Photographing the Moon - Some Benefits

[RustierOne]

Some recent threads in this forum have inspired me to get back to photographing the Moon. This area of astrophotography offers some real advantages for beginners as well as more experienced photographers:

1. The Moon is very bright. This helps keep exposures short (and ISO lower), which can contribute to lower noise and reduce effects of atmospheric seeing and tracking.
2. Our planetary companion has a large apparent size in comparison to the planets. For example one average crater on the Moon can have a larger apparent size than say Jupiter. This can call for less telescope aperture and focal length to achieve some nice results.
3. The Moon is loaded with detail at all image scales. Full-disc images can be as spectacular as more magnified views. Added to that is the constantly changing Sun angle, making for a lunar scene with constantly changing shadows.
4. There are a variety of techniques which can be employed to capture interesting lunar images. Shorter focal length camera lenses which include some foreground earthly elements (like mountains or trees) add interest to the image. Some telephoto camera lenses are capable of providing some nice shots of the Moon. Of course adding a telescope, with its ability to change effective magnification, is of great use in exploring the fascinating lunar landscape. Finally the use of video imaging (or even multiple still images) allows the photographer to stack images creating high resolution views. Such free programs as Registax or Avistack extract the best frames from the image stream, which in turn captures those brief instants when atmospheric seeing is optimum.
5. Finally lunar imaging expands the time available for astrophotography. No longer need the moonlit portions of the month cause astrophotographers to retreat from the night sky, longing for the next clear night, free of moonlight. There are too many other obstacles that prevent us from imaging the heavens. It seems like weather, work, family obligations, or being too tired all too frequently precludes astrophotography. The presence of the Moon in the sky can be an opportunity rather than an impediment.

These are just some of my ramblings. What follows are a few Moon images which show the variety of lunar landscapes as well as to demonstrate a couple of the methods which can be employed.



Best 130 of 299 images stacked with Registax. Time is approximate.Using C-11, 2790mm F.L. @ f/10 and Sony NEX-5N camera, 8.4 MP. Cropped.


Best 130 of 299 images stacked with Registax. Time is approximate.Using C-11, 2790mm F.L. @ f/10 and Sony NEX-5N camera, 8.4 MP. Cropped.


Best 146 of 304 images stacked with Registax. Time is approximate.Using C-11, 2790mm F.L. @ f/10 and Sony NEX-5N camera, 8.4 MP. Cropped.

The following 2 images are from a video camera. The camera operates at 60 fps, which provides a large number of frames which Registax sorts through to find the best ones to stack. Even though the image is only 640 X 480 pixels, multiple images can be stitched together to provide a larger, high-resolution image.


C-11 w/ Imaging Source DMK21U04 Video Camera


C-11 w/ Imaging Source DMK21U04 Video Camera: Best of 17,982 frames stacked w/ Registax; Cropped


C-8, Stack of best 91 of 100 images w/ Registax; Neat Image filtered


C-8, Registax 21 of 23 images; Neat Image filtered


C-8, Registax - 78 of 172 frames; Neat Image


C-11, Stack of 302 exposures using Registax. Filtered with Neat Image. Cropped

In the above image, a close inspection shows some of the seams resulting from Registax using multiple alignment points to align and stack the best images. For some reason, it didn't clean up the seams.


C-8 w/ Olympus C5050, 400 ISO, 0.3 sec., Stack of 8 images

I hope you have enjoyed these lunar images. Give Moon photography a try. There is no end to the fascinating detail to be found in our closest celestial neighbor


Best Regards,
Russ

 

[Railton]

Great shots. I am just starting to work with stacking myself and have a couple of questions.

What do you use to trigger the shots on the NEX-5? With so many frames I guess you don't click the shutter yourself!

With my limited use of RegiStax 6 I have found that it doesn't align the images properly if the moon moves around in the frame too much so I have to manually crop each frame so the moon is roughly in the same place. I don't have a tracking mount. I'm using a NEX-7 on an Skymax 90 with effective FL of 1875mm so the moon moved pretty quick across the frame.


What do you use to convert your NEX-5 video for use in AVIStack? It seems that AVIStack is sensitive to the AVI encoding. Currently I am converting the MTS to AVI using "Any Video Converter" then using VirtualDub to re-save the AVI.


Thanks,

Railton.

 

[RustierOne]

Railton wrote:

Great shots. I am just starting to work with stacking myself and have a couple of questions.

What do you use to trigger the shots on the NEX-5? With so many frames I guess you don't click the shutter yourself!

I haven't done any Lunar/planetary imaging for a few months. For triggering the exposures, my method has varied. Prior to this year, I have used either a video camera or an old Olympus C5050, 5 megapixel camera. For the latter I began just using the remote control to trigger individual JPG shots. When the remote quit working, I would set the camera to sequential shooting with the self-timer to trigger the first shot of the sequence of 5. This sequence was followed by re-centering the subject and triggering another sequence of 5 shots. It was kind of laborious.

This year when I purchased the Sony NEX-5N my method changed. Camera mode was set to speed-priority continuous and a clamp was used to trigger the exposure sequence. The following link has some of my experience using the clamp to produce a sequence of Saturn images:

http://forums.dpreview.com/forums/post/41451627


I have had some reluctance to using the clamp method too much for fear of wearing out the shutter at an advanced rate.

