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Radiant @ 830nm

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#1 chemisted

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Posted 27 May 2023 - 05:15 AM

For the past two years I have been attempting to gather data record information on Elbit image intensifier tubes.  Specifically, I wanted both photocathode sensitivity and radiant @ 830nm values that are specifications on the sheets but are not routinely listed by vendors on their websites.  In the beginning, the vendors were not much help as more than one email went unanswered and I even gave up the quest for a while.  Ultimately, with the help of a couple of CN friends and some more forthcoming vendor interactions I obtained nine paired values of these tube characteristics.  I submitted them to linear regression analysis that resulted in a perfect straight-line equation with correlation coefficient of 0.99 with R2 = 0.98.  The nine paired values were from F9800, F9815 and F9415 tubes.  The equation is:  Radiant@830nm = 0.12537(Photocathode Sensitivity) - 26.  When PS values were resubmitted to this equation, I found calculated Radiant values that either perfectly matched the measured numbers or were no more than 8 mA/W units different.

 

Back when NVD offered their Micro device they listed six different models with varying performance characteristics.  The top three models were the Ultra, VG and YG.  They used the term photocathode response (this is the same as PS) and I have used my equation to calculate Radiant @830nm values for the three models.  The Ultra, with a minimum PR of 2400 was their best offering, and its corresponding minimum Radiant value is 275 mA/W.  This is a very high value and probably shows up in very few tubes so my guess is that there are not many Ultra models out there in the hands of amateur astronomers.  Next in line is the VG whose minimum PR was 2200 (all these values are in units of microamps per Watt).  This results in a Radiant value of 250 mA/W which is Very Good so it is well named.  Finallly, the YG had PR of 1800 and a corresponding Radiant value of 200 mA/W.  

 

As I mentioned above, these were the top three models and other models that were offered at the time had minimum PR = 1350 which calculates to a Radiant @ 830nm value of 143 mA/W.

 

This exercise has satisfied my curiosity regarding tube response.  I have two different Micros that I am very happy with.  One is the Ultra and the other is a VG.  I have stated before that under careful evaluation the Ultra does pull ahead of the VG in a noticeable way.  Nonetheless, if I only had the VG I would not be looking to replace it with anything else.


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#2 bobhen

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Posted 27 May 2023 - 09:25 AM

I've been using my NVD Micro for 7-years and also see no reason to upgrade. It does a yeoman's job in my heavily light-polluted Bortle 8-9 location; Horsehead, Barnard's Loop, resolving faint, previously unresolved globulars, etc.

 

IMO, and within reason, filters have nearly as much impact on image quality as tube specs.

 

Bob


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#3 blackhaz

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Posted 29 May 2023 - 09:19 AM

My Harder HD1520A tube has Luminous Sensitivity of 2300 µA/lum, and Radiant Sensitivity @ 830 nm of 210 mA/W - falls outside the fit. Or Luminous Sensitivity is not the same as Photocathode Sensitivity?

 

Max



#4 chemisted

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Posted 29 May 2023 - 11:30 AM

My Harder HD1520A tube has Luminous Sensitivity of 2300 µA/lum, and Radiant Sensitivity @ 830 nm of 210 mA/W - falls outside the fit. Or Luminous Sensitivity is not the same as Photocathode Sensitivity?

 

Max

Your Luminous Sensitivity is not the same because it is in different units.  The F9800 series tubes express this value in microamps per Watt.


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#5 cnoct

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Posted 31 May 2023 - 05:46 AM

IIRC that "ULTRA Spec" tube from NVDevices is an F9800YG, not to be confused with an ITT F9800N Ultra.

 

F9800N Ultra.png ITT F9800 Performance Specifications.png

 

 

 

 



#6 chemisted

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Posted 31 May 2023 - 07:40 AM

Yes, according to the data record it is an F9800YG tube but its specifications exceed the minimums shown in your table for an F9800VG tube. Here are a couple of examples: S/N ratio = 30; Photocathode Sensitivity = 2502.  It really is a remarkable tube and I'd be curious to know how many others are around like it.  I highly favor the P-43 phosphor and I was recently able to track down another P-43 Elbit tube with PS = 2405 and Radiant@830 = 278 mA/W for another CNer so close to mine is still possible.


Edited by chemisted, 31 May 2023 - 07:50 AM.


#7 cnoct

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Posted 31 May 2023 - 10:33 AM

That method of doing what amounted to hand select made NVDevices so easy to buy from them, kinda miss it.

 

There were quite a few NV astro user who bought NVD "Ultra" graded systems, most I heard about were VG tubes, so long as the tube met the "Ultra" spec, it didn't so much matter what the tube model was.  


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#8 chemisted

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Posted 29 October 2023 - 05:26 AM

I have deleted this post due to lack of interest.


Edited by chemisted, 30 October 2023 - 12:30 AM.


#9 cnoct

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Posted 29 October 2023 - 06:35 AM

Having data sheets from L3 with PS at both 880nm and 830nm, using your formula for estimating PS at @830, I'm getting wild variations in accuracy on the order of 20% lower than actual. 




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