Customer Reviews

The 20-cm Schmidt-Cassegrain Telescope: A Practical Observing Guide

5 star:		(3)
4 star:		(4)
3 star:		(3)
2 star:		(0)
1 star:		(0)

 

 

For those trying to figure out the difference between an SCT (or what SCT means) and other telescopes this is a very useful book. It contains much useful background material and history, but falls short in providing a full understanding of the interworkings of this type of telescope. The inclusion of some "cutaway" or "exploded view" drawing would go a long way in helping the reader visualize the mechanisms behind the covers. This would be very useful to someone trying to fully understand the optical system of the SCT.

I found this book great reading. If you have just bought a SCT or are looking to purchase one, this is highly recommended. Easy to read without all of the Technical Jargon. You can relate to the what the Author is conveying with the practical examples given.

Mr Manly has produced a fine gem of a book, provided you are into SCTs of course.
Although it is not laden with all of the newest technological advancements in goto and GPS, my version is the 2002 reprint, for me me it is quite sufficient as a non-goto Ultima 8 owner. If I get tired of star-hopping (or clod-hopping for that matter), I will mount a Celestron SkyScout planetarium onto my optical tube assembly and have it guide me (as the goto apparatus) to the desired object. But I digress.
I like the humor he puts into the book. It is very easy reading, and I like the information in the appendices. The format is perfect, slightly larger than a paperback novel. In a nutshell; a perfect companion for my other astronomy books and star guides. Nothing negative to say about the book.
And for the price, who can get a better deal? I practically paid shipping only. Shipping was $3.99, and the book was 71 cents, and in new condition. The best 71 cents I have ever spent!

To me the title of this book, "The 20-CM Schmidt-Cassegrain Telescope," suggested that it might be an after-market owner's manual. I was mistaken. Most of its content applies to the first time user of any amateur-class telescope. The only SCT-specific information it provides is: a brief history; a superficial treatment of its optics; principles of collimation; and pictures of an SCT with accessories attached. If you're looking for instrument-specific technical information of even the most meager variety, or maintenance, modification, and "accessorizing" tips, then find another book.

The author's discussion of polar alignment illustrates my point. He describes the use of a home made, 45 arc minute finderscope reticle. Nifty - just what I'm looking for! Alas, he fails to explain how to make one - not in detail, and not even in principle. So the whole discussion is nearly worthless. The author hits on most of the topics I find interesting, but I inevitably came away wanting more details. For example, the author discusses photography, photometry, spectroscopy, computers, image intensifiers and televideo. Impressive, right? But the whole of it is compressed into a mere 40 pages - and no single topic receives thorough treatment.

As suggested by the subtitle, "A practical observing guide," this book discusses the observational possibilities for an SCT owner. It is not a practicum on the use, maintenance, modification or technical aspects of any particular SCT.

These criticisms, however, reflect my own misapprehension of the book's intent. I hasten to say it adequately addresses the question, "What can I expect to do with an SCT?" The author's organizational skill and conversational writing make this 246 page book an interesting read. The narrative flow, however, suffers from the excessive use of footnotes (228 total) - of which the most relevant could have been thoughtfully worked into the text, and the least relevant left out entirely.

You can get a fairly good idea of the material covered by browsing the table of contents online. Be advised: this is a non-technical, non-mathematical, non-detailed, generic SCT oriented book. It is anybody's guess why the author chose such an approach for a geeky market like amateur astronomy. If you can buy it at a deeply discounted price, do so - you'll have a couple of hours of reading on a topic to which you can relate. Better yet, buy a used copy as it will probably not become a part of your permanent reference collection. Best of all, try to borrow a copy from your local library, which is where my discarded copy will eventually end up.

As the author points out, the first economical 20 cm. S-C telescope by makers such as Celestron and Meade revolutionized amateur astronomy back in the 70's and 80's, and their influence is still being felt today. The telescope's design has many advantages over the competition, such as good portability, excellent control of optical distortions, and ease of use. The S-C telescope is distinguished by having a concave paraboloidal primary with a convex hyperboloidal secondary, compared to the Gregorian telescope with it's similarly paraboloidal primary but concave secondary, which produces an upright image, unlike the S-C which is inverted like most telescopes. The corrector plate on the front of the S-C corrects for spherical aberration.

This design is different from the little 3-inch Maksutov scopes from Questar. These use a hyperboloidal primary and secondary. The advantage to this arrangement is that the positive and negative surfaces act to cancel out various optical aberrations and distortions. My understanding is that the Celestron telescopes actually employ elliptical rather than paraboloidal optics, but anyway, tens of thousands of these scopes have proven their worth in the hands of new and experienced amateurs around the world for decades.

If you're an experienced amateur, many of the topics, especially on viewing various sky objects will already be familiar to you, but if you're a new amateur there is much good information here. The author starts out with a brief intro and history of the instrument and then proceeds to a discussion of how to get started in viewing using easy subjects such as the moon and planets, and then proceeds to more advanced and harder to locate subjects like nebulae, star clusters, double-stars, galaxies, and so on. For the intermediate and advanced amateur, there are chapters on special topics such as observing variable stars, asteroids, comets, and multiple Jovian eclipses.

The last half of the book has sections on some of the more modern accessories and topics aspects such as international networking, astrophotography, photometers, spectroscopy, televisions and image intensifiers. There is an extensive series of appendices on topics such as cleaning the corrector plate, how to align the polar axis, collimation of the S-C telescope, mount vibrations, a field operations packing checklist, astronomical nomenclature, and a list of dozens of the brightest stars and nearby stars.

The author's story about how he was the first person, using an amateur group of observers spread out over Arizona, to gather the necessary obsevational data to calculate the size of the asteroid Aglaja during it's occultation of a star, was interesting. And the section on astrophotography reminded me of my first experiences in that area in the early 70's using a 25 or 30-year old Exacta VX Thagee-Oresden camera. Overall this is an excellent user's and observer's guide that should be valuable to new and experienced observers alike.

This is a good introduction to the SC telescope, and when first published it helped to fill a great void. While most of the information in the book is still useful and valid, it needs an update to include the modern computer-enhanced SCT (GO TO scopes). I would love to see a new edition.

This is a very good book; at times humorous, and at times just plain warm-feeling! It deals with many aspects of SCT's , some chapters are a bit too thin for my tastes now.

Although I read it cover-to-cover already; I keep going back to it quite often..

There really are some genuine nuggets of wisdom in this book. One has to become accustomed, however, to the first-person narrative and the sometimes "I'm so cute" humor.

if you can look past the stylistic concerns, there's a lot here to like.

I found this book to be a very good book that clearly explains what a schmidt-cassegrain telescope can do for you. So if you are not sure that a schmidt-cassegrain is for you, before you spend a hefty sum for a good scope check out this book, its well worth it Thank You Geoff Nash

MY REVEIW IS THAT THIS IS A GREAT BOOK