NavList:

Hello!

Like Alex I find SNO-T inverting telescope to be excelent. The 7x power is optimal also for Lunars. Inverted image does not seem a problem to me (but I have heard some users don’t like this). I share the point of view of Alex, that this is matter of getting used to that.

The weight of the SNO-T telescope is only 177g (0,177kg). The weight of my SNO-T sextant (with inverting scope) is 1,54kg. But it is not the lower limit for metal sextant. My SNO-M sextant, for example,  weights only 1,22kg. The difference between the two models is 0,32kg. And for longer multiple sights the difference is noticable. But there are many other metal sextants that are much heavier. And any extra weight from telescop matters.

Some advantages of wires:

-when wild anlges are measured (typicaly for Lunar sights), the wires help to make contact of images close to the center of field of view much easier then without. If the contact is made, for example, with 35’ offset from the center of the view, there will be 0,5’ error in the results, if the measured angle is 110°.  For traditional altitude sights the impact of centering is much much less important, and diminishes for small angles.

-the wires make easy to check telescope’s paralellism to the plane of sextant using lunar sights or star/star distances;

-the wires help to check change of telescope parallelism if the telescope is rised (to reduce brightness of reflected image). My SNO-T does not maintain paralellism. By means of these wires, it is possible to calculate the correction needed for very accurat sights.

-the wires allow to find the offset value, if telescope is out of paralellism, but you don’t want to waste your time for adjusting telescope. I have used this strategy for several times.  The distance between the wires (which is easy to measure with sextant itself) serves in this case as reference for evaluating the offset.    

-the wires help to adjust telescop paralellism under indoor conditions (during table top adjustments).

Disadvantages of wires: I don’t find any.

Alex, you wrote:

"However Soviet engineers did not always fully understand what they were doing. I know two pieces of evidence of this. One is the absurd certificate they issued for my sextant. Another is the amazing, unbelievable fact discovered by NavList participants: it turns out that during the whole period of manufacturing SNO-T, they were attaching the horizon filters assembly UPSIDE DOWN! It does not have any effect on performance though."

I will speculate that the absurd certificate of your SNO-T was a peculiarity of your sextant. Do we have any evidence that this was a systematic phenomenon?

Your claim that horizon shades are mounted upside down is quite controversial. I know that such an oppinion was declared by Bill Morris (outstanding sextant expert and, by the way, the author of the wonderful manual about SNO-T). He presented an instruction how to reverse these shades. The main purpose was to achieve the goal of using the shades also with Galilean telescope (designed as night telescope). And this advise could be useful for those who take sights only using this small night scope. I have tried to reverse the shades according to Bill’s instructions (it should be mentioned that this is a dangeros process, because it is easy to broke fragile parts, while knocking out the pin). But I was disappointed. Why? Because now the shades in work position could not be simply rotated down to the end. They had to be slightly adjusted to the best position. I found this very annoying and returned to manufacurers design. Besides 99,9% of my sights are taken with inverting scope, when the shades are not an issue.

Modris Fersters