Daily Cosmobite: Secrets of the Dark

Today’s Cosmobite is by Sam Knox, an astronomy guide at MAAS – Sydney Observatory.

Almost directly above Sydney at 9 pm tonight is an area of the sky that is particularly dark. So dark that to see anything, you need to stare at one spot in the sky with a very powerful telescope for over 11 days before you can see anything clearly. So on September 25th 2012, light was starting to be collected through the Hubble Space Telescope. When all the light was compiled at the end into an image, the secret of the dark was revealed. The light that we could see had been traveling towards us for about 13 billion years. That means that this light started its journey towards us 8 billion years before our sun was even born. But what did the image look like? The image showed an estimated 10,000 galaxies as they were some 13 billion years ago, at a time near the beginning of the universe.

Image credit: Hubble Ultra-Deep Field (HST)

5 responses to “Daily Cosmobite: Secrets of the Dark

  • A bright planet rises in NE sky after 10:30 pm at east of Orion. This is observed from Newcastle, NSW. Is it Jupiter?



    • Hi Subi,
      Yes it is Jupiter, the Gas Giant, which rises around 10:30pm at night and is a great object to view through even a small telescope. As the weeks progress Jupiter will rise earlier and earlier.

      • > Many thanks for the reply. I have a small 3″ telescope and would like to view Jupiter. The eyepieces I have at the moment is H-20 and S-4 and they are no good. I’m ordering few Plossl eyepieces. What magnification would you recommend for best viewing of Jupiter?



        • Hi Subi,

          Two factors limit the magnification in a telescope, aperture (diameter) and atmospheric conditions.

          It is simple to calculate the magnification an eyepiece will give in your telescope.

          For example, if we have a telescope with:
          Aperture: 20cm or 200mm (8-inch)
          Focal Length (F.L.) * = 2000mm
          Eyepieces: 10mm and 25mm (10mm is higher magnification, 25mmm is lower magnification)

          * The focal length of the telescope is usually on a label on the tube of the telescope.

          Focal Length ÷ Eyepiece = Magnification

          2000mm ÷ 25mm = 80x magnification
          2000mm ÷ 10mm = 200x magnification

          The upper limit for magnification in a telescope can be simply calculated as either twice the aperture of the telescope in millimetres or 50x magnification for every 1-inch of mirror diameter. So for a telescope with a focal length of 2000mm we should get 400x magnification.
          While this is good in theory and in controlled conditions, you are using your telescope outside where atmospheric conditions (turbulence) are continually changing, so in reality, it would be extremely rare to achieve the theoretical limit.

          Essentially you want a sharp image, not a large blurry one so you will generally find you are using a medium and/or low magnification to obtain a sharp image (depending on atmospheric conditions).

          On Jupiter you should see a few of the cloud bands as well as the Galilean satellites (4 largest moons of Jupiter).

          After this, if you are still unsure about which magnifications to select for your system then I would suggest talking to your local astronomical society. Astronomical societies have many members with lots of experience who are usually more than happy to help.

          Mel – Astronomy Program Co-ordinator

  • I Looked up to the sky tonight and saw a light the size of a star and my whole family was witness .it came from the back of the moon to the SE and was traveling fast. We saw it for about 20 seconds and on til it faded out .’It was as bright as a star. White..This was from Lismore NSW Australia. Far out this was cool..Please tell us what it was..Other people must have seen it..???? Please contact us for more details….Time was about 9.32 pm….Thanks

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