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A Silver Bullet Filter?

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#1 Jeff Morgan

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Posted 25 February 2021 - 10:41 PM

I was researching filters for a CMOS camera and came across this one from Chroma:

 

https://www.chroma.c...light-pollution

 

Instead of focusing on nebular lines, this one takes the opposite approach, attempting to spike lines from mercury and sodium lamps, letting the rest of the spectrum thru.

 

Might have very interesting performance on galaxies from the city.



#2 PEterW

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Posted 26 February 2021 - 07:38 AM

High pressure sodium lines are quite broad and with LED you don’t have lines to block, interesting for one shot colour imagers, for NV I’m not so sure.

Peter

#3 Astrojedi

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Posted 27 February 2021 - 12:32 AM

I have tried similar LP filters and they don’t work very well with NV given newer NV devices are most sensitive in the near IR which a filter like this cuts off. The most effective general purpose NV filter I have found is the Lumicon night sky which is basically a 640nm IR pass.

#4 cnoct

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Posted 27 February 2021 - 04:42 AM

My experience was poor even back when HI was HPS.

 

Oh how I miss HPS lighting,  guess the benefit to the extreme output of HI's LED lighting is that even my worst tubes, on the darkest night, perform nicely now. That is for terrestrial use of course, well if aerosols are low.



#5 ButterFly

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Posted 27 February 2021 - 09:06 PM

My Baader UHC-S is somewhat similar, though the bands are not quite that broad.  The OIII/H-beta band exends well into carbon and the H-alpha band is ~35nm.  Much like the Lumicon Deep Sky.  It lets in a lot of stars and only slilghlty hints at the emmission nebulas.  Not much going for galaxies, except for NGC 604 and the like.  Considering the blue dropoff of the NV spectrum, it's no surprise that the 610 longpass does better on galaxies.  A minus-red-taillight filter sounds nice though.

 

If you already have one, why not try it.  My Lumincon h-beta filter is essentially a longpass.  For purchase, it's likely only marginal benefits.  Consider how helpful the lower longpass filters are in your skies as a guide.

 

Forgot to mention that sodium is still dominant here.


Edited by ButterFly, 27 February 2021 - 09:16 PM.


#6 GOLGO13

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Posted 28 February 2021 - 02:11 PM

I won't answer until you switch your photo back! Although I have no clue on your question lol.gif




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