I just read an article in New Statesman saying that some molecular biologists had succeeded in fixing a basic flaw in the process of photosynthesis.

Photosynthesis isn’t very efficient — only roughly 3% iirc.

Apparently plants have a tendency to latch onto O2 molecules instead of CO2 molecules, producing toxins instead of sugars and free oxygen, slowing plant growth by a lot. Since all green plants use the exact same process of photosynthesis, no plant has an evolutionary advantage.

The link is here.

The scientists quoted claim to have figured out a way to get tobacco plants to avoid treating oxygen like carbon dioxide, and that the tobacco plants then produced 40% more biomass.

If their claim is true (I’m skeptical until I read of others replicating their work) then it might very well happen that there are enormous, unintended side effects on the plant itself that we can only guess at. So far, almost all of the “Green Revolution” plant changes have, from what I’ve read recently, not produced much change in output per plant or per hectare. (Fertilizers are a different matter…)

If this experiment is in fact successful, then one worry would be that the CRISPR’d genes (or the plants themselves) would escape from the planted fields into the wild — where they would out-grow, and hence out-compete other plants that didn’t have this photosynthetic “fix”. Who knows what would happen? I don’t but I think the effects could well be catastrophic.

This is potentially an enormous change. Better be very, very cautious about this!!!

“ut even if this trait does spread beyond farms it’s unlikely to cause serious problems, says plant geneticist Maureen Hanson of Cornell University.

“Enhanced growth of a weedy species is not likely to disturb ecology as much as we already disturb it through the environmental effects of traditional agriculture,” she says.”

I’m not so sure about that.

Tonight, Jim K essentially completed his 8″ telescope by putting in the primary mirror, positioning it correctly in the tube by focusing it on the Moon, and achieved FIRST LIGHT!

He also put on the Telrad finderscope and used it to aim the scope accurately on the star Capella with no difficulty at all. I did a brief star-test on that star and found that the scope passed with flying colors! Jim started grinding the mirrors back in the 1970s, put it aside, and brought it to us for help in doing the final polishing, figuring, aluminizing, and designing and constructing the telescope. It looks great and works well, too!

In addition, Pratik T may have finished figuring his 6″ f/8 mirror that he’s been working on. Using the Foucault/Couder knife-edge test measurements I made, the program FigureXP declared it to be 1/4 lambda error on the wavefront. This may be good enough, but more testing would be a good idea, later on.

We are closed all of next week for the holiday.

Yesterday we moved a lot of heavy metal and glass to temporary quarters so that we can mount a modern, heavy-duty Astro-Physics 1600GTO mount on one of our piers.

One of our founders, Bob Bolster, had built with his own hands a very unusual 30-cm Wright-Newtonian telescope and an equatorial mount on a permanent pier. Unfortunately, the drive stopped working and he was unable to get it back into working order before he died. So yesterday we removed it from its mount – and it took five of us with a 2-ton chain hoist, lifting straps, and a custom-built cart to winch it out of the observatory and into our operations cabin.

We all had fun doing it, nobody got injured, nothing got damaged, and the night that followed was the clearest one I’ve seen in a long time! Great open clusters in Cygnus!

I attach some videos and photos of the move.

By the way, that large disk of optical glass you see in the last few photos is for sale. We aren’t sure what type of glass it is, but you can find details here at Cloudy Nights or Astromart. It is 55 cm across, 83 mm thick, and we measured its weight as 59 kg (130 lbs). We calculate its density as 2.99 g/cm^3, and the nearest match in the Schott catalog is N-SF64 which has that exact density, but N-KZFS4 and P-SK57 are close as well (3.00 and 3.01, respectively). It’s definitely way too dense for Borofloat, Zerodur, or any other borosilicate glasses. The glass known as BAK-4 has density 3.05, which I don’t think is close enough, since there are several others between 3.00 and 3.05.  For comparison, the relatively inexpensive optical glass known as BK-7 has a density of 2.5.

We are asking $950 for the blank. If you were to order a brand-new one from any optical glass company it would cost you much, much more!

Nice pix but few details. Here is the link.

Or https://www.nationalgeographic.com/science/2018/10/telescope-festival/?cmpid=org=ngp::mc=social::src=twitter::cmp=editorial::add=twph20181012science-telescopefestival::rid=&sf199912766=1

At the NCA ATM class at the CCCC, we are the fortunate inheritors of a 1960s-era vacuum chamber and aluminizer that was twice given away as surplus (first by the Federal Government or US military, and then later by American University), but which still works.

Much of the credit should be given to Dr. Bill Pala, who snagged it for AU from the US surplus system; the late Bob Bolster and Jerry Schnall, who together ran it for a long time; Dr. John Hryniewicz; Alan Tarica; and several others whose names unforotunately escape me at the moment but who have given excellent advice on repair and maintenance and even provided replacement parts.

Here are four photos of the rig, followed by two of our finished mirrors.

The question came up: (1) how thick are the coatings we generally put on our mirrors, and (2) how efficient is it — that is, of the aluminum that we vaporize, how much of it actually lands on the mirror?

