NavList:

Homer,

Yes, you can absolutely use Stellarium to generate the altitudes to complete your lunar observation.

You wrote:
"The values that I get for the alt sun (apparent) and alt moon (apparent) are a little higher than the displayed values when the effect of the atmosphere is turned off - so this setting seems to eliminate the need to correct for refraction. Is this correct? Also, do I need to do S.D. corrections for the sun and moon, or are the altitudes calculated based on the center of the bodies?"

As you've noticed, you can directly assess the significance of refraction by turning the atmosphere on and off. It's really quite an excellent simulation, and it's fun to try when looking at stars just a few degrees high. They pop up and down as you click the atmosphere on and off. The resulting altitudes include everything but dip and SD. That is, the altitudes correspond to what an Earth-based observer (at the entered position) would measure for the center of each body with a height of eye of zero. Thus these altitudes match reasonably well with the so-called "pre-cleared" altitudes. Dip and SD have been removed by default. Note that the Moon still has parallax included in its altitude. There's a way to get rid of that, too, if you're interested, but I would say that's an issue for another day...

You've already received some good advice on this from other NavList experts. Let me add one more simple approach. I believe you have my "GPS Anti-Spoof app", right? If you have the "Pro" version, you can get Moon altitudes, Sun altitudes, and altitudes for any of the standard lunar stars, too. And these are raw sextant altitudes (Hs) by design. So you can set your app up with a height of eye that suits you, maybe adjust temp and pressure for your local conditions, and then 'tap the app' to get live altitudes just as if you had shot them with a sextant. Take a Moon altitude (with the app) followed by a Sun altitude a couple of minutes before you short the actual Moon-Sun distance with your sextant, and after that reverse the order and get a Sun altitude followed by a Moon altitude (again, from the app). Then the analysis that follows has exactly the pattern that you would follow in a traditional lunar if you had access to a visible horizon. :)

Frank Reed