Fotometri Astronomi dan Koefisien Ekstingsi Atmosfer

Presentasi berjudul: "Fotometri Astronomi dan Koefisien Ekstingsi Atmosfer"— Transcript presentasi:

1 Fotometri Astronomi dan Koefisien Ekstingsi Atmosfer
HLM,II,HS RUT IX 2001 Fotometri Astronomi dan Koefisien Ekstingsi Atmosfer AS3100 Lab. Astronomi Dasar I Prodi Astronomi 2007/2008 B. Dermawan Frequently, presenters must deliver material of a technical nature to an audience unfamiliar with the topic or vocabulary. The material may be complex or heavy with detail. To present technical material effectively, use the following guidelines from Dale Carnegie Training®. Consider the amount of time available and prepare to organize your material. Narrow your topic. Divide your presentation into clear segments. Follow a logical progression. Maintain your focus throughout. Close the presentation with a summary, repetition of the key steps, or a logical conclusion. Keep your audience in mind at all times. For example, be sure data is clear and information is relevant. Keep the level of detail and vocabulary appropriate for the audience. Use visuals to support key points or steps. Keep alert to the needs of your listeners, and you will have a more receptive audience.

2 Radiometry & Photometry
HLM,II,HS RUT IX 2001 Radiometry & Photometry In astronomy the term photometry covers the quite general meaning of radiometry. Noting that most of the quantities to be defined refer to some specified wavelength or frequency. Hence, the correct term would be spectrophotometry

3 Astronomical Photometry
HLM,II,HS RUT IX 2001 Malasan Astronomical Photometry Branch of science that deals with measuring intensity of light In your opening, establish the relevancy of the topic to the audience. Give a brief preview of the presentation and establish value for the listeners. Take into account your audience’s interest and expertise in the topic when choosing your vocabulary, examples, and illustrations. Focus on the importance of the topic to your audience, and you will have more attentive listeners.

4 Definitions Standard Photometry Bradt 2004 Etendue (throughput)
HLM,II,HS RUT IX 2001 Definitions Standard Photometry Bradt 2004 Etendue (throughput) Transported power Monochromatic flux Reduced brightness Luminosity Polarisation Magnitudes Color indices

5 Photometry Through the Atmosphere
HLM,II,HS RUT IX 2001 Photometry Through the Atmosphere Extinction correction must be applied even at wavelengths for which the atmosphere is almost transparent The transmitted frequency Difficult for infrared due to the considerable lack of homogeneity in the space and time distribution of water vapor In order to calculate an emitted intensity, correction for interstellar extinction is required

6 Sistem Fotometri Distribusi energi bintang Sistem fotometri Filter
HLM,II,HS RUT IX 2001 Malasan Sistem Fotometri Distribusi energi bintang Sistem fotometri Filter Detektor

7 Efek Ekstingsi Serapan selektif
Malasan HLM,II,HS RUT IX 2001 Efek Ekstingsi X=1.0 X=4.0 Serapan selektif Obyek tampak makin ‘merah’ jika makin jauh dari meridian

8 Ekstingsi monokromatik
Malasan HLM,II,HS RUT IX 2001 Ekstingsi monokromatik Koefisien absorpsi massa Rapat massa I h+dh=h1 h

9 Massa udara (Air mass) Solusi persamaan hantaran radiasi :
Malasan HLM,II,HS RUT IX 2001 Massa udara (Air mass) Solusi persamaan hantaran radiasi : Jika z  jarak zenit, maka h+dh h I dh sec z z

10 Tetapi z=z(h): Kelengkungan refraksi atmosfer
Malasan HLM,II,HS RUT IX 2001 Tetapi z=z(h): Kelengkungan refraksi atmosfer Jika (,h) konstan, Massa udara Massa udara “Fotometrik” (relatif) :

11 Koefisien ekstingsi pada 
Malasan HLM,II,HS RUT IX 2001 Dalam astronomi: Hukum Bouguer dengan Koefisien ekstingsi pada 

12 HLM,II,HS RUT IX 2001 (Bemporad, 1904)

13 Massa udara: fungsi sudut jam, deklinasi, & lintang
HLM,II,HS RUT IX 2001 Malasan Massa udara: fungsi sudut jam, deklinasi, & lintang

14 Observasi: Fotometri Astronomi
HLM,II,HS RUT IX 2001 Malasan Observasi: Fotometri Astronomi Instrumentasi pengamatan: Photoelectric Photometer Detector: Photomultiplier CCD Camera Detector: CCD chip

15 Fotometri Malasan Ekstingsi atmosfer Bumi:
HLM,II,HS RUT IX 2001 Malasan Fotometri Ekstingsi atmosfer Bumi: Asumsi model Kuat cahaya obyek dikoreksi  magnitudo di luar atmosfer Transformasi ke sistem standar (baku): Radiasi monokromatik obyek langit Filter Detektor  y s z Linierisasi Terang Warna Baku (standar) Internasional Terkalibrasi

16 Malasan Rayleigh Ozon Koef. ekstingsi total
HLM,II,HS RUT IX 2001 Malasan koefisien ekstingsi aerosol Ozon Koef. ekstingsi total Rayleigh

17 Observasi Monitor suatu bintang dalam kurun waktu tertentu
HLM,II,HS RUT IX 2001 Malasan Observasi Monitor suatu bintang dalam kurun waktu tertentu Objek: Bintang baku ekstingsi Cocok untuk jenis fotoelektrik fotometer

18 Fotometri gugus Cocok untuk fotometri CCD
HLM,II,HS RUT IX 2001 Malasan Fotometri gugus Cocok untuk fotometri CCD Obyek: Gugus terbuka baku fotometri Solusi persamaan simultan

19 Reduksi Regresi multivariabel Persamaan dasar: M: Magnitudo standar
Malasan HLM,II,HS RUT IX 2001 Reduksi Referensi: Henden & Kaitchuck 1984, Astronomical Photometry, van Norstrand, New York Sterken & Manfroid 1992, Astronomical Photometry: A Guide, Kluwer, Dordrecht Persamaan dasar: Regresi multivariabel M: Magnitudo standar C: Indeks warna standar Determine the best close for your audience and your presentation. Close with a summary; offer options; recommend a strategy; suggest a plan; set a goal. Keep your focus throughout your presentation, and you will more likely achieve your purpose.

20 Multivariate linear regression untuk sistem fotometri UBV
HLM,II,HS RUT IX 2001 Malasan Multivariate linear regression untuk sistem fotometri UBV Regresi linier multivariat penting dalam memecahkan persamaan transformasi fotometri Tinjau persamaan transformasi untuk warna standar BV

21 Malasan HLM,II,HS RUT IX 2001 Jika terdapat n pengamatan (bisa berarti n bintang standar), persamaan dapat ditulis: dengan Melalui metode regresi linier multivariat, maka dapat disusun matriks normal

22 Pecahkan SPL dengan metode numerik untuk mencari a, b1, dan b2
HLM,II,HS RUT IX 2001 Malasan Pecahkan SPL dengan metode numerik untuk mencari a, b1, dan b2