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Which Color to set Histogram Level?

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#1 John Miele

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Posted 05 August 2020 - 06:43 AM

Hi,

 

It seems that a good practice is to aim for a 50 to 60% histogram reading using the ASI224MC for planets. But which color do you use? I hav every different histograms readings between R, G, and B.  I find the Red color may read 50 to 60% but green will be 40 to 50% and blue may be as low as 25-30%...this is for Mars BTW.

 

I'm thinking you use the Red (or the highest color) or does it matter that much?

 

P.S. I do have a UV/IR block filter in place.

 

Thanks!

 

cs...John



#2 RedLionNJ

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Posted 05 August 2020 - 08:29 AM

Hi John,

 

I use the highest valued color (for Mars, this matters especially, as red can be twice as high as the others at times).

 

You mentioned the UV/IR block filter - was that a deliberate choice, or just the way the IR block came?  I'm not sure the ASI224MC is particularly sensitive into the UV wavelengths.

 

Also - no mention of an ADC?  Inexpensive these days, but well worth it, particularly with a color cam.

 

Grant


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#3 KTAZ

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Posted 05 August 2020 - 08:35 AM

Hi,

 

It seems that a good practice is to aim for a 50 to 60% histogram reading using the ASI224MC for planets. But which color do you use? I hav every different histograms readings between R, G, and B.  I find the Red color may read 50 to 60% but green will be 40 to 50% and blue may be as low as 25-30%...this is for Mars BTW.

 

I'm thinking you use the Red (or the highest color) or does it matter that much?

 

P.S. I do have a UV/IR block filter in place.

 

Thanks!

 

cs...John

Are you asking whether you should increase the other color histograms to balance with the red?

 

Most comments here state that the UV/IR should be used on Jupiter and Saturn, but I've seen several saying not to use it on Mars. I haven't attempted Mars yet, so I'm interested in your outcome.


Edited by KTAZ, 05 August 2020 - 08:36 AM.


#4 John Miele

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Posted 05 August 2020 - 02:11 PM

Hi Grant,

 

'Ya caught me...lol! No ADC. But with Mars at such a high altitude (almost 58 deg. for me) that should not matter.

 

I'm just using a common luminance filter. I believe they typically block both UV and IR. It's a leftover filter from my DSO imaging days with smaller chip cameras pushed into service here. 

 

I'll use the Red channel to set the histogram level. I sort of thought I should use Red, but was not sure.

 

Hi KATZ,

 

I have never tried imaging Mars without a filter! I'll remove it next time and see how it goes. All the Mars images I have posted lately (all 3 of them!) were taken with a UV/IR block filter.

 

Thanks!

 

John



#5 RedLionNJ

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Posted 05 August 2020 - 02:30 PM

Hi John,

 

That 58 degrees is probably the elevation at culmination?  While i fully agree an ADC isn't going to make a whole lot of difference at 58 degrees, nothing in the night sky spends much of its time at culmination.

 

I prefer to "chase it up" these days, starting around 20 degrees (but my seeing is generally better toward the SE anyway). Once I'm a couple hours past the meridian, it goes downhill (the seeing, that is).

 

Grant



#6 KiwiRay

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Posted 05 August 2020 - 03:22 PM

Using the ASI224MC without an IR cut filter

 


Hi KATZ,

 

I have never tried imaging Mars without a filter! I'll remove it next time and see how it goes. All the Mars images I have posted lately (all 3 of them!) were taken with a UV/IR block filter.

 

Thanks!

 

John

Using the ASI224MC without the IR cut filter will affect the colour of Mars.  By all means try it without, but the results I've seen without it haven't looked as natural.
 



#7 John Boudreau

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Posted 05 August 2020 - 05:12 PM

Are you asking whether you should increase the other color histograms to balance with the red?

 

Most comments here state that the UV/IR should be used on Jupiter and Saturn, but I've seen several saying not to use it on Mars. I haven't attempted Mars yet, so I'm interested in your outcome.

It's the other way around. Mars definitely needs the IR cut filter for a good color balance--- and actually Jupiter and Saturn do too, but without one they don't show the color balance issue nearly as strongly as Mars will without an IR-cut.


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#8 KTAZ

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Posted 05 August 2020 - 05:46 PM

So back to the histogram question; does it make a difference if you pick the highest color and bring the lower levels up, or select the lower color and drop the others back? I can’t see why it would make a difference if you end up with all three levels pretty balanced and at the histogram level that you are targeting.



#9 Tom Glenn

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Posted 05 August 2020 - 06:24 PM

So back to the histogram question; does it make a difference if you pick the highest color and bring the lower levels up, or select the lower color and drop the others back? I can’t see why it would make a difference if you end up with all three levels pretty balanced and at the histogram level that you are targeting.

On a planet like Mars, if you the target the histogram to the blue or green, you run the risk of clipping red to 100% and not notice.  




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