Michael A. Covington    Michael A. Covington, Ph.D.
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Ichthys

Daily Notebook

Popular topics on this page:
5.5-mm connectors that don't fit 5.5-mm holes
Three tips for handling information
Why it's not the bandwagon fallacy
Astrophotos:
M29 and Sh2-106
M27 (Dumbbell Nebula)
Nebula Sh2-106
Jupiter and Saturn
Comet C/2020 F3 (NEOWISE)
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2020
July
13

Comet C/2020 F3 (NEOWISE)

Picture

I didn't get up at 5 a.m. to see the comet last week, and I didn't go to Deerlick this evening (as I would have if I'd realized it was going to be clear). But I did hie myself unto the top of a University of Georgia parking deck in order to get a very low, clear northwest horizon. This was actually my first visit to Deck S11 since the pandemic shut down the University in March; I had parked there almost daily for a couple of decades until then.

The comet has swung around into the evening sky, but also has dimmed. It will get dimmer, but farther from the sun, in the coming days, and I hope to get a good picture of it against a dark sky from Deerlick.

As it was, I could see it with binoculars with some difficulty; not with the unaided eye. This is a 1-second exposure with a Nikon D5500 (H-alpha modified, not that it matters) at ISO 400 on a fixed tripod with a Sigma 105/2.8 lens at f/3.2.

This is the same place I photographed Comet Pan-STARRS in 2013.

2020
July
12

Trying out the GEM45

Picture Last night I was able to put the GEM45 through its paces with a much heavier load. My 8-inch telescope, guidescope, and camera weigh about 10 kg. Here you see the mount and telescopes (without cables or laptop), and you're looking at 12.5 kg of counterweights, but they're not as far from the axis as the center of gravity of the telescopes. In any case, this mount is rated to carry 20 kg (45 pounds).

Result? It works. The GEM45 is not quite as rigid as the CGEM (which weighs more than twice as much), but it carries the heavy telescope just fine. I was able to achieve 1-arc-second autoguiding regularly under rather unsteady air. I do sense that a beefier mount would be a better fit to this configuration, but the point is, the GEM45 works, and it's light and easy to transport.

I also learned some things about iOptron's polar alignment processes (of which there are many). I'll write more about this later, but, in summary:

  • The iPolar scope is very easy to use (with a laptop attached) and gives 1-arc-minute accuracy.
  • The polar alignment error displayed after 3-star alignment is accurate to about 8 arc minutes (you might think it's better than this, but it's not). That stands to reason; it is half as good as Celestron's readout after a 6-star alignment.
  • The "Polar Iterate Align" option is a low-precision process that only gets you within a couple of degrees of the pole.

My current thinking is that the best way to polar-align when Polaris is not visible is to do a 3-star alignment, make changes to reduce the error, do it again, and so on. Armed with knowledge of how far each axis moves per turn of the adjusting screw, I can align to within 10 arc-minutes in just three iterations, which is probably faster than Polar Iterate Align anyway.



The Dumbbell Nebula

Picture

Here's the Dumbbell Nebula (M27), which I've photographed many times before, but this may be my best picture of it yet, mainly because the mount guided so well that I was able to use 15 of the 18 exposures that I took. This was the first picture taken through the 8-inch on the GEM45, and I was still fiddling with the autoguider settings.

This is the remnant of an exploded star. It's the same type of object as the Ring Nebula, but viewed edgewise. Basically, this is a side view of a translucent doughnut.



Sharpless 2-106

Picture

The picture of M29 that I posted yesterday contained a small red nebula, and I decided to investigate it further with the 8-inch. This is a star-forming region in Cygnus (which means "in the direction of the constellation Cygnus" — constellations are not objects).

About 2/3 of the way from the nebula to the lower left corner of the picture, there is an unusually red 18th-magnitude star about which little is known. Stellarium tells me its magnitude is 17.95, its color index is 2.46, and its J2000.0 position is 20:27:50.24 +37°17'54.6". It is apparently the star listed in SIMBAD as IRAS 20259+3708 with a slight position discrepancy. It is probably the faintest celestial object that has ever piqued my interest.



