Sunday, September 17, 2017

thoughts after tracking

Some lessons learned from the weekend astrophotography...

The slow-motion control under the barn door tracker worked, sort of. However it does not seem robust. The weight of the camera with grip, the lens, and the tracker itself probably overloaded the small unit. More than once the ¼-20 screw at the bottom came loose! Did it hop a thread? I'll have to inspect for stripping. Also the main tension knob had to be tightened a great deal. It sure was enjoyable dialling in Polaris though...

The Celestron finder scope worked fine. Both nights I simply put Polaris near centre. And that seemed sufficient. But I continue to wonder about how to gauge the true location of the North Celestial Pole. I could try mimicking the entire field of view in software, I suppose...

The top plate is not balanced or does not work in all configurations. For example, after shooting the Pleiades, I pondered the Andromeda galaxy which was straight up. When I moved the camera, the top plate flopped open. The camera cannot hang over the hinge. Perhaps twisting and turning the ball head would let me get to a better configuration but I gave up after brief attempts. At the time, I wondered if a counter-weight would solve the problem. But that seems rather clunky. Maybe it is just a matter of persisting and getting the camera away from the hinge.

The ball head worked really well after the cleaning and lubrication. Fantastic.

I just assumed that the Takumar 55mm would be focused at infinity when I reached the hard stop. It was surprising to find it went beyond.

I had the equipment there but I didn't bother to use it. The netbook connected to the camera would have helped me achieve better focus.

Overall the barn door tracker worked well. The speed knob though is extremely easy to turn. So gets bumped out of position regularly. I need some tape to screw the knob. I will put in the kit box.

I borrowed painters tape for the control knob and the lens focus ring. Need tape onboard for that too.

An extremely long exposure of the Pleiades showed trailing. In other words, I had not dialled it out completely. My workflow is maybe inefficient. Perhaps I should start the other way, shooting for 5 or 10 minutes, and then "working backwards" i.e. when planning to shoot a 1 minute sub. If there's no trailing in a 5 minute then there won't be any in a 1.

Shooting the Pleiades is challenging! It has high dynamic range. So an HDR approach should be taken. A long shot would pull out the nebula. Medium or fast shots will avoid bloating the stars.

I dropped the control unit. Actually, the self-adhesive hook-and-loop strip on the back let go. I dropped the lithium-ion battery. I did not seem to have enough straps and elastics and hooks and lanyards to hold everything to the tripod. Will need more means of secure things.

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