I really love star trails, they have an ancient and magical quality to them, but the real magic lies in capturing them successfully. Light pollution is just one of the bug bears of long exposure astrophotography and I found this out the hard way. Since getting my hands on a DSLR I have wanted to try and have a go at taking star trail images, but as with any new piece of kit it takes time to get a handle on using it.
Having shot some decent constellation photographs I felt it was time to give star trail photography a go. Monday night dished up a reasonably clear sky - transparency was so so with some cloud cover passing over but I decided to persevere with an experimental first attempt. Setting up the camera and the tripod to face northwards towards Ursa Major, I decided to shoot 4 seven and half minute exposures at 18mm with an F/Stop of 5.6 and an ISO of 800. To cut a long story short, it was a disaster! Each of the four exposures were completely blown out and fogged up with the orange / yellow haze of light pollution.
The only real success of the evening was catching a fiery Orionid Taurid gliding like a string of syrup overhead as it traveled south eastwards. A bright fireball with a visible contrail and a red hue, it had an entrance and disappearance arc somewhere between 40° and 50° and lasted about 3 - 4 seconds. My only regret was that I did’nt catch it on ‘film’.
I spent the rest of the evening looking at my four blown exposures and reflecting on what I could do to improve results. I decided a more austere approach was needed and this meant taking shorter exposures over the same period of time.
I was back out on Tuesday night (21.10.08) to put my star trail experiment into motion. Again I set up the camera and the tripod facing northwards and set the camera up using a focal length of 18mm at ISO 800, but this time I opened the aperture right up to 3.5 and set exposures to 30 seconds. As you can see from the result below, it’s not bad for a first attempt. The sky transparency wasn’t great and this image was shot on a second attempt as I had to abort mission first time around due to rainfall.
The image is made up of twenty five 30 second exposures that were combined in a fantastic little utility program called Startrails. The resulting TIFF that was rendered was then post processed in Photoshop to produce the image above.
I’ll definitely be trying more of these kind of shots. While it is a bit of chore doing all of the exposures one after the other, it is really rewarding to put them altogether in Startrails to see the end result. Hopefully if the skies remain clear(ish) I can try and catch another Orionid or two as well!
Tags: DSLR, Orionid, Star Trails, Taurid, Ursa Major