You’ve spent 14 hours shivering and nursemaiding your scope. You’ve processed the image endlessly, coaxing every possible photon into visibility. You’ve excitedly submitted your amazing astrophoto to SkyNews.
Then you open the webpage and discover somebody else has won Photo of the Week. Why? What did you do wrong?
Well, perhaps you didn’t do anything wrong. Maybe it was the luck of the draw. SkyNews receives many beautiful photo submissions from a highly talented stable of astrophotographers hailing from all across Canada. As such, especially on busy weeks, deserving photos can sometimes go unacknowledged.
But there are some criteria that our astrophotography judges use. Being aware of these factors may help you improve your skills and increase the chances of having your masterpiece being recognized. There are also a few common and easily avoidable issues we see with images.
How we judge
In general, we judge photos on two broad criteria — technical and artistic.
Technical criteria are all about appropriate use of equipment, as well as the software used to process images. Did the photographer choose a subject (galaxy, nebula, planet, etc.) appropriate for their gear? Was the exposure long enough to properly capture the object? Did the photo show good focus and guiding? Examining the processing phase, we look for appropriate use of the available dynamic range: sufficient delinearization, with little or no clipping at either end of the histogram. Were any gradients removed? Are the stars round and sharp? Is there good contrast and saturation? How well is the noise controlled?
Artistically, the situation becomes a bit more subjective. Our judges, astrophotographers themselves, have preferences and biases. There are some general criteria. Good composition is one: location and orientation of subject matter. But often, it’s the emotional response an image evokes that guides us. A deep sky full of galaxy cluster members can send a shiver down anyone’s spine. The Milky Way stretching across the sky over a mysterious landscape is a popular subject. Narrowband palettes, typically of reflection nebulae are very much an artistic choice.
Here are some of the most common issues we encounter in judging submitted images:
- Over-processed images. Astrophotographers spend their time coaxing every last available photon out of their frames. It’s all too easy to push the processing too hard, resulting in garish colours, solarization effects, excessive noise. Over-saturation is a very common issue.
- Clipping. Typically, low end pixels are clipped (left pure black) to hide noise problems in the background. A pure black sky often looks unnatural.
- Noise. Too much or too little. Astrophoto processing software has great tools to minimize noise, unavoidable in our light-polluted skies. But it’s a tricky business to master. Too much de-noising leads to plastic appearing backgrounds. Too little leaves “salt and pepper” over images.
- Poor focus. This speaks for itself.
- Problems with stars. The stars are the canary in the coalmine of your image. They will very quickly expose problems during processing. Ringing, bloating, over-saturation, strange colours are some of the problems we see. Narrow band imagers often struggle with star colours.
- Poor or no documentation. SkyNews requires photographers to provide information about the equipment used and exposure details with their submitted images. It also helps to “tell a story” — something interesting about the object imaged (not just copied from Google) or your adventure acquiring it (“An owl landed on my OTA!”).
To be clear, we love receiving your photos. If your photo didn’t win, that doesn’t mean we didn’t appreciate the skill and patience required to take and process it. So many of the images submitted are amazing, and they show the passion and dedication of Canada’s astrophotographers. Keep them coming!
Doug MacDonald is a member of RASC’s Victoria Centre.