Thursday, October 18, 2018

Different Levels of Government, Different Rules

Three Forks of Wolf, Tenn. (1868)
11/29/1868: “[A]n aged widow lady, by the name of Galloway” had the day before received $300 back pay for her husband, who had died in military service.  A robber “most foully and brutally” murdered her and her three daughters in pursuit of that windfall.
Category: residential
Suicide: no
Cause: robbery
Weapon: unknown[1]

[1] “A Whole Family Murdered in Fentress County,” [Memphis, Tenn.] Public Ledger, Dec. 10, 1868, 1.

The story explains these scum were turned over to the federal courts not state courts because blacks could testify against whites in federal courts; remember that after the Civil War, the antebellum rule that a black person could not testify against a white person persisted.

Next Obscure Electrical Question

Are there LEDs that will only illuminate at some threshold  volume, such as 2 VDC.  My reading says that 2.1 VDC is needed to illuminate a green LED.  Here's the application: I really want an LED that tells me if there is enough power from the two AAA batteries that I do not need to change them.  I would prefer to know this before trying to observe for the night.  At the same time, I do not want too much power draw that drains the batteries too quickly.

I can almost visualize a use of XOR and OR gates that would produce a 1 output if the battery pack voltage is below 2 VDC.  But I would expect LEDs, or logic combos with an LED, that already have this capability to light up a low power LED.

Just to clarify since some of the answers seem to show that I failed to communicate my hopes:  I want an illuminated LED when voltage is >2 VDC or thereabouts, and dark below that level.  No intermediate brightness.  I want a "change the batteries LED."

This looks useful; 51 ohms with a 3 VDC battery pack for a yellow LED will draw little current from the battery pack. Now that Radio Shack is no more, where do you buy one 51 ohm resister and one LED?  Here for the resistor.  Here for the yellow LED.  Red would seem the best choice: forward voltage 1.8 V to 2.2 V.   75 ohm resister.  Red LED with resisters for 6 V-13 V (100 units).  I am guessing the included resisters won't be of any use.  20 mA draw at 3VDC would be .006 watts.  That does not sound like a fast drain on two AAA batteries.  This says a AAA holds 750 mA-hours.  Even if I had the power switch on four hours a night, that should be 125,000 hours consumption for the LED, far more than the motor will draw.   Not sure what to do with the other 99 LEDs.  (Make a red night light to avoid destroying my night vision when doing astronomy?)  Am I on the right path here?

Wednesday, October 17, 2018

Help Me Construct the Adjective

hemidemisemiquaver (and, yes, I knew what that was before going to Wikipedia) is a 1/64th note.  We know now that Sen. (Lieawatha) Warren is six to ten generations removed from anyone who might Indian.  So she isn't a half-breed.  A hemidemisemihemidemisemi-breed?  A mouthful.  And yes, this remains one of the most amazing songs by Cher.

Obviously Sent By a Pro-Gun or Pro-Life Extremist

10/15/18 CNN:
A spokesperson for Collins tweeted Monday evening that Collins' husband, Tom Daffron, "today received a threatening letter that the writer claimed was contaminated with ricin, a highly hazardous substance which was used in a previous attack against the United States Senate."
Sen. Collins (sorta R-ME) has always been a squishy Republican.  Do you think this will make her more or less sympathetic to the progressives?

Tuesday, October 16, 2018

Today's Electrical Question

I suspect that I learned this in high school physics 1973-74.  But Nixon was President, so I likely forgot.

You have a 3VDC source (two AAA batteries); you add another 3VDC source to the same wires.  Do they add, or do you only get 3VDC?

STOP!  I have more evidence of how smart my readers are, dozens of answers in agreement.  Alas, mechanical issues rendered my idea impractical.  The Crossbow Equatorial Platform  runs on two AAA batteries (remarkable since it is moving more than 100 pounds of telescope at one revolution per day.  It is good for 120 hours, but you must remember to turn it off when you are done.  The switch is in an awkward position, so easy to forget at the end of the evening. 

I was thinking of hooking up the 12 VDC power source that I use for the Sky Commander through a 12 VDC to 3 VDC gadget that I assembled from parts.  Turn off  the power source when closing up for the night, and the switch does not matter.  But the problem with both cables is that as the telescope turns it winds the cables around the base.  I even thought of bungee cording the power pack to the side of the telescope base so it rotates with the telescope and the Sky Commander, but the platform does not rotate, so the cable to the 12 VDC to 3 VDC converter will wind instead.  Besides, the power pack is very heavy and affects operation of the platform.  I may consult with my wife, who is very good at spatial conception.

I can live with batteries on both electrical parts; replacing 12VDC and AAA batteries after forgetting to turn them off isn't really that hard.

Let Us Now Praise Great Bargain Eyepieces

I think I mentioned the struggle I was having getting my 35mm Plossl sufficiently in focus.  The obvious solution was another low power eyepiece with less in focus.  So I bought this Russell Optics 50mm 2" eyepiece:
Okay the stick on label is cheesy, but it cost me less than $80 delivered.  Wondering what 2" means?  You are obnviously not an amateur astronomer.  Telescope eyepieces come in three common barrel diameters: .965" (an older Japanese standard), 1.25" (the American standard), and 2.00".  The larger eyepiece gives a really glorious feel of looking through the spaceship's portal.  In addition, Televue (an American maker of very fine optics) has produced a great many very wide field eyepieces in 2" format. However, these are eyepieces which are priced accordingly (hundreds of dollars for something that a few amateurs compare to a grenade in mass and dimensions).  

Enough with the tangent.  A 50mm eyepiece gives 18x in my 5" refractor, and 40x in the 17.5" reflector.  So why would I want a low magnfication eyepiece?  The field of view gets larger as the magnification drops.  If you are hunting for low surface brightness, large area objects (like galaxies) a wide field is very useful.  In the refractor this eyepiece gives a 2 degree field of view.  Even in the reflector  this is a .875 degree field.  And objects like the Moon are crisp and beautiful against the inky blackness around it.  My wife was enchanted by how much more AWESOMITUDE this eyepiece gave on the Moon (sorry for breaking into surfer English; I grew up three blocks from the Pacific).

I bought this because some years ago, Russell Optics sold an 85mm cousin at a bargain price.  At the time they said it was a prototype that they had made to decide whether to do these commercially.  It has an acetal barrel which greatly reduces its weight.

As with any long focal length eyepiece, they work great in refractors, but until it gets dark, the central obstruction of the diagonal mirror produces a very noticeable black spot in the field of view.  They warn you about this.  It is a minor nuisance until it gets dark, at which point the dark spot goes away.

Now, what I do with old 50mm eyepiece?  It has no brand name or markings on it.  It is a brass barrel and weighs 15 ozs.  (That weight makes it a bit clumsy on my telescopes because it alters the balance a good bit.)  If it could talk, I suspect that  it would tell stories of sinking Japanese destroyers.  It has the look of something war surplus.  It was one of eyepieces that came with the bargain 17.5" reflector I bought at a Boise Astronomical Society auction some years ago.

Any ideas how to chase down its lineage?

 The  number stamped into the top is 233061-9.

Monday, October 15, 2018