I've never seen one before. I've seen lots of 30 minute ones, and used one that had a 20 minute vernier, on horizontal, and 30 minute on vertical. But, this is the first I've seen that had a 15 minute one.?ÿ
https://www.ebay.com/itm/323887845975
I'm not in any way associated with the seller. It's just interesting.
N
If I'm looking at the vernier correctly that is a 20" transit. It looks like 3 divisions between each minute mark.
No, Dave, it has a big mark in the middle, between the degrees. It's the 30 minute mark. Then, a little mark, at the 15 minute mark. Zoom in hard.
(At least I'm persuaded).
Nate
I vote with Dave.?ÿ?ÿ It's been a while but I have read a vernier (yup, geezer).?ÿ
Reading the outer scale at the arrow tells you which 15 minute segment you are in, with marks 1/4 degree = 15' apart.?ÿ Then you find the marks that match up and read the 15-0-15 scale to get minutes and fractions of a minute.?ÿ The minutes are divided into 3 parts, 20" resolution.?ÿ?ÿ
I believe the fact that it is green makes it a late model instrument which would have been competing with the fast growing theodolite market at that time.
The problem with older equipment is when you have to replace the crosshairs. Go find some repair shop today that has a black widow spider living in the corner. Then again nickel silver wire may now be available in small enough gages.
Paul in PA
I think we are both correct. I'm looking at the least count which is 20" and you are looking at the vernier scale which is 15'. It is 15' in order to spread out the seconds to get more divisions between each minute. I'm not sure what a 30" transit has in terms of minutes, maybe 20?
Nothing special there. STD 20 sec ??Berger? looking K&E.
Plenty of those to go around.?ÿ
I have a 1925 Royal Engineers’ textbook that describes field repair of silk crosshairs.
Step #1: catch a spider.
step #2: place the spider on a 3 inch piece of card stock with large hole cut in it.
#3: flick the card to get the spider to fall
wind up the silk and .... take a candle...
it’s wonderful.
Right. A 30" instrument is illustrated in three textbooks with degrees divided in 3 parts, and zminutes 20-0-20 in 2 parts to read 30".
But there are multiple ways to do verniers.
I have a book illustration of the 20" version in the picture. Degrees divided in 4 parts, minutes 15-0-15 divided in 3 parts.
Another has degrees divided in 3 parts, minutes 10-0-10 and also 10-20-10 over the same marks divided in 3 parts to also read to 20".?ÿ Somewhat more cramped and harder to read.
A 1-minute transit would commonly have degrees in 2 parts and minutes 30-0-30 not subdivided.
Nothing special there. STD 20 sec ??Berger? looking K&E.
Plenty of those to go around.?ÿ
And not looking to be the best cared for.?ÿ I'll be surprised if it sells for that price.
If that goes for 300$, I’ve got a nicer one and would take 300$.
Everyone has one. On display, or in the closet.
@Larry Scott with tripod?
I love those old guns.
That's the 1st one I've seen, with 15 minute divisions, and 20 second least count, (I agree, I think both Dave and I were correct).?ÿ
No longer a practical need for such an inst. Maybe good for setting up a building, or the like.
Time marches on....
Paul is apparently correct too. It's a late model. But, it's the only one configured like that, that I've seen.
N
I used my 1' Dietzgen to stake and Square my deck project (not attached to the house) because I don't have anything else. By myself, distances are short so I lay my tape perpendicular to line and read it, go over set the reference spike.
Witnessed the instrumentman (early seventies) make this field repair several times.?ÿ He had a "kit" of tools including tiny screwdrivers, a card with spider silk wrapped around it in a tiny box, tweezers, a forklike thing that looked like a dental floss holder?ÿ and a small dropper bottle of thickened varnish (shellac?).?ÿ He also carried a tape repair kit. It took him about 15 minutes, including realigning the reticule.?ÿ The spider silk was commercially available in consistent diameter(s), cleaned and prestretched; the idea that spider silk would be collected in the field for the purpose is specious; "wild" spider silk is too inconsistent.
Here's a good article on the use of spider silk in scientific instruments:
"Spiders in the Crosshairs"
I'm a gonna need all 60!
That eBay ad, has been up for a couple of months. It's maybe overpriced, but it does seem to possibly have been more expensive, than a normal transit.
Old transits, tell stories, it you stare at them long enough.
N
This is my 30" vernier/20' scale Lietz transition got off Ebay last year.
Correction 20" vernier
I assume a 15' scale gives easier reading of the vernier
I know I read it as 30 for some reason?ÿ
The upper tangent screw was stuck but the guy just had it run in all the way. Just unstuck it now works smoothly. Only problem is upper motion is a bit stiff otherwise seems to be in good shape.
It was really stuck to the aluminum base. Clamped base down, redwood stake either side of knurled base and c clamp and a little force and it broke free.
?ÿ