Collimating a dob

[michaelg]

Hi all

i have just collimated my 10" dob by using Crosshair Cheshire eyepiece i did it by adjusting the screws at the base of the scope until the crosshair lined up perfectly in the centre of the donut.

my question is when watching this being done on YouTube they used a laser collimator and started by adjusting the small mirror with Allen keys then finished by lining up the laser with the screws on the base.

i did not touch the small mirror or adjust it with Allen keys I just aligned my Cheshire with the screws on the base have I done it correct ?

[bingevader]

You'd usually adjust the secondary mirror as well (usually first) and might repeat the process 2^o - 1^o - 2^o - 1^o until your sure you've got everything as closely aligned as possible.

Having said that, you might find that you don't need to align the secondary much anyway, I didn't last time I did mine.

As with most things, it all depends on how accurate you want to be and how happy you are with the images you are seeing.

To be honest, I don't tend to do mine very often anyway!

Cheers

[Scooot]

Probably. Once the secondary mirror is aligned you shouldn't really have to adjust it often. If you can see all the primary mirror clips when you look straight down the focuser then the secondary is aligned with the focuser and primary mirror. Once this has been done I just tweak the primary, like you have, when necessary. So it depends whether your secondary mirror has been aligned before and whether it is aligned or not.

[MorningMajor]

The secondary doesn't tend to need doing that often as long as it's correct in the first place!

Check out Astro Baby's guide here

Good luck

[michaelg]

Can I align the secondary with my Cheshire eyepiece if so how do I do it

thanks

[scarp15]

I am still fairly new to collimating myself however, for aligning the secondary you need to be able to (just) see the three primary mirror clips, when peeping through the cheshire eyepiece. I find that I can use my cheshire collimator for this, others prefer to make a collimating cap to make seeing the clips a bit easier. Perform this task prior to collimating the primary. Some people, myself included find doing this easier by replacing the secondary screws with bobs knobs.