Collimating Secondary Mirror Question

[bigfish]

Hello Everyone,
I think I'm finally starting to understand collimation!
I bought a laser collimator today and after watching a couple of videos the procedure seems pretty straight forward.
One of the videos I watched said the secondary mirror needed to be centered first or the laser would not work or it would give false results. After watching the whole video it made perfect sense. He used a webcam to look down the focus tube to center the secondary mirror then used the laser to do the primary mirror.
Question: Is there a lens I can mount on my ASI183 pro that would let me focus on the secondary mirror? I see two lenses on the ZWO website but there are no clear descriptions of what they do.
Thanks!
Bill

[Lady Fraktor]

Just use a simple collimation cap to square the secondary. Much easier.
Have you ever read this?: http://www.astro-baby.com/astrobaby/hel ... reflector/
One of the best references available.

[pakarinen]

Haven't seen manicured nails stripping down a focuser before. LOL. It does look like a useful site. I'll have to read her blog.

[Piet Le Roux]

If the secondary appears completely round and in the middle of the focus tube it is centred but the laser will not be reflecting of the centre of the mirror. The secondary of my Obsession is marked on its offset position (they supply a template to do it with) the top section of the OTA also has a mark with which you line the focuser up before you install the secondary mirror. After you have installed the secondary you position it till the laser is on its offset mark. This only needs to be checked once a year. After that is done you only have to adjust the secondary mirror until your laser is hitting the centre of the primary, then you adjust the primary until the reflected beam is returning to the centre of the laser. I have a white ring around the laser hole and the inside of the laser hole has been blacken. So my normal collimation consists of inserting the 2" laser in the eyepiece holder, adjusting the three adjusters on the secondary to centre the laser on the primary, lying down and adjust the three adjusters on the primary till minimum reflected light is visible when looking at the laser. I have to do this every time I assemble the scope.

[GCoyote]

One of the club members who taught me how to do collimation said if your primary mirror does not come with a center mark for alignment, it's worth the time to take it out and out and mark the center with a sharpie. Once you do that, laser collimation is super fast. Of course you still need to center the secondary mirror but aligning it and the primary are then just a matter of getting the laser spot on the centering dot and then making the final adjustment to the primary. We did my beat up second hand newt' in about five minutes.

[Lady Fraktor]

Having the secondary is key though, if it is not you can still align the primary but the telescope will not be collimated properly even though the laser says it is.