A telescope old and new

No, it’s not a home-made pumpkin cannon.

Instead it’s a trap for photons.

Or more conventionally, it’s a fine astronomical telescope** made by a teenager named Stewart S about 50 years ago.

That’s the part inside the white metal tube.

The plywood box that looks a bit like a Civil War cannon is actually a fairly conventional Dobsonian-style plywood alt-az mount that I made over the past few gloriously clear days in the driveway of my house in Brookland (Northeast DC). #

Yes, that tube is LONG – over seven feet long. It’s finely welded aluminum plate, bent into a cylinder and formed by one of my predecessors in leading telescope-making classes in the DC area, Hoy Walls (whom I never met).

The plywood mount used almost all of a full four-feet-by-eight-feet sheet of 3/4″ hardwood plywood.

I was pleased to see that my calculations were all correct, so that the scope just barely fit inside the plywood pieces and that the mount as a whole behaves well. No filing or last-minute sanding was needed. And the balance is pretty good – all I needed to do was add an old three-pound Barbell-type weight to the front end – it’s the dangly thing near the flange in the front. Having that weight imbalance is actually a good thing, because it gives us leeway to add a small finder scope to help aim the scope at objects of interest.

The flange is actually a plywood ring that I cut with a router and a decent commercial template for circles. The plywood ring fit perfectly, which was gratifying. No sanding or filing was needed — a first! I added it because the front end of the tube had been banged up or pressed hard at some point and was no longer circular.

I made an adjustable clamp inside the scope that seems to be working quite well. One can loosen the clamp and then rotate the tube to make it easier for shorter people can reach the eyepiece. Or one can move the tube forward or backwards to fix any future balance changes. And then clamp the tube back into its new position.

The optics were in very good shape – very clean, not a bit of dust or insect debris, on a beautifully smooth and fully-polished out mirror. I checked the optics briefly with a Ronchi test, and found that it had no turned down edge (which is a good thing) on its surface. I did not have time to use the Couder-Foucault Zonal Knife Edge test to calculate how well-corrected the optics are. Correction is a technical term involving changing a near-sphere to a near-paraboloid by carefully removing less than 2 cubic millimeters of glass — all together — in just the right spots, over a period of weeks or months to try to reach perfection.&&

Since the scope is done, the normal final test is to try it out on Polaris or some other fairly bright star with a short-focal-length eyepiece, looking at the diffraction rings when you roll the eyepiece into and out of focus.

Which brings me to why I had to build or modify the mount that it came with.

The mount that Stewart and Hoy made and that Stewart donated to NCA was very, very heavy, being a classical example of a heavy-duty – modified – plumbing – and – automotive – parts style of telescope making that many amateurs used around 30 to 60 years ago, before John Dobson revolutionized amateur telescope making with his eponymous telescope mounts and his unusual mirror-making methods using cast-off naval portholes as substrates for mirrors.

That’s me above on the right, wearing an Escher tessellation Y-shirt, at Almost Heaven Star Party near Spruce Knob, WVa, next to a green telescope I made with Nagesh K. It’s called a Lurie-Houghton telescope design because of the geometry of the lenses and the mirror. Bob B did most of the lathe work for the aluminum finder scope that Jan appears to be touching with his left hand. Unfortunately, this telescope is so far a complete and utter failure although all of the individual pieces seem OK or great. Until we figure out what went wrong, we are stuck in limbo. The mount, but not the scope design, is a Dobsonian.

 

 

The late John Dobson visited our telescope-workshop once, perhaps 10 years ago. He is the oldest person in this picture, facing us, with a bright blue jaket and white hear. It looks like I am doing some sort of incantation over the mysterious batch of molten pitch, but it’s all scientific — no magic spells. *

Unfortunately, the mount on the long aluminum telescope as it came to us was impossible even to roll through doors and was incredibly heavy. We (Mike L, Bob B and I) tried to fix the wheels on the platform that held the mount (sorry, I can’t find any of the photos I took of it), but we then found that the scope literally would not hold still. As a result there was so much backlash that you could not aim it anything and actually look at the object for any length of time at all. I considered putting three jack-screws so that the platform could be jacked up (much the way cranes and RVs will jack themselves up off their wheels) to be stable, but I couldn’t think of any way that wouldn’t require an enormous amount of time or money.

I also wanted to see if I could make a Dob mount in about three days.

I did.

And it worked.

Right now, you can aim the 10-inch f/long scope at an object and the object will stay there in the finder except for the Earth’s rotation. The tube is reasonably well-balanced. With some muscle and the clamp I made, you can change the balance point. Unfortunately, the mount really could use a little bit of beefing up as far as the base is concerned, and I’m contemplating how to do that without adding too much weight.

