What IR-Pass Filter Do You Use, 685nm or 742nm? - Forums

Topic starter

Jul 1, 2021

Hello all you lunar imaging GURU’s!

I have seen some of the incredible lunar images here on AB and obviously with excellent processing techniques there seems to be on thing in common. IR Pass filters to be specific. In doing some reading on what filters work best for lunar imaging, I’ve read everything from just a red filter to more exotic filters like the Optolong IR Pass 685 filters. My understanding is the IR-Pass filters have the tendency to help out with seeing undulations, however cuts a lot of light out so you have to lengthen your exposure time. Another filter that someone had suggested to me was a polarizing filter. I know that will help with contrast but what about the seeing effects?

BTW I do know that NOTHING can beat good seeing so I get that but I’d like to try one of these filters so I’m looking for your input/recommendations for a setup using an 8”f5, 10” f5 & 12” f5 newts, I guess I like to use newts

I use Barlow s as well.

Thanks!
Dale

Respectful Engaging Supportive

Rouz Astro

Jul 1, 2021

Id say the 685nm is a better general purpose filter.
Remember, the longer the wavelength the lower the actual optical resolution.

Have a look at my page, the "IR" images are mostly with 685nm.

Dale Penkala

Topic starter

Jul 1, 2021

Id say the 685nm is a better general purpose filter.
Remember, the longer the wavelength the lower the actual optical resolution.

Have a look at my page, the "IR" images are mostly with 685nm.

I didn’t realize that resolution suffered with these filters. Thank you for that info!
I’ll checkout your pix!

Dale

Jérémie

Jul 1, 2021

You can check this nice comparison of the effect of IR filters on turbulence and details :
https://www.astrobin.com/382079/?nc=&nce=

Rouz Astro

Jul 1, 2021

IR can get a sharper image because longer wavelength cut though turbulence better.
Optically, the shorter the more resolution.
So you have to find the balance point depending on the seeing.
Generally, 685 is pretty good.

Dale Penkala

Topic starter

Jul 1, 2021

IR can get a sharper image because longer wavelength cut though turbulence better.
Optically, the shorter the more resolution.
So you have to find the balance point depending on the seeing.
Generally, 685 is pretty good.

Beautiful work Rouzbeh!
I’ve been getting that impression that the 685 is the sweet spot.

Thanks!

Dale

Well Written Respectful Supportive

Dale Penkala

Topic starter

Jul 1, 2021

Jérémie:
You can check this nice comparison of the effect of IR filters on turbulence and details :
https://www.astrobin.com/382079/?nc=&nce=

Beautiful work Jeremie!
Thank you for the link! I see you have used the 742mn in more of your images. I have to assume you have found that to be the best for your setup and seeing conditions???

Dale

Well Written Respectful Engaging Supportive

Jérémie

Jul 2, 2021 · Edited: Jul 2, 2021

I should have been clearer : pictures are from @CATHALA Luc , not from me :-). He does great pictures and is well known within the French AP community.

He says (my translation):
« When there is less turbulence, I can go down to 685, then 610, sometimes red filter or orange (few times - 2 to 3 times the year -), and green (one time in several years). When going down toward green, you gain details, but you need almost no turbulence at all. Given the magnification I use, I can clearly see the effect of jetstream turbulence. Without filter that’s really worth. Last night I used the IR807 as the turbulence was aweful. The good times are usually before sunrise or just when sun settles. Sometimes after a plane crossed, like boat on the sea »

I understand from that he mainly uses IR742 as a basis with regular turbulence, and go down from there when conditions are better.

By the way, I also read (elsewhere), that the use of a corrector for atmospheric dispersion is also very useful even in monochrome capture, just because the spectrum of what you receive remains wide (but maybe it has more impact toward blue spectrum…).

Helpful

Dale Penkala

Topic starter

Jul 2, 2021

Jérémie:
I should have been clearer : pictures are from @CATHALA Luc , not from me :-). He does great pictures and is well known within the French AP community.

