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)

Thursday, March 9, 2017

Galactic Collision

Antennae Galaxies

Stars have a social life, just like us. They grow in a nursery environment and when they get older became more independent but still in contact with others in the middle of their open cluster neighborhoods. Some of them find a pair to mate with for life and at the end of their lives, we can always find many of them living together in geriatric homes called globular clusters. Social life includes both attraction and repulsion and it also happens at galactic scale. Our galaxy, the milky way and its two nearest friends Triangulum Galaxy and Andromeda Galaxy are getting closer so in about 4 billion years they will encounter face to face (or butt to face?). This collision was initially  thought to be only between the Milky Way and Andromeda, but it seems that Triangulum galaxy will also join the collision eventually. 

Will there be massive destruction, chaos and enormous outbreaks of stellar violence?  Two galaxies crashing sounds a little too cataclysmic, but due to the enormous “empty” space between the stars it would be more like an harmonically mating dance. But remember about the social interactions: there will be attraction and repulsion of everything involved in the scene, like if two big families move to a single house and then they reorganize every single room to fit themselves in the house and yet there is one or two members than can not endure the chaos and leave home.

I am not sure if the human race will be still “alive” in four billion of years to experience that, but one thing is sure; if we get to survive, our house will not be on Earth.  By that time our Sun will have started (or finished) the process of becoming a red giant and then shrinking into a white dwarf and we won´t endure that process living on the surface of our planet.


It sounds like a good show that we will missed, what a pity. There is still a hope to see a replica of that show on the next clear night though: Antennae Galaxies performed by NGC 4038 and NGC4039, two galaxies located at  45 Mly from us.  This is a wide angle picture, courtesy of my Argentinian friend Fernando Buezas (FBUEZAS) where the harmonic mating of the two galactic can be seen with a little bit of detail:
Click in the image for full size
Two galactic bodies merging into each other  can be appreciated in the picture as well as two curved jets, products of the stars and dust ejected from the humongous battle of physical forces.  In my 6 inche aperture under suburban skies I missed totally the anthennas, but I was still able to see the two bodies merging. With averted vision, they looked like a “coma” or a horizontal number nine.

With this pair of galaxies the same phenomenon is happening that I had with other faint galaxies like Sombrero. The whole shape is better seen in low magnification as the light that comes from the surface is spreaded over a smaller surface, therefore the edges  contrast more with the background and it’s easier to see the shape. Once I had that image in my head, I procceded to add more magnification and look for some details in its surface. This was the final result.

Antennae galaxies are located in Corvus. To find them, one can start from the star γ Crv, then hop almost two degrees to an "L" formed by HIP59124, HIP57217 and HIP59195A; then another hop to the 5th magnitude star HIP58587 and northeast of it, there is a patch of light that will reveal the galactic collision.



Happy hunting!!!


LG


Edited by Jennifer Steinberg (editor in chief)


SOURCES

Stellarium

Monday, February 27, 2017

10x50 Binoculars review

Last month I got a new pair of binoculars: Celestron Up-close 10x50. I have been using them a lot these days so I though it was time to throw a review in here. This time I don’t want to enter in tiresome measurements, but rather some descriptions of objects seen and perhaps there may be some room to compare them with my 15x70s.  My intention is not to compare this “low price” binos with other models, but rather than that, show that one does not need a big and expensive telescope to start in amateur astronomy.

So let’s start!

2 things I like the most about these binoculars are their size and the large field of view (FOV). With only 1.7 pounds and almost half the size of the 15x70s (see the comparison in the little picture), they take only 1/4 of the space in my 40cms (15.7”) backpack. The large  FOV allows me to see extensive areas of the sky like the Orion’s belt and sword together or an entire small constellation like Triangulum.  The specifications call a FOV of 7 degrees, but less than that are truly useful. The field curvature makes it hard to discern details close to the edge and it has some vignetting also. I would say these binoculars have an effective FOV of about 6 degrees.

The first night with the binoculars was the 9th of January. I caught a handful of objetcs under my usual Bortle 5 skies. Orion Nebula was only a misty smudge involving two stars, but with averted vision I could make out a winged like shape. Some days later I gazed from a darker location and the winged shape was more evident with direct vision. M3 seemed like a fuzz ball embedded in a dim halo. M13 looked similar to M3, but brighter. On the other hand, Omega Centauri was a much larger cottonish smudge in appeareance like a soft cotton ball.
Other objects I got to see where M51, M81, M82 and M104. All of those were mostly specks of light visible with averted vision.

Days later, I did a short trip to the mountains and took my binoculars with me. I did a short video using the binoculars and my cellphone, both handhold (Click here to see it).

Click for a large image
My last observation with these binoculars was on the 15th of this month. I went to a Bortle 3/4 area  (blue  zone in lightpollutionmap.info) about 7 kilometers north from the edge of the city. The sky at the zenith, north, east and west was considerable dark, but there was a huge dome of light pollution coming from the south. I managed to catch some more objects like the Flame Nebula (with averted vision), M78, Andromeda Galaxy with its satellite galaxies M32 and M110 (with  averted vision), Triangulum Galaxy and the very complex stellar area of Cone Nebula and Rosette Nebula. The  toughest targets I saw were M65 and M66 (Part of the Leo Triplet) which looked like almost impossible specks of light even with averted vision. Although the good skies I failed to see dim objects like M97 (Owl Nebula) and its companion M108 (Surfboard galaxy) and also the tough galaxy M74 in Pisces.

In middle of this dark zone, I took advantage of the good conditions and performed a sketch of M81 and M82, two galaxies located at 12 mly from us. I started adding and adding more stars around the galaxies until  I surpassed the binos FOV so the sketch you see it is not inside the true binos FOV, but rather an intent to show the feeling of looking at the sky with them.

Now, not everything is peaches and cream with these binoculars. The moon at night shows to many reflections inside the binoculars and the coma in brighter objects is bothersome and frustrating. I did succeed taking a picture of the moon in the daylight (which looks beautiful) to compare the FOV and magnification with the 15x70s.  Apparently, some of the biggest lunar features are visible, so there is a small chance to explore the moon with them.



These binoculars won’t  replace a telescope, but considering the situation of many beginners, who do not know the sky and are on a budget, getting an inexpensive pair of binoculars to start with is not a crazy idea after all and much better (and even cheaper) than many of the department stores telescopes that end up in the Attic.

So, here is a short review of them and by the way I will keep doing sketches using them, I will add the link in the comments for more information. It is always a pleasure to share my observations here.



Blessings,



LG



Edited by Jennifer Steinberg (editor in chief).