bitnick

I've looked very carefully at the pictures in the thread but I cannot see the adjustment mechanism. Can you post a detail image of this? DIY friction drives are rare - even more so DIY friction drives that work well! - and it would be very interesting to see how you've solved it. I've been sketching a similar but somewhat simpler astrophotography mount, using a couple of angular contact bearings (single row would be more fitting but turns out to be considerably more expensive in this size and with rubber seals) on a long 3/8 inch bolt that goes directly into the tripod mount thread on a ball head. Under the ball head would be a plate similar to the "arc plate" in your mount driven by a friction drive using a small stepper motor and gear box (these are made to fit together). But I'm a bit stuck with the friction drive; I find it diffcult to come up with a mechanically simple preloading mechanism.

Thanks! Yeah I'm sure it's better than most commercial mounts of the same type; it looks very well made! How do you preload the friction drive? Is it enough to push the motor axle onto the aluminium arc and tighten the screws holding the motor?

What a nice build! Beautiful! Can you tell me more about the friction drive? It looks like it is metal-to-metal contact - steel-to-alu to be exact. Does this work well? Is there some flexibility somewhere in the construction or do you rely on very precise machining of the arc (concentric to the RA axis) to keep the contact force constant? Also, I'm trying to figure out how the RA bearing is constructed. What kind of bearing do you use (radial, single/double angular contact etc) and how is it mounted? Thanks for presenting a very interesting build!

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 %).

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 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.

Here is someone in the US selling what they claim is 1100D sensors for $75 (about £50 before shipping & VAT). Also, I've "only" read the first 50 pages or so of this thread, so maybe this has been said already, but I'm wondering whether some of the failures of Gina's sensors might be due to ESD. The work area did not look ESD safe to me (maybe I'm wrong though, difficult to see), and putting unprotected semiconductors into "generic" (non-conductive/non-ESD-safe) plastic containers is usually a very bad idea. Here is a link to a paper by ON Semiconductor on handling image sensor devices. It starts out ESD is also a danger to the rest of the camera, of course (one of Gina's camera houses stopped working right for no apparent reason, if I remember correctly). I suggest using a properly grounded ESD mat when disassembling electronics like cameras - something like the 3M 68xx maybe? (Avoid the vinyl mats though!) There are of course a thousand things that could go wrong with this mod, but the more a reason to eliminate as many of those things as possible! Anyway, very cool of you to attempt this - kudos!