With 24 exposures, each 4 minutes long, it is possible to animate the comet’s movement among the stars. Just process the photos individually and import into photoshop as an animation, then export as an animated GIF. Just click on the image to view…
A bright comet is always a good reason to drag the telescope out of the garage. In this case it is comet C/2014 E2 Jacques, currently about magnitude 7 in Cepheus. The comet is rising over the house about 9pm and available for shooting from my usual driveway setup location.
Setup went pretty smoothly, I have not changed anything in the basic configuration for a while. Shooting the Canon 6D on the TV-76mm scope. I did have some issues getting the autoguider to calibrate. The low magnification and high latitude meant the the calibration moves are just too small. Realizing that this also meant that any potential guide errors would also be small, I just shut the autoguider off. No guiding errors are visible in the four minute exposures.
Yes, the shot looks pretty bad… The frame is a quick process of a single sub-frame, just a white balance and curve adjustment in Photoshop. As I write this there are 13 completed exposures with another 17 to go. I do not think I will complete the sequence, I do need to go to bed sometime soon, I have to head to Hilo early tomorrow morning for a conference at Gemini.
Given a couple dozen good exposures I should be able to produce a much better image than is seen here. So far all of the sub-frames look good indeed, nice signal to noise, a bit of nebulae showing near the comet, and maybe a trace of the wispy ion tail. It will be a few days before I have a chance to properly process the image.
Taking star trails is one of the easiest forms of nighttime photography. it requires less equipment than full out astrophotography, only a camera that can take a long exposure and a tripod. In a pinch you can do without the tripod.In star trail photography a long exposure is used to reveal the scene. With illumination provided by starlight the needed exposure will be minutes long, during which time the rotation of the Earth will cause the stars to trail. Each star will trace a short streak on the camera detector as it moves through the field of view.
For a number of reasons taking one very long exposure is a problem with digital cameras. Without getting into a technical discussion of noise, dark current and hot pixels we will simply advise taking short exposures. You can always try a twenty minute or half hour exposure and see for yourself. Thus the technique is to take a series of short exposures, usually one to five minutes long, and add these together in processing. By taking a series of short exposures, the final exposure length is limited only by the camera battery or the arrival of dawn.
If the camera is sensitive enough, and you have a fast lens, you might try starscape photography, where the stars are not trailed by the motion of the Earth. In contrast, star trail photography can be done by almost any camera that can take a long exposure. The difference is in the length of the exposures, long versus short, star trail or starscape.
The center of Virgo is thick with galaxies. The nearest large super-cluster of galaxies lies a mere 53 million lightyears away, includes upwards of 1300 member galaxies and spans over 8° on the sky. The center of the Virgo Cluster is marked by the large elliptical galaxies M84, M86 and M87.
The Great Nebula of Orion is a beautiful object, the brightest nebulae in the sky. It is also quite easy to photograph, making it somewhat of a standard target. I, like many astrophotographers, use the nebula as something of calibration target to check new equipment and processes.
This shot was taken with a Canon 6D and a TV-76mm telescope, a combination I want to work with this summer. I also changed up my processing flow a bit, re-ordering the steps, to achieve better calibration. The result is a more neutral color tone in the original, I can then saturate the image to taste for display or printing. Th original might be a bit closer to true color. Of course, “true color” is a bit of an illusion in astrophotography, where everything is relative.
The Pleiades were not my primary target for the night, but that was setting and I was in no hurry to shut the gear down when there was a lot of dark remaining in the night. I glanced around the sky looking for a target appropriate for the field of view of the gear and just chanced to look at the star cluster.
For my first pass on the Rosette I used about an hour of data. Ten four minute exposures, ten one minute exposures and ten 15 second exposures. The stack is designed to capture a wide dynamic range by using several different exposure lengths. Multiple images taken at each exposure to reduce the noise inherent in long exposure astrophotgraphy. All of this data is aligned and stacked to produce the final image.When looking at the result it was apparent that I had not been successful in reducing the noise far enough. More exposure time was needed. The shorter exposures were not the problem, I needed more of the longer four minute exposures to reach the faint nebulosity.
The next night I acquired and shot again, another 24 exposures on the Rosette, another 1.6 hours of exposure. A planned astrophoto outing to the MKVIS at 9,200ft elevation offered a chance to get even more high quality exposures. This time I got 30 more exposures, another two hours of total exposure time.
Combining all 3.8 hours of exposure resulted in a notably nicer image. The noise in the fainter sections of the image is pleasantly reduced. It should be with 54 four minute exposures used.
I need to do some sort of systematic comparison of the data gathered in my driveway versus the data obtained at the MKVIS up on the mountain. Having a series of exposures taken with the same gear, on the same target, and at the same time of night just a few days apart should allow a reasonable comparison. I was unable to expose any longer at the VIS despite the colder temperatures (the camera was about 10°C colder). How much better is the VIS? Can I get data nearly as good without packing up the gear and heading up the mountain?