In this picture, three different filters (r' i' and z') have been combined to show how red the quasar (indicated by the arrow) is compared to stars or galaxies in the field. To be that red is a good indicator that the object is a very distant quasar, though a spectrum is needed to confirm its distance (see below).
Image size is 350x350 pixels, or 56"x56" on the sky
© Canada-France-Hawaii Telescope Corporation 2006
This spectrum of the quasar from the Gemini-South Telescope shows the brightness (flux) as a function of wavelength. The peak at about 9000 Angstroms is the redshifted Lyman alpha emission line. The position of this emission line defines the redshift and therefore the distance. There is very little flux below 9000 Angstroms due to absorption by neutral hydrogen in front of the quasar. The lack of flux here explains why the quasar looks so red in the image (above).
Click on the image for a larger version.
The whole mosaic image on which the quasar was found is shown
here in the z band.
The 36 CCDs are clearly seen as 4 rows of 9 rectangles,
each of them 9.5 MPixels (see at the bottom of this page for a picture
of the CCD mosaic itself in the camera).
The quasar is on CCD number 29, the third one from the left on
the bottom row... See below for a closer view of this CCD.
Click on the picture for a larger one, and here for a high resolution
version (322KB)
The quasar was found on CCD29, one of the 36 CCDs of MegaCam. This
image shows the whole field of that CCD, with a square on the upper
left corresponding to the field of the color image above, and the two
black and white images below. Tens of thousands of stars and galaxies
are visible on such an image!
If you want a high resolution picture, go here (1.16 MB)
This animation is a blinking view of the quasar field (same
scale as the color image above, 56"x56") made of the r- and z -band
images. The quasar is indeed seen, relatively bright, in the z
band while it is not visible in any of the other bands. See the color
picture above to get its location if you can't find it...
The r-band image is here.
The z-band image is here.
The Canada-France-Hawaii telescope structure is based on an equatorial
mount design, with one of the axis of rotation set parallel to the axis
of the Earth¹s rotation. The mirror cell (the white circular
structure
at the bottom of the telescope, seen just above the person giving the
scale
on this photograph) holds and protects the most precious element: the
3.6-meter
diameter mirror.
Light from distant objects enters the dome through
the slit, bounces back from the mirror such that it will focus, and
create
a crisp image at the prime focus, MegaPrime, where the image is
captured
by MegaCam, CFHT's
wide-field digital camera (340 MegaPixels!) .
By today's standards, the CFHT telescope is a heavy
structure compared to the diameter of its mirror: the total mass of the
telescope is 325 tons, with 250 tons for the mobile section alone. Yet
the telescope can point to any location in the sky with an accuracy of
3 thousandths of a degree - and can follow astronomical objects with an
even better accuracy, thanks to an automated guiding mechanism that
compensates
for the apparent motion of the sky due to the Earth's rotation.
At the focal plane of MeagCam seen in this photograph, there are 40 CCDs. Each of them, known as the 'e2v 'CCD42-90'', account for more than 9.5 megapixels. 36 of them are used to image the sky, bringing the total number of pixels for the MegaCam mosaic to a staggering 340 million!
Want to know more about MegaPrime/MegaCam? You can go here (first light of the camera) or here for more technical information.
Various resolution downloads:
[Full scale -
954x805
- JPEG - 84Kb]
[Scaled
1/2th
- 476x402 - JPEG - 19Kb]