Shortened 130P - Focuser, collimation or normal?

[John78]

So yesterday I decapitated my 130P tube by 18mm and moved the primary up so that I could reach focus with my Olympus EM-5 - that worked OK but the images seem soft - it was starting to get slightly foggy when I took this disappointing shot of the moon at the best focus I could achieve...

The focuser is bad, it leans badly as you wind the knob - see video...  

 

That obviously is going to have to get fixed - any tips on how to do that?

Then finally this morning I videoed a Pigeon about 30 meters away from indoors - is the focus drifting in and out because the tube is warm and indoors - in effect a seeing type artifact or is there something wrong with my image train (other than the focuser) because of my modification to the move the mirror?

 

 

Thanks for any pointers!

[happy-kat]

Have you collimated it since you reassembled?

[John78]

I tried, but it was my first ever attempt - its been foggy so have not been able to star test it yet.

[goose35]

There are 2 small grubscrews one eitherside of the lock knob. Under these is a shim so teak the screws to reduse /remove the slop

[goose35]

While youre messin with that it may be worth a strip down to clean the tar grease and regrease as i did last week. So much better.

[John78]

What is the recommended new grease?  I agree that the supplied stuff isnt very good!

One of the grub screws is missing from my shim (the one nearest the tube) I will replace, and re-test.

[goose35]

Different views on this but i ise a teflon grease from halfords just because i had some around from doing cyles

[John78]

I bought some teflon grease from the local bike shop - fetching red colour, we do have some molykote greases at work which are probably more suitable but for now its back together and no more slop with the missing grub screw replaced - what's more its possible to focus the images now, and they are sharp so maybe my effort at collimation wasn't a disaster...

 

[Mick J]

You seem to be on track with this,          sorry - you know 

[Andy Mitchell]

You may only have about 15cm worth of "depth of field" in which you will be in reasoable focus, and it looks like that tree is blowing about quite a bit.

Getting focus spot on with telescopes is supringly hard, you need such tiiny movements. Don't know your camera, but in general ,the best bet is to zoom in the live view and pixel peek. That should work in the day but can be quite useless at night if your camera isn't super duper sensitive. Assuming you are collimated OK you should be able to get very sharp, at least in the centre. Do you have a coma corrector? You may get away without one on a small sensor camera as coma increases with distance from the centre of the image circle.