Collimation....again!

[rikyuu]

I've read quite a few things about collimation so far and recently settled on using small hole in a lens cap to centre the secondary and then a laser collimator to do the primary as this enables me to adjust the scope by myself. I read many things saying the laser is not the best way and even when it's pointed at the centre of the circle and reflection is aligned into the target in the collimator, that even a fraction of a degree out will ruin everything! This seems to pale into insignificance though when you factor in movement in the focuser and collimator/eyepieces depending on how they are fixed into the eyepiece holder. There can be quite a lot of slop, moving the laser a good 5mm off the primary centre dot and off it's target.

I was wondering therefore, when using a camera (or an eyepiece), is it usual to perform a final star collimation with the camera fitted in place, with all it's adapters etc? The weight of the camera alone at various scope angles seems to affect how it fits into the eypiece holder. I found the other night that the 'out of focus star' showed the secondary shadow to be quite a bit off centre and when bringing into focus it was a bit elongated. I presume I did the right thing therefore, by recollimating to get it all central again, but just wanted to check it was normal practise.

Thanks

[kniclander]

Rikyuu, maybe I misunderstand you but in my experience a "star test" is only to confirm whether your scope is collimated or not. It is very difficult (in my experience) to actually collimate based on a star test and it is impossible to do it on your own (ie adjust collimation based on star patterns that you see).

tbh, when you start off in this great hobby, you wonder why some scopes cost 100 quid and some cost thousands. Then, when you use a cheap scope, you realise its limitations - it seems to me that you are finding the limitation of your scope early on. Having said that, in a small reflector (which I assume you have) visually you aren't going to see any difference between a scope that is well collimated and one that's a bit off - there's actually quite a big margin of error unless your scope is very fast (ie F5 or less). I suspect likewise if you are imaging but I have never imaged so I may be wrong.

Don,t get obsessed with colllimation unless you want to be an optical technician and not an astronomer

[kniclander]

rikyuu, sorry I just noticed you have a 10" F4.7 newt so scrub most of my comments above :oops: :oops: :oops:

oops

[rikyuu]

I wasn't going to say anything !! But thanks for your comments. ps. I usually do the star test with the camera attached so I can view the image in the monitor, which makes it quite easy. I think I'm doing the right thing tweaking it, otherwise my stars are mishapen. If I put the laser back in, it's usually off, but jiggling it around can make it all line up so I presume it's just what ever position the camera, adapters and focuser have settled in.