Noticed my Secondary is pinched how badly and what affect will it have on imaging

[StarDuke82]

The other night while collimating my SCT I noticed that the airy disk on either side was flattened which can only mean pinching, I managed to get one side to return to the normal arc but as soon as I tightened down the collimation the opposite side was always slightly flattened. My question is how badly will this affect imaging different objects? I know it can cause aberrations in Stars and DSO’s but what about localized objects like planetary imaging, I also suspect my Secondary is out of alignment though the angle of orientation clockwise may just be an aesthetic preference and not an actual alignment issue though the outer housing that unscrews so you can swap out the Secondary for a Faster Camera did become loose a few nights ago.  My main concern is the pinched optics.  I will note that the ambient temperature was near 80 with 90% humidity and a dew point of 70 the last few nights so could it also be the conditions and not just the optics? 

Edited July 4, 2023 by StarDuke82
Added the weather conditions

[Peter Drew]

I would be surprised if your secondary is pinched, most SCT secondaries are not constrained in their cells and usually bonded to the backing plate with an adhesive pad.  If the optics were pinched at 80F they would be crushed below freezing point.  What brand of SCT is it?  I would suggest trying to release the tension of the screws holding the corrector ring.    🙂

[StarDuke82]

30 minutes ago, Peter Drew said:

I would be surprised if your secondary is pinched, most SCT secondaries are not constrained in their cells and usually bonded to the backing plate with an adhesive pad.  If the optics were pinched at 80F they would be crushed below freezing point.  What brand of SCT is it?  I would suggest trying to release the tension of the screws holding the corrector ring.    🙂

It’s a Celestron Nexstar Evo purchased within the last 3 years and yeah I read it’s pretty near impossible to pinch the secondary of an SCT well if you did you would likely end up shattering the mirror in the process, I have loosened the tension on all three collimation screws for the time being just enough to relax their tension but not so much that they are loose, unfortunately I can’t check or adjust my collimation for at least a couple of days due to rain so I don’t know if it worked, though I have considered making a makeshift artificial star using a bit of fiber optic filament and a Christmas tree bulb on a dimmer so I can do collimation in my basement for such occasions. I really need to learn to leave let enough alone I get it near perfect rough collimation (24 mm ep) then I increase magnification (10 mm ep) for fine collimation and end up cods-walloping my efforts for perfection. 

[bosun21]

I think @Peter Drew was referring to the retaining ring around the circumference of the front plate and not the secondary collimation screws.

[Peter Drew]

3 hours ago, bosun21 said:

I think @Peter Drew was referring to the retaining ring around the circumference of the front plate and not the secondary collimation screws.

Yes.   I have heard of this causing similar problems if the screws are too tight.