Saturday, April 8, 2017

Melotte 25, The Hyades

Embedded in the midsts of the Bull, there is a bright Star Cluster. It hosts Aldebaran, an orange giant star which is also the alpha star of the constellation Taurus.  You actually don’t need a telescope to enjoy this huge star cluster, but a good pair of eyes will do a good job even under light polluted skies.

If you are able to locate Orion and The Pleiades, it won´t be difficult to spot the Hyades. It is possible you have seen it before because it is located right in the middle of those. With just the eyes, it look like an isosceles triangle formed by 6 bright stars (7 if you are able to discern a double star in it) including, of course, Aldebaran. If the plan is to explore inside the cluster, a pair of binoculars will do the job well. The cluster is large and therefore a wide FOV, larger than 5 Arc degrees, is preferred to see it all at once.  A small pair of binoculars (10x50 or 7x50) or a finderscope (8x50 or 9x50) will do an amazing job gathering the whole cluster and leaving some magnification left to see more stars in it.

I sketched this cluster for the first time back in 2012 from my severely light polluted skies in Bogota. With just the eyes, I was able to see the traingular shape playing in the sky with the Pleiades and Jupiter at that time was sailing through Taurus´territory.  

In these days, the Bull is following the sunset so it may be available for just 1 hour before the dawn of the sun. I have been able to see 10 stars in the triangular area at the edge of my suburban skies. How many are you able to catch with just your eyes?




Clear skies,



LG



Edited by Jennifer Steinberg (editor in chief).

Tuesday, April 4, 2017

Stars that are not Stars

Cetus A Galaxy

When stargazing with binoculars I have been warned that many DSOs such as galaxies and globular clusters may appear stellar in appearance. For some people this may be a big disappointment, but for binoculars stargazers it is an incredible achievement because the fact that one is looking at objects located millions of light years from us with a simple pair of binoculars.

Here is M77, also known as Cetus A Galaxy, due to its location in the constellation Cetus, the Sea Monster. According the mythology, Cetus was sent by deity Poseidon  to punish queen Cassiopeia for her never-ending boasting, but later on defeated by Perseus, who used Medusa’s Head to turn Cetus into a stone.

Now, lets talk about the galaxy itself. It does look like a stellar object, but it may still reveal some nebulosity halo around it with averted vision.  I have seen it in my telescope with 100x and the view is similar, but enhanced by the magnification: a roundish and bright core surrounded by some nebular halo.

The best thing about it is, as I said before, that one is looking at a spiral galaxy located about 60 million light years away. With moderately dark skies, it can be easily found by aiming at the 4th mag star Delta Ceti  and then less than 1 degree east of it.               

Happy bino-hunting!!!



LG



Edited by Jennifer Steinberg (editor in chief).

Monday, March 20, 2017

The colors in the night sky

Mirach and its Ghost

Click to enlarge


This is a frequently asked question and the cause of many disappointments among newbie stargazers: why can’t color be seen in this or that object? It is not the telescope’s fault but actually our own eyes. The few amount of light we get to hunt down from DSOs is not strong enough to activate the perception of color performed by our cones photoreceptors. Yet there have been reports of seeing color in Orion Nebula or specks of blue and red in the edges of  Ring Nebula. I personally had the feeling of seeing some color in Ring Nebula, but other than that, I can’t recall seeing color in other deep sky objects.

On the other hand, stars are bright and concentrated enough to trigger the sense of color in our cones. Some of the best views are provided by red stars like Antares or Arcturus, blue stars like The Pleiades or Rigel and even double colorful systems like Albireo in Cygnus.

This time lets look at Mirach, the beta star in the constellation of Andromeda. We have used this star before to find the way to the Andromeda Galaxy (M31). Apart from M31, Mirach has a closer friend:  the galaxy NGC404 also known as the Ghost of Mirach.  

While one is enjoying the bronze shine of Mirach, it is possible with the use of averted vision to catch a glimpse of its ghost.  I have to admit that I hadn’t seen the galaxy till I started to look for it. It was not hard to find though. The trick here is to avoid seeing directly to Mirach and start to look for an smudge in its periphery. In fact, some stargazers advice trying to take out Mirach from the FOV as it is a distractor of the peripheric vision, but the problem comes if the view in the eyepiece suffers from vignetting. The few 6 arc minutes that separate the star from the galaxy could not be enough to get a decent view outside the dark edge of a regular eyepiece. In my case, the Luminos 15mm does not show image aberrations at the edge (or at least very noticeable) so I could move away the star and its glance far enough to detect the galactic smudge.

I think the color of Mirach plus the ghosty image make a good couple. It is definitely one of the targets worth keeping the eyes to the eyepiece for a couple of minutes and if one is looking for color in the sky, the stars are there to show us the color of their skin.


Clear skies,


LG

Edited by Jennifer Steinberg (editor in chief)