[gregbradley]

I have had it happen a few times now that dovetail fittings with grub screws to tighten and hold it have not been fully seated. The FLI cameras have a dovetail at the front for mounting, the MMOAG has one both front and back and so does the Atlas focuser.

So I smeared a small amount of Teflon grease on them and they feel a lot better when engaging.

I think sometimes little dings from past tightened grubs screws can cause a slight catch and the dovetail does not slip into a fully engaged position. This can cause the camera to not be square to the scope or perhaps slip a tad when the scope is pointing fully up and go out of focus.

I had a large number of subs get wrecked the other night by exactly that. About 20 or more 10 minute subs had one side out of focus and had to be trashed.

I thought I would pass the observation on. A little bit of misalignment you can get away with at F8 or F7 but at F3.8 you can't get away with anything.

Greg.