It's been ages since I posted on this subject - there never seems enough time to do everything, especially since I retired (an often heard complaint!). Which is a shame because eventually I got the tracker to work quite well.
The main problem turned out to be the stepper motor. The original was a one-off purchase through eBay, and I began to suspect that the motor was not turning evenly. These are really cheap units of questionable quality, so I got some more from a different source. There seems to be many manufacturers/retailers of this motor, so it's probably pot-luck as to how good they are. I bought a pack of 5 which came together with the ULN2003 driver.
Having replaced the motor with one of these, results were immediately improved - to the extent that the speed adjustment controls I'd built-in didn't need to be used as the tracker and software behaved pretty much as designed.
Stability
I think any remaining image issues are down to the lack of stability of the mount. I'm using a decent camera tripod (Manfrotto 190XPROB with an XPRO geared head) but it's just not up to handling the combined weight of the tracker +camera + lens. My camera is a Canon 5D mk3 and from my small lens collection the only suitable one is a 70-200mm F4 L zoom, the combined weight being 1.7kg. I do have a longer lens but it's far too heavy. The tracker is 1.5kg so the total weight is 3.2kg (the assemblage is not well balanced) and I'm sure it moves even in a slight breeze. If I lived somewhere with good skies then I'd build a solid pier as a permanent mount - but then I'd already have a decent telescope, observatory ...
Photos
Because I'm limited to a 200mm lens, or 4x magnification, there aren't really any deep-sky objects available to me. I'm also restricted to what parts of the sky I can photograph at home because of the need to see Polaris to orientate the tracker, and my house inconveniently gets in the way. So I've used the tracker to photograph solar system objects that would normally be too faint to see - e.g. Neptune, Uranus and now some asteroids. (Remember that my suburban sky is not good - Polaris is only just visible to my naked eye.) It's nice to see how sharp (or sometimes not!) star points the tracker can produce. Fortunately my house restricts me to viewing south, and thus the ecliptic.
This recently taken image surprised me in its ability to show some of Saturn's moons. I like it! I use Stellarium to locate and verify the objects in view.
Another showing Jupiter's moons, and compared with an untracked variant.
... the satellite positions shown in a screen capture from Stellarium:
This blog doesn't let me include images that can be popped out to enlarge them, so these and more images can be found on my Google Drive, here.
So nothing particularly impressive, but nonetheless show that it can work.
Chris
No comments:
Post a Comment