Refractor / Focuser Collimation

[samtheeagle]

I grabbed some quick flats with my new C80ED-R first thing this morning before work, and using the free trial of CCDInpector I was presented with the following flat analysis...

As you can see, the alignment is clearly way out of whack I'm hoping that it's just the focuser that needs adjusting, as I don't think this scope has a collimatible lens cell.

So trying to get my head around what the analysis shows... The '+' mark is the centre of the image, and the 'X' is the brightest point? So to get the two to align is the target, so I need to adjust the focuser so the draw tube angles down inside the scope more? I think that images is saying the the focuser is effectively looking up inside the tube rather that along it.

And yes, the stock focuser is famously poo, and I should replace it with a moonlite etc., but for now I have no money, so I just want to get this thing sorted out

Cheers.

[John]

I use a simple cheshire eyepiece to check my refractor collimation following this approach:

Refractor Collimation

With no objective cell collimation adjustment your main method of correction would be to tilt the focusser to better align it with the optical axis. If you have heavy stuff hanging off the backend of the focusser that can cause "drooping".

[samtheeagle]

Thanks John, I saw one of your posts with that link. I'll have to try the instructions about using a laser collimator, I sold my cheshire a while back.

[John]

Thanks John, I saw one of your posts with that link. I'll have to try the instructions about using a laser collimator, I sold my cheshire a while back.

I'd reccommend getting a cheshire for this if you can - too much room for error with a laser IMHO. I use a really cheap plastic cheshire like this one:

Rigel Rigel 1.25" Cheshire Eyepiece