Astro-Imaging Projects for Amateur Astronomers by Jim Chung

Author:Jim Chung
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

In the United States and increasingly in Canada we are witnessing decades of worker’s rights eroded by the spread of globalization. Wages and benefits have been cut, job security lost and health and well being of worker’s families undermined while corporate profits and executive compensation continues to obscenely grow, often untaxed in offshore locations. Where are the Abbé’s of the twenty-first century?

Real Time Narrowband Visual Viewing with Image Intensifiers

New attendees at city star parties are typically very excited at the prospect of looking through a real telescope for the first time in their lives. Looking at the Moon, Jupiter or Saturn never fails to disappoint and can be a moving, spiritual experience. And truth be known it’s really because I’ve been kissed and hugged so often that I keep hosting star parties! However when it comes to observing deep space objects its caveat venditor all the way. From the city only globular clusters are easily seen and they all look like variations of each other and can get stale fairly quickly. Galaxies and nebulae are what people are looking for but they have unfortunately been spoiled by the glorious long exposure images from the Hubble Space Telescope and are expecting to see the same through your eyepiece. Techniques like dark adaptation, averted vision, and the use of specialized contrast enhancing visual filters will be of no benefit in the city because the sky is simply too bright to see any of these structures.

It’s getting increasingly common at star parties to see emission nebulae imaged with short exposures by sensitive ccds through Hα filters and displayed on a laptop screen with some rudimentary histogram adjustments to improve contrast. I’ve resigned myself to the fact that it is impossible to see galaxies from within the city so at least this is a wonderful way to demonstrate a subset of nebulae with details hinting at the images found within the pages of Sky & Telescope but the public is left at best half satisfied. There is no real involvement between observer and the telescope because the images do not occur in real time but take minutes to develop. Then there are the skeptical observers who insinuate that you’re running a sleight of hand slide show. And frankly they’re right. The public needs to be able to look through an eyepiece and see these sights for themselves.

While Hα filters are excellent at negating light pollution and revealing emission nebulae, they are not visual filters as the eye’s sensitivity in low light is particularly poor at these wavelengths. The attenuation of light intensity is so extreme one would require a telescope with a massive aperture and extremely fast optics in order to transmit enough light through such filters for the human eye to be able to even register an image. Enter the image intensifier.

Image intensifiers are vacuum tubes that amplify the photons which impact on the cathode end by converting them into electrons via the photoelectric effect. These are then accelerated by high voltage to strike a phosphor screen at the anode and form an image.

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