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Do I need an LP filter as Luminance for Mono CCD?

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#1 mcbbcn

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Posted 20 July 2019 - 12:40 PM

Hi,

I have a QHY9M Mino CCD and sometimes I image from the the city. I would like to get Luminance filter but can it be a plain luminance filter and do I need a special luminance filter with LP protection?

Best,

Miquel

#2 bella123

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Posted 20 July 2019 - 12:53 PM

Hi miquel , I would use a regular luminance filter, mono cameras are more sensitive, and when you combine your lrgb subs, most of the color gradients, you get from a color camera imaging from the city, will not be near as bad as a color camera.



#3 bobzeq25

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Posted 20 July 2019 - 01:01 PM

Hi,

I have a QHY9M Mino CCD and sometimes I image from the the city. I would like to get Luminance filter but can it be a plain luminance filter and do I need a special luminance filter with LP protection?

Best,

Miquel

Either can work.   Here's the most important thing to know.

 

Pretty much all even semi-serious imagers use gradient reduction in processing to reduce the effects of light pollution.  It's surprisingly effective.  Some additionally add a broadband light pollution filter, some don't.  Some add one only for emission nebulae, where they're most effective.



#4 mcbbcn

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Posted 20 July 2019 - 09:56 PM

Thanks everyone for the guidance. I appreciate it



#5 PeteM

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Posted 20 July 2019 - 11:04 PM

I am going along the line with bobzeq25 and say I do not use a LPR and imaging mostly from a light polluted location. Processing gets rid of any gradient without much issue. I go with somewhat long total integration to get around the LP also, so that has worked out well. For sure would experiment with both with/without the a LPR, but work on processing skills.


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#6 denny-o

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Posted 21 July 2019 - 02:25 PM

An LPR filter can be a big help (along with processing skills) 

Backyard-astro.com has tried a new one with a double bandpass that he seemed to like.

 

OK, went looking and it is

https://optcorp.com/...nhance-filter-2

The price will get your attention.



#7 ChrisWhite

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Posted 21 July 2019 - 09:08 PM

You can also skip luminance as well and only use rgb. These color filters will block some lp.
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#8 Monkeybird747

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Posted 21 July 2019 - 10:05 PM

Red/Orange zone here and no LP filter. I shoot luminance too, and only see pretty mild gradients that are pretty easy to remove in software. I'm east of town and don't typically image over the city though. I tried IDAS LPS D2 as luminance and had halos, so it sits on my desk waiting for reassignment. I tested an Astronomik L3 luminance and it seemed pretty solid.

 

That L-enhance filter appears to have lower transmission rates compared to others. Would that be of concern? I suppose it is a trade-off. Interesting concept, and I've seen some nice images on AB taken with it.

 

When shopping the idea of LP filter as luminance keep in mind the filter thickness if using an OAG. Most of the LP filters I ran across when I was considering doing this were arround 1-1.5mm thick (the L-enhance is 1.85mm). If you are pairing it with 3mm Astrodon or Chroma filters you could run into a problem where your guide cam won't be in focus when you switch between the thinner and thicker filters, i.e not parfocal with the rest of your set. Food for thought.



#9 bobzeq25

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Posted 22 July 2019 - 09:43 AM

Broadband LP filters work because they rip out chunks of the spectrum.  That can work if the chunks mostly contain the light pollution you want to rip out.  Mostly on emission nebula.

 

The drawback is that they reduce signal as well as noise, and distort color.

 

Narrowband filters work because they rip out _very_ large chunks of the spectrum.  They can work better on specific targets. like emission nebulae.   They reduce some signal, but here you're mostly trying to capture a very specific signal.   People doing narrowband often don't care about "realistic" color, which is good because you won't capture it.

 

The L-enhance is something of a hybrid between them.   Trying to achieve some of the virtues of narrowband, at less cost.  There are others, often going by names like dual band or tri band.  Some are very expensive.

 

It was suggested above that another strategy is just to shoot RGB.  That's a technique some people use, but it requires substantially more total imaging time.  LRGB is a clever trick hat uses the nature of our eyes to significantly reduce total imaging time.

 

Lots of methods, for lots of imagers.  There's no universal "better", it's site, target, and imager specific.


Edited by bobzeq25, 22 July 2019 - 09:46 AM.


#10 mcbbcn

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Posted 22 July 2019 - 11:30 AM

Fantastic information. It's great to learn from all of you.  I appreciate you took the time to provide as much information as possible, so I can make a decision. I have decided to go with a luminance filter, not necessarily an LP filter, but a filter with a broad spectrum. If I need to do some processing. Also, although I'm imaging from a city (due to time constrains), I'm getting more flexibility in the future, and I'll be spending more time in darker skies, which I believe the Luminance filter will make a big difference, specially on reflection nebula. Thanks everyone again for sharing your wisdom. bow.gif



#11 jgraham

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Posted 22 July 2019 - 12:03 PM

I use a standard set of LRGB filters in my filter wheel. However, since I image under Bortle 8 skies I use an Orion Imaging Skyglow Filter as a pre-filter in the nosepiece of my camera. Soooo, I don't use an LP filter as my luminance filter, but as a light pollution filter in front of all of my filters. An LP filter can also serve as an IR cut filter.




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