Cassiopeia – the W in the sky

Some constellations are easier to spot than others.  Cassiopeia with its distinctive W is visible year round in the northern hemisphere above the 34th parallel. In the image below it easily stands out from the fainter background stars.

Cassiopeia above the three line - Benoit Guertin

Cassiopeia above the three line – Benoit Guertin

The five stars drawing a W in the sky are all naked eye magnitude 3 and brighter stars, and in the image above I used a layering technique to increase the color and brightness of those stars to really make them stand out.

  1. Duplicate your base image, and set this layer to lighten only
  2. Apply a blur to the top layer(about 8-12 pixels)
  3. Increase the color saturation and brightness.  Play with the curves to brighten the bright stars, but not the background sky.
  4. Use a mask as required to filter out the bright foreground elements, such as light reflecting off a building roof-line in my image above.

Canon Rebel XTi
17mm f/4
4 x 20sec ISO800


This Weekend: 4 Planets in Plain Sight

If you are able to get out of bed early before sunrise and the sky is clear, you can catch a view of our three closest planets, and if you include Earth that makes 4.  Mercury was at the greatest elongation on September 12th (furthest from the Sun when viewed from Earth) which makes it a good time to spot without the glare of the Sun.  But it happens that Mars and Venus are also on that same side of the Sun, making a chanced planetary alignment.

The sky map below [click for larger] shows the position of Mercury, Mars and Venus for the morning of the 16 to the 19 of September.  Bright star Regulus and our Moon are also there to make this a worth-while event, especially on Monday the 18th.

September_AlignmentMars and Mercury will be closest on the 16th, while the 18th will probably be the most photogenic as the Moon will be a thin crescent in the middle of this alignment.

Ursa Major

Ursa Major, or Big Dipper is one of the most recognizable constellation in the Northern hemisphere. People often use it to locate Polaris, the North Star.  Can you find Polaris? (Hint: upper right)

Ursa Major (Big Dipper) low in the sky in late summer around 11pm

Ursa Major (Big Dipper) low in the sky in late summer around 11pm

Canon Rebel XTi (450D)
17mm f/4
Stacking of 4 x 20 seconds @ ISO800
Post processing with GIMP

Moonlit Mountain Under the Stars

When I took the four shots to create this image below the Moon was just starting to rise above the tree-line behind me.  A full moon may be 1,000,000 times dimmer than the Sun it’s still bright enough to cast shadows and considerably light up the scene in a long exposure photo.

Over the mountain top a loose grouping of stars identified as Melotte 111 open star cluster.  These are about 40 bright stars laying 280 light years away all moving together.  It lies in the Coma Berenices constellation.


Canon Rebel XTi (450D)
17mm f/4
20sec @ ISO800
The sky is a stack of 5 x 20sec.  The foreground is a single 20sec shot.