My First Lunar Images

[Colorado CJ]

Well, I put my guide camera (ASI120MC-S) on my small Nexstar 4SE to try my hand at lunar imaging.

It is definitely a different process than deep sky imaging. You have to shoot video instead of stills. I am still learning, but so far it is a lot of fun! It is also a little more instant than deep sky imaging as you get an image much quicker.

Anyway, here are my first two lunar images. The first is of Mare Imbrium. The second of the southern limb.

 

[AlanLichty]

Wow - I like the looks of this. If these are just first efforts shots I am looking forward to what comes next.

 

[Brian]

Those are absolutely stunning. Especially that first one. Well done.

 

[JimFox]

Wow Andrew! You really have gotten some awesome images here with these. My favorite is #2, but both are very good.

Question... so why the Video to capture it. I remember Craig saying he used video also to capture his moon shots, but his were older so I just thought maybe that was the way it was back then. But you also did it so I am wondering why video to take a still shot of the moon?

 

[Colorado CJ]

Thanks everyone!

Wow Andrew! You really have gotten some awesome images here with these. My favorite is #2, but both are very good.

Question... so why the Video to capture it. I remember Craig saying he used video also to capture his moon shots, but his were older so I just thought maybe that was the way it was back then. But you also did it so I am wondering why video to take a still shot of the moon?

I think it is because the moon and planets are so bright. A single photo would be something like 1/250 at 200 ISO. When you take video, you are taking between 30-60 frames a second, so you just get more information. These, for example, were 500 frames each. The stacking program actually throws out a percentage of frames and only keeps the best ones. I had the rejection set to 50%, so the final images were 250 stacked frames.

 

[Ken Rennie]

Terrific images Andrew. I assume that the images are "better" than what you see just looking through the telescope or do I have it completely wrong. Ken

 

[Ben Egbert]

Great stuff, and thanks for the video explanation, I had the same question, now I know.

 

[JimFox]

Thanks everyone!



I think it is because the moon and planets are so bright. A single photo would be something like 1/250 at 200 ISO. When you take video, you are taking between 30-60 frames a second, so you just get more information. These, for example, were 500 frames each. The stacking program actually throws out a percentage of frames and only keeps the best ones. I had the rejection set to 50%, so the final images were 250 stacked frames.

That makes sense! Thanks for explaining it.

 

[Craig Zerbe]

Nice job. As you get into higher resolution, you will need to set the rejection rate much higher, though the limiting factor will be the atmosphere. At least tradition, would dictate rotating both images clockwise 90' to conform to the view from earth. Plato, which is the large crater toward the lower left of your first image, is one of the challenges many lunar imagers go after. There are a number of shallow 4-5 km craters within Plato that are hard to capture and take a very still night to see through the telescope. At least you are not shooting 640 x 480 video. Since I have not done this in many years, it's also possible that 250 images is overkill. I often stacked 200-300 images, but I think video was a lot noisier than. The purpose of stacking, at least for me, was to reduce the image noise level enough to allow me to process the image.

The other reason for video is as the magnification increases, the atmospheric distortions are amplified, so it becomes a game of shooting at that "optimal" moment when the "seeing" is best. With video, I get 30 chances a second. If I shoot one frame at a time, I am hoping to just get lucky. For lower resolution images its not much of a factor.

 

[Leslie Hunter]

These are great!

 

[Mike Lewis]

Great results Andrew!

yes, as Craig described so clearly, the usage of video allows you to employ the technique of 'lucky imaging', where you use higher frame rates to get many more images per second, and allow the post processing software to use specific criteria to cull out only the frames with the best instantaneous seeing, making a much cleaner result than could typically be captured from the ground with a single image. Some of the most sought after planetary cameras can achieve frame rates well above 100 fps, although there are also tradeoffs to be made with exposure once frame rates get high enough:

https://astronomy-imaging-camera.com/product/asi174mc

These cameras also typically have smaller sensors and lower megapixel counts, but since any objects other than the sun and moon render as quite small even with larger magnifications, having a smaller sensor with a lower overall megapixel count is not the disadvantage it might be if you are shooting traditional deep sky astrophotography targets.

That having been said, very good results can be achieved just using the movie mode on your DSLR (running with Backyard EOS or Backyard Nikon software, or perhaps APT) For those of you wishing to dip your toe into this using a DSLR, I can heartily recommend the following CD book on the subject:

http://www.astropix.com/gdpi/gdpi.html

Unlike other types of astroimaging, where dark skies are very important, for planetary imaging, seeing (the stableness of the airmass between you and the target) is of primary importance. For us here along the front range of Colorado, just 'downstream' of the Rocky Mountains, typical seeing can be pretty poor. So with our typical local seeing along the front range, Andrew has posted a very good result!

ML