The goal of this project is to revive an old webcam and an old telescope to take some images of the night sky. I have many ideas in mind that will stem from this.
Step 1: Find your image
Simple optics will tell you that an image coming from very very far away will resolve as an image in plane at the focal length of the optics assembly.
The location of the image plane is important as when imaging, this is where you want to place your 2D detector (i.e. CCD chip from a webcam).
Here is an example of the process. I removed the eyepiece from my Tasco Newtonian (700mm focal length), pointed it at the moon and stuck a piece of cardboard near where I knew the image plane to be located. At the image plane, you will see a very sharp image of the moon. This is where your CCD chip should be.
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| The bright light on the piece of cardboard is an image of the moon resolved in plane at the focal length. |
Some small detail: you'll also want to double check that the image being resolved is well centered coming out of the focus. If it's not, then adjust your secondary mirror. Note: if you're not sure, don't touch the secondary mirror. Often this piece does not need to be aligned and if you bring it out of alignment, it can be frustrating to bring back (it has 3 degrees of freedom, and is often a delicate effort to adjust the screws that control its orientation).
Step 2: Make the focuser
I haven't received my focuser yet, so I decided to concoct something out of regular household materials. Picture will say all...
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| The makeshift focuser. I cut and shorten the diameter of one tube so it can slide in the other. I add tape to add more friction. It works quite nicely. |
Step 3: Mount the webcam, point and measure!
The scope mounted, connected to pc. I use cheese (free open source) for the image capture.
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The end result |
Since we know we see just brightness and darkness on the moon (grayscale), not color, we can sum the colors together. Here is the image again in grayscale. Unfortunately, it's saturated. Will have to attenuate the image next time.
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Grayscale version of the end result. |
After thoughts
Why is the moon pink?
When I use the webcam with the lens, I don't see pinkish colors. When I use it without the lens (for the telescope), I do see the pink colors. The conclusion must be that the lens must also be filtering out red light. This also suggests that the webcam's red is more sensitive than it should be. Will check this out later.
If you see a photo of the lens below, you see that it reflects red.
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The webcam on a toilet paper tube. |
Time lapse evening log
Finally, here's proof of the non-astro friendly weather tonight :-( :-((Cleardarksky.com was much more optimistic than the end result this time)
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Time lapse at Custer institute. We waited 2 hours, no signs of clearing. |
