Peter Sütterlin replied to the topic 'Image Overlays' in the forum. 1 month ago

Absolutely cool feature Hy!

One suggestion would be a toolbar button to easily switch the overlay on and off.


If you point to zenith, where do you end up?

If I do it here, the FOV is centered 1 RA minute (15 arc minutes) east of the meridian line. So if your experiment relied on the meridian line, the question is: Is that line drawn correctly?
Did you check hour angle at the position where you slewed to?


Fitchie said:

But even the most expensive mounts/piers never will be completely rigid and in addition a small imbalance is desired to improve the guiding, so that there is always a small force against the leading or trailing edge of the worm.

As long as worm gear mounts are used without spring pressure on the worm, probably the backlash as result of using symmetrical positions before & after the meridian, will make a greater contribution to the PAA inaccuracy than the flexing caused by the imbalance. And of course FL and the weight of the telescope will play a major role.

However, with spring loaded mounts there seems to be an advantage by using symmetrical positions before & after the meridian to polar align, no matter how small the flexing / bending may be.

First, RA backlash is irrelevant. There is no requirement for accurate movement in RA, you just need any three positions. The selected step size, AFAIK, isn't used anywhere in the calculations.

DEC is another thing, so if there is substantial backlash that might affect the result. However, the assumption for the algorithm is that there is no movement in DEC, so in that case the asymmetric version (keeping the DEC gear always on the same edge) would be the better choice.

Imbalance of the scope will only affect gear meshing, on which edge you sit. I don't buy that even a more severely imbalanced scope will cause a noticeable static bending.
Or, the other way around: If it's so imbalanced that it causes bending, PA will be your smallest problem....

That said, I'm always doing my PA symmetric, starting at -45⁰ going to +45⁰ ;)
And I don't move back to home/park afterwards, and only revert direction for the next run (if needed).


Yes, mirror flop was the first thing jumping to my mind when reading this. Like Hy, I think PA should not be affected by cone error. Mirror flop would explain it. As well as play in the optical train. Is it all threaded connections?

With an EC mount you should be able to just track (unguided) through meridian and watch for a systematic shift of the image. How far can you track past meridian? iOptrons aren't particularly good at that :-(


20 degrees is a LOT. The only thing immediately coming up as explanation would be a too tight declination gear meshing that makes the motor lose steps when slewing. Are you close to the mount? Can you hear 'strange' noise?


Running self-compiled 3.6.6 here.
I updated the satellite data (which stopped with an error halfway, not finding Gorizont data; found no way to proceed past that point).
I can see them in the download list (clicking on the '>' symbol). With 'Show Satellites' enabled they are drawn on the star map, and I get info for them.

They do however not show up in the Find Object dialog, so I have no way to search for a specific one :(


Great! Will test it ASAP (but we are plagued by a low-pressure system at the azores, and the mountain is in clouds since almost a week :-((

I also saw some changes regarding the fit ("long tail" whe the fit isn't good) As I also experienced those I'm curious if that helped...


Ah indeed! I had never looked at that page, as star detection had worked OOTB :D
It was set to finally keep 100 stars. I've now increased that to 180, and will check if/how that improves the procedure.