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Collimation of LX200R 10 inch OTA


Before and after

After several years using a LX200GPS 12" in altaz mode, I now have a 10" LX200R OTA mounted on an AP Mach1 mount.

Here are two different zones of an image near M42. 1 minute image, ST8XME at bin 1x1, f 10.

Left image is before collimation and right image after collimation.

Collimation of the LX200R OTA (No diagonal used):

The issue with that OTA is that the images on the left were taken AFTER collimating the OTA !!!

... but ...

... what I did is collimate accurately in the Out focus position... and it turns out that in the In focus position, the collimation is then way off ....

Images on the right were taken after I collimated to a level where Out focus is slightly decollimated (top is pinched) and the In focus is slightly decollimated (bottom is then pinched).

The end result is satisfactory (see image below, 70 minutes of H alpha data at bin 1x1 (NGC2359).

I have read several posts on the internet about this issue and wonder what causes that behaviour...

Same night image of NGC 2359 at H alpha wavelength: