In Part 1 of this series I presented a few color astro photos that represent what you’d see, if your eyes were super sensitive. In part 2, I’m presenting similar images, only these will be presented in one color, the color of H-alpha. Hydrogen alpha is likely the most important emission, for imaging the night sky. In my astrophotography blog series, I discuss the importance of H-alpha and how to image these nebula with a modified DSLR.
The images in part 2 were all photographed in the H-alpha wavelength (656.28 nm). The exposures are long. The equipment is expensive. The tracking is critical. But the results are some of the most stunning images that I’ve ever photographed, all of which are invisible to the naked eye.
All of these H-alpha images required a series of 30 minute long exposures. These are then stacked and processed to achieve the final result (again, see my astrophotgraphy series). Like their color counterparts, the subjects of these images are so dim that they are invisible to the naked eye. This makes locating the subjects somewhat tricky. The use of a computerized mount reduces the time needed to get the telescope pointed at the target. Then it’s just a matter of fine tuning and framing. The focus is set, , the guide camera is calibrated, the filter wheel rotated to the proper filter and the exposures begin. Thirty minutes later, I check the resulting image to see if I hit the target as intended. If so, the imaging continues until the object is too low in the sky to continue.
Sometimes, I’ll look up an uncommon object and point the telescope in the general area and shoot a test exposure. Many times, this technique isn’t too fruitful, but once in a while, a gem is recorded. This is the case of the image below. I scoured the web looking for similar images, to no avail. So this particular area, rarely photographed, is one of my favorite subjects.
Probably one of my all-time favorites is my mosaic of the Orion area. This is an 8 frame 60 megapixel mosaic that required many nights to shoot and many more nights to assemble and process. Anyone that has processed very large images in Photoshop will sympathize on the amount of work required of the computer and it’s operator. Each frame was individually processed. When they were all complete, each one was registered in a special piece of software called Registar. Then all 8 were imported into Photoshop, assembled, blended and processed. more than 40 hour of post-processing was performed on this image alone.
Imaging deep sky targets is not for everyone. It can get complicated quickly, with steep learning curves on both the imaging and post-processing sides. Imaging with a DSLR can be a superb entry into this field. If your interests lie in photographing H-alpha, like the images here, the DSLR will need to be modified, and an H-alpha filter purchased. An astro-modification or a full spectrum modification can be performed to allow the proper H-alpha wavelengths to pass. My preference is the latter for the maximum throughput and flexibility. It allows my DSLR to be used for astrophotography, IR photography or any other application I can dream up.
I hope you’ve enjoyed this short series highlighting some of my favorite images. A modified DSLR is a great way to get started doing astrophotography. If you’re interested in giving this a try, take a look at an H-alpha modified DSLR or a full spectrum version.