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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 1.5.  

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.

Map of the Virgo Bowl

click on to the above for a more detailed image of Virgo or use the Annotated Image below.

Annotated Image


Link to a full size unannotated image


Drizzle

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

Zoomed Components

Since the above image is rather large even with the Zoomify here are some reduced size images

Markarian's Chain

Markarian's Chain in NB4Stars
click for a full size image

M 84/86 Area

Map of Central Virgo
Normal Drizzle Processing
Central Virgo using NB4Stars

This is a full resolution image extracted from the above full frame image.  Click on the above for a 1280 x 720 image
Central Virgo using Drizzle Processing

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

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 marked improvement

Map of M99 area depicted below

Normal Drizzle
M99 using NB4Stars

This is an extract from the full size image.  Click on the above for a 1280x720 image
M99 using NB4Stars processed with Drizzle

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

M88

M 88 is a Sbc spiral galaxy in the upper left of the full frame.  Again Drizzle revealed a lot more detail.



Drizzle
M88 using NB4Stars processed by Drizzle

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.

Processing Details


The images were processed with PixInsight.


Filter
Exposure
Ha20 (Red)
27 x 900
sYel (Green)
29 x 900
sV (Blue)
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.

Deconvolution

Normally deconvolution is not useful on my wide image shots.  I found it dramatically improved the drizzled images.

Masked Stretch

On 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.

Long Term Plan

This represents 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.

Copyrights for Photos


Creative Commons License
Except as noted, all work on this site by Robert J. Hawley is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. This permits the non commercial use of the material on this site, either in whole or in part, in other works provided that I am credited for the work.