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Secondary mirror collomation woes

the big o

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the big o

the big o

Posted
Posted

Hi all,

Whilst attempting to collomate my skywatcher 150p dob I feel I may have made an error. Although the primary mirror looks collomated the centre point does not hit the cross hairs of my cheshire collimator which appears slightly to the left of the centre "sweet spot".where am I going wrong?

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itmo

itmo

Posted
Posted

collimation is an iterative process. Also when you are learning, it pays to just do it again and again, quite quickly you will get the hang of it. Read astrobaby's guide and other guides on the net and dont be afraid. One thing the guides dont often mention is the fact that secondary mriror rotation and tilt can intermix to create errors which are difficult to diagnose for beginners. so make sure your mirror is level and unrotated when you start. 

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Accident!!

Accident!!

Posted
Posted

Hi,

I'm also new to the whole armature astronomy thing. Got my first telescope (Celestron Astromaster 130EQ) last November. Obviously when I got it neither of the mirrors where aligned correctly.  I therefore proceeded to make things worse by "fiddling" with the screws on both the primary and secondary mirrors. 

After a few minutes of making my telescope totally unusable, I decided to buy a laser collimator. When thus arrived I couldn't wait to get things sorted. However, I was very disappointed, he laser tool didn't help much. Obviously there was a lot more to this alignment process than I'd assumed.

I therefore trawled the NET looking for information regarding the collimation process. This is the information I collated from several sources (I'm sorry, I no longer have the links):

  1. Place the laser collimator into the eye-peice and turn it on.
  2. Look down the main tube at the primary mirror.
  3. Adjust the secondary mirror so that the "red dot" is hitting the center mark (if there is a mark, or by eye if there is not) on the primary mirror.
  4. Remove the laser collimator.
  5. Drill a 2mm hole through an old eye-piece dust cap (make sure it's dead center).
  6. Place this dust cap into the focuser (without any lenses) and secure it with the securing screws.
  7. Look through the drilled hole. You should see an image of the secondary mirror. It will probably be off center.
  8. Adjust the primary mirror until you see the image of the secondary mirror centered within the image.
  9. Remove the dust cap with the drilled hole, and replace the laser collimator in the eye-piece.
  10. Now fine tune the secondary mirror until the red dot hits the center of the collimator target.
  11. You should be done. 

(The primary mirror on my telescope does not have a center mark, so I roughly judged where it should be and aligned the red dot with that imaginary point. The notes that I picked up from the NET showed the application of a "ring binder sticky hole support) to the center point or the primary mirror, but I didn't want to take my mirror out, so I guessed)

It took me about 2 weeks to get this information together, but only 10 minutes to correctly (I'm assuming) collimate my telescope. I now no longer get any ghosting on the image, and everything looks to be pin sharp.

Obviously, I'm very much still a newbie at all of this and may have gotten all of this wrong, so please correct me if this is the case.

Kind regards

Carl

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wookie1965

wookie1965

Posted
Posted

Hi,

I'm also new to the whole armature astronomy thing. Got my first telescope (Celestron Astromaster 130EQ) last November. Obviously when I got it neither of the mirrors where aligned correctly.  I therefore proceeded to make things worse by "fiddling" with the screws on both the primary and secondary mirrors. 

After a few minutes of making my telescope totally unusable, I decided to buy a laser collimator. When thus arrived I couldn't wait to get things sorted. However, I was very disappointed, he laser tool didn't help much. Obviously there was a lot more to this alignment process than I'd assumed.

I therefore trawled the NET looking for information regarding the collimation process. This is the information I collated from several sources (I'm sorry, I no longer have the links):

  1. Place the laser collimator into the eye-peice and turn it on.
  2. Look down the main tube at the primary mirror.
  3. Adjust the secondary mirror so that the "red dot" is hitting the center mark (if there is a mark, or by eye if there is not) on the primary mirror.
  4. Remove the laser collimator.
  5. Drill a 2mm hole through an old eye-piece dust cap (make sure it's dead center).
  6. Place this dust cap into the focuser (without any lenses) and secure it with the securing screws.
  7. Look through the drilled hole. You should see an image of the secondary mirror. It will probably be off center.
  8. Adjust the primary mirror until you see the image of the secondary mirror centered within the image.
  9. Remove the dust cap with the drilled hole, and replace the laser collimator in the eye-piece.
  10. Now fine tune the secondary mirror until the red dot hits the center of the collimator target.
  11. You should be done. 