Thankfully, John H actually measured how thick the coatings are as we coated a mirror. He found that the average thickness is about 93.4 nanometers (billionths of a meter, or thousandths of a micrometer, or millionths of a millimeter), and that the coatings looked like this when blown up sufficiently: ”

 I have attached some scanning electron micrographs of the top of the film.  The grain structure is very fine, you can compare the size with the scale bar at the bottom that shows you the length of the total bar (10 ticks, between each pair of ticks is 1/10 of that number).  There are some particles or perhaps larger grains on top.  They are still very submicron, a couple of tenths at most.

The way the mirrors get coated is basically three steps:

(1) We get the mirror very, very clean, using both with a special detergent (Alconox) bbefore it goes into the vacuum chamber, and high-energy electron bombardment while the pumps are working;

(2) We get the pressure in the chamber very, very low, so that there are relatively few air molecules or atoms between a coiled tungsten filament and the mirror. (We get the pressure down to somewhere in the range of 7*10^-5 to 4*10^-4 Torr, depending on which gauge you believe. This is quite low indeed – roughly the air pressure at the altitude of the International Space Station; this is needed so that the aluminum atoms won’t tend to bounce of the molecules of nitrogen and oxygen and lose their energy.

(3) We melt, and then boil off, a small quantity of pure aluminum from the filament, which goes off in all directions, fairly evenly; the Al atoms that happen to be going in the right direction ashere to the mirror. There, they form a very even, reflective layer.

You may wonder, how do we prevent this layer of aluminum from oxidizing once it comes back into contact with the normal atmosphere? Answer: we don’t. Aluminum oxide is the main component of rubies, sapphires, and corundum, which are very hard. Since the stuff we deposit is relatively pure, it doesn’t have the red or blue color of those pretty and precious gems, and it is transparent, so it forms a hard, transparent, protective layer all by itself. If your coating tarnishes or gets extremely dirty, the aluminum-and-gunk layer is pretty easy to remove with a little bit of hydrochloric acid mixed with copper sulfate. Then you clean it off and re-aluminize.

(Yes, commercial labs do overcoat their mirrors with stuff like Silicon Monoxide and Silicon Dioxide (aka quartz), but we haven’t collectively figured out how to do that with our minimal budget.)

So, again: how efficient is it? What percentage of the atoms of aluminum headed to the mirror, actually adhere to the mirror?

To answer this, it helps to pretend that the filament is at the center of an imaginary sphere, shown below, and that the mirror (facing down, towards the mirror) happens to be at the top of this sphere. Recall that to a good approximation, the aluminum that evaporates off of the coil goes in all directions, i.e., it coats this entire imaginary sphere equally – or it would, if there wasn’t all sorts of pipes and wires and glass bell jars in the way.

The filament and aluminum is located at the center of this sphere.

I measured the distance from the filament to the mirror, and found that it’s just about 20 inches, or roughly 500 millimeters. Archimedes figured out long ago that the surface area of a sphere is equal to four times the area of any circle contained in the sphere, or 4*pi*r^2 in our current notation. So that imaginary sphere, on which the aluminum is deposited, has an area of about 3.1 or 3.2 million square millimeters.

We currently use slugs of aluminum that are about 15 mm long (give or take a couple of mm) and cut (not at right angles, because the pliers won’t do that) from wire with a diameter of 5 mm (radius 2.5 mm). If we pretend the slugs are cylinders then the math is much easier: we can use the formula pi*r^2*h to get a volume of about 295 cubic millimeters, and we will pretend that all of the aluminum boils off (and none of it sticks like glue to the tungsten) and goes equally in all directions. (Probably not the case, but in practice it doesn’t seem to matter much.)

Now if we divide the 295 mm^3 of aluminum by the total surface area, 3.2 million mm^2, we get the average thickness. I get a result of about 9.1*10^-5 mm, which converts to 91 nanometers. Which is very close to the result that John H found.

On the other hand, most of that aluminum is wasted, because it’s NOT aimed at the mirror. If you have an 8-inch diameter mirror (about 20 cm diameter or 100 mm radius), its area is 10,000*pi square millimeters, or about 31,000 mm^2 – and that’s only one percent of the area of the entire imaginary sphere.

Oh, well, aluminum wire is quite cheap.

… sharing this from a discussion on learning math on Quora. I agree with the writer on most of it:

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Prasad D made a great mirror in our telescope-making workshop here at the Chevy Chase Community Center, and then proceeded to machine a wonderful Crayford focuser, from scratch, after I showed him how to use our 1944-era South Bend lathe. A very friendly fellow, he unfortunately (for us) moved to Philadelphia, which is not really close, but he’s kept up doing excellent ATM work.

As an example, on Tuesday last he brought in a brand new German equatorial drive and controller system that he had cobbled together from various parts. He replaced the original motors in the drive head with stepper motors, and then put together an Arduino board, a wireless communicator, and two stepper-motor controllers. All of the circuit is controlled from an app that he devised, on his Android device. We didn’t have any clear skies to try it out, but I could certainly see the motors slewing to various invisible objects such as the star Procyon and Messier Object 42..

Really first-rate job, and very nicely done! (He said he didn’t want it to look half-baked, and it doesn’t!)

I’ll post some still photos here and then upload two short videos to Youtube – which I cannot embed on this blog, but can only link to. If you click on the photos, you can see larger images.

Here is the first video that I took of his device in operation: https://youtu.be/Md06jD35CUg

Here is the link to a shorter video, not as detailed, that I took of the device:  https://youtu.be/bH_i58LhtiY

If you have problems viewing any of this, please let me know by leaving a comment. Thanks.