Virgo Galaxy Cluster
April -May 2014
One of the objects that I most wanted to capture once my equipment
returned from Japan was the central part of the Virgo galaxy cluster.
This thick collection of galaxies represents the center of
the supercluster our Local Group (Milky Way, Andromeda, et al) orbits.
The center part of this is an asterism known as Markarian's
Chain. It starts with the huge super galaxies of M 84 and M
86 and extends in an arc of 1.5º.
The entire area between the bowl of Virgo, Coma Berenices, and the end of Leo
is filled with galaxies. In a dark sky (i.e. not here) you
can easy pick up layers of brighter then dimmer galaxies. Using NB4Stars it is
possible to image these from the city and produce respectable images.
This is a first portion of a project that will last several years. I intend
to create a mosaic
of most of the area in the Virgo bowl over the next few years.
Each of these projects will likely be an entire spring
season. However, next year's imaging will focus on M 81/82 so I can
complete that project before the tree that was previously blocking my
view has a chance to grow back.
click on to the above for a more detailed image of Virgo or use the
Annotated Image below.
to a full size unannotated image
This also is the first demonstration of the new PixInsight feature Drizzle Integration.
This technique originally developed for the Hubble
makes use of a common noise correction technique called dithering.
The algorithm takes advantage that as you shift the image you
are actually capturing more information than just what integer pixels
are able to. With Drizzle I am able to expand the image by a
factor of 2 which converts my 3.5"/pixel camera into 1.75"/pixel which
is at the seeing limits (or beyond). I did find that the
image has to have good S/N. I also tried to drizzle the M 51
H alpha project which was released at the same time. Unfortunately I
could never get an acceptable image
Since the above image is rather large even with the Zoomify here are
some reduced size images
click for a full size image
M 84/86 Area
This is a full resolution image extracted from the above full frame
image. Click on the above for a 1280 x 720 image
This image is a thumb of the drizzle processed image. At this
resolution it looks virtually identical to the image on the left.
Click on the above for a 1920x 1280 full size drizzled image.
I had a bit better luck with some of the noise reduction. So
the improved quality of some of M84/M86 is post processing not drizzle.
M99 is a spiral that is one of my first Virgo targets in my Messier
Marathon guide. As such I am familiar with it
visually. Unfortunately even in the 30"
Challenger it is difficult to see the spiral structure.
The galaxy is rather small at 3.5"/pixel so drizzle made a
This is an extract from the full size image. Click on the
above for a 1280x720 image
This is an extract from the Drizzle processed image. Note the
additional detail in M99 (right) and NGC 4302 (edge on on left) even at
this resolution. To see how much detail drizzle reveled
click on the above for a 1920x1280 image
M 88 is a Sbc spiral galaxy in the upper left of the full frame.
Again Drizzle revealed a lot more detail.
I did not bother
producing a breakout of this object from the unDrizzled frame.
Consult the scrolling image above if you are curious.
This is full resolution.
The images were processed with PixInsight.
|27 x 900
|29 x 900
|32 x 900
Color Calibration.Color Calibration in the original
image was based on a G2V star with the ratio of (.210, .166, 1.0).
I found this ratio did not produce good results in the drizzled
image. Instead I used Color Calibration with the center of M86 as
the white reference.
DeconvolutionNormally deconvolution is not useful on my wide image shots. I found it dramatically improved the drizzled images.
Masked StretchOn the full resolution image I used the masked stretch technique described by Harry's Shed
to reduce the size of bright stars. Unfortunately this technique
did not work on the drizzled image. For a comparision look at
HIP: 60089 in the two images of M99. This star is the orange star
at 11 o'clock from M99.
the central slice of the galaxy rich area of Virgo. This chart
will show the two additional frames I intend to capture in future years.
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