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Should I accept or reject this tube having low PCR?

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#1 simoneb

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Posted 22 January 2020 - 11:22 AM

Hi Everyone,

This is the first time I post something on this forum, I started with astronomy six months ago and I have actually read so many info in here that I can say all my knowledge about astronomy is indeed based on this forum. So thanks to everyone who always contributes!

I just receive a night vision tube from TNVC (Gen 3 L3 WP unfilmed), but I am primarily concerned with the low level I got for the PCR, and secondarily for the Gain.

 

Here are the specs:

PCR: 1950 (lowest I saw published in this forum I think)

GAIN: 60600 

SNR: 34

EBI: 0.1 (this is good)

HALO: 0.7

RES: 64

 

On the other hand the tube has a very good EBI. I essentially live in New York City, and my view is above Manhattan, so we are probably talking about the highest light pollution one can get. I would like to know from more experienced night vision astronomers what they think about this. I only do visual.

Thanks to everyone,

Simone  



#2 chemisted

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Posted 22 January 2020 - 04:01 PM

While it is true that both those numbers are lower than usual, so is the EBI which is definitely in the Unicorn league for that parameter.  If it were me, I would keep that device despite the PCR since the very low background illumination of the tube will allow you to see loads of detail.  Make sure you read Eddgie's current thread where he shows test results for four different tubes.  The one with 0.1 EBI really stands out.  My 18 year old Collins I3 has EBI in this range and much poorer PCR and gain than your tube and yet I see stars to the 17th magnitude and wonderful nebulosity with H-alpha filters.  Also, the SNR ratio for your tube is superb.

 

One other thing.  You put EAA for the tag on this but you should really use NV.  I almost didn't click on it and I'll bet there are others that may be missing it.


Edited by chemisted, 22 January 2020 - 04:15 PM.


#3 simoneb

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Posted 22 January 2020 - 04:30 PM

Thank you for your response! I was unsure about the EAA, I did a mistake, I wonder if I can change it now...

Thank you very much for your feedback, I just read the thread you pointed out, so I guess that is a good news for me. I have another potential bad news though, as I just tried the tube in a dark room and I saw the presence of a tiny dark spot almost in the center of the field, it is tiny but visible, like a dot. Is that something normal? Again, sorry my inexperience here but I really wanna make sure that I received something with no major defects... Thank you!   

 

 

(Moderator's note: The thread tag has been changed from EAA to NV.)

 

Welcome to Cloudy Nights, Simone!


Edited by star drop, 28 January 2020 - 05:44 PM.
Thread tag was changed.


#4 chemisted

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Posted 22 January 2020 - 08:29 PM

I have no experience to guide you on that one.  You will have to decide for yourself.  You might PM Eddgie if you want some advice.



#5 SeymoreStars

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Posted 22 January 2020 - 09:08 PM

These were my specs when I bought. Paid about 4K as I recall. The device works well.

 

PC sensitivity  2529
Gain              60240
EBI               0.6
SNR              34.3
Resolution     72
Halo             0.7



#6 SeymoreStars

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Posted 22 January 2020 - 09:10 PM

User ID - Eddgie could probably give you a good evaluation of your specs.



#7 jdbastro

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Posted 22 January 2020 - 09:29 PM

Thank you for your response! I was unsure about the EAA, I did a mistake, I wonder if I can change it now...

Thank you very much for your feedback, I just read the thread you pointed out, so I guess that is a good news for me. I have another potential bad news though, as I just tried the tube in a dark room and I saw the presence of a tiny dark spot almost in the center of the field, it is tiny but visible, like a dot. Is that something normal? Again, sorry my inexperience here but I really wanna make sure that I received something with no major defects... Thank you!   

The dark spot is either inherent to the tube or possibly a spec of dust.  If dust, the ocular would have to be removed and the output screen cleaned with a cotton swap soaked in a bit of acetone.  If it's a dark spot, it cannot be removed.  Dark spots are quite common in image tubes.  Most tubes have them and they can be located anywhere on the output screen.  The highest grade tubes tend to have spots located well off center in Zones 2 or 3.



#8 simoneb

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Posted 22 January 2020 - 09:48 PM

Thank you both. I paid 4K myself. It’s a bit frustrating to spend this kind of money and being unsure on the quality of what you are getting. Mostly because of my ignorance...:-)... I will try to contact Eddgie for advice. From the comments I start to think the specs might be ok because of the low EBI, but I am unsure about the dark spot. Thanks again!!!
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