February 25, 2019

The Sky's the Limit

by Daniel Dall'Olmo, MD

I've been fortunate in life to have many interests to occupy my time and brain. My career in medicine was a fantastic journey as an interventional radiologist. Training in the early ‘80s (‘81–‘86), IR was a relatively new subspecialty; hence, my career was like riding the crest of a wave as I incorporated new tools and techniques for diagnosis and treatment. Since retirement I have been able to "dive" into another one of my interests: astrophotography.

Astronomy has been a lifelong interest of mine. I learned my way around the night sky as a youngster, and as an adult, would bore my children with astronomical facts (although they are now teaching their children the same).

I've had a telescope since I was young and always enjoyed "visual" astronomy. Looking at the moon, planets or some brighter deep sky objects (DSO) always fascinated me. However, I was always in awe of DSO photos. The variety of DSOs (galaxies, nebulas, comets, star clusters, etc.) is extensive and many are not well visualized even through a telescope.

M31, Andromeda Galaxy (40 x 1-minute exposure; 200mm lens)
M31, Andromeda Galaxy (40 x 1-minute exposure; 200mm lens)
  NGC6992, Eastern Veil Nebula (24 x 10-minute exposure; 11' telescope)
NGC6992, Eastern Veil Nebula (24 x 10-minute exposure; 11" telescope)
  M13, Great Globular Cluster in Hercules (13 x 3-minute exposure; 11' telescope)
M13, Great Globular Cluster in Hercules (13 x 3-minute exposure; 11" telescope)


Additionally, by viewing an object with the aid of a telescope, the object’s color is not appreciated with the naked eye. To bring out the full beauty of these objects, you need long exposure photography.

I assumed as a professional imager (radiologist), the transition to a different form of imaging would be relatively straightforward. Well, I completely underestimated the process of deep sky imaging. The last two years have been like going back to university. Astronomical imaging can involve different types of cameras (dslr, ccd) with different sized sensors (full frame vs. APS-C). The pixel sizes in these sensors vary, which translates into different resolutions depending on the pixel size of the sensor. This is important when determining which objects (planets vs. nebulas) to image given your type of camera.

Furthermore, once images are obtained, the post-processing of the data (that is, the integration of multiple dim images to make a brighter final image) is a deeply involved process that can take hours to complete.

As an example, one could take 24 ten-minute images (a total of four hours of exposure), stack the images together to produce a single, four-hour integrated image and then do various post-processing maneuvers to "clean up" the image and enhance the object of interest.

To make the process even more complex, equipment considerations must be addressed to obtain quality data (images). Issues such as polar alignment, telescope guiding and focusing are critical to obtaining sharp images.

In reality, this is a great hobby for an interventional radiologist! I have traded my catheters, balloons, stents and baskets for other tools such as cameras, mounts, guiding equipment and telescopes. Each set of tools requires evaluation for the task at hand and some ultimate tinkering or adjusting to suit the situation. The difference is that there is no pressure or risk to this hobby, and I am up at 2am for fun and not because of my beeper!

Here are some long exposure images of DSOs. You can't see color and detail like this looking through a telescope ... Enjoy.