13028HNT Collimation

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Armin Lukas avatar
Hi,

I recently purchased the OCAL for collimation for my Sharpstar 13028. During collimation I noticed I can not get the secondary mirror a perfect sircle while maintaining a concentric circle of the reflection of the primary mirror. The secondary mirror keeps being an oval shape.
Is there a way to fix this?






Can the collimation be improved? Or is there anything i missed?
Thanks!
Reg Pratt avatar
As long as the reflection of the primary mirror is fully visible and centered under the focuser you're fine. Your collimation looks good you just need to tip the secondary slightly. As an added check you can make another circle and size it to be a little smaller than the body of the OCAL inside the focuser. If that is also concentric you're good to go. If it isn't, your primary mirror spot may not be placed well and won't be a good reference to use for collimation.
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Esteban Pineda avatar
Thats because your secondary is oblicuous. It's well centered with your focuser and primary mirror, but you'll get distorted images on 2 corners.
Leonardo Landi avatar
As far as I know, the illuminated circle in newt scopes matches the primary mirror reflection. So if it's well centered and fully visible in the focuser tube, you will be ok. Please do not use the center mark to center it, but use the OCAL body. Create a new circle a little bit larger or smaller and collimate the primary mirror with it. If you read the OCAL manual, they discourage the use of the "eye" of thecamera too, because it's not precisely centered with the body (that's why you need calibration codes). I found several scopes with uncentered mark. In SW scopes they missed the right spot by 7-10mm.
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Andy avatar
Struggling with this now with my 130hnt. What does a star test look like ?
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