I think I finally saw the airy discs!
Posted 05 August 2021 - 01:51 PM
Posted 05 August 2021 - 02:14 PM
the rings seemed to be only appearing in the lower part of the star, was this due to the seeing or maybe astigmatism or smth like that?
This, plus the fact that you saw as much as three or four rings around Polaris strongly suggests that the scope is badly miscollimated and may also have spherical aberration.
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Posted 05 August 2021 - 02:38 PM
Posted 05 August 2021 - 02:46 PM
Its a refractor, and views through it are quite sharp, i doubt it would have severe spherical aberration or be misscollimated
And what do you have to compare it with? How do you judge its sharpness?
The fact that you saw so many diffraction rings, and only to one side, on a modestly bright star such as Polaris, VERY strongly suggests that something isn't as it should be in that telescope. Views may still appear fairly good, but much in your reports indicates that it could be better.
In a good 4" refractor in excellent seeing, Polaris is a sharp disk, surrounded by a single, faint, unbroken ring.
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Posted 05 August 2021 - 02:47 PM
The collimation will be out if its not even rings in the centre of the field. If it shows even in one part that should be the centre and the tilt of the lens needs adjusting. Makes quite a difference and there are collimating tools to sort this as long as you have adjustment screws.
The collimating tool is inexpensive and easy to use
I own one and have used it on several refractors over the years. Its easy to use.
As some of us are aware with refractors there can be a big difference between quite sharp and a top end apo sharp
Edited by Phil Barker, 05 August 2021 - 02:50 PM.
Posted 05 August 2021 - 03:00 PM
Strongly agree, the telescope needs to be collimated. Does the lens cell have adjusting screws?