He says (my translation):
« When there is less turbulence, I can go down to 685, then 610, sometimes red filter or orange (few times - 2 to 3 times the year -), and green (one time in several years). When going down toward green, you gain details, but you need almost no turbulence at all. Given the magnification I use, I can clearly see the effect of jetstream turbulence. Without filter that’s really worth. Last night I used the IR807 as the turbulence was aweful. The good times are usually before sunrise or just when sun settles. Sometimes after a plane crossed, like boat on the sea »

I understand from that he mainly uses IR742 as a basis with regular turbulence, and go down from there when conditions are better.

By the way, I also read (elsewhere), that the use of a corrector for atmospheric dispersion is also very useful even in monochrome capture, just because the spectrum of what you receive remains wide (but maybe it has more impact toward blue spectrum…).

Hello Jeremie

Thank you for the explanation! So basically his go to is the 742 and a good starting point for me or anyone I suppose wanting to try one of these filters is the 685.

I have found pretty much the same about when to image the moon as well.

Thanks for all your help and input! Looks like I’ll be getting one fo the IR Pass 685 to try out and see how that works for me.

Dale

Dale Penkala

Topic starter

Jul 12, 2021

I’m going to go with the IR Pass 685nm filter but I have a couple more questions for you all.

1st, I’m using either a 294mc pro and or 071mc pro both ZWO. Is it ok to use these IR Pass filters with OSC cameras? I’ve read where most are using these with Mono cameras.

2nd, Maybe this isn’t important, but is there one brand thats better than the other? I’ve been looking at the Optolong and Baader brands. The Optolong brand is a bit less then the Baader so I’m just wondering if there is a reason I should look at the Baader over the Optolong. And the $18-$20 difference isn’t a big deal just wondering if there is a reason I should get the Baader over the Optolong?

Thanks!
Dale

Respectful Engaging

Jérémie

Jul 12, 2021

@Dale Penkala well for the first question concerning OSC camera : you are putting a red (IR) filter in front of a bayer matrix, so you will end up with 3/4 of your pixels black (2/4 green and 1/4 blue won’t receive any IR photons). Per se that’s not a problem as long as you know how you will process that (interpolation between red pixels) and the impact in terms of resolution. That’s why usually you would use a monochrome camera with these filters.

Helpful Insightful Concise

Dale Penkala

Topic starter

Jul 12, 2021

Jérémie:
@Dale Penkala well for the first question concerning OSC camera : you are putting a red (IR) filter in front of a bayer matrix, so you will end up with 3/4 of your pixels black (2/4 green and 1/4 blue won’t receive any IR photons). Per se that’s not a problem as long as you know how you will process that (interpolation between red pixels) and the impact in terms of resolution. That’s why usually you would use a monochrome camera with these filters.

Well now your seeing just how dumb I am here Jeremie. Your over my head with your last statement. I’m familiar with my OSC having the RGGB format so to speak.
If the IR Pass filter won’t work with OSC cameras thats fine. I’m just asking that question. Actually that was my original question when I posted this a while back.
It’s on me that I didn’t think about the OSC issue. In fact thru my findings thats how this question come up. I didn’t know that most use them with monochrome cameras.

Dale

Robert Gillette

Jul 13, 2021

I find the 685nm provides the best seeing benefit with the least reduction in brightness. Monochrome camera is preferable, as all pixels are at work. See my gallery for examples.

CS, Bob

Dale Penkala

Topic starter

Jul 13, 2021

I find the 685nm provides the best seeing benefit with the least reduction in brightness. Monochrome camera is preferable, as all pixels are at work. See my gallery for examples.

CS, Bob

Wonderful work Bob!
So then using an IR Pass filter on a OSC camera would have 0 benefit?

Dale

Robert Gillette

Jul 13, 2021

Dale,

Thanks. I don't know about zero, but as noted above, you'd be excluding a lot of pixels. I can only say, try it and see what you think.

CS, Bob

Dale Penkala

Topic starter

Jul 13, 2021

Dale,

Thanks. I don't know about zero, but as noted above, you'd be excluding a lot of pixels. I can only say, try it and see what you think.

