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Posted: 3/12/2007 8:13:57 PM EDT
| Is this bad? Its on a stano 2ng gen pocket scope. Also what are the two potentiometers on the back of the IIT? And no I have not touched them. Any help would be appreciated. Jim |
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Not knowing exactly what tube you are using I can not say what the pots are but most likely they are gain and brightness. Do NOT mess with them unless you have some means of measuring this on a test set. I am stealing this explanation from a physiscs website. Moderen Night Vision Equipment is basically a gigantic photomultiplier tube that is used to "see" at night. As an individual photon enters the NVD (night vision device), it strikes a highly charged cathode plate, which emits multiple electrons. That spray of electrons then strikes the phosphor plate (just like inside your TV) and what you "see" is an image at night that looks some what like it does in the day. As a matter of fact, it is possible for things to be SO dark that you can't see even with NVD's. It's so dark that you can see the electronic "noise" from inside the tube. It's like visual static, and that phenomenon is called "scintillation". So scintillation is something that exists in all tubes, the question is how much of it do you get. IPSC_GUY SIERRA II ALPHA |
| From what I have read on the subject, the scintillation is related to thermal noise. If the signal-to-noise ratio (SNR) is higher on the tube, or the temperature of the tube is lower, it will reduce the scintillation. The gain level will also affect it. Since it is an analog device, increasing the gain will amplify both the signal and the noise. Consequently, a lower gain will give less scintillation, but also a dimmer image. |
That is exactly right. In my typical gotta mess with stuff approach on things I cranked my top end gain down on my PVS 14 so that that high end gains is less than what it was by about 10% but I was also able to extend the bottom end as well allowing me to almost turn my tube off with the gain pot. I was consequently WARNED that going back up with out a HOFFMAN to measuer the top end could be very dangerous, If I were to get the gain to high I would risk smokin the tube. BUT I get very liitle "snow" in my image when in very low light environs. Now the cool thing about this is I run my unit turned down most of the time anyway so as to keep my unadjusted eye somewhat closer to ambient lighting conditions. If I have to come off the mono quick for some reason or other I won't be AS blind for the few moments till my eye adjusts. How much fo this effect are you experincing in your NVD? IPSC_GUY SIERRA II ALPHA |
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Ok so its like the tubes in tube amps, more voltage more noise. The IIT is a 18mm mcp 2gen according to the website. The potentiometers are are located at the the twelve and three o'clock positions. The power supply wires are at the twelve position. As to the amount of sparklies its noticeable, especially in low light. Last night no moon. I think the gain may be cranked to compensate for the objective that is on the scope. Its set up to use standard c mount camera objectives. Arent the military objectives specific to night vision applications as in allowing more light into the IIT? Also the IIT needs to stabilized from backwards movement. I have a o ring in there now. Would silicone be acceptable to use? Is there a specific type? I really appreciate the help folks. I have not heard from Stano. Thanks, Jim Edit to add: The IIT is the standard tube used in the an/pvs-5 nods. I found pictures at nvdepot.com. Everything looks the same but with only two wires coming out of the tube. |
| The pocket scope you are talking about have wery well used early gen2 pvs-5 tubes. And scintillation is absolutely normal with them. The lens they use is slower than the military lenses and so it makes it suck a bit more. Plus as I mentioned the tubes are well used, so who knows how far into their life they are (tubes get dimmer/less sensitive with age) I wouldn't expect the stano unit to work well at all in a no moon situation but the one I had worked well at about 1/4 moon or better. |
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Harlikwin mine works well in partial moonlight as well. I was mainly worried about the sparklies being a symptom of a problem. I am aware that the scope was made from surplus. For the application its used for it works fine. I saw someone on the property next door last night. I dont know what was going on but it wasnt the owner.Last night there was no moon and partly cloudy. They really stood out. I was very surprised. I'm only out around five hundred for this scope so I'm not stressing to much. It way better than a ELF. Thanks, Jim |
Hi Jim, the sparklies are a very normal phenomenon on the original gen2 gear. And for the price its much better than any gen1 devices of the same size, I wouldn't really mess it with much if I were you. |
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