TAL-2 colimation problem

[BokiAristarh]

Dear astro friends,
I recently bought a TAL-2 Newton reflector telescope and tried to collimate it because it has not been used for over 20 years. I noticed that the secondary mirror could not come to the correct position, just below the focuser. See the picture ... When the secondary mirror is moved to the maximum to the left, it still needs to be moved a little more to be exactly in the middle below the focuser. In this position, the central screw is fully screwed on and can no longer be moved backwards ... Other components such as the secondary carrier (spider) or the focuser cannot be moved but are fixed. I wonder if any of you have had similar experiences with this telescope and how this can be solved?
Thanks in advance for the help,
Slobodan Nikolic, Serbia

[AAV]

Расчёт телескопа системы Ньютона

[lx75]

When the secondary mirror is moved to the maximum to the left, it still needs to be moved a little more to be exactly in the middle below the focuser.

Центр вторичного зеркала должен быть смещен относительно оптической оси телескопа ( параметр Z на показанной выше оптической схеме). Проведите процедуру юстировки  и наслаждайтесь видами космоса!

[BokiAristarh]

Thanks AAV and lx75,
it is ok what you are talking about offseting secondary mirror.
But as I know offset and parameter "z" is achieved when observer see that secondary mirror in collimator tool looks both "centered in focuser tube and also circular in shape."
In my telescope secondary mirror could not be moved more to the left side looking through collimator, which means it is not located well... or I am wrong...
In opposite, how can observer make right "z" shift if not by proper colimation?

[lx75]

Ось фокусировщика совпадает с оптической осью главного зеркала. Центр вторичного зеркала не совпадает с оптической осью, поэтому вы видите в коллимационый окуляр круглое децентрированное вторичное зеркало, это нормально. Смещение вторичного зеркала задаётся при монтаже к оправе и регулировке не поддается.

[BokiAristarh]

Than if I understood well telescope is collimated OK as on below pictures?

[lx75]

Эту настройку с помощью юстировочного окуляра можно считать достаточной. Более точную юстировку можно провести лазерным коллиматором.

[yas]

For Tal-2 the secondary mirror size is about 40 mm and the off center shift distance is about 1 mm as seeing from the eyepiece end.
 (Shifting the mirror's center from the eyepiece's tube center)
Please keep in mind the optical alignment of the telescope is mostly to eliminate mirror's tilting.
It seems your scope still need collimation.
The most accurate method to do this is a star testing.
You need a brigth star (Vega is a good one) to do this.