Figure 4.2 shows a (schematic) CCD spectral image, obtained using a single-slit
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Question
Figure 4.2 shows a (schematic) CCD spectral image, obtained using a single-slit grating spectrograph, containing the spectra of two stars. The CCD comprises 800 × 800 pixels arranged in a square array and has a linear size of 10.0 mm along each side. The telescope used to obtain the image has an effective focal length of 4.00 m. (a) What is the image scale in the plane of the telescope, in arcseconds per mm? (b) What is the field-of-view at the detector in arcminutes? (c) What is the angular scale of the image in arcsec per pixel? (d) What is the angular separation of the two stars? (e) If the spectral scale of the image is 0.4 nm per pixel, what is the difference in wavelength of the two emission lines (labelled Ha and H) in each spectrum? 800 600 400 200 400 pixels 200 600 800Explanation / Answer
CCD is a semiconductor chip. it is connected with the electronics that control it and power it. and allow the data present in it to be read out to make it useful for the astronomical devices.harge that accumulate in each detector is initially tiny electric current but later this current get converted into number call ADU. The ADU value is the measure of charge. In order to qualify the number of photons, ADC factor is applied to the number in ADUs.
(a)
The image scael is equal to the inverse of the focal length, that is,
I=1/f=1/4=0.25
(b)
The field view in the near infrared red wave is equal to 0.2 square degres and in the VISTA telescope it has 0.6 square degrees.
(c)According to the image quality, the pixel size can be 2-3 arc sec per pixel if the image quality is inhgerent. And less than 0.5 arc sec per pixel if the samplin has inherent image.
(d)A pair of eclipsing binaries 50 million km apart at a distnace of 110 light years have an angular seperation of ZERO.
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