Fullframe Autofocus with elongated stars

[Kaban]

Hello.

When i use the full frame autofocus, the images acquirted show elongated stars along the process.
Anyway, the final focus seems to be correct. Is this normal? I guess not!

Thanks.

David Cejudo.

[Iver]

That never happens when I focus. Do you have guiding active when you focus? If yes pause the guider and see if that helps.

[Kaban]

Hello.

No. Guiding is not active.
Besides, if i get a single image just before or after focus, the image is perfectly normal with round stars!

[Dunmunro]

Hello.

No. Guiding is not active.
Besides, if i get a single image just before or after focus, the image is perfectly normal with round stars!

Is your mount polar aligned?

[Kaban]

My mount sits in an equatorial wedge very well aligned.
Even if i do not use guiding, any shot shows round stars even with long expositions.

Just before focus i usually acquire a simple image a few seconds long that looks fine.
Besides, the Full Frame autofocus uses 4 seconds shots.

Also, the camera is well aligned to the north but those elongated stars are slanted.

David Cejudo.

[Iver]

Have you checked all the connections between the camera and scope especially the focuser ? Maybe just a lose connection that flexes during auto focus.
Good luck

[Kaban]

Connections are fine. That is not the problem.

I have two telescopes on the same mount. If i shoot with the other telescope's camera while full frame focusing at the same time, the other camera shows perfectly normal stars while AstroArt's Full Frame Focus shows them elongated.

How is that possible?

David Cejudo.

[fabdev]

Hi, if it's 100% sure that the telescope is not moving, maybe something else is sliding (the focuser after the movement ?)
Fabio.

[Kaban]

The images are 4 seconds long. Can the focuser slide for that long after moving?
For the FF autofocus the setup steps are 60, that is, 170μm in my EAF focuser. It moves pretty fast, under half a second.

I will try some more tests. Maybe lowering the number of steps. Also i will try to image at the same time the focuser is moving and see what happens...

But still, i can´t see how the focuser would keep on moving during four more seconds!

Thanks.

[fabdev]

Looking again at the screenshot, it's possible that it's an extremely skewed image.
Some ASCOM drivers had that bug some years ago, when using big subframes.
Try to reset the subframe to 100%. If it works, try 81% or 79% until you find a percentage which is liked by the driver. Maybe it's possible to solve updating the ASCOM driver (the one of the manufacturer, not the Astroart plugin 2.73).
Let us know,
Fabio.

[Kaban]

Well, at last!

Setting the subrame to 100% solved the problem. But it does not work with 90% or other settings, though.

Anyway the focusing was correct even with those elongated stars.

I did not try to update the drivers yet to see what happens. My drivers are updated to 2024, but i noticed there is a newer update at ZWO's website.

Thank you!