Jupiter and Saturn

Picture Picture

To close out the session I took images of Jupiter and Saturn, which are low in the southern sky so that we view them through a lot of unsteady air. These aren't great pictures, but they show that the planets are still there, I can still photograph them, and the Great Red Spot is still much smaller than it was when I started observing planets about fifty years ago.

2020
July
11

First light

I'm not sure if it's appropriate to use the phrase "first light" when the new equipment is just a mount, not a telescope. But here it is, the first picture taken with the iOptron GEM45 mount.

Picture

In the center is the star cluster M29 in Cygnus. At the top, you see red wisps of the Gamma Cygni cloud of nebulosity. And at the lower left, I was surprised to see the little-known nebula Sh2-106 (Sharpless 2-106), above "2020" in the caption. This is an active star-forming region.

The picture is a stack of thirteen 2-minute exposures with an AT65EDQ 6.5-cm f/6.5 telescope and Nikon D5500 (H-alpha modified) camera, autoguided with a separate guidescope. To my delight, the autoguiding went very well; each of the 13 frames was essentially perfectly guided. This mount doesn't have much backlash (3.1 arc-seconds as measured by PHD2). Admittedly, I had it carrying a relatively lightweight setup; we'll see how it does with the 8-inch telescope soon. If it doesn't carry the 8-inch well, I'll start saving up for its big brother, the CEM70.

For autoguiding aficionados, here's a guiding graph. The precision achieved, 1.0 arc-seconds, was limited, I think, by atmospheric steadiness, not the equipment. And I had made little effort to tune the guiding algorithm. Some periodic error is visible in R.A., so I should switch to the algorithm in PHD2 that measures periodic error and corrects for it.

Picture

2020
July
10

Why it's not the bandwagon fallacy

About controversial medical matters such as COVID, I keep advising people to follow the bulk of experts, and distrust experts who don't agree with many of their colleagues. The dissenters are appreciably less likely to be right.

But isn't this the bandwagon fallacy? We normally caution people not to "jump on bandwagons," not to adopt opinions just because they're popular. When a foolish idea sweeps through a crowd, you don't want to be caught up in it.

No, it's not the bandwagon fallacy, because the community of experts is not a bandwagon.

More precisely, the community of experts is not a crowd of laypeople following the most popular opinion. They're experts. They're constantly presenting facts and logic to each other and evaluating what they see. Unlike you and me, virus experts can actually judge the evidence that their colleagues present to them.

It's almost like a basketball tournament. To find out which is the best team there, don't take an opinion poll; just let them play the tournament and see who wins. Likewise, to find the best theories, let a lot of experts examine the evidence, and see which theories win out.

2020
July
8

Three tips for getting reliable information — no, four

COVID continues to be bitterly controversial, and as various theories and claims are passed around, I have three pieces of advice for the reading public — no, four.

Tip #1: Claims aren't true just because they cite sources or bibliographies.

It is always better to cite sources than not to. But sources need to be checked out. Are the sources good? Do they actually say what the author claims? And are they cherry-picked to leave something out? What else ought to be there and isn't?

I've seen quacks try to impress people with citations of prestigious medical journals while counting on you not to actually look them up.

Tip #2: Every statistical study (e.g., of medical treatment) has a chance of getting the wrong answer because of random variation.

That's why you have to look at all available studies, and not just pick one that gives the answer you want.

The chance of a wrong answer is estimated to range from 5% (on strict Fisherian principles) to as high as 30% (taking Bayesian effects into account).

And the purpose of statistical studies is not to get statistics, but to figure out how things work. Science progresses by combining many separate results.

Tip #3: When someone commands you to "Do your research" or "Watch this video," you don't have to obey.

"Do your research" has become almost a tag-line of the loony right. Some people try to silence all critics by saying they haven't done their research.

The implied claim is, "This is true unless YOU can prove it's false."

No. It's false unless THEY can prove it true.

The burden of proof is always on the person making the claim, not the person who is skeptical of it. Otherwise we'd all have to labor all day refuting every strange thing anybody ever said.

