One second gun VS five second gun.. Optics

I have a 5sec gun and have it set for 1sec display.

It will perform better than 5sec and will double an angle observation down to one second. It does not always do so, but under normal contitions within the 5sec.

The 5sec rating is the gun's worst expectation of normal operation.

The optics should be the same, especially when you check the range of the optics on the specification description for each gun.

> I have a 5sec gun and have it set for 1sec display.

My Pentax displays to 1" also.

I was told, that Leica guns, were all built to the same specs, and that their accuracy was only determined post production. I have run Topcon,Sokia,Pentax, and Leica instruments in my time. I found the Leica optics The best.

The question becomes do you have a one second tripod, target, tribrach, crosshairs. Probably not.

Good point, nice hat.
Old Crew Chief on hiway jobs used to say to me, "We're not building a Swiss watch here"

It's not so much the optics, it's the tangent screws that are more critical.

Leica motorized knobs are pretty good at least when they actually respond.

My Topcon is OK in the tangent screw department but could be better.

David

> It's not so much the optics, it's the tangent screws that are more critical.

A larger diameter objective lens allows more light in and gives a better target. I am sure you know that though.

So the answer is.....

No. A 1" gun has the same seeing ability that a 5" gun does.

David

When I purchased my Total Station I looked at the 2", 3" and 5" models. I concluded the price difference wasn't justified for the work I do so I purchased the 5" model. I think in the Topcons the 3" and 5" are essentially the same instrument but the 2" has more angle sensors built into it so presumably it can read the internal vernier a little more precisely. The 2" instrument was nearly double the price.

PAUL

The ability to measure angles more precisely is a different matter from being able to POINT the instrument accurately. One is optical clarity and level of magnification and the other is angular precision. Without a side by side comparison it would be hard to tell which instrument has better optics at longer distances. My guess is that a more expensive instrument, such as a Leica, would have better optics than a Pentax and therefore you would be able to sight more accurately with a 5" leica compared to a 5" second pentax. The spec sheets probably have numbers for this feature. I just checked and they do. A pentax V200 has 30x maginification. My old 5603 has 2.4x and Lieca makes eyepieces with different levels of magnification.

PAUL

in general, a lower least count on a theodolite, or an auto level, also, the better the resolution, the better the magnification should be. quality of optics improves with quality of posted accuracy/precision.

check my statement out against a manufacturer's instrument list.
maybe put a monitoring total station against a builder's theodolite. compare least count versus magnification. they should be inversely proportionate

I'm such a skeptic that when it's different accuracy specs for the same model, I think it's mostly marketing. I read a few years ago that a lot of the work that used to be done by a highly skilled machinist at the instrument factory is now done by measuring errors and correcting for them electronically in conjunction with the dual axis compensators. So it would be very easy to make all the guns the same except for the calibration. Not too different from software that is fully featured, you just need to pay for the key code to activate it. It's standard in all retail that you need a range of prices so a customer can be proud of being a big spender or savvy shopper. That's us, too.

Dane

It's not about measuring, it's all about clarity of sight.

PAUL

The least count, precision, improves with the improvement in the angular encoders.

Dane

I believe that the average human eye can resolve about 1 arc minute without magnification, so with a perfect 30 power scope, the limit of resolution would be about 2 arc seconds.

I have wondered why they don't make a survey instrument with a zoom lens, especially for close work.

Probably not, but my old T2 is still great optics. We have a Trimble VX, which is essentially a S8 1" gun with a scanner internal. The optics are Carl Zeiss and are out of this world.

Side note about optics though.

For years and years, I've bought what I could afford for hunting scopes. My father has always bought Leupold. Well, a couple of years ago, I got a very nice hunting rifle. A 7mm mag with 28" stainless bull barrel with synthetic stock in Remington 700. Well, I said that I was going to buy a good Leupold. I spent nearly $500 on the scope and love it. Well, turns out, my mother thought my dad needed a new rifle that year, so he ended up with a Browning A bolt in 7mm mag (much nicer than my gun). After I showed him my set up, he went out and bought a Zeiss $800 scope.

I don't know that I'll ever show him up, but damnit, it's getting expensive to try at this point. 🙂

Generally speaking, each company's instruments all have the same optics for their high accuracy surveying instruments. Leica and Trimble have a higher level of recognition (Trimble uses Zeiss optics) for their optics. Of course, in the old days, when one purchased an instrument that could read directly to a more accurate determination, one also got better optics with that instrument. Wild normally put a 30x scope in the T2, a 40x scope in the T3 and a 80x scope in the T4. The latter 2 were substantially heavier (the T3 weighed about 26 pounds in its' carrying case and the T4 weighed about 120 pounds in its' case) than anything you would ever want to carry around and were designed for use to establish 1st and 2nd order control networks.

Dane

The number I had heard was that good eyes can resolve 0.7 minutes, pretty close to what you said. But is that the same thing as finding the center of something? You might be able to line up two blobs to better accuracy than you could make out features on them.

Zoom lenses would be difficult to make so that they held pointing accuracy as the focal length changed. It's hard enough to keep pointing as focus is changed on a fixed-length lens.

One second gun VS five second gun

I was told the same thing as Bob H posted above.

The instruments within a model series (i.e., TPS 403, 405, 407 etc.)are all manufactured to the same spec......then they are tested prior to final labeling.

Those that perform up to 1 second spec get the 1 second label.
Those that perform within the 3 second spec get the 3 second label, and so on.

The optics within each series are the same.

Paul

My experience is that there is a difference in the brand of gun more so than the sepc. for the accuracy of the gun. My old Wild T2 was the best I ever had for optical resolution but the T1 I used was very similar. The Topcons (still have one) were also good guns, the 5" and 3" models had the same clarity but were not up to the quality of the Wilds. There are some brands that I've tried that I didn't like mainly because they just weren't clear and didn't focus well-never looked through a Pentax.

1200' is not very far for any instrument: in my experience anyway. I think there may be an issue with the optics in your Pentax or there are atmospheric issues-heat waves, smog (I have to admit here that I've never worked in a large smoggy city). The same gun that would have no trouble resolving a backsight at 5 miles on a clear day with minimal heat waves wouldn't see 1000' along a runway in the middle of the day-and no gun will fix that.