SCT collimation

[Martyn87]

So as of yet, I've not got round to buying any tools for collimating my SCT, and have only really had chance to properly check it last night with some clear skies. I get that a bahtinov mask of some description is recommended to help with this, but as I don't have one yet, I figured I'd just do a quick star test. It looks pretty even and the obstruction from the secondary seems centered, but I was expecting more concentric rings. Have I just gone too far out of focus? 

 

[alan potts]

Looks decent to me, maybe come back a bit. Out of focus star was all I ever did with my Meade 12 inch and I felt the results from it were always good.

Alan

[Cosmic Geoff]

All you really need is a star test (e.g. on Polaris) and look for asymmetric rings when in focus. Make small adjustments of the secondary screws and check if you are making it better or worse.  If it is badly out of collimation you would know...

[Mr Spock]

You don't need collimation tools for an SCT. Star test is the way to go. What you have looks fine. Next is to fine tune with an in focus star at high power - seeing permitting. You should have an airy disc with a concentric and evenly lit diffraction ring.

[Martyn87]

Thanks for the responses all. Pretty happy with how it is considering I don't think it's ever been collimated since it left the factory, and it must be at least a couple of years old at this point. I guess it's holding pretty well! I think I'll just leave it alone until I'm ready to start imaging properly, don't want to make it worse! 

 

Meant to add, this was on vega last night, about the brightest star I can see from where I am at the moment. 

Edited June 13 by Martyn87

[Mr Spock]

SCTs are very stable. I had a C9.25 which hardly ever needed adjustment.

[dweller25]

3 hours ago, Martyn87 said:

So as of yet, I've not got round to buying any tools for collimating my SCT, and have only really had chance to properly check it last night with some clear skies. I get that a bahtinov mask of some description is recommended to help with this, but as I don't have one yet, I figured I'd just do a quick star test. It looks pretty even and the obstruction from the secondary seems centered, but I was expecting more concentric rings. Have I just gone too far out of focus? 

 

That is OK but too out of focus and has not cooled down enough to confirm accurate collimation.

As others have said use a high power at perfect focus and fully cooled to judge collimation.