CS, Bob

Hi Bob,
Thanks for the info, that is kinda where I’m headed it sounds like. Just wanted to see what other people’s opinions on this setup would be. It’s looking like a 3x Barlow and Optolong IR Pass 685 filter will be ordered here very soon.

Thanks!
Dale

astropical

Perfect post

Jul 14, 2021

Hello Dale,

In astro-imaging everything depends on something in that there is no clear answer to (almost) any problem.

In a nutshell, an IR642nm or IR685nm for your 8" Newton and a IR742nm for your 10" or larger Newton.
Reason being, small apertures are less prone to turbulences than large apertures. When you
experience great seeing, use an IR-Cut filter and image in color or thread an IR610nm Red Filter.

You can use IR-pass filters with OSCs too when recording in mono8 or mono16 mode or just convert
the stacked and processed image to gray scale. Theoretically, a monochrome camera delivers higher
resolution. I have the ASI290MM (mono) and ASI462MC (color). When using an IR640nm, or IR742nm I can
hardly find a notable difference probably because the ASI462MC is highly responsive to IR.

Quality filters sport a high permeability of over 95%. You need longer exposure times with IR-pass filters
because the camera's sensitivity in IR is way lower than in visual. Also, resolution is sacrificed as the
IR-pass filter wavelength increases, but not that dramatically.

As other fellow AP'ers have written, the IR685nm would be most suitable for most seeing situations with 8 inches.
Since I am imaging with a C8 I mostly employ my IR640nm filter. When seeing is lousy I have a beer and go to
bed with my dogs. As you wrote, nothing beats natural good seeing.

My filters are from Sightron (640nm) and Astronomik (742nm) and I believe that you will enjoy Baader
filters as well.

Though still a newbie myself, I have summarized my experience so far in a web site:
https://www.astropical.space/moon/

CheerS,
Robert

Helpful Insightful Respectful Engaging

Dale Penkala

Topic starter

Jul 14, 2021 · Edited: Jul 14, 2021

Hello Dale,

In astro-imaging everything depends on something in that there is no clear answer to (almost) any problem.

In a nutshell, an IR642nm or IR685nm for your 8" Newton and a IR742nm for your 10" or larger Newton.
Reason being, small apertures are less prone to turbulences than large apertures. When you
experience great seeing, use an IR-Cut filter and image in color or thread an IR610nm Red Filter.

You can use IR-pass filters with OSCs too when recording in mono8 or mono16 mode or just convert
the stacked and processed image to gray scale. Theoretically, a monochrome camera delivers higher
resolution. I have the ASI290MM (mono) and ASI462MC (color). When using an IR640nm, or IR742nm I can
hardly find a notable difference probably because the ASI462MC is highly responsive to IR.

Quality filters sport a high permeability of over 95%. You need longer exposure times with IR-pass filters
because the camera's sensitivity in IR is way lower than in visual. Also, resolution is sacrificed as the
IR-pass filter wavelength increases, but not that dramatically.

As other fellow AP'ers have written, the IR685nm would be most suitable for most seeing situations with 8 inches.
Since I am imaging with a C8 I mostly employ my IR640nm filter. When seeing is lousy I have a beer and go to
bed with my dogs. As you wrote, nothing beats natural good seeing.

My filters are from Sightron (640nm) and Astronomik (742nm) and I believe that you will enjoy Baader
filters as well.

Though still a newbie myself, I have summarized my experience so far in a web site:
https://www.astropical.space/moon/

CheerS,
Robert

Hello Robert,
Thank you so much for this! It very much appreciated! You know now that you mention the fact about shooting in 8mono which I have that ability with my 294mc pro and 071mc pro I think I read that as long as I’d use that format the IR Pass filters will work.

I currently have changed to my 10” for right now and was going to get the 685, but now that you state a 742nm for a 10 and larger maybe I should go that route? Am I understanding that the 742nm is going to be darker and thus the added light gathering power of it would help make up for what the 8” and 685nm would do?

I’m glad I posted more for clarification on this because I didn’t know that the nm range made a difference for aperture size.

