Star testing Bresser 127 L Achromatic refractor

[neil phillips]

After doing some observing. In the cold air. Run off some star tests. Figure aside. which shows typical chinese under or over correction. Collimation is clearly quite good. The slight fuzzy edge is the refractor still cooling i belive. processing was the same on either side of focus. Though camera settings differed

What it can do under good seeing last summer 

Edited January 5, 2022 by neil phillips

[NGC 1502]

It could be my iPad, but nothing seen regarding images, just empty boxes.  You’ve mentioned that the scope had not fully cooled. To fully evaluate I’d suggest a scope and in particular the optics do need to have cooled to ambient.

Ed.

[neil phillips]

1 minute ago, NGC 1502 said:

It could be my iPad, but nothing seen regarding images, just empty boxes.  You’ve mentioned that the scope had not fully cooled. To fully evaluate I’d suggest a scope and in particular the optics do need to have cooled to ambient.

Ed.

Agreed but with the cold air if i wanted to do that i could be waiting a few hours. Perhaps in the summer i will do it again. But have seen what the star tests look like already visually on a few occasions. Already decided i do want to keep it. 

Was still editing should show now. 

[NGC 1502]

Thanks, star test images now visible. Understood re long cooling times. Whilst I’m no expert on evaluating star tests I’ve seen far far worse and yet the scope gave great views.  
 

Optical guru Al Nagler (TeleVue) has said don’t worry what the scope produces when out of focus, it’s what you see when infocus that counts👍

[neil phillips]

29 minutes ago, NGC 1502 said:

Thanks, star test images now visible. Understood re long cooling times. Whilst I’m no expert on evaluating star tests I’ve seen far far worse and yet the scope gave great views.  
 

Optical guru Al Nagler (TeleVue) has said don’t worry what the scope produces when out of focus, it’s what you see when infocus that counts👍

That is true to a degree. But for collimation purposes star testing is pretty much the acid test. By which all other collimation procedures are revealed. Using a colli cap and cheshire for example. looked quite good on my 8" Classical cassegrain. Upon star testing. Not so. it revealed a slanted secondary mirror tilt. And focusser tilt.