While taking pictures through the GSCI pvs-14, some particles are visible on the photos, but these are barely visibly at night when the tube is on.

Bright spots on the first one?





Are these particles cleanable, or fixed blemishes? And if they are cleanable, how so ?

Thanks !

Are they considerably more visible if you close down your camera aperture, and less if you open it up? If so, then they are probably on/in the eyepiece optics. Could be debris, can't say from the pic, but their shape would suggest blems instead. Debris tend to be curved / non-circular, but of course they can, and the photos aren't clear enough to say.

In case of debris only way is to open it up and clean, but afaik with GSCI you lose warranty by opening it up by yourself. I use isopropyl alcohol and good q-tips.

They seem to be at the surface of the tube somehow, as you say its visible when I get the surface of the tube in focus. Don't blemished occur further in on the microchannel plate ?

The phosphor screen and the optical fiber bundle can have defects too, but I have not heard of fiber defects being this visible. Single fibers are so small that they would not be that visible in the photo.

If they seem to be on the surface then camera aperture would not affect anything, so no need to try that out.

But you're right, not the usual place for blems as far as I know. Could very well be dust / debris on the tube. They just look so black & round, but that kind of debris could come from the threads when they screwed the eyepiece in. Or is the color from the flash? There seems some "bumps" where the reflection from the flash is, are those black too if viewed from a different angle?

There are true experts here and I am sure someone has seen exactly what you are seeing.

Very good point, it looks like black coating "dusted" on the tube after its been screwed on.

I hope someone in here can maybe confirm that, in the way it looks. It also seems like they are only on one side
of the tube. The same is actually seen through with the tube on, clean on one side and the dark dots on the other.

Being on one side is quite usual both powered on & off, except if a blem is visible on the photocathode then it will obviously show on both sides when the tube is powered on.

I hope that's dust from the housing itself and thus the black color. Though I suppose GSCI will want to clean it themselves anyway and surely do it for free as that is no little mistake when putting it together. Also if they turn out to be blems then it sure seems the surface area of them combined is way higher than I suppose is allowed.

If the black spots are not as much in focus when you actually look through the device (at a white wall with perhaps the IR emitter on) then they surely are on the surface and not inside the tube. Light bleeding around them might make them less visible though, so too bright of an image could mask them.

Edit: not on phosphor screen, but photocathode, edited the first sentence.

It seems they are blemishes after all. Interesting how many of them there can be, but only five of them visible in a high contrast background, giving it still the impression of a very clean and crisp tube during normal use.
Maybe all tubes have this, but one needs to take a picture with flash from behind to see them ?

Are you sure? Dust/debris can be very deceiving. The fact that most of them disappear might still suggest debris as the output surface is not the same exact plane where the image appears. Meaning there is a slight bit of focus difference to the image assuming the spots are on the output glass surface. Then light could also easily get around them to mask then invisible, unlike if they were malformed fiber optic tubes for example, then they would just be black and sharp no matter the viewing conditions.

In your spec sheet there could be a max allowed surface area of blems and even if not, Katod has such internally (on their website for example). In my view, be it either debris or blems, GSCI should handle this for you.

Most small blems aren't even visible in a picture, only when looking through the tube. There can be many many little blems, but then they tend to be so tiny that even if especially looking for them they may go unnoticed.

Visible blems tube powered off on the phosphor screen side of the tube are not that common as you said, and I have not seen even one image with as many as you have here. It was only their shape & stark contrast that suggested blems instead of debris. Nor have I seen such in my tubes when either handling them outside of a optic altogether, or taking close up pics in either inside an optic or outside.

Like you said again, dark particles at the "glass" end of the tube, and that the light goes around them.

Here is with IR on:
More visible





In other words it shouldn't be this much ? I would imagine the "zones" that are allowed with particles only counts when they are "visible" particles or blemishes?

Thanks for the pics. You're right the allowable number of them, or combined surface area, per zone, are for visible blems. I don't know the exact conditions they are measured at, so if they still are visible at some light levels it could be they are counted as blems (assuming they are such). My knowledge stops here as whatever these are, they look nothing I have direct experience of.

