Celestron NexImage Manuel utilisateur
Quick-Start and Tutorial
Imaging Basics
Registax User’s Guide
Troubleshooting
Table of Contents
Quick Start
Make sure your NexImage comes with all of the following:
1. Plug camera into the USB port of your computer.
2. Double click the Amcap icon on your computer’s desktop
to start the program.
3. Make sure “Preview” is selected from the
Options menu. If “Preview” is not already
selected (checked), click on it once.
4. Select an easy target like the moon to begin with. Center and focus your
telescope on the specific feature you wish to image.
5. Remove the barrel cap from the 1.25” barrel of the imager.
Remove the eyepiece from the telescope and slide the barrel
of the imager into the eyepiece barrel of your telescope.
You should see bright light displayed in the imaging window of Amcap.
6. Use your telescopes focuser to focus down the image until the moon is visible
and sharp.
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USB Cable
1.25” Barrel
Installation CD Rom
Adjust the Brightness and Gain
settings to make sure the image
is not over or under exposed.
In order to control the gain
setting, deselect (uncheck) the
Auto box under the Exposure
group of controls.
Once the desired image is focused and centered in the imaging window you are
ready to capture a video image. Before taking the image you must first set the
frame rate, time limit and resolution for the video.
8. From the Options menu select
the Video Capture Pin.
•Set the output size
to 640x480 resolution.
• Set the compression to I420
9. From the Capture menu, choose Set Frame Rate.
• Check the Use Frame Rate box
•Set the frame rate to the desired frames
per second. For example 30 f/sec.
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7. From the Options menu select
the ideo Capture Filter.
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10. From the Capture menu, choose Set Time Limit.
This determines how long of a video image will
be recorded.
• Check the Use Time Limit box
•Set the time limit to the desired amount of time.
For example 20 seconds.
Now you are ready to capture the image.
11. From the Capture menu select Start Capture
• Select OK to begin
image capture.
The bottom of the imaging window will display the amount time of video
recorded and the number of frames captured.
12. Once recording stops select Set Capture File from the File menu. Select
a location on your hard drive and name the file that you have taken
including the .avi extension at the end, for example, moon.avi.
Now that your video stream has been captured the individual frames can be
inspected, aligned and stacked using the included RegiStax software. Before
you begin processing your image, take a moment to read and use the tutorial
provided in the next section.
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RegiStax Tutorial
Your NexImage CD ROM comes with a sample .AVI file which you can use to
learn and experiment with the features of the included RegiStax software. This
tutorial will guide you through the steps you need to align, stack and process
video frames into a single high quality image.
1. Start RegiStax by clicking the icon on your desktop.
Press the Select Input button to select the directory where the NexImage
CD is located.
2. Select the file called Lunar Tutorial.avi from the Celestron folder
and press Open.
3. Next, indicate what type of image is being processed. Is it a color image
of a planet or a black and white image. Since the image being processed
is of the moon, color is not important. Uncheck the color checkbox otherwise
leave this checkbox checked.
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4. Now its time to choose which frame from the video file we want to use as
a reference. All the other images will be compared and aligned using the
reference-image. To find a good candidate use the slider on the lower part
of the screen. Just select the slider and step through the images to find an
image that looks high in contrast and sharpness.
Alternatively, you can check the Show frame list box in the lower left corner
and scroll through each frame individually.
5. Once the alignment frame has been selected, you need to set the size of the
alignment box. Ideally this box will contain either the whole object you have
imaged or a bright, high contrast feature. You can set this box to a square of
32, 64, 128 or 256 pixels in size. Select a size and move your cursor over
the image. For this example choose 128 and move the square around one
of the major craters and press the LEFT mouse button. RegiStax will now take
you to the alignment page.
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Alignment Page
Here you are presented with many different controls that are discussed in detail
in the User's Guide. For this tutorial we will only discuss the most important
features. On this screen you should see two smaller windows that are on top of
the RegiStax Aligning window. One of them is the FFT-spectrum and the other is
called Registration properties. They are displayed using the two checkboxes
under the Options box. Both of these panels are useful when aligning images.
6. FFT-spectrum. This filter is used to estimate the alignment shift between the
reference frame and the rest of the frames in the sequence. Your initial image
should show a multi-colored square with a red circular area in the middle.
The red area in the middle represents where the program estimates the best
alignment. The FFT-spectrum is used to calculate the similarity between
images and estimates the best shift when aligning the images. Increase the
value of the Alignment filter to 12 and press the Recalc FFT button. Notice
that the red-area becomes smaller and the blue line in the Registration
properties graph changes position. Ideally only a small group of pixels
in the image should become red. This part of the image is used to register
(align) the images more accurately.
The next step is to weed out the blurred frames from your video sequence. The
Quality Filter Band shows the distribution of large and small details on each
frame. Images that show a high number of small features are a good indication
that the image is sharp.
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7. Set the "start" quality filter to 10. This will position the two green lines so
that one is to the left of the blue line and one is to the right of the blue line.
Setting the band “width” filter to 9 defines the area under the Registration
Properties graph that is calculated as a proportion of the total area below
the graph. Ideally one of the vertical green lines should lie on the lower part
of the red curve while the other is positioned where the red-curve nearly
touches the bottom.
8. Press Align & Stack and Registax will automatically start the alignment
process. During this stage the program determines how much the object is
misaligned compared to the reference for every frame in the AVI file. Next
is the optimization process where only frames with good image quality are
optimized further. This is a more precise way of aligning the images. Once
all the frames are aligned and stacked you will automatically go to the
Processing Page.
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Processing Page
The power of RegiStax sits in the usage of Wavelets. This is a special filtering
technique that is very good for enhancing details in images. Each wavelet layer
carries part of the image within it. The lower numbered wavelets control the fine
detail stored in the image whereas the larger numbered wavelets control the
coarse detail. Each layer can be adjusted individually to reveal the desired
amount of detail for your image. The processing page is where it all happens!
9. Before processing your image it is a good idea to save the aligned and
stacked image as a Registax file before processing. This will allow you
maintain your pre-processed image without having to go through the Stack
and Align process over again.
10. On the right side of this screen are the six wavelet sliders that are
numbered from 1 to 6. Start by moving slider #1 to a value of 50 and
watch the image change when you release the slider. Move slider 1 back
to its origin (or press Reset) and now move slider 2 to a value of 50, notice
that this slider also changes the picture but in a much different way. As you
will see the sliders with a larger numbers display more “averaged” images
with less fine detail. Whereas the lower numbered sliders bring out more
fine detail (and sometime unwanted "noise"). Now play with some of the
layer-sliders to enhance your image to a desired effect. Press Reset to return
to the normal settings.
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11. On the lower bottom there are two additional sliders called Contrast and
Brightness, these can be used to prevent the image from becoming too
bright. Notice that when you enhance the image with the layer-sliders the
image contrast increases. You can control this by reducing the overall
contrast with the contrast slider.
Once you are happy with the appearance of your image you can save it as
a BMP, JPEG, TIFF or FITS file. Or you can “tweak” the image further on the
Final processing page.
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