And here's a fourth tip:

Tip #4: Scientists are supposed to change their minds when they get new information.

I've heard people claim "we were being lied to" when we received recommendations about the virus back in March that aren't the same as today's recommendations. Or else that the new recommendations are lies because "the truth hasn't changed."

The truth hasn't changed, but our knowledge of it has improved. Remember, COVID-19 wasn't discovered until December or so. More is known about it now than then.

The two most important discoveries are: (1) masks do more good than people first thought, because transmission is mostly through exhaled droplets; (2) "herd immunity" isn't coming, because the virus apparently doesn't give lasting immunity, so instead, we must kill off the virus by cutting down its spread.



Let's not forget there was a lockdown...

What do you think of the following logic?

(1) I was thirsty.
(2) I drank water.
(3) I am not thirsty now.
(4) That proves I didn't need to drink water.

Not very good, is it? But I have heard that argument about the COVID lockdown.

There are legitimate reasons to ask whether a less strict lockdown would have done nearly as much good and would have had other benefits. But I've seen something much more naive. It was simply a chart of death rates (with the lockdown) and an analysis ignoring the fact that the lockdown took place.

The epidemic was growing explosively in March, and its growth was arrested. The new second wave, though regrettable, is not like the initial explosive growth. Read on for a little more about that.



Do we compare amounts or rates?

Which is worse, having 1000 cases and adding another 1000, or having 10,000 cases and adding another 1000?

Both are bad. But the first one reflects a kind of rapid spread that the second one doesn't.

That's why there are two kinds of graphs of the spread of COVID. Linear-scale graphs go up the same amount for the same number of cases. Every time you add 1000, the curve goes up the same amount.

Log-scale (logarithmic-scale) graphs go up the same amount for the same proportion of increase. Every time the amount doubles, the curve goes up the same amount.

Somehow, a lot of us switched from using log-scale graphs early in the epidemic to using linear-scale graphs now. That conceals how bad the initial explosive growth was compared to what we have now.

Here is the U.S. total number of new cases daily, smoothed with a 7-day moving average, using a linear scale. You can see that we've added as many cases in the second wave as in the first.

Picture

That is sad — I want this epidemic to end! — but now look at it on a log scale:

Picture

Here you can see that in the early days, we had explosive growth that we don't have now. The number of cases was doubling about every two and a half days. It's not doing that now.

What next? Now that we know more about how the virus is transmitted, what I want my fellow citizens to do is wear masks and avoid crowds. We need to get the spread rate (R) down below 1.0 so the virus will gradually go extinct. That is easily within reach if we'll do it!



And one more spooky thing about COVID

[Updated.]

One strange but heartening thing about COVID is that the death rate is plummeting. In April, nationally, about 7% of the people diagnosed with COVID died of it. Today, 1%. And both in Georgia and nationally, the actual number of deaths is going down even while the number of cases is going up sharply.

This is surely the result of several things, among them:

(1) The tragedy of the nursing homes is past us. Reportedly, over 40% of U.S. COVID deaths were in nursing homes! And many were attributable to the tragically bad decision to send COVID patients to nursing homes for convalescence. Nursing homes are not equipped to contain contagious diseases.

(2) More generally, COVID is moving into a younger and less vulnerable segment of the population.

(3) Medical treatment is surely better now that doctors have more experience with COVID.

(4) Death may be more delayed due to medical progress and/or younger and more vigorous victims. If the length of time that it takes to die is gradually being stretched out, that will drive down the death rate, and will also mean that we are now seeing the death rate that belongs to the lower case rate that we had in May rather than the current case rate.

(5) At least conceivably, the virus may have mutated to become both more contagious and less deadly. This is speculation on my part. But most mutations make an organism less powerful, simply because they are random changes.

(6) It looks as though increases in testing are not the explanation. The total amount of testing has only gone up modestly in most places, and the percentage of tests coming back positive has not gone down. (Georgia's has gone up a little.)

