Cheap astrophotography - Galileoscope and Logitech C270

[bitnick]

How cheap can you get? Well, I wanted to know.

I also bought my first telescope a while ago - a 127 mm Maksutov OTA at a nice discount. However, being an OTA only it didn't come with a mount, and I decided to build my own. This is taking some time however, and I felt a bit frustrated about not being able to take advantage of the cloudless nights with the moon, venus and jupiter all being visible from the balcony.

So I dug out my old €45 Galileoscope - a plastic-tube 50 mm achromat with a 500 mm focal length (so focal ratio of 10) - and a €28 Logitech C270 webcam that I had lying around. I also rummaged through my drawers to find a plastic lid for a 5.25" computer case slot and a black marker pen.

Unfortunately I didn't take any pictures of the dismantling of the webcam, but it's very easy: the front just snaps off, and then there's three small screws to remove to open it to get to the lens. The lens just screws out, but leave it in place as long as possible to avoid getting any dirt on the sensor. I also removed the hinged arm attached to the webcam body. There's a screw going through the hinge - peel away the small rubber rounds at the ends of the hinge, remove the screw, and push out the plastic pin holding the webcam to the arm.

Here is the plate with a hole drilled for the sensor and some scribbling with the marker pen:

I removed the LED that shines when the camera is active, to avoid getting any light pollution. The LED is very small, so I didn't want to put my large soldering iron in there. Instead I just used some precision side-cutters to snip at the solder until it came off:

(What looks like a little claw is in fact part of a cat's claw; these precision, flush-cut pliers are better for trimming cat's claws than any purpose-made pliers I've tried - also a lot more expensive though. The LED is the small square thing.) Here you can also see the sensor module with the lens still in place. The metal can is a microphone. The LED is designated D1 on the printed circuit board.

Next I removed the lend and inserted it temporarily into the plastic slot plate (this is to position the camera in the next step):

You can also see that I've blackened the plate here to maximize contrast. The lens from the back side:

The webcam is nicely positioned by placing it over the lens:

I simply hot glued it in place:

I then attached one of the parts that came with the Galileoscope, a 1.25" sleeve for one of its plastic eye-pieces, to the front of the plate:

... And now I'm out of upload space. Continued in the next post.

[bitnick]

The whole contraption looks like this:

... and from the camera end:

Now, I didn't have too high hopes for this: the tripod is quite horrible (very unstable, lots of flexure, there's way too much friction to overcome to move the head, etc), the camera is cheap, the focus is simply a tube one pushes in or out of the main scope tube, and the scope itself is made of plastic and creaks when I touch it...

Also, I think the seeing was quite horrible today. Even bright Venus twinkled to the naked eye, and there was thin sheets of cloud high in the sky. Anyway, here are some star snapshots:

I think I must have succeeded with the focus, right? That's the airy disk and its first ring that's visible, if I'm not mistaken?

The C270 has a pixel size of 2.8 µm square, and a resolution of 1280x720, so the sensor size is 3.58 mm x 2.02 mm. 12 Dimensional String tells me that this combination of telescope and camera gives a resolution of 1.16'' per pixel. The field of view is 25' x 14' or there abouts. This page tells me that the resolvable resolution for a scope of this size is 2.7'', or 2.35 pixels - so even with perfect focus, everything will look blurry, I guess.

Here's an overexposed venus and a blurry jupiter:

And finally a snapshot of the moon:

All these images are unprocessed single snapshots. The camera seems to be capable of about 20 frames/s at full resolution. It will be interesting to try it out on the Mak later, in better seeing!

[bitnick]

Oh, and I used a Linux system and guvcview for the captures. I used all manual settings, left the brightness and contrast at defaults, turned gain down to zero, disabled power line flicker compensation, set color balance to 7500, and used an exposure of between 50 and 65 out of 10000 for the moon. A bit higher for the star (~80).

I celebrated my first ever astrophotography results with some salty peanuts and a Budweiser (3.5 %).

[saac]

Good project there bitnick, it will be interesting to see how far you able to push the imaging.  

[inedible_hulk]

Cool [emoji41]

Sent from my iPad using Tapatalk

[Soupy]

Great going bitnick, but I bet you could get it even cheaper... Cheap Webcams in ASDA in UK go for about £7, €12, these are easily modded as well

[mwayne]

Congratulations! I would've celebrated with something better than Budwiser, like Belhaven unless you're waiting for photos with your Mak do do that.

[chemist]

On 24/05/2015 at 20:51, bitnick said:

The whole contraption looks like this:

... and from the camera end:

Now, I didn't have too high hopes for this: the tripod is quite horrible (very unstable, lots of flexure, there's way too much friction to overcome to move the head, etc), the camera is cheap, the focus is simply a tube one pushes in or out of the main scope tube, and the scope itself is made of plastic and creaks when I touch it...

Also, I think the seeing was quite horrible today. Even bright Venus twinkled to the naked eye, and there was thin sheets of cloud high in the sky. Anyway, here are some star snapshots:

I think I must have succeeded with the focus, right? That's the airy disk and its first ring that's visible, if I'm not mistaken?

The C270 has a pixel size of 2.8 µm square, and a resolution of 1280x720, so the sensor size is 3.58 mm x 2.02 mm. 12 Dimensional String tells me that this combination of telescope and camera gives a resolution of 1.16'' per pixel. The field of view is 25' x 14' or there abouts. This page tells me that the resolvable resolution for a scope of this size is 2.7'', or 2.35 pixels - so even with perfect focus, everything will look blurry, I guess.

Here's an overexposed venus and a blurry jupiter:

And finally a snapshot of the moon:

All these images are unprocessed single snapshots. The camera seems to be capable of about 20 frames/s at full resolution. It will be interesting to try it out on the Mak later, in better seeing!

How was this pixel size obtained? I am trying to use a C270 in my optics lab.