NavList:

Gene V., you wrote:
"My sextant is setup with a 7x scope. Would it be better to use a zero magnitude sight tube when taking star sight?"

You don't actually need to grab a sight tube for this. Just take the scope off for the initial alignment. It's a little weird lining your eye up with the place where the scope is supposed to be, but it works (just don't poke your eye out!). Once you have the star crudely aligned in the field of view, you can put the scope back on, and you'll be in the right range. 

The idea of "bringing the star down" has become rather firmly ingrained in recent navigation lore, but it's not really necessary and the benefits are debatable. It's easy to lose a star on the way down... A method that's often easier is just to estimate the altitude of the star. Set the sextant to the estimated altitude, and then scan near the horizon on the same azimuth as the star. It should pop right into view. This is commonly used to find Polaris in brighter twilight. For Polaris, you set the altitude to your estimated latitude. This works well.

You can also make yourself a short list of the bright navigation stars in advance with estimated altitudes. This might sound like cheating, but you're only trying to get the estimated altitude to the nearest degree or two, and that would be reasonable in real navigation. So before you hit the lakefront, open up an app that provides altitudes and set it to the approximate time and location. The desktop "Stellarium" app is excellent for this --get it at stellarium.org. You can also use an app with text output like my web app (the "clone" of the old USNO web app). There are many other options. 

You can also estimate altitudes quite well by comparison with star patterns that have known angular sizes. Do you know the length of the Big Dipper in degrees from the leading edge of the "cup" to the end of the handle (it's about 26°)? Or maybe the size of the Summer Triangle from Deneb to Altair (about 38°)... The sky is full of angular scales, and you can use them to estimate the altitudes of stars easily.

There's another method with a sextant that you may want to try. Turn the sextant upside-down. Set it to 0° and aim the horizon side right at the bright star your'e shooting. Now reach up --feels strange at first-- to the index arm release which is now up high on the sextant. Slide the arm slowly but keep the star centered in the field of view. There's nothing to chase here. Slide the arm until the horizon appears on the other side... You're seeing the horizon in the index mirror side! You now have the angle correct more or less. You can complete the sight like this with the sextant standing on its head, but most people find this uncomfortable. Instead, after you have the star and the horizon both in the field of view, just flip the sextant back over and use it as normal. 

Frank Reed