Odd imaging

Friday night was clear and the temperatures were pleasant, so I stayed up to play with my camera under the stars. However, rather than open the observatory and tie everything to the telescope I decided to try imaging with the regular camera lens on a simple tripod. The idea was to take pictures every ten seconds and build a movie from that. The camera timer/remote control can only take up to 99 frames, so the maximum time for each imaging session was only 15.5 minutes, and the resulting movie at the end of a session is just a few seconds long. Next time I’ll use a laptop to trigger the shutter so that I will be able to image in longer continuous runs.

I grabbed the frame sequences without particular difficulty, but combining them into a movie at full resolution turned out to be more of a problem. Most of the software I googled would not take jpeg input, but instead expected to receive images directly from a video camera. About the best of the lot was AnimaideXT which was able to read in the jpegs but like the others it expected to produce output as video, and reduced the size of the images. That’s acceptable in, say, a time-lapse image of the observatory (rather fun to see the shadows whipping around) but not of a series of astronomical images.

I’m still working on the images, but one thing was interesting – I combined the frames using Nebulosity to sum up 35 images of the area around delta Cygni, imaged through the 17-85 mm lens at 85mm f/7 or so and ISO 1600 for 3 seconds. I was curious as to how faint I could get, and was surprised (but pleased) to get down to magnitude 10.

Integration of 35 three-second images This image has been contrast adjusted, stretched in both size and dynamic range, and passed through a number of filters in Photoshop CS2 to reduce background noise. Image centre is close to 19h14m 49° 43′

This is a small section from the region around HIP94336 (the brightest star at magnitude 5.84) , and stars at least as low as 10.6 can be discerned (the original image may show slightly more stars – it’s a judgment call).

For comparison, here is the same area from Starry Night 4.5 adjusted for the same orientation (the image was scale adjusted to match the SN map as closely as possible).

Starry Night Pro chart of 3-seconds area This is a screen shot from SN Pro 4.5.2 running on a MacIntel iMac.

From a series of 3-second exposures on a regular photographic mount, I’m impressed.

More on the time-lapse later….

More experiments with VR

After building the 360-degree panorama from pictures taken at the Distillery District I decided to experiment further, this time using an application new to me, DoubleTake. Here is the result of stitching 360 degrees of images from the street in front of my house.

This was made without a tripod using a Canon SD600 in pano mode, which allows you to see the previous image and match to one side of it. Pano mode is useful but not imperative – basically you need to keep your camera level and sweep in a horizontal plane (a tilt will mess up the image matching) and overlap by around 1/3 in each image. The DoubleTake site shows a number of examples of stitching panoramas together, and extending them to 360 is fairly straightforward — once all the pictures are loaded into the software and lined up horizontally you select a menu item and the image on one side is duplicated so you can match it up on the other side. You may have to make a few compromises in matching depending on how level your images were, and it’s really best to use a tripod.

Even with a tripod I have image sets which make me unhappy – the tripod wasn’t level to begin with, and the only way I can match the images together results in a strip of images which is ridiculously thin, or which has a lot of white space above and below a tilted horizon. The great thing about digital imaging is that you can experiment – all you lose is time. That’s an investment, I suppose, but easier to spend in most circumstances than cash. I will post more panorama shots soon, and I hope that some of these will be astro-images, or at least, astronomy-related.