Color Balance "Auto" button

[oopfan]

Hi Robin,

First off, my apologies for running SC 3.1 (one minor version before 3.2).

For the solar eclipse this past summer, I dusted off my ASI120MC. I had monkeyed around with the red & blue color balance sliders. Three weeks ago I imaged the Moon with those same settings, but the image was severely biased towards red. I proceeded anyhow, thinking that I could process it out, but the results were disappointing. Last night I had another chance at the Moon. This time I pressed the CTRL key when opening the camera. The reset worked...everything except the color balance. I panicked a bit, but decided to try clicking the "Auto" button on the red and blue channels. That worked. I could see that the RGB color traces in the histogram snapped together.

Question: Tonight I want to insert a Wratten #12 filter (minus blue) into the optical train. What affect will this have on the histogram? Will I see a flat line for the blue channel? That is what I want. However, my concern is that the blue channel will be amplified to match the power level of red and green.

Thank you!
Brian

[oopfan]

Hi Robin,

No need to reply. I discovered through experimentation that the AUTO color balance setting seeks to white balance the subject, however, this can be an issue if the subject is red by nature.

Last night I also discovered that I don't need to utilize a Wratten #12 filter. I simply need to null out the blue channel in post-processing (using Affinity Photo.) My goal is to create "false color" using my technique of transforming the RG channels into RGB like I do with Astro Pixel Processor. I'm not quite there yet (mostly having to do with having to learn Affinity Photo since my APP subscription is expired.) However, what I can show you are two images of the Moon that I captured two nights ago. One is much sharper than the other.

As you know, my wonderful refractor is marketed as "APO-like", however as it turns out it is only good in red and green, not so good in blue. With my mono cam, I tackle this issue by only imaging in red, green, and a Wratten #12 for luminance. Recently I dusted off my ASI120MC, so now I am capturing red, green, and blue. Since blue is horribly out of focus, I need a solution.

The two attached photos are identical in all respects. They come from the same 2000 frames, processed using PIPP and AS3. The only difference is in what I did in Affinity Photo. The sharper of the two images has the following phrase in the file name: "Channel-Mixer-Minus-Blue".

Brian

[admin]

Hi Brian,

the difference in the two images is very clear, so a good technique for dealing with the poor blue focus from your refractor

One other approach I might suggest would be to try using the ZWO colour balance controls to drop the blue level to zero (or as close as you can get) and maybe even the same with red, leaving you with a green image. If you are happy with a monochrome output for the moon then this approach *may* have two benefits...

1) you can tune the best focus for the green channel rather than needing to tune for green and red
2) the stacking application may do a slightly better job of picking the best frames - it is not going to be distracted by the blue channel which you are going to throw away anyway.

whether these effects really exist (and are significant enough to be worthwhile) is anyone's guess

cheers,

Robin

[oopfan]

Hi Robin,

Thanks for your reply! Actually I am very much interested in capturing the Moon in color. I was inspired by a recent image at NASA's IOTD website: "The Mineral Moon". In a normal image of the Moon there isn't much color to speak of, but if you really push the saturation, you'll see that the Sea of Tranquility is blue due to rich deposits of titanium.

Here is the same 2000 frames taken on the same night as above, BUT it includes the out-of-focus blue channel. Color saturation is pushed hard. You can see the destructive effects of the out-of-focus blue channel. Chromatic aberration galore. I am hoping that my technique of "re-creating" the blue channel from the red and green will produce a much better quality image.

Brian