NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: A Lunar
From: Jim Hickey
Date: 2008 May 30, 10:13 -0700
From: Jim Hickey
Date: 2008 May 30, 10:13 -0700
Frank, Alex and I were and are trying to answer a few questions along the lines of what you are asking. By recording the type of sight, the conditions, the sextant and the telescope power etc. and in a uniform manor we were hoping to quantify the significance of some of these factors a little more. It was also the basis of my appeal to the group to submit sights to be entered into our spreadsheet some time ago to accomplish this. With the 100 odd sights collected so far it is difficult to come up with definitive statistics, however, a few comments (well adjusted sextant, good IE, experienced observer etc. assumed) I would feel comfortable making based on what we have so far are as follows 1. I would stick by the within 0.2� limit using a good sextant on land, standing up, with a scope on the lower magnification side (in my case 2X) and perfect observation conditions (i.e. not windy, clear sky and nearly full moon). 2. For the simple expediency of adding further stability to the sextant by resting your elbows on your knees while crouching against a rest you definitely get better results and I find I am closer to your 0.1� limit. 3. If I move to the 12X scope, taking the sight standing is a bit of a bear as the field of view is quite narrow and it is difficult to hold still enough (at least for me!) to take full advantage of the extra magnification so I am back to the 0.2� limit, maybe a bit better. 4. I totally agree with the 0.1� error if I go with the 12X scope and then somehow add more stability (i.e. lawn chair, elbows on knees etc.). 5. And most important when considering the above, you have to be really really really careful about all those things Frank mentions earlier in this thread! 6. The optics I have for my Oaklet sextant are not top end optics and I do believe that better optics although they may not ultimately improve the accuracy, they would make getting the accuracy you have easier. I am going to keep adding sights to what I have so far and in particular want to add more while out sailing. My sense of what I might get under sailing conditions (42� sailboat, gentle sea, long wave period) is that I might get pretty close to the 0.2� but we will see. Obviously it will go to hell fast with a little chop. As an aside I have taken lots of LOP�s while sailing and found in excellent conditions (use your imagination) getting an LOP within 1� is pretty reliable. On May 30, 8:55�am, frankr...@HistoricalAtlas.net wrote: > Jim, you wrote: > > "We used 5 sights and averaged the results. We found that we were > within 0.2' �of the predicted lunar distance" > > So your results are about half as accurate as mine. At that level (0.1' > versus 0.2') it's certainly not a big deal. You could apply observations > with that accuracy to any... ahem... "practical" purpose, but do you > have any idea what would make your observations more accurate? What power > telescope do you use on your sextant? > > �-FER --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---