Don Pensack's Article on Collimation

[themadgaffler]

"Here is the same view with a slightly smaller secondary in the view to emphasize the lack of concentricity of the secondary mirror reflection’s outline to the other images. The dot is centered, and the sight tube’s crosshairs are removed to make it clearer that the crosshairs do not cross the image of the secondary reflection in exactly the same way as the reflected spider vanes. This is a slight exaggeration of the appearance through the focuser in the “New Model” collimation (more on that later), but serves to illustrate the secondary’s outline does not appear concentric in a properly collimated telescope."

This is the answer to the question I have been wondering about for a few cloudy nights now. The image illustrates exactly what I see in through my collimnation cap. Haven't had a clear night to star test yet. Thank you for posting.

[sammiefields22]

Wow, thanks a lot for the tutorial, this will really come in handy for my Dob. I was quite scared about the whole collimmation thing, so I did some research. According to this review on the skyquest xt8 - Orion SkyQuest XT8 Classic Dobsonian Telescope Review - there's even a whole section on there titled "Do I Need to Worry About Collimmation?", apparently the OTA comes fully collimmated by the manufacturer.

I had some trouble getting a proper image at first, so I consulted a friend who knows a little more than I do. he told me it wasn't collimmated. I'm gona give it a shot now and see how it goes.

Thanks again for the guide.

[andyp180]

that is one hell of an artical on collimation!!
so in depth and precise.
thanks for the link to it.i've now added it to my
favourites list.
clear skies,
andy

[70charger500]

Wow, that is a fantastic tutorial, thank you all for putting that up here (and keeping it up all this time!)

Off to give it a try.