This is only a guess, but I speculate that (2) and (4) are the biggest factors, and (2) can backfire, because older and more vulnerable people can catch the virus from young people who are spreading it with abandon. At many colleges, many of the older faculty are afraid to go back because they don't want to be in the younger people's germ pool. We may see some unplanned, economically costly retirements of highly productive older workers in many fields, not just academia, because people my age want to get out of the germ pool!

2020
July
5

New baby, or rather telescope mount

Picture Having a new telescope mount is almost like having a new baby at home, at least when it's as big a technical change as I'm encountering right now. The new iOptron GEM45 is really different from my two Celestron mounts. And we haven't had a single clear night since it arrived a week ago. Nonetheless, I've been busy learning as much as I can about it, making sure it works as far as I can, and confirming software interfaces.

It has been out under the stars twice, briefly, dodging clouds.

Of course I'm being thorough. I don't just want to get it working; I want to understand it at least as well as I understand the CGEM and AVX. And I'm going to write a lot about it. But nothing is ready quite yet.

In the picture at the right, you see the GEM45 in the carport, with no telescope on top, tracking imaginary stars. It has spent a good bit of time doing that this week. I figure I should give it some run time to shake out any possible problems.

At one point, there was some evidence of a loose connection, and iOptron kindly sent me a two-page guide on how to re-seat all the electronic connectors inside the mount. I did so, although the loose connection was apparently just that one of the modular plugs to the hand box was not fully plugged in. (Error message: "Mainboard connection error.")

That is what I consider high-class customer service. Much better than sending it in, waiting a few weeks, and perhaps paying a service charge.

And of course I got a really good look at what is inside (and took pictures). Not surprisingly, the circuit boards say CEM40, not GEM45. Those two mounts are the same soul in different bodies. That is, they are mechanically different on the outside, supporting the counterweight a different way, but very much alike on the inside.



Against political extremism

Trump has become markedly unpopular in the last few days, and as he falls from favor, I want to caution my conservative and moderate friends not to feel compelled to endorse positions farther to the left than they normally would. It seems the loony right and the loony left are fighting it out, and I've already encountered people who think that anyone who loses confidence in Trump must be ready to toe the whole left-wing line and dive into the excesses of political correctness.

No; let's continue to stand for what we stand for.

I long for the return of careful, fact-based policymaking instead of fantasy politics.

2020
July
1

Not all 5.5-mm connectors fit 5.5-mm holes

Picture

The power connectors for my Celestron and iOptron mounts are both specified as 5.5 mm o.d., 2.0 mm i.d., positive center. But the one from the Celestron won't plug into the iOptron. What's going on?

It turns out that American-made 5.5-mm connectors run large (such as 5.55 mm) but Asian-made ones run small (typically 5.47 mm). Here are two being checked with calipers:

Picture

Picture

To plug into the iOptron, the connector has to go through a hole that is 5.50 mm in diameter, not a smidgeon more. (iOptron's precision engineering may have been a bit too precise!) The power supply provided by iOptron has a connector whose diameter is about 5.47 mm, and it fits, tightly. Rummaging through my junk box, I found one that measured 5.45 and am going to make a power cable with it.

Meanwhile, the Switchcraft S761K that I use on the Celestrons is officially 0.218 inch in diameter (rounded up; that makes it 5.54 mm) and has a 0.005-inch tolerance, so it can be as big as 5.66 mm. No way is that going to go through a 5.5-mm hole. I think Switchcraft, an old-line American manufacturer, may have been using inch-calibrated tooling to make this metric-specified part.

The key point Switchcraft missed, I think, is that this is a part that fits in a hole and frequently needs to fit sockets from other manufacturers, and so its specified diameter should be understood as a maximum (just like a bolt or pin). You can't just make them whatever size you want and make sockets to fit them.

Please note: I am not talking about different specified diameters (5.5 vs. 5.0 mm) or center pin sizes (2.5 vs. 2.0 mm, the latter also stated as 2.1 mm). The manufacturer's specifications are 5.5 mm o.d., 2.0 mm i.d., which is a widely used standard.

So much for today's technology news. Maybe soon the weather will let me do some astronomy. I'm going to write a lot about the iOptron mount as I become more familiar with it.


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