Issue with derotator: Solved?

lukas_demetz

Hi guys,

as you might have noticed, the derotator of the iDK20 in Namibia sometimes created interesting images - albeit not in the way we intended 😅

Turns out it was (with about 95% probability) a driver issue that we think got handled with a small change in our software. Keep a watchful eye out there and let me know if some "star trail" image comes out again 🙂

Clear skies

SkG

Seems like there are still problems with the iDK-20. When looking at the image preview of Sh2-313 that's up on the Dashboard this morning from about 00:51 UT 2022-06-02, I can see small trails on several stars at the edges of the frame. I've noticed it on other recent images too.

lukas_demetz

@SkG There are sometimes issues with the derotator when very close to zenith. But there are fewer than we used to have. The main issues these days are due to the wind, and the derotator not reacting to it as fast as the mount, resulting in "uneven" trails if one could say. But the wind gusts make imaging a challenge anyway 🙁

SkG

Perhaps that's the set of issues, but whenever I've glanced at imagery from the iDK-20 lately the stars are not sharp - they are oval-shaped. The imagery I've taken on that telescope recent;y is part of a multi-year research project on galaxy morphology that has involved several telescopes and observing bands. I need the images to be sharp so as to not distort whatever details the image can offer.

lukas_demetz

@SkG true. It's indeed a set of issues: derotator that gets "blocked" by a stuck cable, imperfect tracking, and wind.
Winds have been extreme over the last week or so. I am in contact with Planewave to let them check about the motor tuning.

SkG

Ok, Thanks.

lukas_demetz

Ok, so it seems we have an unknown issue with the mount tracking. Planewave support is on it.
Wind seems to play a role here, but it is too sensitive. Example?

This is a no-wind tracking, at the beginning, followed by a small gust:

I am more and more convinced that a collimation "issue" - say, a not very good collimation - is layered on top of this issue.

We are on it. Not as easy to fix as I hoped for 😰