Another question Robert, In both my camera’s case I can only shoot 8mono. If I shoot in Raw16 using an IR PASS 742nm filter, then after stacking in AutoStakertt converting it to greyscale in Gimp save that and, post processing in Registax would that work then? Thats right now what my work flow would be based on what I’m learning here. If I follow that process with the Raw16 would the IR Pass filters work?

Thanks!
Dale

Dale Penkala

Topic starter

Jul 14, 2021

Hello Robert,
Something I just thought of is I have my ZWO 290mini (guide camera) that I wonder how well that would work on the moon? I know that the 290MM have the USB3 interface allowing a faster FPS but I just wonder what you think about the mini. The USB2 FPS rate is only 20.4 and I know that a minimum is desired in the 35 FPS range but I wonder if the IR PASS filter would work with this mini camera?
I’d think that it should but just don’t know what the quality of the image would be.

Thanks!
Dale

astropical

Perfect post

Jul 15, 2021

Dale Penkala:
Hello Robert,
Something I just thought of is I have my ZWO 290mini (guide camera) that I wonder how well that would work on the moon? I know that the 290MM have the USB3 interface allowing a faster FPS but I just wonder what you think about the mini. The USB2 FPS rate is only 20.4 and I know that a minimum is desired in the 35 FPS range but I wonder if the IR PASS filter would work with this mini camera?
I’d think that it should but just don’t know what the quality of the image would be.

Thanks!
Dale

Hi Dale,
I sent you a few views in response to your PM.
Cheers, Robert

Well Written Respectful

Dale Penkala

Topic starter

Jul 15, 2021

Dale Penkala:
Hello Robert,
Something I just thought of is I have my ZWO 290mini (guide camera) that I wonder how well that would work on the moon? I know that the 290MM have the USB3 interface allowing a faster FPS but I just wonder what you think about the mini. The USB2 FPS rate is only 20.4 and I know that a minimum is desired in the 35 FPS range but I wonder if the IR PASS filter would work with this mini camera?
I’d think that it should but just don’t know what the quality of the image would be.

Thanks!
Dale

Hi Dale,
I sent you a few views in response to your PM.
Cheers, Robert

Thank you Robert

Dale

Rouz Astro

Jul 16, 2021

Dale Penkala:
Hello Robert,
Something I just thought of is I have my ZWO 290mini (guide camera) that I wonder how well that would work on the moon? I know that the 290MM have the USB3 interface allowing a faster FPS but I just wonder what you think about the mini. The USB2 FPS rate is only 20.4 and I know that a minimum is desired in the 35 FPS range but I wonder if the IR PASS filter would work with this mini camera?
I’d think that it should but just don’t know what the quality of the image would be.

Thanks!
Dale

I will work but USB2 is pretty slow. You ideally want several thousand frames. Id shoot about 100 FPS for Jupiter and double or more that for Mars.

The 290mm is fantastic, but you need to learn how to use Winjupos with mono.

Concise

Dale Penkala

Topic starter

Jul 16, 2021

The 290mm is fantastic, but you need to learn how to use Winjupos with mono.

Hello,
I don’t know what “Winjupos” with mono means? Sorry

I know with the USB2 20fps is slow, but its what I have for now as far as B&W cameras. I can shoot 8bit mono with 294 & 071mc pro’s but was attempting to so do it with my true B&W camera.

Dale

Olaf Fritsche

Jul 16, 2021

WinJUPOS is a software to "derotate" pictures of planets. You load stacked frames of videos taken one right after the other into the program, and WinJUPOS calculates out the rotation between the frames to create an overall image. This gives you more time to shoot for fast rotating planets such as Jupiter.
Homepage of WinJUPOS.

Well Written Helpful Concise

Dale Penkala

Topic starter

Jul 16, 2021

Olaf Fritsche:
WinJUPOS is a software to "derotate" pictures of planets. You load stacked frames of videos taken one right after the other into the program, and WinJUPOS calculates out the rotation between the frames to create an overall image. This gives you more time to shoot for fast rotating planets such as Jupiter.
Homepage of WinJUPOS.

Thank you for the explanation Olaf! Had no idea what it was.

Dale

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