[Dennis]

Hi Geoff

Don't worry - Rome wasn't built in a day and it seems I have jumped in over your head - my apologies.

The histogram of an image is a graphical representation of the tones between black and white, where black=0 and white=255.

If you imagine a cross section through a gently rising range of hills, where you start out at sea level on the left, climb slowly to the top of the range in the middle and then descend to sea level again on the right, then the area underneath the cross section is a “picture” of the tones in the photo, from black through grey through white.

So, if you have a big mountain on the left hand side and not much too the right, you have a lot of shadows or dark tones in the image, such as the night sky - there is a lot of black in most images of stars and galaxies.

If you have a big mountain on the right hand side of the histogram, then you have a lot of white tones in the image, such as the very bright areas of the Moon.

Ideally, most of the mountain range peaks should lie in the middle region, meaning that most of the data covers the mid tones, which produces a nice smooth image, from black through grey to white.

Here is a screen print from one of my photos of the Moon and if you look in the top right hand corner, I have labelled the histogram. It would be worthwhile googling histogram and trying to get to grips with understanding it, as it will undoubtedly become your best friend in image processing. Don’t be overwhelmed by these concepts, they will certainly come to mean more over time as you continue to take photos and inspect the histogram.

Hope that helps.

Cheers

Dennis

EDIT:
I’ve also attached a copy of your photo showing the histogram. If you compare the two histograms, you will see that yours is “compressed”; that is, the tones are huddled together in the middle whereas the other one has them spread more evenly across the whole range, although it doesn’t quite go all the way to white.