With my limited use of RegiStax 6 I have found that it doesn't align the images properly if the moon moves around in the frame too much so I have to manually crop each frame so the moon is roughly in the same place. I don't have a tracking mount. I'm using a NEX-7 on an Skymax 90 with effective FL of 1875mm so the moon moved pretty quick across the frame.

I have found the same issue with Registax. It works best with a video stream, where the shot-to-shot movement is easily tracked by the program. I saw a reply to the tracking issue where the forum member said that telescope tracking is not mandatory with Registax - even a Dobsonian mount will work as the Moon moves across the field of view. As long as the movement is regular and predictable (by Registax) the image stream is usable. With your fairly long focal length, the Moon moves across pretty fast. And triggering each shot manually might cause the placement of the Moon to vary in a way Registax can't follow.

You might try using a remote to trigger individual shots. That way you don't have touch the telescope, and movement of your subject would be smoother, more easy for Registax to follow.

What do you use to convert your NEX-5 video for use in AVIStack? It seems that AVIStack is sensitive to the AVI encoding. Currently I am converting the MTS to AVI using "Any Video Converter" then using VirtualDub to re-save the AVI.

I haven't had any success in converting the Sony's AVCHD video stream to AVI for use by Registax. Razor2277 notes that Sony's video mode is not of high quality. Note his comments in the follwoing link.

http://forums.dpreview.com/forums/post/50152988


Still having a 2 megapixel video stream is tempting. And its in color. So I will have to see about the issue of converting to an AVI format usable by Registax or Avistack. There are a lot of video converters available. But as you note, the programs seem to be sensitive to what kind of AVI file is produced. I guess if all else fails the clamp method for JPGs works.

Best Regards,
Russ

 

[a1man]

Great shots, Russ.

I am curious, do you get any benefit from stacked moon shots? Moon is a sun lit object and sunny 16 rule applies. There should not be any exposure problems such as very dim light levels. Do you gain any noise advantages from stacking? Maybe it is good for the morning/evening sections of the moon where sun rays are at a very low angle.

 

[Railton]

Thanks Russ for the comprehensive reply. When taking stills I am using a remote but the moon moves pretty quick across the frame so I agree with your view that Registax can't handle the large deltas.

The NEX-7 will shoot about 10fps until the buffer fills then drops down to 3 or 4 (I think) only problem is that I can't trigger it with the remote. I fired off some manually during yesterdays full moon so will see how they turn out when processing.

 

[RustierOne]

a1man wrote:

Great shots, Russ.

I am curious, do you get any benefit from stacked moon shots? Moon is a sun lit object and sunny 16 rule applies. There should not be any exposure problems such as very dim light levels. Do you gain any noise advantages from stacking? Maybe it is good for the morning/evening sections of the moon where sun rays are at a very low angle.

For lunar/planetary imaging the problem is usually atmospheric "seeing", rather than exposure. Seeing is a term used to describe how steady the atmosphere might be between the telescope and (for example) the Moon. A live view most often shows the subject being distorted by different temperature air masses, moving and smearing the image. The effect is much like looking through a turbulent water surface or "heat waves" to what's beyond. A night when the stars are twinkling a lot (particularly low in the sky) is one with poor seeing.

So where does stacking fit in to this? Back to the live view through a telescope, an observer will often notice that while the entire Moon may be swimming around due to poor seeing, there are brief moments when the seeing improves so that more can be seen. This might be so only in one or more small parts of the image. Or it might hold true for the entire image. The human brain is able to sort out these brief instants of improved viewing and tease out some details that are, for the most part, lost in the bad seeing. This is not true for a photographic exposure, which just records the average of what took place during the exposure. This is where stacking fits in.

The process of stacking by a program such as Regisgtax is a multi-step process. In short this is what it does:

• First it takes the entire set of images (whether video frames or single JPG frames) and estimates each frame's "quality". Quality of each image is strongly related to the instantaneous seeing during exposure.
  
• It then rearranges the sequence of the image stream starting with the highest quality on down to the lowest quality.
• The user decides which frames to use by selecting a limit, beyond which all lower quality frames are excluded from further processing.
• Registax selects alignment points (either automatically or with user input) and aligns each frame with all others. This takes care of any image drift or rotation caused by tracking errors or seeing.
• The program then stacks the set of images. During this process any digital noise tends to average out to zero, while image details are reinforced. This produces a single "master image" resulting from combining high quality, aligned and stacked images.
  
• Finally Registax utilizes something called "wavelets" whose function totally eludes my mental capacity to understand. Nevertheless this step can produce great results, changing the master image into a planetary image with details beyond what would have been visible by just looking through the telescope.

I hope this somewhat lengthy answer to your question helps clarify matters for you. I don't claim to be an expert in planetary imaging and stacking, but I believe the above points capture the essence of how its done. Take a look at the following link which shows the fantastic results obtained in planetary imaging by an expert, Damien Peach in the UK:

http://www.damianpeach.com/


Best Regards,
Russ