SCT Collmination

[Starman73]

Hello All,

I have an old classic Meade LX200 10" tube on a Skywatcher EQ6 Pro mount. I have never collminated the optics of the scope. From what I can tell the image the scope produces seems to be clear enough to me, and I have defocused a star and the rings produced seem to be central. I have had the scope in the car while I have driven over dirt roads in the past.

I am going to be getting into astrophotography soon so I want the scope to produce the best images possible. I am not the most mechanically minded person out there so I don't want to go and start playing around with the collmination especially if I muck it up when I had no need to.

Thanks for your help.

Paul

[bmitchell82 (Brendan)]

de focused star to see diffraction rings or the airy disks is the best and only way to do it. In saying that if you don't know what your doing. don't touch it. good luck

[toc (Tim)]

SCT collimation is pretty straightforward - there are a few good tutorials that will help.

I like good old Rod Mollise's guide http://skywatch.brainiac.com/collimation.pdf- this guy really knows his SCT's

Its really worth spending time getting it as right as you can - I was very surprised how much more detail you can eek out of mars, the moon, and Saturn when the scope is spot on

If you haven't already got them, I would recommend some 'bobs knobs' - these make life a lot easier. http://www.bobsknobs.com/

Thing I love about SCTs, is just how easy they are to collimate, and how long the collimation seems to hold.

[casstony]

The only bad thing you could do (if you were really dopey) is unscrew the collimation screws a few turns so that the secondary mirror falls out of it's holder. Short of this, if you somehow got lost doing a collimation the people at Bintel would have it sorted out again within a few minutes - so there's nothing to be scared of.

After ordering bob's knobs, get used to what the mirror reflections look like from various distances in front of the ota (looking in through the corrector in daylight from 6 to 12 feet away). You could turn one screw 1/8 of a turn to see the change in the reflections, then turn it back. Instructions come with bobs knobs telling you how to re-center the various reflections to acheive rough collimation.

Then follow one of the guides for collimating on a star.

Or, if it already looks good on a defocused star at high magnification you could leave it be

[browndog (Ian)]

Hi Paul

The following link has some information on collimation and how to do it.
http://legault.perso.sfr.fr/collim.html

I purchased some 'Bob's knobs' and have found them to be very simple to install and use. I have found that my SCT seems to keep its collimation for a long time. I usually only need to 'tweek-it' about every 12-months or so.

[AlexN]

I always used a defocused star with my C11.. Collimating the SCT is a no brainer.. It usually takes between 3 and 7 minutes to go from a fairly poor alignment to spot on collimation. The trick is to get it looking right in a 40mm EP, then get it right in a 20mm ep, then in a 10mm... Once its perfect in a 10mm EP, for a camera, it will be spot on..

A note - If you plan on using the SCT for photography, then do your collimation in the same configuration.. For example, with my SCT, I used to have a moonlite focuser with the 6.3 reducer inserted inside the focuser. I would image with the camera seated squarely in the focuser with no diagonal, no other bits and pieces. So collimation is performed the same way.. Having the diagonal in for collimation is a recipe for disaster. if the diagonal is not perfectly collimated, then your scopes collimation will not be perfect... Collimate the scope for imaging, without a diagonal!

Good luck with it mate.

[Starman73]

Hello Everyone,

Thank you so much for your help everybody. I will have a look and give it a go see if I have to do a collmination. It sounds fairly easy if I do need to. I guess the benifits of doing it will definitely outweight the negatives and there is always Bintel .

I will keep you all informed.

Paul

[AlexN]

Good luck mate.. The C11 was the first telescope I ever attempted to collimate and was so incredibly happy once I did it.. The image quality was amazing once it was done...

The beauty is that once its done, you may not need to do it again for months... I did the C11 twice in the time I owned it.. the second time was because I had installed bobs knobs collimation bolts.

[Paul Haese]

Paul SCT collimation seems more daunting than it really is. Follow Rods tutorial and you will be fine. Small adjustments is best. Owning a newtonian or SCT collimation is a must to learn. Once learnt it is quite simple to check and work on.