5 replies to this topic

[smith99]

Is there any way to correct the astigmatism in the optics of my LX5? I tried a mask and can get good star images thru a 3" circular diameter opening but not with the whole aperture.

[Mark Sibole]

Have you tried to columinate the scope?
There may be a mis alignment between the primary and secondary mirror.
I know the LX5 is an old scope and I do not know what kind of optics were used way back then but it may simply be out of adjustment.

Regards

Mark

[smith99]

Thanks for the reply!  Yes, I have collimated the scope by centering the image of the secondary against the image of the mirror on a de-focused star. Although that is important, I still get a poor star image upon focusing again. A slightly defocused star image is football shaped and on the other side of focus, it is again football shaped, oriented 180 deg from the previous image. I was wondering if the Televue eyesight astigmatism corrector might help or perhaps a coma corrector.

[Mark Sibole]

Im not sure if that will help.
The coatings could finally be breaking down.
Like I stated im nor real familiar with the LX5 so I dont know what direction to go.
Sorry I couldnt be more help.

Regards

Mark

[smith99]

After experimenting on this for a while, I've found that I can effect the image by loosening the retaining ring and rotating the corrector plate with respect to the optical tube. I also found that the secondary has a little lateral play on the corrector plate as well. I haven't totally fixed the "astigmatism", if that's what it really is, but I can effect the image and make some modest improvements. I also tried backing out the collimation screws on the secondary almost all the way and then recentering the image of the secondary, but that didn't really effect anything.

[avenosod]

Try it again by using ONLY an eyepiece, no diagonal. Rotate eyepiece to see if oval ratates with it. If yes, bad eyepiece. Only make adjustments to corrector plate and/or secondary witout diagonal. Did you return corrector to original position. It came factory set so this is important. Secondary can come loose and move or rotate. I would try rotating and re-centering secondary only to get round out-of-focus image. Then collimate in the time tested manner.

Dennis