(The primary mirror on my telescope does not have a center mark, so I roughly judged where it should be and aligned the red dot with that imaginary point. The notes that I picked up from the NET showed the application of a "ring binder sticky hole support) to the center point or the primary mirror, but I didn't want to take my mirror out, so I guessed)

It took me about 2 weeks to get this information together, but only 10 minutes to correctly (I'm assuming) collimate my telescope. I now no longer get any ghosting on the image, and everything looks to be pin sharp.

Obviously, I'm very much still a newbie at all of this and may have gotten all of this wrong, so please correct me if this is the case.

Kind regards

Carl

Just dont get a cheap laser that may need collimating itself.

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Accident!!

Accident!!

Posted
Posted

Thanks wookie1965. I did buy a "cheap" laser, and then read all of the posts regarding the possible issues with such a device. I was therefore pleasantly surprised when I did the "roll test" and found the laser to be bang on center. I guess I was lucky.

"If everything went smoothly, you'd never learn anything  :grin:"

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wookie1965

wookie1965

Posted
Posted

i give up! anyone want to but a telescope?

Dont give up collimation is like riding a bike once you have learned to do it you will wonder what all the fuss was about have a good read of the links i posted for you take your time and do the steps slowly. If you do have to adjust your secondary once you have done this you will not have to touch it again unless you really bang or drop the scope, the primary is very easy to collimate after will take 2 minutes.

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wookie1965

wookie1965

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Posted

Your primary could be too far up the tube but then your primary might need a tweak i couldnt tell unless i looked through a Cheshire dont panic just leave it a lone thats what i did and then come back to it fresh i used the first link not astrobabys with the coloured card that will give you a good idea if your secondary is right.

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Accident!!

Accident!!

Posted
Posted

Yes. Don't give up. As wookie stated, when you finally work it out, it's simple. I found the link I used. This gave some very good and simple steps that I could understand and follow:

http://www.skyandtelescope.com/howto/diy/3306876.html

I'd spend a few weeks with a telescope that was unusable, until I came across this article. With that in hand, it took me approx 30 minutes to work through it and get the job done. Having done it once, I'm sure that it would only take me a few minutes to repeat.

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bambuko

bambuko

Posted
Posted

Biggest problem with collimation of secondary is not actually understanding what's happening but the design of the ****** thing.

Starting with adjustment screws biting/digging into secondary body (easily solved with a bit of DIY, I know, but I am sure not making it any easier for the unwary beginners).

Than the worst - three adjustment screws, which when loosened allow the secondary not only to rotate around the centre spring loaded screw, but also drop/float freely any which way it feels.

It is un-neccesarily complicated (and primitive at the same time).

There are certainly a lot better designs - here is one, and here another one.

Unfortunately none of this helps a beginner faced with the job of collimating secondary.

Of course majority of amateur astronomers are no necessarily into DIY/ATM and have to make do with what they buy :embarrassed:

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BritAngler

BritAngler

Posted
Posted

There are three essential things a beginner needs when attempting to collimate a telescope for the very first time. These are shown below but please note that cheaper tools might not work as good and could even lead to personal injury.....

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Charic

Charic

Posted
Posted

Hi all,

Whilst attempting to collomate my skywatcher 150p dob I feel I may have made an error. Although the primary mirror looks collomated the centre point does not hit the cross hairs of my cheshire collimator which appears slightly to the left of the centre "sweet spot".where am I going wrong?

You can only learn from errors if that's the case. I've sent you a tube link that demonstrates the simple way of collimating. Watch it and see if there's any help there. Then maybe try your cross-hairs again?

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