This tutorial will show you how to capture and create a lunar mosaic using a
Depending on the sensor size of your camera and the focal length of your telescope, you may or may not be able to fit the entirety of the lunar disk within a single frame. If you cannot, building a mosaic following these steps will allow you to easily construct a full-disk image. And even if you can fit the full-disk into a single frame, by adding a barlow lens or a focal extender in front of the camera can allow you to capture more detail on the lunar surface. The resulting composite image (mosaic) will offer better resolution and treat the eye with nice sharp detail of the Moon.
In order to accomplish these steps, you will need the following tools:
A telescope
A mount
A
Appropriate USB cable
A laptop computer
Capture and processing software
Your telescope can be of any design, though scopes with a larger focal ratio (slow scopes such as SCTs and MCTs) will capture smaller portions of the Moon in each panel, often necessitating more captures to build the mosaic. Scopes with smaller focal ratios (fast scopes), such as shorter refactors and reflectors, will typically encompass larger swaths of the Moon, and that means fewer panels for your mosaic. In addition, faster scopes will gather more light quickly, needing shorter exposure time compared to a slower scope.
For your telescope mount, a motorized mount is the best option as this will allow the Moon to remain in position during the capture process. This is doable with a manual mount, but be prepared to hold the scope on target as carefully as possible. This can be a bit frustrating at first, but practice makes perfect when using a manual mount.
A laptop computer is handy as it can be easily taken outside and placed next to the mount and provides the means to operate the
For the purposes of this tutorial, I will be using freely available software: SharpCap 3.2, Autostakkert!2, Registax 6,
First things first. You need a reasonable clear sky with the Moon available. Since the Moon is quite bright, it can readily cut through thin clouds and sludgy skies and does not require full dark to capture. It is helpful, though, when building a mosaic, to work as quickly as possible if it is not fully dark yet. Otherwise, some of your frames may have a lighter background compared to others as the Sun is still sinking lower below the horizon.
Set up your mount and scope as appropriate, install your
I am assuming at this point that you are familiar enough with your equipment that you can get the Moon located and reasonably centered in the frame and have some experience doing this.
For this tutorial, I will be using my Stellarvue SV102T telescope (a 4” apochromatic refractor) with my Celestron Advanced VX mount (a motorized, electronic equatorial mount), my ZWO ASI174MC color
It can be helpful to pan around a bit on the Moon while watching the view on the laptop. This will help you determine how many individual mosaic panels you will need and also adjust your exposure so that the brighter areas of the lunar surface are not blown out (over-exposed). For my cam, scope, and barlow, I find that 3 panels will cover the entirety of a thinner crescent Moon, while 6 panels will nicely cover a quarter to full Moon. The Moon we are capturing on this night is just past quarter phase, so I’ll need to capture 6 panels.
You’ll notice that the image of the Moon on your laptop screen is showing the effects of atmospheric turbulence. The Moon will appear as if it is at the bottom of a pool of water. The more turbulent the atmosphere is, the more the Moon will appear to waver and undulate. This can make it difficult to capture a nice clean shot. To get around this, we’ll not be making single exposures. We’ll be capturing data as a video (
Next, I’ll select a starting point for my first video capture. In this case, I’ve got the scope sitting on the northeast (upper right) portion of the lunar disk. I’ll be working my way down the disk from this point. Once at the bottom, I’ll move west (left) and work my way back up. Since there are many craters on the lunar surface to use as reference points, it is fairly easy to keep your bearings and ensure that each capture overlaps the previous ones. This is beneficial so that your resulting mosaic does not have any unfortunate gaps in the image. Allow yourself plenty of overlap so that you can crop out stacking artifacts later during processing.
Make sure you are focused as best as you can achieve. Watch the prominent craters and try to make them as sharp as possible. It will not be as sharp as the view through an eyepiece but do try to make it as sharp as you can on the screen.
Here is what my laptop screen looks like at this point:
My exposure time is set for 18 milliseconds, my gain is at 50, and I am capturing a SER video file as RAW16. It is important that you not change these settings until you have finished capturing all of the panels for your mosaic.
After clicking the “Start Capture” button on the upper left of the screen, I’ll set my number of frames to 1000. Thus, my resulting SER video file will contain 1000 frame of lunar data. Depending on your exposure, computer memory, and processing speeds, a 1000 frame SER file will take between 30 seconds to a few minutes. Using the
Once SharpCap indicates your capture is complete, it is time to adjust the field of view to encompass our next portion of the lunar surface. Using the craters along the bottom of my present field of view, I’ll move the scope until these craters are higher up. Watch the right side of your screen as well to try to keep the Moon in a similar position with regards to side-to-side framing. It doesn’t have to be exact by any means. Reasonably close will suffice. This will help you out later on during the mosaic building process.
After moving the Moon up some, my screen now looks like this:
Click “Start Capture” again and hit the OK button to pull in your next 1000 frame video file. Once that is done, adjust again and repeat:
Now that I am at the bottom of the lunar disk, I’ll adjust the field of view by sliding the Moon to the right:
Capture that field of view, and then work your way back up:
And then for the last panel:
Once that is done, you have now successfully captured your required panels for your mosaic. For my utilized settings, these six panels have resulted in 24.6 GB of data collected in less than 10 minutes!
At this point, you can stop and bring the laptop back inside, continue to capture more data, or whatever you wish to do. Enjoy!
