After nearly two months of rain, rain, and cloudy skies — we finally have been able to see the sun and very blue skies. At night, I’ve taken the opportunity to get night sky images, as well as lunar images through some of my exotic 300, 400, 500, and 600 mm lenses. One of the problems I was having for the overnight time-lapsed images was that the lens would get covered by condensation during the night and ruin the night sky images. ARRG! As the weekend progressed, the temperature rose and the relative humidity decreased. I finally got a full night image set with limited problems with condensation. The first time-lapse video and star trail was recorded with a Nikon D3x camera and 14-24 mm f/2.8 lens @ 14 mm. There was a bit of condensation that affected the end of the video from this lens. The second time-lapse video and star trail image was recorded with a Nikon D3 camera and 16 mm f/2.8 fisheye lens looking north from my deck.
Lessons learned: 1) I need to look into a resistive heater to keep the lenses warm enough to prevent condensation. 2) I didn’t know that the 14-24 mm lens would creep if pointed straight up — during one night the focal length changed from 14 to 18 mm. For the last night, I used Gaffer tape to fix the focal length of the lens at 14 mm. 3) My tripod/heads are not strong enough to prevent movement when I change batteries. Look into an external power supply and not batteries for long overnight image session.
Early Early Morning Star Trails. With the continuing clear skies, I set up two cameras to record star trails early this morning. I started at 3:00 AM after the moon set. I was still worried about condensation on the lens. I pointed a Nikon D3 camera with a 16 mm f/2.8 fish-eye lens north, and a Nikon D3x camera with a 14-24 mm f/2.8 lens at 14 mm pointed south. I used some gaffer tape to prevent the focal length lens creep on the 14-24 mm lens that ruined a previous star trails session. The Nikon D3 camera stopped recording after 2 hours. After the fact, I realized that I used a EN-EL4 rather than the higher capacity EN-EL4A battery. The D3x camera with a EN-EL4A battery ran until I went out to get the cameras at sunrise. Unfortunately, condensation on the lens started distorting images after about 5 AM. Both the North and South facing Star Trails ended up about 60 images (2 hours). The really bright trail in both the Northern and Southern view is Jupiter.
Star Trails. Following Hurricane Irene, we had a couple of days and nights with very clear skies. You could even see the Milky Way (although a lot dimmer than in locations with less light pollution). I set up a Nikon D3s camera with a 16 mm f/2.8 fisheye lens to do star trails last night. The settings on the camera were manual (ISO 400, 16 mm, f/4, bulb). The exposure time was controlled with a MC-36 itervelometer (delay 5 sec, long 59 sec, interval 1 sec, N —). In camera long exposure noise reduction was turned off. The 1 second interval is required to allow the data to get transferred from the camera to the card, and effectively have one image taken every 60 seconds (1 minute). The MC-36 is required for exposures longer than 30 seconds. After the images were transferred to the computer, the RAW images were processed with Lightroom, and converted to JPG. The JPG images were then processed using Startrails.exe program to make composites. The following images show a single exposure, then startrail composites of 2 minutes, 5 minutes, 15 minutes, 30 minutes, 60 minutes, 120 minutes, and 300 minutes. Some high level clouds came in for the 300 minute (5 hour) image.
Late August Star Trails. Since it looked like the sky was going to be clear last night, I left a camera out on the deck to get some star trail images. The first one was before midnight, and the second one after midnight. I did this set with a fisheye lens to get as much of the sky as possible. There is a tree in the front of the house that is blocking the northern star. I also used the images to create a time-lapsed video of the night sky.
Star Trails and Lens Distortion. One problem I had with the star trail image I just published was that the circles looking toward the north star were not exactly round. This is probably due to the non-linear distortions characteristics of wide-angle lenses, especially toward the edges. There is a program, DxO Optics Pro that corrects for distortion of various cameras and lenses. (Note that the current version of Adobe Camera Raw also does lens corrections for some camera/lens pairs, but not for the Nikon D3s camera and 24 mm f/1.4G lens used for this image). I used the DxO Optics program to process and correct the 328 images. It took over 12 hours for DxO to process all of these images.I then ran the reprocessed images with startrails.exe program. Let me know (comment, or send me an e-mail) if you think the resultant image looks better, no different, or worse.