Altair Astro Wave Series 115 ED triplet APO

[spudlet]

Spudlet, test results look good.

Are these taken with the reducer in place?

No reducer or flattener. Just the scope and my camera. I'm cheap

[Dougie]

Doug - do you get the same-off centre effects without the flattener?

Francis, without the Flattener I get elongated stars in all four corners with the M26C. This means that the flattener is doing it's job, so is it the OA which is causing the problem in one corner?

[fwm891]

Hi Doug, Sorry for the late reply.

Are the star elongations all the same or does the problem corner have longer/shorter star images?

If they are all exactly the same without the flattener then I would look at the centring of the reducer as being the problem.

If the elongations are worse in the problem corner then I would look at the centring of the main optics.

You may have to overlay one image on top of the other to assess these which will mean rescaling one to match the other.

That would be my approach at this stage to try and identify which part of the optical train is causing the problem.

Hope that helps

[Dougie]

Francis

I would say they are the same length, but at slightly different angles.

On my next test, I'm going to remove the IDAS filter from the image train, to see if this is the culprit.

[fwm891]

Sounds like a plan

[fwm891]

I've added an update to this but put it here:

Similar format

[Dougie]

Terry at SX has tested my M26C on his Tak 106 and sent me an image with no elongated stars.

This has now ruled out the CCD window.

Ian King is now looking into this for me.