2,519 Brands 483 Categories All Departments

Is collimation the answer?

Need our opinion on a telescope Optics Planet has on sale, go ahead and ask! Post some hints and tips on various telescope brands and configuration.

Is collimation the answer?

Postby mr130mph on Tue Oct 12, 2010 2:36 pm

I have a Zhumell eyepiece and filter kit. The 32mm EP is perfect, absolutely a 10+. My problem, if using the 12.5 EP I have difficulty finding anything and with the 6 and 4mm EP's all I see is black. I have collimated the 'scope but am not sure what the problem might be. Any suggestions?
Thanks, Mike
Posts: 1
Joined: Tue Oct 12, 2010 12:12 pm

Re: Is collimation the answer?

Postby Jne_K on Wed Oct 13, 2010 8:11 am


Collimation will improve image clarity by correcting optical aberrations from improper mirror alignment, but it will have no affect on image brightness. That is a function of the magnification/eyepiece you are using and your telescope's aperture.

What size scope do you have? A basic law of optics is that image brightness drops as magnification goes up, which it is when you use the 6 mm and, especially the 4 mm. In other words, it is perfectly normal for things to get darker as eyepiece focal length gets shorter. The only way to compensate for this loss of light is to go to a scope with a larger mirror or objective lens. In a small telescope, though, things get dark in a hurry, since small mirrors or objectives don't transmit enough light to support higher magnifications, In other words, a small telescope can't support as much magnification as a large telescope and, if you have a small scope, that 4 mm and 6 mm eyepiece may be too much. Don't overdo on magnification - the number one beginner's mistake in astronomy. SeeTen Top Telescope Eyepiece Questions.

Then, too, you field of view is also pinching down, drastically, when you go from your 32 mm (low power) to your 4 mm (high power eyepiece). If you did not center the object you wish to see, perfectly, in the center of the 32 mm eyepiece field of view, it will not be visible when you switch to the 6 mm or 4 mm. That is quite a drastic jump in magnification. Your finder scope will really have to be exactly adjusted, too, at such magnifications, but always start out at lower magnifications and work your way up when trying to locate objects. You may also want to see my article, Telescope FAQsas how to set up your telescope
Thanks for posting with us
Joanie K - Your personal optics expert


Phone: (800) 504-5897
Fax: (847) 919-3003
Site Admin
Posts: 7665
Joined: Wed Sep 24, 2003 3:09 pm