Alan T helped me take out the guts of the telescope, wrestle the tube into the plywood mount, and then re-assemble the optics. We looked through it at Hopewell Observatory last night. The Moon, Mars, and Saturn were well placed and looked pretty good, and it seemed like the air was pretty stable. We did not crank up the magnification very far, and the Moon was so bright we all cast shadows on the grass, so very few stars and no Milky Way were visible. A formal star test will need to come later.

On behalf of National Capital Astronomers, I would again like to thank Stewart S for donating this fine telescope.

 

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# I hope my neighbors will forgive me. I didn’t work on it at night.

* Some of us amateur telescope mirrors will admit to uttering curses from time to time, but unlike what happens at Hogwarts, they never work. Guess we are just Muggles, condemned to obeying the laws of physics and the other sciences.***

** This scope is not my personal property, nor does it belong to the Hopewell Observatory in northern VA where this photo was taken and of which I’m a member and current president. The telescope tube and a different mount were donated by Stewart S to National Capital Astronomers and is currently housed at Hopewell as a service to NCA. Stewart is obviously no longer a teenager!

*** Actually, I’m rather glad that the laws of physics and other sciences don’t seem to be under the personal command of any individual, and that they seem to be exactly the same for all people and – as far as we can tell so far — everywhere else in the universe. (Yeah, I know that some astrophysicists and cosmologists make claims that certain basic constants of nature change in certain ways over time, but I’m reserving judgment on that. OTOH I hope I live long enough for someone to figure out what ‘dark matter’ is. It remains spooky and awesomely mysterious that with all of our current state of ever-expanding scientific knowledge, most astrophysicists still believe that the vast majority of the matter and energy in the universe is still completely unknown. We don’t know what it is. I find that the idea that the universe has immutable rules, many of which have not been discovered, much more comforting than having a universe where somebody else could get mad at you or me and change the laws of physics in your immediate vicinity with the purpose of doing us harm — and that all those powers are accessible by certain individuals who claim that they have been in personal communication with a personal deity, who uttered cryptic messages and incantations and rules that must never be questioned. How could powers like that NOT corrupt somebody?

 

&& like a small sand grain.

Suggestions for Improving the Remake of Cosmos – A Different View of Giordano Bruno

If you haven’t looked at any news about the intersection of science and popular culture recently, you may have missed the fact that astronomer and popularizer of science Neal Degrasse Tyson  is starring as the replacement for the late astronomer and popularizer of science, Carl Sagan, in an updated remake of the series COSMOS, about, uh, the cosmos we live in.

(I got to see a preview of the film a week or so ago at the National Geographic HQ in DC; email notices were sent to probably every single amateur astronomy group in the US.)

I thought it was pretty good, and particularly liked the way that Tyson explained what the scientific method really is — using not a single word in the various definitions of “scientific method” that students are often expected to memorize in their middle-school science courses.

Unfortunately, even though I have a full set of the original Cosmos VHS tapes, I’ve only watched bits and pieces of the original. So I’m not one to compare them. Again, I liked it, and am looking forward to the rest of them.

But I do have some criticisms or comments about this remake:

1. Looking back, I think there were probably too many special effects, but I’m probably in the minority on this one.

2. I think that Rupert Murdoch and Fox “News” are despicable, and that they actively promote anti-scientific hogwash of all sorts. I was really surprised that the Fox network co-sponsored these shows. (I realize that fox ‘news’ and network are 2 different groups, but they have mostly common ownership, right?

3. I was surprised that they spent so much time on Giordano Bruno. I thought I remembered he was a minor, dissident priest burned at the stake by the Catholic Inquisition for believing that there were other solar systems with people in them, among (most likely) other heresies. In the first episode, Tyson points out that Bruno wasn’t a scientist and that his theories about other solar systems, while recently proved to be correct,  was merely a lucky guess.

So if Bruno wasn’t an astronomer or a scientist, then why spend so much time on him?

A Jesuit friend gave me additional background on Bruno; apparently he was very fond of making enemies. If you read the Wikipedia entry, you’ll probably find out that he had a famously prodigious memory, and that he made money teaching important and wealthy people how to memorize things.

My attention has also been drawn to another article, making suggestions about how they could have improved the episode, by putting in the person from whom Bruno may have originally learned about infinite space:  Thomas Digges.

