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Dark Side of the Moon, January 15, 2021

astrophotography imaging moon refractor
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#1 james7ca

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Posted 15 January 2021 - 11:27 PM

Taken on the evening of January 15, 2021 at 6:08PM PST using a Stellarvue SV80ST2 with 0.8X reducer (e.f.l. 384mm, f/4.8) and a ZWO ASI183MM Pro (33 x 2s, gain 200, offset 10).

 

Capture software SharpCap, processing with PixInsight and Photoshop CC2021.

 

I took a series of shorter exposures that I may try to use to create an HDR, which should allow detail on the fully sunlit side of the moon (in addition to the earthshine)

 

C&C welcomed.

Attached Thumbnails

  • Dark Side of the Moon (small).jpg

Edited by james7ca, 15 January 2021 - 11:30 PM.

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#2 Tom Glenn

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Posted 16 January 2021 - 02:33 AM

Looks good James.  It's always interesting to see the tiny spots of sunlight near the poles, most prominently towards the South Pole in your image here, similar to Baily's beads during a solar eclipse.  


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#3 james7ca

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Posted 16 January 2021 - 02:49 AM

Tom, thanks for the notice.

 

As for the "beads," I particularly like seeing those on thin crescents when doing a normal capture on the sunlit side of the moon. If I can see those then I know that the image will at least be passable sharp.

 

I didn't spend a lot of time trying to capture tonight's moon. However, since I was already set to do some DSO imaging (starting with the Orion Nebula) I decided to take advantage of the clear skies during the late twilight. However, the seeing (as could be expected) was pretty bad, given that we're having another Santa Ana.


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#4 Tom Glenn

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Posted 16 January 2021 - 02:52 AM

However, the seeing (as could be expected) was pretty bad, given that we're having another Santa Ana.

Yes, I actually didn't have time to even setup tonight, but I suspected it would be bad when the temps nearly reached 90 degrees with 10% humidity.  I didn't need to check the weather map to know that winds were coming from the desert.  



#5 james7ca

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Posted 16 January 2021 - 03:14 AM

It looks like NASA's Visualization Studio simulation (Dial-A-Moon) shows the same feature I captured on the far left. I was hoping that they might have a label identifying the parent feature, but no label and it looks like there isn't any notable object near to that spot. Could be something that is just over the horizon (well, pretty much obviously, but what I mean is that the parent feature is over the horizon).

 

Here is a clip from tonight's Dial-A-Moon...

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  • Moon Bead (NASA Dial-A-Moon).jpg


#6 Tom Glenn

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Posted 16 January 2021 - 04:29 AM

It looks like NASA's Visualization Studio simulation (Dial-A-Moon) shows the same feature I captured on the far left. I was hoping that they might have a label identifying the parent feature, but no label and it looks like there isn't any notable object near to that spot. Could be something that is just over the horizon (well, pretty much obviously, but what I mean is that the parent feature is over the horizon).

 

Here is a clip from tonight's Dial-A-Moon...

James, the libration tonight was strongly to the north, which puts many south polar mountains and crater rims on the horizon.  I used LTVT to map your point of light to approximately -84.19S, 46.52E.  There are actually a collection of light beads in this area, and they cluster to a mountain peak that is actually part of the rim separating the polar craters Scott and Nobile. See LRO map below.

 

https://quickmap.lro...RFOOZLRfImqnioA

 

I also had an image of this area taken under different conditions.  The white arrow below points to the feature.  In your image, this feature is on the extreme limb, projecting above the horizon.  

 

spot_on_limb.jpg


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#7 james7ca

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Posted 16 January 2021 - 06:23 AM

Tom, thanks.

 

I had actually looked at that same LROC polar projection to see if I could follow the major craters that were to the south of Clavius, but I couldn't find anything past about Moretus. Your spot is a lot further south than I would have expected.



#8 Borodog

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Posted 16 January 2021 - 07:47 AM

Beautiful. I can’t wait to see the HDR. May I ask if my posts in my Imaging Earthshine thread inspired the attempt?

#9 aeroman4907

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Posted 16 January 2021 - 12:47 PM

Very nice capture of the dark side James!  I would be very interested in seeing your treatment of an HDR image should you choose to do one.  The area around the terminator gets super tricky to blend properly, especially in higher resolution.  I've had very limited 'success' with HDR lunar images, particularly in color.  I had some success with the 2019 lunar eclipse, but I only did one image.  That is actually a series of data that I really need to pick up again and finish off more properly.

 

Steve



#10 Tom Glenn

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Posted 16 January 2021 - 03:19 PM

Tom, thanks.

 

I had actually looked at that same LROC polar projection to see if I could follow the major craters that were to the south of Clavius, but I couldn't find anything past about Moretus. Your spot is a lot further south than I would have expected.

