Hi Yanhe,
easy question first (2) Yes

As for (1), if you just want to use the position of some atom (or approximate center of some group of atoms), you don't need to figure it out and then enter numbers in the dialog. Instead you can just either

(A) select the atom(s) and use the menu: Actions... Set Pivot
<https://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/menu.html#actpivot>

- OR -

(B) use the "cofr" command
<https://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/midas/cofr.html>

...and specify one or more atoms, for example

cofr #1:50.A@CA
cofr #1:50.A
cofr sel

...where "sel" means currently selected atoms.  However, if you have calculated X,Y,Z that you want as the center using some other method you can also specify them with the "cofr" command:

cofr 5.5,14.2,15.0

I hope this helps,

Elaine
-----
Elaine C. Meng, Ph.D.                       
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

>
> From: Yanhe Zhao <yanhezhao1990@gmail.com>
> Subject: choose the rotation center
> Date: February 1, 2022 at 1:02:12 PM PST
> To: chimera-users-owner@cgl.ucsf.edu
>
> Hello there,
>
> I want to fixed the center for my rotation but have two questions here:
> 1, how I easily read out the xyz coordinate of the point I want to use as center?
> 2, as attached, what the xyz sequence here, xyz from top to bottom?
>
> Thanks and appreciate for your help!
> Yanhe
> <Screenshot from 2022-02-01 14-53-52.png>