to its diameter (D) f-ratio of 3 to 6 : wide fields of view and faint objects, but image is small. f-ratio of 10 to 20 : more details on Moon or planets
Fundamental limit to the detail in the image is the effects of diffraction. Assuming that the telescope has a circular aperture, then the image formed by a point source is a central disc surrounded by a number of concentric rings rapidly decreasing in brightness.
θ = 1.22 λ/D (1) The mathematical solution of Airy Diffraction is employing the Bessel Function. The zeroes of first kind Bessel function related to the 1.22 of the constant of equation. If one consider a 150 mm telescope observing in green light of −7 5.5x10 m wavelength, the Airy disc size is −7
5.5x10 −6 rad rad θ = 1.22 = 4.4x10 −6
0.15 x θ = 4.4x10 57.3x3600 arcsec = 0.9 arcsec
The resolution is limited by seeing - a function of turbulence in the atmosphere. At high location, there is far less atmosphere above the telescope and the air tends to be less air turbulent.
Ocular : A lens that we use to view an image formed by the objective. In a reflector telescope, the objective is a mirror (primary). The secondary is another mirror to direct the reflected beam from primary to a better position for viewing. Catadioptric telescopes, such as the Schmidt and Maksutov systems, have a mirror with a spherical curve.
Finder : a small telescope to aim a telescope at a celestial object. Wide field, mounted on and aligned with main instrument.
Binoculars are good for scanning wide areas of sky and viewing the Moon. The image is upright and visible with both eyes. True binoculars have a pair of prisms in each optical path. They are classified by a pair of number for example : 15x70
It means the magnification is 15x and the diameter of each objectives lens are 70 mm.
The mounting is intended to 1 2 hold the telescope 3 keep it steady enable the observer to keep it pointed at a celestial object as Earth rotates.
Mounting types : Altazimuth and Equatorial.
Altazimuth : Altitude and Azimuth Equatorial : It has one axis of rotation- the Right-Ascension axis (polar axis) and the declination axis.
Right ascension : the celestial equivalent of terrestrial longitude. Declination is equivalent to the latitude.
Magnification f obj M
= (2) f ocu To enhance the magnification, we can use Barlow lens.
Barlow lens, concave lens that is located before the eyepiece (oculer). The Barlow lens has the effect of diverging the light cone and giving the effect of having an objective of greater focal length. The effective focal length is usally doubled.
eastexastronomy.blogspot.com Newtonian Telescope
There is spherical abberation on mirror. Hence, the correction of the abberation by putting the lense in front of it.
by user. Go To Telescope System : The telescope system that has hardware and software which has ability to point the telescope to selected object
South is at a height of 2737 m on Cerro Pachon, Chile. Gemini Observatory comprises two 8.1-m telescopes; Gemini North is located on Mauna Kena, Hawaii at a height of 4214 m whilst Gemini gemini.edu
telescopes. They have primary mirrors of 10 m diameter each composed of 36 hexagonal segments whose positions are adjusted to act as a single mirror. The twin Keck telescopes, located at a height of 4200 m at the top of Mauna Kea, Hawaii, are the world’s largest optical and infrared
Hobby-Ebberly Telescope at The McDonald Observatory in Texas. It has a spherical 10 m mirror made up of 91 hexagonal segments. The telescope is tilted at at fixed angle of 37 degrees from the zenith and moves only in azimuth. The South Africa Large Telescope (SALT) is the largest telescope in the southern hemisphere and its innovative design is based on the star.arm.ac.uk
James Web Telescope
Paranal in the Atacama Desert, northern Chile, at the height of 2600 m. independently or in combined mode when it is equivalent to a single 16-m telescope-making it the largest optical telescope in the world. It can observe over a wavelength range from the near UV up to 25 µm in the IR. The VLT is located at the Paranal Observatory on Cerro The Very Large Telescope is operated by the Southern Observatory (ESO) and consists of four 8.2-m telescopes which can either work nicolascretton.ch
star is observed, the fringes become les and less important. Two beams that were captured by two telescope were combined. If the distance between the two telescope is increased when a particular
Rolloff Observatory : The observatory that has the opening roof by sliding it to the side
The HST’s primary mirror is 2.4 m across so that in green light its angular resolution is given by: the visible to the near infrared (0.12µm to 2.4µm). Hubble Space Telescope (HST) was launched in April 1990 to observe universe over a wavelength range that extends from the UV through ∆θ = 1.22 λ/ D = 1.22 x 5.1x10 rad ∆θ = 0.053 arcsec 2.4 −7 spacetelescope.org