- Jeff Kuderna
Unexpected Trip to the Lagoon
Updated: Feb 23, 2020
What had started out as a late night imaging session of the Markarian Chain (web image shown below), quickly was derailed. I noticed several potential issues right off the bat. First was the size of the object to be imaged. With a field of view of 101.5 arcminutes wide by 68.4 arcminutes high, the Markarian Chain consists of 8 well known galaxies, and an additional 35 minor galaxies. This field of view would have been to large for my 4 inch refractor, and therefore would have required a mosaic. My current acquisition program, BackyardEOS, is deficient in this area. I am looking into possibly buying Sequence Generator Pro, which has a more robust plate solving capability along with a "Frame and Mosaic" wizard capable of automating the panorama-type effect I would have needed.
The second issue I encountered was focus. What I had mis-diagnosed as poor auto-guiding (was averaging 1.5 arcsecond rms error) was in fact an out of focus imaging train. Having started the night off with an ideal focus, the rapid descent in temperature and cooling of my telescope resulted in a loss of focus. It wasn't until the Markarian Chain was beginning to descend into the East behind my house, that I realized my miscalculation. Maybe for my birthday next fall, I can acquire one of those nifty auto-focusers. Along with the SGP software, it would not be difficult to run relatively frequent automated focus sequences, ensuring pin point focus throughout the night.
With the night slowly fading away from me, an interesting target was presenting itself just over the trees to my Southwest. M8, the Lagoon Nebula, was within my grasp within minutes of plate solving via AstroTortilla. I was surprised to see that at my modified Canon T3i's sweet spot of ISO 800, I could obtain the requisite exposure in 60 seconds. This would be ideal given the constraints of my autoguiding performance and the late hour.
I was able to acquire 53 light images of the Lagoon Nebula, of which 28 were best suited for stacking. Using the white t-shirt method, I collected 20 Flat Calibration images. I then, broke down my setup around 8 am, and fired off 20 Dark Calibration images in the house. Leveraging the 20 Bias Frames from my M51 acquisition a few weeks earlier, I had all the data I needed.
The next day I went to work pre-processing and post processing my Lagoon Nebula image. Following the www.lightvortexastronomy.com tutotials for PixInsight, I was able to create my final image. The Lagoon Nebula, M8, was captured via a modified Canon T3i and Astronomik Clipin CLS filter, connected to an ES127 APO. An Orion Starshoot Autoguider with a 50mm mini guide scope and PHD2 was employed for autoguiding. The mount was an Orion Atlas EQ-G Go-To. Total integrated time was 28 minutes comprised of 28 60" images.
The Lagoon Nebula, Messier 8 (M8). At a magnitude of +6, it would appear faint to the naked eye in good seeing conditions. At a distance of 4,100 light years from Earth, the size of the nebula is 110 x 50 lights years. The brightest part of the nebula, known as the "Hourglass Nebula" is a region of hot gas and star formation. This image is comprised of 28 one minute exposures taken with an Explore Scientific 127 APO and processed in PixInsight.