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My Virgo Deep Field
This is a very simple project that anyone can do with a DSLR a medium telephoto lens and a tracking mount. It shows an area of the sky between Virgo and Coma Berenices full of galaxies known as the Virgo/Coma supercluster. I was curious about what can be captured with a DSLR and in this case a 135mm lens and I was surprised at both the number of galaxies photographed and the level of detail that can be seen when zooming into the photo.
For this project I used my Canon 60Da DSLR with a 135mm lens and an Astrotrac portable mount. I took 1 minute exposures at F2.8 and ISO1600. I stacked about 60 of those exposures to reduce noise. I took the photos from a rural area, the cluster was low in the sky from my location so I had to take the photos quickly before it disappeared behind some trees.
The next photo shows an annotated version of the photo, it won't be readable but the zillions of green labels will give you an idea of the number of galaxies that are in this area of the sky and can be captured with simple equipment.
Can you count the labels? Wow!
Here's a zoomable version: http://zoom.it/LQeD
And a zoomable version with labels: http://zoom.it/6fdYq
After taking the shot I decided to do some crops and try to see at low resolution what can be seen about the most important galaxies in the photo.
The first crop shows the Markarian chain, a group of galaxies that from earth form a well defined and smooth chain. Some of the members in this group are related and move in the same direction at about the same speed but some others are just overimpossed by perspective. It's a remarkable group of big and bright galaxies and a very popular target for astrophotography.
This is M100 or NGC4321 a Grand-Design Spiral Galaxy that is almost face-on. I was surprised at the level of detail, this galaxy is 55 million light years away and we are using a wide angle lens but even then the spiral arms and the nucleous of the galaxy are clearly visible, even the faint outisde arms are visible in the image. A very surprising result and a beautiful galaxy.
Now an Spiral Galaxy but seen from its edge: NGC 4216 a metal rich galaxy. The halo of globurlar clusters around the galaxy center can be inferred from the photo.
Now two interacting galaxies: NGC4435 and NGC4438 also known as "The Eyes", the galaxies are distorted by the gravitical interaction between them, it's surprising how this can be seen even at this scale.
This is NGC4654 an assimetric spiral galaxy, it can be seen clearly in the small scale crop that the arm on the left is more prominent.
Messier 91 is a barred spiral galaxy, the central bar can be seen as well as the two most important arms extending from the end of the central bar. To give a scale about brightness this is a magnitude 11 galaxy.
Another beautiful galaxy with a particular structure: M99. An unbarred spiral that has a normal looking arm and an extended arm that is less tightly wound. Can this be seen at this scale? Yes! The magic of pixels.
Messier 90 is a bright spiral galaxy. It has a peculiar satellite galaxi: IC3583 that can be seen at the top left of the galaxy as if they were two stars joined by a stream of light. So we got to a point where even small satellite galaxies are seen in a wide angle image.
NGC 4567 and NGC4568: The Siamese Twins. Two galaxies that overlap in the sky and scientists believe are just begining to interact.
M60 and NGC4647. M60 is not a spiral but an elliptical galaxy the pair it forms with NGC4647 is known as Arp 116. Arp is a catalog of peculiar galaxies. This is the third brightest galaxy in the Virgo cluster and a giant galaxy that dominates its subcluster area.
Messier 88 an active spiral galaxy.
Finally M87, a giant elliptical galaxy one of the biggest galaxies near the Milky Way. It's an almost featureless ellipsoid and also one of the greatest sources of radio in the sky. A big monster!
This wide field shows detail that wasn't expected and we can go from a wide view of thousands of galaxies to details in the arms of spiral galaxies. I think this technique is also goot to monitor for supernovas as I think a bright supernova in one of the field galaxies would show up without any problems in the photo. A quick blinking between photos taken at different days can search for a supernova not in one but hundreads, even thousans of galaxies at the same time.
The resolution and detail can be enhanced augmenting the number of pixels in the image, this can be done using a longer focal length and making a mosaic. Mosaics are very common for high resolution astrophotography but even without a mosaic a good level of detail can be obtained.
Photographing galaxy clusters is fun and compared to other types of astrophotography the adqusition and processing are simpler, there are several clusters that can be photographed with modest equipment and the photos produced are not only beautiful but also informative and might be even useful to science in the event of a supernova.
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