Yes, these beads of light correspond to almost imperceptible details on the extreme limb that just happen to be oriented such that they are uniquely illuminated, while surrounded by darkness, and also oriented such that they are visible from Earth.  Shown below is the region from overhead, drawn in LTVT with the terminator indicated.  On the left is the standard LRO WAC map, and on the right is a simulated illumination at the time.  There are several features that lie just off the mean terminator yet are illuminated due to elevation.  Of these, only a subset is visible from Earth, with the Earthview coming from the top of this map, and solar illumination coming from lower right.  The white arrow indicates what I think is most probably the source of your bead.  In the second figure below is the region, shown from Earth perspective, but illuminated with a high Sun (actually an impossible Sun, located directly over the Pole).  This was done to better see the topography.  The arrow indicates the slopes of Scott and the illuminated peak in question.  This would be barely discernible as anything with detail from Earth, yet stands out as a bright spot in your image.  Some of the adjacent illuminated peaks could also be combining with this location to create the bead, although looking closely at a simulated LTVT Earthview (not shown here), most of the light source is coming from latitude and longitude coordinates that correspond to the region indicated by the arrow.  

 

LTVT_bead_overhead.jpg

LTVT_bead_Earthview_highSun.jpg


Edited by Tom Glenn, 16 January 2021 - 03:24 PM.


#11 james7ca

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Posted 16 January 2021 - 07:53 PM

Borodog, thanks for the notice. As for being "inspired," I guess I was reminded and since I already had the scope ready for some DSO imaging I took the opportunity. I say "reminded" because I've posted a lot of earthshine images here to CN, going back over several years (in your original thread I posted links to some of those events).

 

Steve, thanks. I've done HDRs of earthshine before, below is one post that is on CN:

 

  https://www.cloudyni...e/#entry7736169

 

On the latter, I guess I need to go back and combine the remainder of the sequences, since I'm sure I could produce a better result (my initial post was sort of a draft).

 

Tom, thanks again for your help to identify the feature.


Edited by james7ca, 16 January 2021 - 07:55 PM.

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#12 Borodog

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Posted 16 January 2021 - 08:42 PM

I blew my chance to get my exposures for my attempt at the HDR Earthshine Moon tonight. The Earthshine was perfect. I couldn't get a telescope in position (well, I could have but it was cold and I was lazy) but I took the Sony a6000 out to shoot it at 210 mm. But I had the brilliant idea that I did not need multiple shutter speeds. I would shoot a hundred or so frames exposed for the light side, stack them, and then stretch them like a DSO image to bring up the Earthshine. Needless to say, it was a disaster. I just don't have the right software to bring it out of the stack without blowing out the illuminated limb; I'm sure it's in there, if noisy. But I just can't find software that is capable of stretching the bottom without blowing out the top. APP is a flop. So are AstraImage and Registax. I don't have PI.

 

Also my master dark did not calibrate out my noise in Autostakkert. I don't think it was even using it? And I can't figure out how to make DSS or APP stack an image with no stars. Bah.



#13 james7ca

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Posted 16 January 2021 - 09:10 PM

PI has a few tools to help handle high dynamic ranges, but it's still not enough to span the dark and bright sides of the crescent moon.

 

As for "noise," calibration with darks doesn't remove shot and read noise (which is what you are probably seeing on the dark side of the moon). Darks help to remove bright pixel defects and the sensor's bias signal (plus any amp glow and the thermal signal/noise). Calibration may also help with a sensor's pattern noise but most DSLRs don't have a lot of the latter (anymore, it use to be a significant problem with certain Canon cameras). That's not to say the pattern noise isn't a problem, it's just not as noticeable on most modern CMOS sensors and it typically doesn't become a issue until you stretch very hard with low signal images (like for DSOs). 


Edited by james7ca, 17 January 2021 - 02:02 AM.

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#14 Tom Glenn

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Posted 16 January 2021 - 09:27 PM

But I had the brilliant idea that I did not need multiple shutter speeds. I would shoot a hundred or so frames exposed for the light side, stack them, and then stretch them like a DSO image to bring up the Earthshine. Needless to say, it was a disaster. I just don't have the right software to bring it out of the stack without blowing out the illuminated limb; 

This can actually be done, if the goal is simply to detect the Earthshine side, but it requires many more than 100 frames, and the result looks pretty horrible.  I've posted about this before:

 

https://www.cloudyni...ge-of-the-moon/

 

The result doesn't look good, and there would be no way to blend this into an HDR composite, but there are certainly some details recorded.  But the stretch is so extreme that you can even see the shadow of the secondary mirror.  I only did this as a test of the capabilities of the sensor.  If your goal is a good looking HDR composite, you will need multiple exposures.  


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#15 Borodog

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Posted 17 January 2021 - 09:46 AM

Thanks guys. Every time I go out I learn something new, even if it's the hard way. ;O)




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