Tuesday, June 28, 2016

Thoughts On Opera Glass

In 2004, during my first visit to the Wolf's Head Bookstore in St. Augustine, Florida, following my return to the state, I picked up a classic book by Garrett P. Serviss, "Astronomy With An Opera-Glass". This was an older edition, from 1910, making it now over a century old. It is still in great shape, and was then, but because it had been a library book, the price was low.
Anyway, it is a wonderful book, one of the first really written for the average person using tools that were easily available, an opera glass. The author suggested that the reader obtain at least a 1 1/2", 4x power pair. As it turned out, these were somewhat  common, though not particularly inexpensive at the time the book was originally written (1888).
I set the book into my astronomy shelf at the time, and considered it something of a curiosity more than anything else.
Not quite a year later, I chanced upon a Lemaire Fabt. opera glass at a community yard sale. It was only a couple of dollars, so it came home with me. The book came back off the shelf.
Since that time, I have been interested in the way the night sky was enjoyed in previous eras, and especially with earlier instruments. The opera glass, and its brethren, have allowed many thousands of people to view the night sky without the heavier commitment of a telescope. After all, you could always go back to using them for other things, whereas a telescope is a bit more specialized.
But it wasn't enough for me to be interested, I wanted to have the experience as well. The opera glass I bought at the yard sale was a little smaller than the ones that Serviss recommended. A short time later, I found a pair of Tasco mini binoculars that were really not modern binoculars at all, but field glasses. Like the smaller Lemaire opera glass, these consisted of two objective lenses and two simple concave negative lenses for eyepieces, effectively Galilean. Aside from size, the modern Tasco pair had another advantage, in that the objective lenses were true achromats, not the simple single convex lens of the older Lemaire opera glass.
That didn't prevent the Tasco from being useful for getting an idea of what Serviss wrote about a century before. My first night with them provided me with views of the Hyades, the stars that make up the head of Taurus, or a faint view of the milkiness of the Great Orion Nebula.
However, this was still not an honest experience. The objective lenses in the Tasco were coated optics, something relatively unknown at the time. Even though the objectives were smaller in diameter than what Serviss recommended (30mm, a little less than 1 1/4", versus the 1 1/2" Serviss recommended), the views were probably better. What I needed were some genuine field glasses of the older optic design.
A few years back, I found such a pair, from the Chicago based company Airguide. These were 4x40mm, with the old Galilean layout and simple objectives. They are from the 1940's or 50's, but are really not much different from what Serviss wrote about.
What can you see through these?
Galilean optics, by their nature, have a narrower field of view, and that's the case with all three of the instruments, but especially so with the Airguide. Nonetheless, the views were precisely what he wrote about, accounting for some light pollution.
I've written about this before here, how I've been into "retro-astronomy". It isn't something I suspect that everyone will be into, but it is a learning, and indeed, a humbling, experience. That they were able to accomplish so much with the simple tools they had at their disposal says much about their determination. Astronomy has evolved, and we take so much for granted today. Even some of the instruments we deride as garbage were better than what they had to work with many times.
That's what this taught me, and it helped me to be a better astronomer as a result. 

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