NavList:

Bill wrote:

"I am voting for the old K-mart."

 

Ah, the fascinating K-Mart discussion continues... ;-)

 

And you wrote:

"We can set the sextant(s) up on a piece of
wood at home. Level the frame fore and aft, and get our laser set up in the
middle of the scope eyepiece, hitting the junction of the glass/mirror of
the horizon mirror and centered so we have some hope of using the portion of
the scope and mirror we use in the field.  Then move that calibrated or
fixed unit to the site."

 

It's not that hard. But really I would recommend doing this indoors, or if you're outdoors, somewhere that is inaccessible to the public. Even a 100-foot hallway would be sufficient. I can get IC accurate to about +/-0.15 minutes of arc in a 50-foot room. If you're outdoors, you have to worry about curious passers-by, kids who want to play in the laser beam, theft, and of course the elements. Additionally, you may get ticketed. Many communities have laws about outdoor laser light. Goofy laws, yes, but that's not gonna help if you get a by-the-book police officer interested in your activities.

Back to the test...

You should find that when the telescope is focused correctly, the two dots on the target are almost too intense to look at, but they have nice diffraction spikes extending several inches above and below. That's where you measure. Using dividers is very helpful and you can immediately transfer your observations by poking them into a piece of paper. I just ran a set using Alex's SNO-T sextant. The result is IC = -0.65 +/-0.15, which is consistent with previous observations. I tried both telescopes just to see if there was any effect. The results were identical. A few days of Moon sight averages yields IC = -0.70, and that's the value that I trust.

 

As for additional tools, this test doesn't require any fancy leveling. I use a phonebook and a notepad under the laser to get it high enough to aim through the sextant's telescope. My "target" is the trash can from our kitchen which has a nice screen-like white side, and it has the advantage of being easy to move around. :-)