Tuesday 10 October 2017

Cassiopeia Photographed with an iPhone 7 – October 2017



Cassiopeia with iPhone 7 – October 2017


I took a few photos of the main asterism in the constellation Cassiopeia, on a recent very clear October morning, with my iPhone 7 camera.  The early fall can be a great time for very clear skies around my area, even in a fairly large light polluted city.

Here’s the result, with a little labelling and photo enhancement in GIMP.

2017 iPhone 7 photo. 



The upper photo has had the brightness and contrast pushed in GIMP.  That gives the sky a somewhat mottled appearance.  The thing on the left of the picture is a tree.  The lower picture uses the GIMP brightness threshold filter, to only show pixels above of a certain brightness level.  This effectively isolates the main stars of the “W”.

Here’s an inverted picture of the second image.





You can see how the iPhone picked up pretty well all of the stars of the “W” of Cassiopeia.

Note that the stars are somewhat blurred, though not by very much.  Since the iPhone 7 was hand-held, there was naturally some blurring.

Below is a photo that was “pushed” even further in GIMP.  This has picked up some of the less prominent stars in the constellation.   I have labelled those stars in yellow and have given their magnitudes (lower magnitudes are brighter).  I also included a map of Cassiopeia (from Wiki, but originally from Sky and Telescope) and oriented the photo to be similar to the map, so that the two can be more easily compared.

As you can see, the iPhone photograph captured a number of the “non-W” stars in Cassiopeia, which are labelled in yellow.  Interestingly, it seems to have picked up the fact that Sigma Cass is an optical double, even though one of the companions is actually rather dim, listed at 7th magnitude.  Of course, there is some scope for mis-identification.



When you take a photograph of the sky with the iPhone, your first reaction will probably be that there isn’t much there.  It helps to take the picture when the seeing is exceptionally good, if course. As noted earlier, the autumn months are often the best time of year for this, as the atmosphere is relatively dry and clear (vegetation is not very biologically active, so the air is dry).
After taking the picture, you have to push the image in an imaging processing program, like GIMP or even the iPhone’s own photo editing app.  Turn the brightness way up, the raise the contrast slowly as well.  The stars will come out, like magic, though you will want to experiment with settings, to get the best effect.  Some of the other features of GIMP (like the threshold filter, or the sparkle filter) can also help bring things out, or eliminate background clutter.
I will use Wiki’s article, to give a brief overview of Cassiopeia:

  • The most recognizable part of it is the W asterism.
  • Since it is a circumpolar constellation (always above the horizon in northern regions), and not far from Polaris (the north star), it actually rotates around the north star, so sometimes the W is upside down.
  • It is easy to find, as long as you can find the Big Dipper.  Just look along a line from the dipper pointer stars to Polaris, then about the same distance across the sky, until you see the W shape of Cassiopeia.
  • The five stars in the W are all bright, and three of them are variable (their brightness changes over time):
  • o   Alpha Cass is magnitude 2.2, and about 230 light years (l.y.) from Earth.
  • o   Beta Cass is magnitude 2.3 and about 55 l.y. from Earth.
  • o   Gamma Cass is magnitude 3.1 to 1.6, as it is a highly variable star.  It’s about 550 l.y. from Earth.
  • o   Delta Cass is magnitude 2.7 and about 99 l.y. from Earth.
  • o   Epsilon Cass is magnitude 3.3 and about 410 l.y. from Earth.
  • As for the dimmer stars that the iPhone captured:
  • o   Kappa Cass is magnitude 4.2 and about 4000 l.y. from Earth.  As you might imagine, being visible from that distance, it is huge and extremely bright.
  • o   Eta Cass is about magnitude 3.5 and about 20 l.y. from Earth.  It is very similar to the sun.  In fact, if you could see the sun from Eta Cass, it would look like Eta Cass looks like from Earth.
  • o   Theta Cass is about magnitude 4.3 and some 135 l.y. from Earth.
  • o   Zeta Cass is about magnitude 3.7 and 590 l.y. from Earth.
  • o   Sigma Cass is a binary, 5000 l.y. from Earth and magnitude 4.9.
 
  • Cassiopeia has a number of deep sky objects, nebulae, open clusters and galaxies.  A favorite is NGC457, the E.T. cluster, which does look rather like a friendly alien beckoning to one, from across the cosmos.
  • Cassiopeia is useful for locating the Andromeda galaxy, via a line drawn from Alpha Cass, in a direction moving away from Beta and Gamma.

-----------------------------------------------------------------------------------------------------------------
Now that you have read some real science (astronomy and astrophysics), you should read some science fiction.

Kati of Terra

How about trying Kati of Terra, the 3-novel story of a feisty young Earth woman, escaping from criminal aliens, and bringing them to justice, with the help of an alien police agent and a curmudgeonly, somewhat criminally inclined but brilliant brain implant.




The Witches’ Stones

Or, you might prefer, the trilogy of the Witches’ Stones, which follows the cold war intrigue and adventure of a future democratic Earth confederation, an opposing dictatorial galactic power, and the Witches of Kordea, a third power which doesn't trust either side (they’re psychic aliens, not actual witches).







No comments:

Post a Comment