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When you are ready to process your video files, you’ll need two pieces of software from the list provided above. For this step in the process, we’ll be using Autostakkert!2 and Registax 6. Autostakkert!2 will open each of our video files that we captured, analyze and sort each frame by quality and then stack the best of these into a single image. We’ll then be moving these stacked images over to Registax 6 for some wavelet sharpening.
I find it helpful to have both of these programs open at the same time. On my PC, as soon as Autostakkert! is done stacking, the image will automatically open up in Registax. That is a handy little feature that can speed up the process some.
In Autostakkert!, locate your video files. SharpCap will typically create a folder on your desktop (or where ever you told it to) called SharpCap Captures. Inside this folder, you’ll find a subfolder typically named with the date of your imaging session. Inside of the subfolder you’ll find your video files, typically named with the time of capture.
Open the first video file in Autostakkert!. Your screen should now look similar to this:
On the left panel, you’ll see the large “Open” button. Directly under that, you will see an array of options. You’ll want to choose “Surface” under Image Stabilization. Under Quality Estimator, I find that Gradient and Local (
Over on the right-hand panel that contains the image of the Moon, make sure the green X within the green box is sitting somewhere on the lunar disk. If you need to move this, place the mouse pointer to the desired location, press the CTRL button on your keyboard, and click the mouse at the desired spot.
Next, click the “Analyse” button on the left.
Autostakkert! will evaluate each frame and then sort all of them by quality, best to worse. I find that I get the best-stacked image by using only those frames with a quality rating of 75% or better. This is typically done by using the best 10% of the frames, in my case. To select the best 10% of the frames, find the “Stacking Options” area on the left panel. I always select TIF as my output format and under “Frame percentage to stack” I put 10 (for 10%) in the left-most box.
After analyzing has completed, we now need to set our Alignment Points (
Next, move back over to the left panel and click the “Stack” button. Autostakkert! will now begin aligning the best 10% of the frames and stacking them into a final stacked TIF image. Once that is done, your screen should look like this:
It is time now to move over to Registax. If you had both Autostakkert! and Registax open, you should find your stacked image waiting on you when you switch over to that program. If not, you can open it in Registax by going to the appropriate subfolder and selecting the image. Autostakkert! will create an additional subfolder within the folder containing your video files to place your stacked images in.
Once your image is open in Registax, you should see something like this:
On the left-hand side of the screen, you will see a series of sliders. These are the adjustments for wavelet sharpening. You can spend some time adjusting these to your liking and the image on the screen will change accordingly. Just make sure you use the exact same settings for each of your individual images.
I have played around with these wavelet sliders quite a lot and I’ve found that for my personal taste that I like to move only the first two sliders. How far you need to adjust these can also depend on the scope used to capture the images with. If I am using my SV102T
Once you have your sliders adjusted to your liking, click the “Do All” button on the upper left. This will apply your wavelet settings across the whole image. If you don’t like the results, adjust the sliders and do it again. Be sure to make note of your settings so you can use the same ones on your subsequent frames. You can also “Save Scheme” so that you can easily recall the same settings in the future.
After that, click the “Save Image” button to the right of the “Do All” button to save your sharpened image. I always save these to my desktop or a special folder so that I don’t get them intermixed with my stacked images out of Autostakkert!. Less confusion for me that way.
Repeat the Autostakkert! and Registax process for each remaining capture.
Here is the first panel image after stacking in Autostakkert!:
And here is the same image after applying wavelet sharpening in Registax:
You will notice that on the sharpened images, the edges contain either a white line or small gaps in the image data. These are stacking artifacts and we need to trim that off. This is where allowing plenty of overlap during capture with SharpCap comes into play.
You can trim off these stacking artifacts with any image editor and its cropping feature. In my case, I’ll be using
Notice how clean the edges are now? This is key to getting a nice seamless mosaic with the next steps.
To composite these 6 images into a single image of the lunar disk, we’ll next go to Microsoft’s Image Composite Editor (ICE). ICE makes mosaic building a very easy process.
Once you have ICE open, you should see something like this:
Click the “New Panorama” button at the top left and select all 6 of your sharpened and cropped images you’ll need to assemble the mosaic (or however many you have).
You should now see something like this:
Now, click the “NEXT” button on the far upper right. ICE will now analyze your images, get them properly aligned, and present you with the results underneath a grid overlay.
You can adjust the roll setting to orient the Moon to your liking. Since I was careful with my camera orientation prior to capture, I will make no adjustments here. Click “NEXT” again.
This screen will allow you to crop the edges of the mosaic to make it nice and square. Once you get that done to your liking, click “NEXT” again.
You will now see your final image. On the right, you will see options for saving your mosaic. I always use TIFF format and keep my image scale at 100%. Click the “Export to disk” button and save the file where ever you like with the appropriate file name.
Congratulations! You’ve just built a lunar mosaic!
At this point, you are essentially done. You’ve got a very nice lunar mosaic on your hands. Great job!
*The following steps are completely optional using further image processing steps. Here I am using
I like to go one step further to bring out a little more color in my image to really highlight some lunar features. To accomplish this, I use the color module in
Once in
I find that this particular
Anyway, that is my process in a nutshell. I hope you have found this useful and insightful!
Best of luck with your own lunar imaging. I look forward to seeing your results!
**NOTE: These processes can be easily adapted by users of