Is there any sight tube or collimation eyepiece that will work on a SC? thanks.
SC collimation
Started by cbator, 01/16/2003 01:14PM
Posted 01/16/2003 01:14PM
Opening Post
Posted 01/17/2003 04:11PM
#2
Hi:
NO. Using a sight tube or other newtonian style collimatin device on an SCT is a recipe for miscollimation. There are two ways to do it: get a laser designed for an SCT (ala' Kendrick's) or collimate using the diffraction rings of a slightly out of focus star. There are a couple of "collimation eyepieces" designed to help you determine whether the rings are concentric, but they are not necessary. Keep in mind, too, that the lasers require you to do a "manual" collimation on a star, real or artificial first, before you can use them.
Peace,
Rod
NO. Using a sight tube or other newtonian style collimatin device on an SCT is a recipe for miscollimation. There are two ways to do it: get a laser designed for an SCT (ala' Kendrick's) or collimate using the diffraction rings of a slightly out of focus star. There are a couple of "collimation eyepieces" designed to help you determine whether the rings are concentric, but they are not necessary. Keep in mind, too, that the lasers require you to do a "manual" collimation on a star, real or artificial first, before you can use them.
Peace,
Rod
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Posted 01/17/2003 05:33PM
#3
Chris,
Try this!
Focus Jupiter at high power 500/600x, straight thru without diagonal. Get the best focus you can! If your SC is slightly miscollimated, you will note a blue/green ghost halo off to one side of the planet. Adjust your secondary collimation, using very very small screw adjustment, until there is no sign of that halo anywhere along the limb of the planet. You will note the drastic improvement in resolution immediately. It is absolutely not necessary to fine tune your collimation on a star. I can collimate on the limb edge of the moon! Other friends have used Jupiter and/or Saturn. It is a much easier way to go. If you read about people collimating their telescopes on the net using the defocused star method, the comment I most often hear, is that the seeing wasn't good enough to do a good collimation. If you do use a star, the secret is to defocus a tiny bit only, and note if there is a light projection off to one side. Collimate to get rid of this projection. The tiny black spot should be dead centered in the star.
As I mentioned previously, you can collimate using a Hartmanns mask, and doing so isn't so "seeing" limited. The technique involves taping off one hole in the mask and then rotating the mask around the ota, tightening and loosening the collimation screws in conjunction with the mask. To involved to fully describe here..but the information is available on the net.
Try this!
Focus Jupiter at high power 500/600x, straight thru without diagonal. Get the best focus you can! If your SC is slightly miscollimated, you will note a blue/green ghost halo off to one side of the planet. Adjust your secondary collimation, using very very small screw adjustment, until there is no sign of that halo anywhere along the limb of the planet. You will note the drastic improvement in resolution immediately. It is absolutely not necessary to fine tune your collimation on a star. I can collimate on the limb edge of the moon! Other friends have used Jupiter and/or Saturn. It is a much easier way to go. If you read about people collimating their telescopes on the net using the defocused star method, the comment I most often hear, is that the seeing wasn't good enough to do a good collimation. If you do use a star, the secret is to defocus a tiny bit only, and note if there is a light projection off to one side. Collimate to get rid of this projection. The tiny black spot should be dead centered in the star.
As I mentioned previously, you can collimate using a Hartmanns mask, and doing so isn't so "seeing" limited. The technique involves taping off one hole in the mask and then rotating the mask around the ota, tightening and loosening the collimation screws in conjunction with the mask. To involved to fully describe here..but the information is available on the net.
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