How to collimate a Nexstar 8se

[kenpresley]

Ok, this is all on me. Recently got a Celestron 8se which was very precise. Everything looked good. But since i had purchased Bob's knobs for the Dobs i have had, I got some for the 8se also. Now it appears I have screwed it all up. Last night (the first clear night we have had in weeks) I could not see much of anything. Even Jupiter was blobby.
Do I use a normal collimator? Laser collimator? Play with it at night until I see clearly?
Should I take the Bob's knobs off and put the original screws back in?
Any help or video links are appreciated.
Thanks folks!
ken

[chicagorandy]

IF it's OK to post a link to another forum from 2013?

https://www.cloudynights.com/topic/4042 ... telescope/

There are also a few youtube vids on the subject

[Ozman]

Put the scope on a fairly bright star. Many times we use Polaris because it doesn't drift out of view, but as your scope is tracking, any brighter star will do.

Defocus the star into a small doughnut shape. You will notice that the doughnut is not concentric and stretched to a side if the scope needs collimating. You can determine which collimation screw needs adjusting by holding a rod like a pencil across the front of the corrector plate from the edge to the center (like the hand of a clock) but be careful not to touch the corrector plate. You will see the shadow of the rod, when it is centered with the stretched area of the doughnut pay attention to the position of the rod. If it is close to an adjustment screw, that one needs adjusting. If it is in between adjustment screws, the one on the opposite side needs adjusting.

Adjustments need to be made by very slightly backing off the other two first (to give adjustment room) and then slightly tightening the one needing adjusting. Make VERY small adjustments and do not pinch the optics (over tighten), if you notice the stretching is getting worse, work back the other way. It is not hard, but it can be tedious. Once the doughnut is concentric on both sides of focus, the scope is collimated.

[JayTee]

Hi Ken,

Make a Duncan Mask from the lid of a recently delivered pizza box lid (a GREASELESS lid) and use that. It takes about 20 minutes to make and then another 20 minutes to use to get back into near perfect collimation. Always do a star test afterward (that whole de-focus routine that Ozman just described above) to sanity check your collimation.
http://alpha-lyrae.co.uk/2013/12/31/sch ... ncan-mask/

I use a Duncan Mask to collimate all my SCTs.

Cheers,
JT

[kenpresley]

IF it's OK to post a link to another forum from 2013?
https://www.cloudynights.com/topic/4042 ... telescope/

Randy, wanted to follow up after I got a chance to work on this. Finally had a clear night, some time (and patience) and used this link you provided: http://www.starrynights.us/Articles/Collimation.htm

Once I figured out all the instructions related to viewing the scope from the front (not the eyepiece) end, it worked well. I now have my telescope back in working order.

Thank you my friend!
Peace and clear skies
ken

[Tim456]

Glad to hear you are back in business. For future reference, it is also worth reading through https://astromart.com/reviews-and-artic ... cumstances.

[Gulf Coast Guy]

Try this. https://garyseronik.com/no-tools-telescope-collimation/ It was written for newts but the priciples apply to SCTs. I use it on my Meade LXD 75 8". Pretty quick and easy to master.

GCG

[Graeme1858]

Here's another one for STCs:



Just posted by Dylan O'Donnell

Regards

Graeme