Collimation yet again.

[nowayjose256]

Sorry to keep harping on about this collimation thing but it's starting to drive me nuts.

OCD Starting ???

Just received my Cheshire this morning and again was very surprised to see how far off it showed me that I was when using the end cap process which in itself showed me far how out my laser was.

I would tend to believe the Cheshire this time also checking with a star test, assuming I ever again see the sky in cloudy Glasgow.

So just to confirm I'm starting to understand this.

Centred the secondary in the tube, adjusted the secondary to aligned the doughnut on the primary with the tube crosshairs and finally adjusted the primary screws to bring the image of the cheshire in to the centre.

This went back and forth a few times to narrow it all down.

Does that all sound about right?.

The only strange thing was I had to offset the spider vanes to centre the secondary. I thought it should have been centred.

You have all been a great help to this newcomer and again, sorry for the basic questions.

Cheers

[umadog]

That sounds right. I guess if your focuser is tilted then you may have to offset the secondary. Star test it and you're good to go.

[nowayjose256]

Thanks for that.

I didn't think to check the alignment of the focuser but will do some other rainy day.

Cheers.

[umadog]

BTW, by "offset" I'm assuming you mean left/right as viewed from the focuser. Note that another situation where you may have had to do this if you have tilted the secondary a lot in trying to adjust it. A large amount of tilt may well move the secondary substantially to the left or right.

[Tinker1947]

I think you need to center the secondary by using the spider vanes, then use the secondary center screw and the 3 adjusting screws to line it up with the focus tube, then with the paper circle on the primary...i used a large set of dividers to get the secondary center screw as near to the middle as i could, took a bit of time but its a one off, as it shouldn't move once set properly

[Zachariah]

I just used a cap and then did a star test, looks ok so I leve well alone!

[nowayjose256]

Sorry, by offset I meant from top to bottom as viewed through the focuser.

Oh and the scope is a explorer 200P.

Left to right I managed by adjusting the centre screw in the secondary holder.

After everything looked ok I noticed that the secondary apeared too near the top through the cheshire and all I could think off was to adjust the spider to correct this. This didn't feel right as I thought the first step was to centre the spider vanes.

Still everything looks OK and I'll check the focuser is square with the tube. This may be causing this spider offset.

Thanks for your help.