Cheap webcam just for secondary alignment

[Robculm]

Despite many attempts at collimation, I still don't think I'm quite there. I've used a combination of Cheshire & laser pointer. Blocked out the primary to get the secondary centred in the focus tube etc & all looks good, except I;m really not convinced I;m getting the rotation of the secondary correct. It's very difficult to see when it's exactly circular.

I downloaded ALS Collimation aid, which provides a circle on your computer screen, but of course I need to view down the focus tube with a camera.

Ha, yes, of course that's what we always do when we're imaging! But unless I'm doing something stupid (or unless perhaps I just am stupid 🤔), that won't give me an image of the secondary. I also tried the guide camera, but didn't seem to work either, again because neither has a lens, just sensor I assume).

So, am I correct in thinking I need some kind of webcam, with built in lens?

If so, can anyone recomend something really cheap, as I only want to use it for this purpose!

Cheers,

Rob

[CraigT82]

You can get a meteor lens for your guide camera which will allow you to view the secondary. As long as no part of the lens is wider than the 1.25" section of the camera you're good to go.

I have this one from modern astronomy. https://www.modernastronomy.com/shop/accessories/qhy-accessories/meteor-lens-for-qhy5-ii-series-cameras/

You will need to ensure what whichever lens you buy (there are a few different ones) has a thread that is compatible with your camera.

 

 

[Spile]

I would not obsess about the secondary. I use the Cheshire eyepiece and sight tube combination tool and am happy when I can see it is circular,  and all three clips are equidistant. If it is cloudy and you have time on your hands, take a photo through your sight tube and post it here.