Astrochonum

This time the LX90, at least it's primary mirror, volunteered for the phase contraste test. As it is a spherical mirror (i.e. no spherical aberration at the radius of curvature), i used my most fine and sensible plate : D 1.8 and 0.3mm width. The 1.8 gave better results than the 1.4 or the 2.1.

It's clean !

I did also the full telescope (Plate+secondary+primary). But the light decomes scarce, a the focus point changes the result depending which optical component you're imaging.

I'm just back from Imagine Optic where i was trained to use my incoming Shack Hartmann wavefront analyser. My FS60 was one of the guinea pigs.

Thanks to the Haso, the telescope was tested on it's best optical axis. I say best for the two lenses of the doublet aren't perflectly aligned -which is impossible- so the axis is somewhat a compromise.

Thanks to this, we could make a measurement keeping all the off axis Aberrations.


L/23 RMS, L/5.5 PTV. Strehl 0.926

To compare with the Bath previous results, we removed the 3rd order Coma and Astig.

Haso :


That's L/46 RMS, L/9 PTV and Strehl at 0.951.

Bath :


RMS L/40,5 at 635nm, up to L/41.5 at 650nm (Haso's source was 650nm).

Overall difference between the Bath and the Haso is a mere 15,6-14= 1,6 nm. That's quite amazing !

Here is a small  video that shows the measurement speed and the stability of the Haso.

This test is much more stringent than for the Orion Optics that has been tested previously. With the same protocol as for the OO, nothing shown up. I had to close the slit and take a narrower phase constrast blade to get some defaults. That shows that i need some qualification protocol. Airylab will acquire an adjustable slit some Newport and i just bought a densitometer from Gretag.

The Foucault shows no defect.

With the phase constrast, nothing to be seen with the bare eye. The pictures shows a couple of scratches of no incidence, and some low level bounces. Nevertheless the polishing has been very good, that confirms the star test that gives a very clean diffusion free Airy figure.

No Bath test due to the central hole.

I tested a one year old Orion Optics mirror with the Lyot test and a Foucault to check the surface aspect.

First contrast test, then the Foucault.

Comparaison between the Bath and the Zygo wavefront :