ETX105 collimation

[RT65CB-SWL]

Does anyone have any thoughts on ETX105 collimation?

I am getting a slight 'ghosting' on the right side from a point of light, ie mainly planet and bright stars, (the Moon and anything terrestial appear unaffected).

I have looked at Mike Weaseners ETX site and I dont know whether it is worth doing or leave well alone as many have said.

[NGC 1502]

Hi Philip R. Collimating the ETX 90/105/125 is doable, but the problem is that the collimating screws (there are six, three adjustment and three lock screws) are only accessed by first removing the rear plastic cover that has the flip mirror and eyepiece port.

So it's trial and error, adjust, refit the back cover, check with a defocused star (or an artificial star ) note if the error is worse or better, remove the back cover, adjust...........etc etc.

You can get an idea of the pair of screws to adjust first, by viewing a bright out of focus star, note which way the rings are skewed, placing a pencil or similar into the light path, look through the eyepiece, shift the pencil to coincide with the most skewed side, trace back down the tube and put a sticker on the tube.

So it's not an easy process. It could test your patience and you may make it worse, so have a long hard think before starting this.

I'd read lots of Weasner's excellent website.

Best regards, Ed.

[NGC 1502]

Further thoughts - the ETX Maks generally hold collimation very well. Most will never need attention unless dropped.

It's worth checking if the flip mirror is correctly seated. You could try operating the control firmly a few times. If the flip mirror has not fully seated it's just possible that could be the source of the problem. Also, if you have the necessary adapter, you could try viewing straight through via the rear port, with the flip mirror out of the light path, that would tell you if that's where the problem is or not.

The flip mirror is held in position by a spring clip. It is relatively easy to tweak it to provide more tension. You would need to remove the back cover to gain access, and this will not alter collimation, unless you shift the collimation screws that are revealed.

Again, a thorough read of Weasner's ETX site is a good idea.

Hope you sort it, Ed.

[RT65CB-SWL]

I have had the back of my ETX105 modified* last year by a local engineering company near my home as it did have a drop (from about sixteen inches) two years ago when it fell of my sofa onto the carpet when I was cleaning the OTA. The rear cell took most of the impact, cracked the plastic casing and damaged one of the mounting points. :)

* I will add some photos at a later date.

Note to self: telescope OTA's don't bounce.