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Questions regarding PVS-14 and PVS-7

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#1 Huan

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Posted 16 June 2021 - 12:03 PM

Hello, I'm new to the forum and have zero experience in NV. I saw beautiful photos from Gavster ( https://www.cloudyni...ery/?p=10090539 ) and really want to achieve the similar visual effect.

 

I have read Best of Night Vision (NV) by Eddgie and did some research on PVS-14 and PVS-7 but still have many questions.

 

1. What do those FOM xxxx Min mean? Do the differences justify the price difference for visual astronomy use? What is L3Harris Unfilmed?

 

xl9qgaJ.png

 

2. I suppose there's a binoviewer integrated inside PVS-7? Since the images are electronically enhanced, light loss is no longer an issue? Why don't everyone just go with PVS-7?

 

3. I have a Tak FC-100DZ and a C8, do I need a faster scope to fully utilize NV equipment?

 

4. What else do I need for NV other than the monocular/goggle? My budget is from $5k to 10k. I live in NYC and the sky is heavily polluted.

Any suggestions would be greatly appreciated!


Edited by Huan, 16 June 2021 - 12:04 PM.


#2 shohin

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Posted 22 June 2021 - 04:40 AM

Welcome to the NV side of the house.

 

1.  FOM = S/N x Resolution, higher is better.  The better the tube, the more you'll see, so get the best tube you can afford.  The stated FOM is the minimum you will get for the stated price.  FYI some vendors will let you request individual tube specs like EBI and Gain, rather than go by FOM.  L3 Harris is a manufacturer of tubes.  Unfilmed is a type of tube (also thin filmed).

 

2.  US manufacturers don't seem to be making astro-quality tubes for the PVS-7.  Also there's no manual gain on a PVS-7 so you can't dial out scintillation like you can with a PVS-14 or Mod3.
 
3.  Faster f-ratios will give you brighter views (e.g. for emission nebula) but any scope will work.

 

4.  You'll need a few adapters, depending on what device you buy and what viewing configurations you want.   How do you plan to use the device - afocal, prime focus, with repurposed SLR lenses, 1x, etc.?  And you'll need filters - long pass (685nm or maybe 640nm) for stars and clusters, H-alpha (12nm or narrower) for emission nebulae.   $5-10k is more than enough budget to get a top quality NVD and everything you need to use it.

 

In addition to the PVS-7 and the PVS-14, also consider the C-mount version of the AB Mod3 which supports prime focus.  Note that the PVS-14 does not support prime focus, if that is a requirement.



#3 Highburymark

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Posted 22 June 2021 - 09:05 AM

I observe with a PVS-14 and very good Photonis 4G tube from central London. I use a Tak Epsilon 130 F/3.3 for nebulae with a 3nm Ha filter - the narrowest possible. For star targets like globulars and galaxies I use an FC-100DC, F/7.4, with a 685nm long pass.
In urban light pollution, your F/8 Tak should be ok for the brightest targets on the right evenings (transmission makes a big difference), but you’ll probably want something faster to open up fainter objects. The C8 will be great for M42 and a few other highlights of the Northern Hemisphere, but again, you’ll soon be hankering for a much faster set up. In my experience with Bortle 8-9 skies, NV is not a one-stop cure for city centre light pollution, but with patience and experimentation, it will replicate what other, wider aperture telescopes achieve from the suburbs. But if you get the chance to take it to a dark site, it will provide transformational results.

#4 maxmir

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Posted 22 June 2021 - 03:08 PM

I vote for a Mod3c in unfilmed WP too. 

Request a tube with both EBI of 0.5 or lower and SNR 34 or higher.

Best to get zero blems too.

 

Res 64 LPI ok for visual , 72 might do better for photos.

 

FOM is Res x SNR. I don t recommend buying this way.

Low EBI is more import than resolution.




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