NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2025 Feb 26, 06:07 -0800
Dave W., you wrote:
"Maybe not so hard."
Do you have a single-day scenario in mind? Unlike a Messier marathon, you'll presumably need to be in a tropical latitude to see them all. Northern limit about 15° N to pick up Miaplacidus at some point during the night. Southern limit about 2° N if Polaris is counted (and really it should be counted), or maybe 12°S if we make a technical exception and exclude Polaris. That's still far enough north to spot Kochab.
If we go to the equator, the problem simplifies a bit since we're looking for a day in the year when the Sun and its twilight glow don't spoil the view. At the equator, that's equivalent to finding a band of RA/SHA larger than about 15° with no nav stars in it. So if I sort the navigation stars by RA/SHA and then subtract values for neighbors, I can spot gaps. The largest gap is from Aldebaran to Mirfak. So in late May I can try to catch Aldebaran just after sunset (very difficult) and Mirfak just before sunrise (difficuly but it turns out Acamar may be more trouble). I'm assuming the Sun has to be at least 7.5° below the horizon, and also that extincted magnitudes are not fainter than 4.0.
I haven't done any more extensive search than as described above. There are probably better latitudes (still in the range 2°N to 15°N if we hope to see them all) on a few dates.
Frank Reed
