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Viewing through the Collimation cap

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#26 Vic Menard

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Posted 12 October 2018 - 07:13 PM

...That was great advice, Vic. Those steps seem to have helped me make some progress. How does it look now? 

A little better. You actually applied a bit too much correction--but we may be able to use it.

 

If you think it through, the secondary mirror tilt adjustment screw (green circle) moved the primary mirror center spot toward the primary mirror (green arrow). If you find the secondary mirror tilt adjustment screw between the two spider vanes at 12 and 3 o'clock (red circle) and turn it the same direction, it should move the center spot closer to the center (red arrow). You should also see the spider vane end attachment at 12 o'clock disappear. You'll know you're very close when the spider vanes all look the same and the bright primary mirror reflection appears "centered" in the secondary mirror. If you rack the focuser out a bit, it should make the bright primary mirror reflection look larger in the secondary mirror, which will make it easier for you to see the alignment improvement.

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#27 Vic Menard

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Posted 12 October 2018 - 07:19 PM

And to clarify--the secondary mirror tilt adjustment screws I'm talking about are located behind the secondary mirror (not the primary mirror like the circles I provided might seem to indicate). The circles show where the screws are located relative to the front aperture of the OTA.


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#28 Vic Menard

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Posted 12 October 2018 - 09:15 PM

...You need to tilt the far end of the secondary mirror (the end closest to the primary mirror) away from the focuser side of the OTA. This will bring the primary mirror center spot into the center of the field of view...

I got a PM from Jason who caught my mistake--to bring the center spot into the center of the field of view you need to tilt the far end of the secondary mirror toward the focuser side of the OTA--push the cross hairs, not the center spot...

 

My apologies, although the OP seems to have found the right direction on his own! That's what I get for being in a hurry. Fridays!


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#29 SteveG

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Posted 14 October 2018 - 01:33 PM

That's the last thing I want. Thanks for the heads up.

 

 

I can't seem to make it any better than the following picture (I can't spot much offset from my original position tbh). The spider vane end attachment has been stubborn. Another thing I noticed is that whatever adjustments I make, I'm unable to get the last spider vane attachment into the view (the one opposite to the stubborn one).

 

attachicon.gif 2.jpg

Just so you're clear, collimation is not done by adjusting spider vanes. The vanes should be very tight, and perfectly straight across, with the center exactly in the center of your optical tube.



#30 druhela

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Posted 14 October 2018 - 02:06 PM

Thanks guys for all the help! I'm quite near perfect collimation, if I'm not wrong. But I'm running with what I have for now. Star tested on Capella, and it doesn't seem all that bad. I've got the whole process in theory. Have also come to the conclusion that it's really hard to make the adjustments of the secondary accurately without using a pointing tool. So I'm going to acquire a cheshire+sight tube combo tool soon. Once I do, will attempt another collimation and post pictures on this thread for you guys to see how that looks.

Edited by druhela, 14 October 2018 - 02:07 PM.

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