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Anyone use filters for Moon pictures?

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#1 jeffry7

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Posted 19 November 2019 - 03:58 PM

My main camera lens for taking pictures of the moon is a mirror lens and has filter threads on the back side. It made me wonder if and when folks filter their moon shots.

 

I know I have read of people using this filter or that one to get sharper images. Or as a way to do away with chromatic aberration.

 

Do you use filters when taking pictures of the moon? Why or why not? If you use filters, what kind do you use? How does it help?



#2 Stargezzer

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Posted 19 November 2019 - 04:18 PM

Several years ago I got a tip from one of the CN members who had posted some very clear moon photos. He said he was using a red filter. I tried it and it really improved my clarity. I used a red #25 filter with my ZWO 120MC. When you process the file(s) you need to use gray scale to get rid of the red.


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#3 Euripides

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Posted 19 November 2019 - 05:29 PM

I’ve just started some sessions with SVBONY IR CUT & SVBONY Moon filters on my ASI224 MC. Everyone says that with this camera you must have an IR cut filter.
I believe that both of them gave me better contrast - I am not that experienced to analyze that further - but personally I do not know if I have to make also an appropriate selection in firecapture filters. For example, while I was using the moon filter I could see more clear with firecapture filter B setting activated.


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#4 TOMDEY

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Posted 19 November 2019 - 06:01 PM

I use a Wratten green filter on my 100mm F/5 APO and it improves the resolution by a lot... not supposed to, but it does. Possibly because it blocks the NUV and NIR, but I think it's more than just that. As good as (good!) APOs are --- they are still refractors and suffer chromatic aberrations. Going less than broadband often helps, especially when you are going for the best possible resolution.

 

Is the atmosphere steadier in the red and NIR? I think that's an old wives' tale... in the sense that it only improves in terms of fractional wavelength... but not in angular resolution improvement. I can explain that, if anyone questions my assertion.    Tom



#5 Tom Glenn

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Posted 19 November 2019 - 06:41 PM

Is the atmosphere steadier in the red and NIR? I think that's an old wives' tale... in the sense that it only improves in terms of fractional wavelength... but not in angular resolution improvement. I can explain that, if anyone questions my assertion.    Tom

Imaging in red or near-IR will have slightly reduced resolution versus green, which would in turn have slightly reduced resolution versus blue, but in reality there is absolutely a wavelength dependence on the distortion we see from turbulence, which works in the opposite direction to these theoretical resolution advantages.  Blue is almost never the best choice for imaging the Moon, and shows the least amount of detail, despite having in theory the higher resolution.  If we were able to image from above the atmosphere, a blue filter would be a good choice, however.  I typically image with a green bandpass filter on the Moon, because I frequently have good conditions, but many lunar imagers use a 610nm or 685nm pass filter with excellent results.  The loss of resolution versus green (or blue) is inconsequential because the images are almost never diffraction limited even at 685nm, at least with larger scopes.  Smaller scopes could benefit more from shorter wavelength filters.  


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#6 bunyon

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Posted 20 November 2019 - 09:08 AM

Tom's statement exactly matches my experience. I rarerly have good conditions so usually use a red filter. I've done the test. On an average night, I successively imaged through IR, R, G, and B filters in 3 sets. In each set, B was terrible, G was okay and R and IR were evenly matched. 

 

Almost never does it work out when looking at RGB images of planets that the B channel has the highest resolution. 



