NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextants, vernier and micrometer.
From: Henry Halboth
Date: 2006 Oct 31, 19:57 -0500
From: Henry Halboth
Date: 2006 Oct 31, 19:57 -0500
Alex & George, I must apologize for not having viewed the vernier picture properly. You are quite correct in stating it to be a 12-second vernier, which does prove that I have most certainly not seen everything or read everything either for that matter. It is, however, rather amazing that I have not run into this before - I presently own 3-vernier sextants, and any number of a vintage equal to yours have passed through my hands over the years, and I simply have never seen other than 10 or 15-secnnd verniers. Again, my apologies. Henry On Tue, 31 Oct 2006 08:17:49 -0500 (EST) Alexandre E Eremenkowrites: > > > Henry, > Close investigation shows that this is a 0.2' > vernier. Indeed, each degree on the main arc is divided into 6 > parts, > 10' each. Now the vernier has 10 big divisions (1' each) > and each big division is divided into 5 small divisions > (=1/5 of a minute=0.2'). > This is also confirmed by the certificate which says > that the vernier reads to 0.2'. > And accordingly, the table of corrections is given in > even decimals of a minute. > > This sextant seems to have only one visible defect: > the Index mirror is somewhat deteriorated on its upper edge: > http://www.math.purdue.edu/~eremenko/pic2.jpg > and probably needs re-silvering for good performance. > If you are curious to see the horizon mirror as well, > it is pic3.jpg. > > The seller says that there is no adjusting tool. > It seems to me that on this type of a sextant, one > does not need any tool to adjust the mirrors: > the screws can be rortated with fingers, am I right? > > Another question on this sextant: does anybody know > what were the requirement for a sextant to be qualified > as Class A? I know the similar requirements for Soviet sextants > in 1960-s, and they seem to be more restrictive than those British > of the beginning of XX century. > > Alex. > > On Mon, 30 Oct 2006, Henry C. Halboth wrote: > > > > > > > Alex, > > > > It looks to me to be a 10 second vernier. Most older > sextants/octants had > > either 10 or 15 second reading verniers. > > > > Henry > > > > On Mon, 30 Oct 2006 12:42:58 -0500 (EST) Alexandre E Eremenko > > writes: > > > > > > > > > Dear George, > > > Could you look at the picture of the vernier > > > of that Hezzanith on e-bay we just discussed: > > > http://www.math.purdue.edu/~eremenko/pic1.jpg > > > It is supposed to provide 0.2' reading. > > > What do you think of it? > > > > > > One more request. As I understand, you had that > > > bad sextant (which you returned) in your possession > > > for few days. Could you recall some detail about > > > it which would permit to exclude the possibility that > > > this one is the same? > > > > > > Like the number and power of the scopes. Presence/absence > > > of eyepiece filters? > > > Anything about the certificate? > > > Was it a 10" reading vernier? (This one is 0.2' reading). > > > > > > Thanks. > > > Alex. > > > > > > > > > > > > > > > > > > > > > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---