Night Vision AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

[GBMaryland]

Ok,

This has been answered by another Hide member, but it doensn't make sense to me yet.

There is a TVS-5 Forward Observer's (FO) mildot based reticle. The spacing is 10 MILS between the reticle lines according to the TVS-5 manual.

My question is this. Does magnification affect the reticle? ...or are the devices different in some other way that the PVS-4, using the TVS-5 FO reticle, would not be 10 MILS between the lines?

 

[cj7hawk]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question


Wow. What a question. It's not one I can answer from theory either since I don't have enough information on the lens assembly for both devices and haven't seen a TVS-5 up close, but I will add a little background information.

The eyepiece and tube housing assembly is not relevant to this question. Since we're talking mils ( angular distance ) and magnification, it's all to do with the front lens.

The magnification of the lens is affected by the mirrors. The reticle sits inside of the mirror section of the lenses, so from that perspective, it would be likely to change between the PVS-4 and the TVS-5. It does go through the correction lenses, but that's not likely to correct for that kind of magnification variation at all.

However the optics within the reticle section itself could be changed to adjust the "zoom" so as to affect the scaling of the reticle.

Did they design them that way though?

I have no idea. Please let me know when you find out -

David

 

[GBMaryland]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

That's what I was thinking as well... In general terms.

The pvs-4 is 3.6x and the tvs-5 is 5.6x - the differnece in the mirrors is huge.

I guess the easiest way to test this is to center at 100 yards, then use the first tic to see if the POI changed by 3.6 inches...

I'll use an AR-15 and a tripod.

 

[One-Eyed Jack]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

Yes, the difference in magnification between the PVS-4 (3.6x) and TVS-5 (5.8x) affects the reticle subtension. There is a Forward Observer mil dot reticle for each of these NV scopes with different part numbers.

If you use the FO reticle for the PVS-4 in a TVS-5 (just what I will be doing when the reticle comes in next week), the mil dots won't be 1 mil apart, but will be 3.6/5.8 = 0.62 mils (about 2 MOA) apart. The reticle itself will appear the same, but the subtension of the target image is larger because of the higher magnification. Thus, the "mil" dots will subtend a smaller angle relative to the target image.

I should add that the PVS-4 and TVS-5 have second focal plane reticles, so think of it that way.

 

[GBMaryland]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

I tried another method and I'm wondering which is more accurate... or if we're both just mental cases?

If you have (155mm/10MILS)=(95mm/xMILS) you get 6.129MILS per tick.

(The FO TVS-5 reticle is a 10MIL spacing from line to line according to the manual.)

Does it make sense that the PVS-4 using the TVS-5 FO reticle would result in about 6.1 MILS per tick?

 

[One-Eyed Jack]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

I dunno, I haven't checked the calibration of my TVS-5 FO reticle yet. I would probably use a day scope with a mil dot as a ruler and compare the two. The ratio of subtensions between the TVS-5 and PVS-4 with the same reticle is the quotient of the magnifications (5.8x and 3.6x), not necessarily the diameters of their lenses - unless they have the same focal ratio.

I don't have a mil dot scope here to do the comparison, but will next week and can report back.

 

[One-Eyed Jack]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

If the manual says the TVS-5 FO reticle has 10mils between dots, then the same reticle cell in a PVS-4 would have (5.8/3.6) x 10 mils = 16.1 mils between dots.

 

[One-Eyed Jack]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

Knowing that the FOV of the TVS-5 is 9 degrees, I've confirmed that the separation between dots in the TVS-5 FO reticle is 10 mils. So, it would be 16.1 mils between dots for the same reticle cell in a PVS-4.

 

[GBMaryland]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

Wow.... that makes it a great long range reticle! -grin-

 

[GBMaryland]

Re: AN/PVS-4 vs AN/TVS-5 Rectile Projector Question

(...and thank you....)