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[milielba]

I am a new member and new to astronomy. I have a Celestron C6-N that I purchased new last new. I have been reading about collimation and how important it is. The problem that I am having is this: The directions that came with the collimation eyepiece are pretty vague and what I see through the eyepiece hole differs from the pictures provided. It seems as if the focuser is not square to the tube. I do not want to start taking things apart until I have talked to someone or have someone show me the proper way to do it. From the reading I have done, shipping can be pretty harsh on a scope. Any help highly appreciated. Clear Skies
Mike

[Chicago Astronomer - Astro Joe]

Hi Mike,

Thanks for your membership and your first post on the Chicago Astronomer.

Collimation, in my opinion, is probably the most frustrating and difficult part of amateur astronomy. My tube always gets bumped around, and with all the public sessions it goes through, gets out of whack quite often. Most of the time I just accept what it gives me, but at least a couple times a year it goes through a thorough collimation.

This looks like the the scope that you mentioned. It's a fine scope and will provide decent views of the heavens. Good seeing depends on how the mirrors in our scopes play with each other, and when they don't, things degrade. Let's see what's going on:

It seems as if the focuser is not square to the tube.

It sounds like the secondary mirror on the "spider vane" is not aligned to the focuser tube and main/primary mirror.

I think yours will look like the one on the left

Near the open end of the main tube, are three silver adjustment knobs. These apply tension to the spider vane holding the secondary mirror. It should be an elongated hole where the adjustment knob seats into. Loosen these just a little bit, and while looking down the focuser move each loosened adjustment knob within the travel of it's hole.

Here we are looking down the main tube of my reflector. You can see the secondary mirror on the central spider vane. Along the outside top rim of the tube, you can see the three adjustment arms protrude through the tube with knobs on the outside.

While looking down the focuser tube without an eyepiece, look at your eyeball in the mirror. Try to move these adjustment knobs to a point where the focuser tube and secondary mirror make equal concentric circles - like the second image shown above. It will take some time to get all three adjustment knobs just right. Tighten them down finger tight. If the holes are not elongated then you will need to loosen one screw while tightening the others.

After this is accomplished, then you can use your collimation eyepiece to finalize the alignment of the secondary to the focuser/primary mirror. I doubt that your primary mirror needs adjustment, but that is another procedure!...

Instead of attempting to rewrite the total collimation procedures, it will be more efficient to visit and learn from those who have already written well about it.

There are a number of on-line step-by-step collimation sites and here are good ones with images among the many out there:

One of the best is from Sky & Telescope:

skyandtelescope.com/printable/howto/scopes/article_790.asp

www.fpi-protostar.com/collim.htm

homepage.ntlworld.com/robin.scagell/collimate.html

www.schlatter.org/Dad/Astronomy/collimate.htm

I have a laser collimation tool, but I find that my own hand & eye techniques provide a better adjustment and sharper image.

This is just a starting point for you Mike, and if you get stuck, just drop us a line here and we will get you aligned!...

[milielba]

Thanks for the information. I am going to give it try tonight and hope the haze clears.
Mike

[ripps1]

Here's a good video showing the collimation procedure:

[ftp]http://www.andysshotglass.com/Collimating.html[/ftp]

There are, however, two things I would add to the video:

1) Secondary mirror rotation - The secondary mirror should appear to be a
perfect circle when viewed through the focuser. If it appears elliptical, it
needs to be rotated until it does appear circular.

2) This is mearly a helpful hint for first-time collimators who are often
confused when looking at the multiple reflections during collimation. When
adjusting the position & rotation of the secondary it's helpful to block the
reflection of the primary mirror. Loosely wadded newspaper placed in the
tube between the secondary mirror and the primary mirror works good. Also
holding a white sheet of paper behind the secondary mirror assembly
(opposite the focuser) makes the assembly stick out like a sore thumb.

Rip

[Chicago Astronomer - Astro Joe]

Dennis,

Pictures are more helpful than text, and movies are even more instructional. I remember watching this awhile back and found it quite helpful.

Thank you for the link as it it easy to follow and a great reference.