The STV from Santa Barbara Instruments Group is a neat device for real-time imaging under the stars. Easy to use, even right out of the box, it displays images on an internal screen as well as a video monitor. So far, I’ve used the STV three times, once with my 8” equatorial Schmidt-Cassegrain and twice with the club’s 10” LX-200 in alt-az mode. I’ve heard the STV called a “toy,” but I don’t think that’s giving it enough credit. It’s not just a sensitive TV camera stuck where the eyepiece usually goes. True, you use it by punching buttons and turning knobs, and it is fun to use. But there is some learning curve to it, and the fun kicks in after a couple of evenings. And you do need to read enough of the manual to be a bit familiar with its modes and settings if you want to get the most out of it. Unfortunately, there’s not really a single term that really describes precisely what it is or what it does.
At right are some of my images of Jupiter, Saturn and the Moon. For the planets I used the mosaic mode that captures six separate images from the center of the CCD chip (shown half-sized and unsharp-masked, 10” scope at f/10, 0.01 and 0.05-s exposures, Jupiter's disk is 45” across). I’ve sharpened the best images I obtained and cropped them to show the planets individually. The Moon is a composite of two frames (8” scope, f/6.3, 0.001 s) made with the best images mode that continually capture frames and keeps only the sharpest.
With two planetary sessions under my belt, here’s what I’d like to try next. If the weather would settle down, we might get some good seeing. That would be a chance to see what the optics and electronics can do at longer focal lengths like f/20 (adding a Barlow) or longer (eyepiece projection). Turning up the gain on Saturn overexposes the disk and the rings, but is also reveals a handful of Saturnian moons. Perhaps the brighter moons of Uranus and Neptune could be seen this way as well. The video monitor turns into a big advantage here. Alone or in a group, you can see, point to, compare to a chart and identify what you’re looking at. No more squinting through partly dark-adapted eyes trying to match a chart with a mirror-reversed image. And how’d you like to be able to show Pluto to your neighbors? Just point to it on the screen. Even simpler and much more nostalgic would be re-exploring the Moon, turning the monitor in to your personal lunar module window. Can you locate the landing sites of all the Apollo lunar missions?
In addition to imaging through the telescope, the STV has what are called monitor modes. These allow wide-field imaging, quantitative measurement of the quality of your optics, accuracy of your drive, and the seeing present at your observing site. The setup for these tasks is more involved but the return is in hard numbers and plots, not tentative subjective judgements. And the STV should prove useful as an autoguider even if you’re not yet ready to enter the digital imaging age.
This summer, Mars comes closest to Earth since 1988. The STV will be excellent for sharing this viewing opportunity with groups of observers. No lines waiting for a few seconds at the eyepiece, while someone tries to describe in words subtle, fleeting images. Gather the group around the video monitor and point to the polar cap, dark features and maybe even dust storms and Martian clouds. Any hint of the canals that Percival Lowell drew so meticulously? Watch the planet shimmer in our atmosphere's turbulence. Keep cool with a refreshing drink. That’s observing in style!
Speaking of creature comforts, the STV would be a great accessory for the Australian Survivors to have. From down under, Mars will be almost overhead, an ideally set between the much fainter Antares and the Milky Way. No doubt they’d want to try the STV on nearby deep sky objects as well, from the Eagle Nebula (M16) to the Lagoon Nebula (M8) to Ptolemy’s Cluster (M7). To the south, the Southern Cross and Jewel Box are swinging low towards the horizon while the naked-eye globular cluster 47 Tucanae and the Small Magellanic Cloud rise up.
I’ve found that deep-sky objects are a bit more of a challenge, from alignment to tracking to processing the images after they are downloaded. I’ll report on my experiences with the STV and deep-sky imaging in a future Moondark installment. Lots of other fine STV images by Keith Lohmeyer, Paul Gray, Frank Sheldon and Chris Mazzola are posted at the club’s web site. Have a gander!
Moondark is written by Doug Miller, published on the web , and printed in the Delmarva Star Gazers'Star Gazer News and the Delaware Astronomical Society's FOCUS. Please address comments and suggestions to dcmiller@dmv.com. This document was last revised on 28 January 2001. All text and images copyright © 2001 Douglas C. Miller, All Rights Reserved. This material may not be reproduced in any form without prior permission.