Here’s why Digges’ ideas were important: if the earth is the center of the solar system, as it is in the Ptolemaic system, and everything rotates around the earth exactly once a day, then the stars simply can’t be spread out into infinite space, because their rotation would be faster and faster the farther away from the earth that they happened to be located, which didn’t make sense. So Ptolemy and Aristotle and the Roman Catholic Church believed the stars were all located on more or less of a sphere — one that was larger than the rest of the solar system, but not too far away, on a cosmic scale. So there couldn’t also be solar systems around those stars.

(zame source)

However, when Copernicus worked out the details of a sun-centered solar system, then it was just the earth that was spinning on its own axis once a day, and revolving aroudn the sun once a year, just as the other planets did in their turn. And with this new system, there was no need for the stars to be located along an invisible black sphere – they could certainly be other suns, and the universe could well be infinite, just like the mind of God .

The second article makes it clear that Digges, about whom I knew nothing at all, could have profitably been the cartoon hero of the first Cosmos episode.

The relationship between science religion gets interesting. While the Catholic church continues to condemn basic things like birth control or divorce, it has abandoned the idea that you can calculate the exact beginning of the universe by adding up all the phrases like this:”And Noah was five hundred years old, and Noah begot Shem, Ham, and Japheth” — a method that is a lot less reliable than going out, taking cross-sections from old and young trees, comparing them and lining them up by comparing relative sizes to known climate events, and cross-referencing that with sediments in ponds and lakes, and to layers of ice in Greenland and other places. You know, doing it scientifically. Unfortunately for us, there still are some people who claim that the ONLY evidence they believe comes from certain sections of the Bible (but in fact they discount the rest).  Some of these people hold their hands over the ears of their children when they visit the Grand Canyon if an actual geologist is giving a talk explaining how the various layers of rock were laid down over the past few billion years. Fortunately, the Catholic Church has actual scientists and astronomers on staff. Even Galileo thought he was a good Roman Catholic Christian until his dying day…

(apparently this drawing was made in the 19th century, hundreds of years after Diggs, Bruno, Galileo or Copernicus)

In any case, I’m skeptical of all accounts of the beginning of time — we just don’t have a tremendous amount of evidence. Yet. A case can certainly be made that there was a Big Bang about 14 billion years ago, and it seems to me quite clear that the Earth was formed over 4 billion years ago (we even have zircons and other rocks and minerals that seem to prove it), but what on earth caused that Big Bang? Are there other universes, as was illustrated in the movie? We can make a case for dark matter, but there might be other explanations for the effects that lead astronomers to believe that there is some sort of unknown, invisible substance in and around our galaxy that causes things to rotate in ways that they shouldn’t, otherwise.

(If you didn’t know, celebrated astronomer Vera Rubin, who lives in the DC area, was one of those who discovered those strange rotational speed anomalies back when I was a kid by taking very careful measurements of redshifts and blueshifts of stars orbiting in spiral galaxies. Last time I asked her, a couple of years ago, she said she thought it was entirely up in the air whether the best explanation for this phenomenon was dark matter or that we simply don’t understand the laws of gravitation fully in the first place.)

When certain cosmologists tell us precisely what happened “Between 10^–43 second and 10^–36 second after the Big Bang”,  we should keep in mind that we weren’t there to witness it. Sure, those accounts are in accord with a very complex physical model that right now is the most=accepted standard model. I won’t do a John Dobson and accuse those cosmologists of dishonesty; this is the best model we have right now, according to people who have studied his stuff very hard and very carefully. Is there actually ‘dark energy’? I am more skeptical about that. Perhaps; but the evidence is built on such a long string of extrapolations from very difficult observations and calculations that we should keep in mind that it very well may be that future observations with better instruments of some sort will change that model. In fact, every single time scientists have devised and used new instruments to look at and examine the universe (under our fingernails or up in the sky or in the center of the earth), all of humanityy learns new things that we never imagined could possibly be.

Who could have dreamed of paramecia, amoebas, viruses, or the genetic code of DNA before the microscope — at first very crude ones, but now of the electron or x-ray diffraction or scanning tunneling varieties? Each improved microscope showed us much more than the previous ones and are responsible for the fact that we no longer have a third of our newborn children dying of diseases before they reach their fifth birthday.

Galileo’s first, crude telescope showed us the moons of Jupiter, the phases of Venus,  the rings of Saturn, craters on the Moon, and clouds of stars in the Milky Way — all complete and utter surprises. The 60-inch and 100-inch and 200-inch telescopes at Mt. Wilson and Palomar first showed us that many of those mysterious ‘nebulae’ in the night sky were actually other galaxies, millions or billions of light-years away.

I’m sure all of this will be illustrated quite well in this series. I need to figure out how to record it — just changed to a cable service bundle after getting rid of separate DSL, telephone, and satellite dish services…

Read the articles and let me know what you think.