#7 MalVeauX

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Posted 20 November 2019 - 12:25 PM

Heya,

 

Long wavelengths are less effected by atmospheric turbulence. You will find most large aperture imagers are using something in the 610~850nm range of red to infrared wavelengths to help steady the seeing conditions for high resolution imaging. The longer wavelengths have lower angular resolution than shorter wavelengths, but they are again less effected by atmospheric turbulence so allow a larger aperture to have calmer seeing conditions to image in, then lucky imaging does the rest (ideally with a monochrome sensor). If you want higher angular resolution for the same aperture, one can image with a shorter wavelength such as 500nm (green) or even shorter, however, this is not common with larger apertures because they are heavily affected by atmospheric turbulence and so require a lot better seeing conditions. Shorter wavengths like this are useful to get the most out of smaller aperture instruments under ok seeing conditions, such as something up to 150mm aperture, and all the smaller apertures below that, if seeing allows, a 500nm green filter would be useful to squeeze out more angular resolution for the aperture's limits, provided you block the IR wavelengths with it. As you go to 150mm or larger apertures, 200mm, 300mm, or larger, virtually no one uses short wavelength because the seeing conditions do not support the aperture, so with larger aperture, again, you'll find long red to infrared wavelength filters being used, with a monochrome sensor, such as 610nm Red, 685nm red-near infrared, 742nm infrared (very popular) and upwards of 850nm infrared. Again, the longer wavelengths have lower angular resolution, but with calmer seeing conditions and a big aperture scope, one can image higher resolution lunar surface images.

 

I use a Baader 610nm Red Longpass filter and Proplanet 742nm IR filter with a monochrome sensor (ASI290MM & ASI174MM) with my 200mm and larger aperture instruments for lunar imaging. For full disc lunar imaging with smaller apertures (80mm to 120mm) I tend to use a Baader 500nm Green filter with a UV/IR block filter and the same monochrome sensors, to get the higher angular resolution of the shorter wavelength.

 

Ex, 80mm APO with a 500nm green filter for full disc:

https://astrob.in/full/189dg3/0/?real=

 

Ex, 200mm SCT with 742nm filter for high res surface:

https://astrob.in/fu...=MalVeauX&real=

https://astrob.in/fu...=MalVeauX&real=

https://astrob.in/full/i1u9g0/0/?real=

 

Very best,


Edited by MalVeauX, 20 November 2019 - 01:10 PM.


#8 Euripides

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Posted 21 November 2019 - 11:54 AM

Guys, the correct approach is to use the same firecapture settings as the filter? For example while I am using IR cut filter, which should be my proper selection ? Or it is totally irrelevant those 2 things?



#9 Tom Glenn

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Posted 21 November 2019 - 03:03 PM

Guys, the correct approach is to use the same firecapture settings as the filter? For example while I am using IR cut filter, which should be my proper selection ? Or it is totally irrelevant those 2 things?

The filter selected in FC is meaningless.  It only serves to make note of it in your log file.  This is also true for the object selected (Moon, Jupiter, etc.).  Those selections don't do anything, other than change the default region of interest on the sensor and some exposure settings, which you need to adjust manually anyway.  


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#10 Rouzbeh

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Posted 23 November 2019 - 01:37 PM

Imaging in red or near-IR will have slightly reduced resolution versus green, which would in turn have slightly reduced resolution versus blue, but in reality there is absolutely a wavelength dependence on the distortion we see from turbulence, which works in the opposite direction to these theoretical resolution advantages. Blue is almost never the best choice for imaging the Moon, and shows the least amount of detail, despite having in theory the higher resolution. If we were able to image from above the atmosphere, a blue filter would be a good choice, however. I typically image with a green bandpass filter on the Moon, because I frequently have good conditions, but many lunar imagers use a 610nm or 685nm pass filter with excellent results. The loss of resolution versus green (or blue) is inconsequential because the images are almost never diffraction limited even at 685nm, at least with larger scopes. Smaller scopes could benefit more from shorter wavelength filters.


Excellent response. Its seeing dependant as Tom said.

Longer wavelengths are less affected but the atmosphere. If you had perfect seeing it would yield less resolution vs blue.

Similar to why sunsets are red, the sun doesn't change color. It just happens the red frequencies make it through the thicker atmosphere at that shallow angle and it looks redder.

#11 RedLionNJ

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Posted 23 November 2019 - 03:09 PM

When the seeing conditions are substantially above-average (for my area) and the moon is reasonably high in the sky, I often use an IR610 filter with one of my mono cams.

 

This can give very pleasing results.




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