Blems I've seen stay visible, and dust / debris also tend to stay more visible than in your examples. Not disappear almost totally given how large they are when the tube is powered off.

It looks to me as the direction of your flash makes them look either black, or look like little bumps that produce shadows slight. If you look where the flash is shining back at you there is distinct bump looking things. Maybe that's just an optical illusion, can't tell. The fiber optics do react to light direction, but if they were shut off fiber tubes then like said they would remain black (or dim at least).

I don't know that much of the manufacturing process if it could be possible to leave those kinds of "bumps" under the final coating on the surface. But if they are there, whether they are considered blems in regards of the allowable limits I don't know.

I wouldn't count debris off yet. It's a pity a one true expert was banned from the forums (though maybe there was good reasons, depends who you ask I guess). I bet he would know. Will send you an IM with his contact info.

Any debris on the output side of the tube is very noticeable.  All those little specs would stand out like a sore thumb if they were debris.

Sent him a message included with example pictures, I will let you know how it goes, thanks so much for the help !

Next up is a test with no light pollution and crystal clear skies, 1200 meters above sea level.

Staying in touch.

Something else i've noticed, these bright spots, are there any experts in here that knows what this is ? :



Is it lack of film maybe on certain areas ?

Sorry I am quick with the trigger when I see an email notifying an update to your thread, but I can't help myself

I am still baffled by your blems/debris, because close to the flash reflection the look like bumps (or then they are not the same ones as the ones showing as black). I am still thinking that they, whatever they are, show different depending on the angle of the light coming in from the flash, and equally could show differently when light is coming from the tube itself. If they were true bright spots / emission points, then that tube, not by a long shot, fits into any sensible criteria of a clean tube that can be sold as that. Even one bright spot can be too much in tubes from most manufacturers.

Does the brighter dots vary in their intensity and do they stay bright also when you totally shut the tube off of incoming light but keep power on? Emission points stay bright no matter the input light level. The guy who you emailed knows about EP's / BP's a lot too.

Not that I am helping here much, but just bringing this to your's and other's attention:

Haha love it, i wouldn't be able to help myself either.

The picture with the "Bright spots" only, and I say ONLY appear when the tube is turned on during high light conditions. Such as daytime with the blinders infront of a window.
So when the tube is in absolute darkness, there are no emission points from those areas, everything looks as normal. As in the videos posted, the tube performs very well, but its still weird to see that.

Maybe im just so picky about it that I would find this stuff in many peoples tubes if my fingers were let loose :P
I mean, how many people actually do close up shots of their tube surface during high flash contrast.

Protip: don't use your unit daytime (I don't see the black ring caused by the pinhole cap in the above pic so assume you are running it "naked") Short exposure is OK, but even turning down gain does not protect the photocathode. Autogating does, but not 100% by any means.

Edit: and now looking at it again, maybe the green portion of the image is smaller and the tube edge is visible, so maybe you did have the daycap on. Disregard related stuff in this post if so.

Believe me there are plenty of people obsessed about the image on their tube. Maybe you are quicker to dive into it than other's though.

Can't say what my current tubes look in daylight without the pinhole cap, and I won't try heh. The fact they aren't visible in dimmer situations is good, not emission points then and no risk of premature death of the tube due to those.

Tubes are never perfect and are unique one of a kind items. Each of them have some sort of "defects" and unique image quality. Some tubes can have hundreds of tiny black spots for example, though in those cases so tiny that it's hard to say they are single spots even. What you have are quite large in that sense and quite numerous, and I hope they are debris or blems that count as such and you get a replacement. I believe you will have the answer soonish.

To my view, the "black spots" do actually react to the "flash" from the phone, since they are not visible with a normal flashlight, and the surface of the end of the tube is completely spotless to my naked eye.
Still a mystery..

Edit, yes one spot visible, but only the one seen in pictures.

Really looks like fine debris on the output of the tube.

And a LIF does absolutely nothing to help protect a tube.