Atmospheric effects on moon photos

[StewartR]

These days, when I want to photograph the moon, I tend to take a bunch of images and combine them using RegiStax. It seems to bring out details that aren't available in any of the individual photos. The reason for this, I think, is because atmospheric turbulence degrades the individual images, but it affects each of them differently, and RegiStax can somehow sort through that.

Anyway I thought it might be interesting / amusing / instructive to show that turbulence directly.

My last moon photo (here) was compiled from a burst of 35 images. They were shot with a Canon 7D Mk II at 10 frames per second, so the burst lasted only 3.5 seconds and the time interval between successive images was only 0.1 seconds. I've compiled images 17, 18 and 19 from that sequence into an animated GIF here. Unfortunately something in the GIF construction process has degraded the image quality a little bit, but it's still useable. Take a look at the craters down at the bottom of the image near the terminator, and notice how the shape and illumination changes from one frame to another. That's atmospheric turbulence for you. And remember, these images were only 0.1 seconds apart!

 

[Byker28i]

Interesting, as the moon was bright I've never thought of stacking.
Is there any impact from the speed the moon moves across the sky or not as these were 0.1. sec apart?

 

[StewartR]

Interesting, as the moon was bright I've never thought of stacking.

Compare my stacked image with these frames: there's a lot more detail, and it's not just created by sharpening.

Is there any impact from the speed the moon moves across the sky or not as these were 0.1. sec apart?

No. The moon moves across the sky at a rate equivalent to its own diameter in 2 minutes. Shooting at 1000mm (500mm f/4 + 2x Extender) on a 7D Mk II, the diameter of the moon on my sensor was about 2400 pixels. So the moon is moving by about 2400 / 120 = 20 pixels per second, which is 2 pixels between frames. Registax can handle that easily.

 

[sk66]

I think you are doing manual "pixel shifting" which increases resolution/DR/etc. And being able to eliminate OOF/odd bits due to atmosphere with stacking must also be a factor.

 

[Nod]

Looking at that 3 frame GIF (glad you've found a way to post GIFs BTW!), one of them seems to be a bit sharper than the other 2. Is Registax easy to use (as in pretty much foolproof) and free?

 

[StewartR]

Is Registax easy to use (as in pretty much foolproof) and free?

It is free. But that's the end of the good news.

It is without doubt the most baffling, frustrating and obscure piece of software it's ever been my misfortune to use, by a considerable margin. It has zillions of options and parameters which are essentially undocumented and which interact with one another so it's difficult to experiment with them systematically. I stumbled across a set of parameters that seem to work half-decently for processing images of the moon (as opposed to deep-sky images, for example) so I wrote them down and apply them every time. I have no idea whether i could be doing a little better, or a lot better. But I'm happy to share them if you think that might be helpful.

 

[Jannyfox]

I tried out Registax once ages ago for deep sky stuff as an alternative to DSS. It was, as you say, utterly baffling, and rejected most of my images for some reason I couldn't fathom. That was when I could get it to run at all. That didn't last long! I now use PixInsight, which is utterly brilliant, documented, but not free......... I have an idea that Registax is more intended for video/webcam, but I may be wrong. There was a guy in an astro soc I used to belong to whose speciality was close up lunar imaging with a web cam. I think he used Registax for integrating and his images were very good.

 

[Nod]

Registax might be free but it could cost me a new computer by the sound of it! I have a feeling that someone has mentioned an easy to use and free app for stacking images but I'm jiggered if I can remember anything further than that! I'll just have to cope with what I can get SOOC and continue to enjoy the better shots from other people!

 

[Mark Johnson]

Odd that we such different views on Registax. I guess it took me several goes to get it working. Many YouTube videos on it. And I found that it likes the quick bursts of photos rather than several photos in different parts of the screen. Go with the Registax defaults to start with, after that there are only a few tweaks needed.

Wavelets need some fathoming, but again help is available on YouTube...

I doubt you will need huge computing power, it can take several minutes to stack, go make a coffee..............

 

[Nod]

It was more my frustration with non-intuitive software causing a 'puter/hard surface interaction! And I hate trying to learn off YouTube - I'm fine face to face so I can get the tutor to go back over something and answer immediate queries but learning from video isn't for me.

 

[Jannyfox]

What I like about PixInsight is that although there are video tutorials available, someone's also written a very good book. I can't learn from videos either. Not that I'm advocating anyone who isn't seriously into astrophotography buys PI................ It's also not exactly intuitive (seems to be a common feature of that type of software). Before I got my new desktop and I was running it on my laptop the processes to integrate an image would tie it up for most of the day.............