Getting a MMOAG to work

[gregbradley]

I bought a MMOAG some time ago to use with my ST402ME.
A fairly common setup.

However after going through a wall of adapters I could not get the ST402 to come to focus with the MMOAG.

Last week I was able to get stars to come to focus but that was a different setup - the TEC180 and reducer. So the setup obviously has a large impact on it.

I believe there are some here who are using the MMOAG successfully and I'd love some advice.

At this stage I think I need the negative lens for it.
I have various adapters so it is also probably a spacing problem. But it seems a long way from going into focus not just a bit with the Planewave CDK and FLI PL16803.

Greg.

[Bassnut (Fred)]

Are you sure you actually have a star showing, out of focus, or just nothing?.

[rally]

Greg,

The setup has everything to do with it - but nothing unusual about a MMOAG not coming to focus !

You just need to make sure that the metalback distance from your focusser to the image plane (or field flattener in the case of some refractors if one is in use) of the optical path is the same for the CCD camera as it is to guide camera.

Work it out on paper first before buying or messing around with adapters and lenses.

The Tak 1.25" EP holders will actually screw into the MMOAG, thereby yielding a shorter path in lieu of the Oasis helical focusser supplier.

Cheers

Rally

[gregbradley]

Originally Posted by Bassnut

Are you sure you actually have a star showing, out of focus, or just nothing?.

Yes that was my first thought - maybe there is no star there.
So I slewed to the moon and got a really big bright blur.

I then tried other areas and I would get a large round halo which looks like a super out of focus star which would shrink slightly when the cam was moved further out. But it needed to be out (it appeared - I could have it wrong) a long long way, like 100mm which can't be right.

Greg.

[gregbradley]

Originally Posted by rally

Greg,

The setup has everything to do with it - but nothing unusual about a MMOAG not coming to focus !

You just need to make sure that the metalback distance from your focusser to the image plane (or field flattener in the case of some refractors if one is in use) of the optical path is the same for the CCD camera as it is to guide camera.

Work it out on paper first before buying or messing around with adapters and lenses.

The Tak 1.25" EP holders will actually screw into the MMOAG, thereby yielding a shorter path in lieu of the Oasis helical focusser supplier.

Cheers

Rally

Thank you for the clear advice. I have talked to Don before and it got very confusing with several possible adapters depending on the setup.
Good to know the Tak eyepiece holder works.I'll see if I have one of those.

I'll get out a ruler and measure it all up.

Cheers,

Greg.