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Saturated Daylight Moon Revised

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#1 Borodog

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Posted 16 May 2021 - 10:47 AM

Thanks very much to Tom Glenn for the feedback that caused me to revisit this image. Thanks to his prodding I think this version is vastly improved. The colors are more subtle, but the magenta fringing, the adverse gradient to blue on the right, and the sickly green tint are greatly reduced.

 

As a reminder, this was shot in the clear blue sky at about 4 in the afternoon. C8, 6.3 reducer, ASI183MC.

 

gallery_346195_16100_410909.jpg


Edited by Borodog, 16 May 2021 - 10:47 AM.

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#2 GSBass

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Posted 16 May 2021 - 11:01 AM

Interesting, I did not share this one yesterday but did try to image the moon around 310pm yesterday with the 485c because the chip was big enough to get full disc in one shot through the edl…. That cam is not sensitive to infrared so did not use a filter, ended up with a blue very low contrast fuzzy image but processed the ser anyway and then adjusted the hell out of it, obviously ir is better but it does show you can image without a filter in daylight

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Edited by GSBass, 16 May 2021 - 11:11 AM.

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#3 StarBurger

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Posted 16 May 2021 - 11:03 AM

Very nice Borodog. Were any filters used?


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#4 GSBass

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Posted 16 May 2021 - 11:16 AM

I always find it cool when I see images taken around the same time from different locations…. Especially during the day, that has to be much rarer :)


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#5 Borodog

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Posted 16 May 2021 - 11:37 AM

Interesting, I did not share this one yesterday but did try to image the moon around 310pm yesterday with the 485c because the chip was big enough to get full disc in one shot through the edl…. That cam is not sensitive to infrared so did not use a filter, ended up with a blue very low contrast fuzzy image but processed the ser anyway and then adjusted the hell out of it, obviously ir is better but it does show you can image without a filter in daylight

 

Nice capture. I believe there are ways to deal with the "blue haze", especially if you are working with a color camera and willing to accept a mono image. The first thing you can do is use the green channel only. You might think red would be better, and it is in the sense that it has much less contrast-reducing scattered background light, and it is less susceptible to seeing. However, given that the green channel has two subpixels for every red, I find that you often need to stack a prohibitive number of frames to get a decent mono image out of the red channel. Also, telescope optics are almost always optimized for green light. So it's a good compromise. The second thing you can do is stack to FITS format and do your pre-stretching in GIMP before exporting to a friendlier format like png or tiff. Because FITS is a 32 bit float format, if you are stacking many hundreds or a thousand (or more) frames, you actually have a lot more bit depth than you think. So if you pre-stretch the FITS before exporting to a 16bit format, you will have all the bit depth you need to process an 8 bit image downstream.

 

Very nice Borodog. Were any filters used?

Thank you. Yes, a UV/IR cut filter. It's impossible to get a good color balance out of the ASI183MC without it. Even with it, you cannot really boost the blue channel to where it should be; it's a few percent too low and you have to correct it in post.

 

I always find it cool when I see images taken around the same time from different locations…. Especially during the day, that has to be much rarer smile.gif

 

I agree. I was really interested to see that Tom Glenn and I had posted nearly identical images from last month (coincidentally nearly identical in phase to this image as well). I pictured me and someone else both imaging the Moon separated by hundreds or thousands of miles. In the case of Tom's image it was the entire continent of North America.

 


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#6 Tom Glenn

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Posted 16 May 2021 - 03:09 PM

Mike, this looks much better to my eye.  Still something green about it, but you have avoided some of the extreme colors of your other image.  IMO,  the "problems" I had with your other image simply come down to pumping saturation to extreme levels.  This has become quite popular, but more often than not, it is creating something completely artificial, with no basis in lunar soil geology (or anything for that matter) and is trying to get more information out of the data than actually was possible under the conditions.  


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#7 GSBass

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Posted 16 May 2021 - 03:14 PM

Tom, I’m still kinda confused on how you process photos to show correct geological info from a color photo, your saying don’t use saturation… ok what do you use?

Mike, this looks much better to my eye.  Still something green about it, but you have avoided some of the extreme colors of your other image.  IMO,  the "problems" I had with your other image simply come down to pumping saturation to extreme levels.  This has become quite popular, but more often than not, it is creating something completely artificial, with no basis in lunar soil geology (or anything for that matter) and is trying to get more information out of the data than actually was possible under the conditions.  



#8 Tom Glenn

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Posted 16 May 2021 - 03:23 PM

Tom, I’m still kinda confused on how you process photos to show correct geological info from a color photo, your saying don’t use saturation… ok what do you use?

Unfortunately there is no "correct" way.  You do have to saturate the image, but then you need to check the results to see if they make sense.....checking against calibrated NASA standards.  If color casts, and color differentials, between various regions of the Moon don't follow well established patterns, then the result is artifact, and represents flaws either in the data or the processing (or both).  

 

It's nearly impossible to get accurate color information from regions near the terminator.  In a crescent Moon, the entire visible Moon is near the terminator, and so the image IMO is not suitable for color enhancement.  Full Moon is the best, not only because there is not a significant terminator, but because the angle of incidence of solar radiation is much more direct, as well as the emission angle back to Earth (at least for large portions of the lunar surface).  


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#9 Borodog

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Posted 16 May 2021 - 06:11 PM

Mike, this looks much better to my eye.  Still something green about it, but you have avoided some of the extreme colors of your other image.  IMO,  the "problems" I had with your other image simply come down to pumping saturation to extreme levels.  This has become quite popular, but more often than not, it is creating something completely artificial, with no basis in lunar soil geology (or anything for that matter) and is trying to get more information out of the data than actually was possible under the conditions.  

Thanks, Tom. Sometimes when processing at midnight I make poor choices. ;O)



#10 PhotonJohn

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Posted 16 May 2021 - 06:52 PM

Very nice re-dux Mike, great imaging tips to boot.


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#11 Tom Glenn

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Posted 17 May 2021 - 02:39 AM

Thanks, Tom. Sometimes when processing at midnight I make poor choices. ;O)

I wouldn't say poor choices, just different choices.  On many occasions I've revisited images after deciding that my original version had some weaknesses.  Sometimes this becomes obvious the next day, but other times it takes weeks, or even months, before you decide you prefer a different approach.  In many ways it's what keeps processing fun and refreshing.  




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