Consensus on Rotating Focusers


Ted Mickle
 

I would like to image multiple targets during the night without having to set an alarm at a set time and manually rotate the camera.

I’ve done some initial study into the pros and cons of using rotators for automated astroimaging, particularly possible impacts on image quality, but can find no consensus.

What are some thoughts and recommendations from members of this forum?

Ted


Roland Christen
 

If you rotate everything behind  the focuser, then flats would not be a problem. That includes the field flatteners and filters. If you have a scope that has a built-in field flattener (like the Tak FSQ series) then flats will be needed for every rotation angle.

Rolando

-----Original Message-----
From: Ted Mickle via groups.io <tedmickle@...>
To: main@ap-ug.groups.io
Sent: Fri, Nov 19, 2021 3:52 pm
Subject: [ap-ug] Consensus on Rotating Focusers

I would like to image multiple targets during the night without having to set an alarm at a set time and manually rotate the camera.

I’ve done some initial study into the pros and cons of using rotators for automated astroimaging, particularly possible impacts on image quality, but can find no consensus.

What are some thoughts and recommendations from members of this forum?

Ted








deonb
 

Interesting. I've always done flats at every rotation angle.

What about dust on the objective or asymmetry in the vignetting?


 

Hi Ted

I am all for rotators - we regularly use a rotator for all our targets.  I have not seen any quality issues related to rotation, although it does introduce operational challenges (such as making sure nothing catches, changes to the balance, watch for image train tilt, etc.)

Regarding flats, I have found flats calibrate perfectly fine without having to take them at each rotation.

We use an integrated focuser/rotator (planewave IRF90) and it's very high quality imo.


Brian

On Fri, Nov 19, 2021 at 1:52 PM Ted Mickle via groups.io <tedmickle=me.com@groups.io> wrote:
I would like to image multiple targets during the night without having to set an alarm at a set time and manually rotate the camera.

I’ve done some initial study into the pros and cons of using rotators for automated astroimaging, particularly possible impacts on image quality, but can find no consensus.

What are some thoughts and recommendations from members of this forum?

Ted









--
Brian 



Brian Valente


Roland Christen
 


What about dust on the objective or asymmetry in the vignetting?
Dust does nothing. It simply reduces the image brightness slightly. Does not cause any kind of effect on flats.

Rolando

-----Original Message-----
From: deonb <deonb@...>
To: main@ap-ug.groups.io
Sent: Fri, Nov 19, 2021 5:08 pm
Subject: Re: [ap-ug] Consensus on Rotating Focusers

Interesting. I've always done flats at every rotation angle.

What about dust on the objective or asymmetry in the vignetting?


Eric Claeys
 

I have a couple Optec Gemini rotator/focusers for two scopes and love them.  I have SGP set up to get within 0.03 degrees of error and it usually achieves that in 1 or 2 tries (about the same as for centering).
I agree with Brian on the "operational challenges".  They can be overcome but it's something you need to think about and play with.

I'm surprised people are able to use the same flats for any angle.  I understand dust on the objective doesn't matter, but I've seen different vignetting at different angles.  Does that not matter, or do other people have perfectly symmetrical vignetting?