AstroTrac 360?

Started Mar 21, 2018 | Discussions thread
swimswithtrout Veteran Member • Posts: 3,719
Re: AstroTrac 360?

rnclark wrote:

But I believe there is a hidden problem that buyers may not be aware of unless they have loaded a astrotrac type device: that is the problem of wind. As one pushes up focal length and resolution to the sub 3-arc-seconds per pixel, stability is more important, not just tracking accuracy. With a big optical tube on a very light mount, the flexing in wind destroys stability, and tracking, even with autoguiding.

In my recent trip to Tanzania, I tried for 2 nights to image the Eta Carina nebula at 300 mm f/2.8 on my astrotrac. Wind destroyed most of my exposures, often shaking so much the star images are amazing patterns 30 to 60 arc-seconds across.

It is not worth trying to get images with my 300 f/2.8 on my astrotrac if there is even a moderate breeze. The only solutions are: 1) only work on clear calm nights, 2) make a wind break. I'm working on #2 but do not yet have a good solution. 3) Use a heavier mount.

Roger

+1

Out of my past 12 trips to the Pawnee Grasslands, on at least 6 of those nights, the wind has been blowing 10-15mph +++. With judicious parking of my truck as a wind block, I can still manage 5 -7 min subs @ 1-1.5" RMS guiding, even with the wind, using my 75lb mount, and my 4 lb OTA.

On two nights, I was just barely able to grab my laptop after a wind gust blew it off my table, but my mount and OTA held steady.

I'm down to a 30-45min complete setup time now, faster than any of my optics can cool, so speed of setup is a non issue.

If I had to wait for a calm night to image, I'd never get to image at all.

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