Telescope Reviews: The apochromatic H-bomb has finally exploded!

Thank you all for your congratulations, guys.

However, we didn't succeed on 100%! We were able to exceed the 0.95 energy concentration like Schott did it earlier (but for much smaller sizes). Before actual serial manufacturing, we really need to see how these remaining 5% of energy are distributed around the image when observing, for example, planets and brightest stars. If all will be OK with under the real sky tests, then we will announce this and start to take orders. If the remained 5% of light energy are (scattered light) will behave poorly, then we will need to take care about this. But how long this will take we don't know now.

I need to clarify what do I mean.

Imagine, for a minute, that our objective does concentrate all incoming enerly perfectly - perfect diffraction picture - Airy disk and surrounded diffraction rings of decreasing brightness. Airy disk in this perfect case has intensity of 1. If the optical system is not perfect, then Airy disk has lower than 1 intensity, say, 0.9 (or 0.95 as in our case). Remaning 0.1 (or 10%) of energy are redistributed around the Airy disk. These 10% of energy are mostly in diffraction rings closest to the Airy disk. This cause widening of a so called Point Spread Function (PSF) and decreasing of image contrast at middle and high spatial frequencies. In the case of planetary observing this mean lowering of details contrast and their detectability.

Let speak about two objectives - one is a standard apochromat and second is an apochromat with a DOE (diffraction optical element). First one has polychromatic (summarizes across visible spectrum) Strehl factor (relative Airy disk intensity) 0.85 and second one (with DOE) has polychromatic Strehl 0.92.
It is obviously, that second objective has less scattered energy and narrower PSF and should deliver sharper and more contrasty planetary images than first objective.
However... one important for amateur astronomers thing: we know well where these 0.15 of energy are distributed - in the closest (to Airy disk) diffraction rings. In the case of diffraction APO (APO-D) scattered 0.08 of enery are distributed absolutely differently - more or less uniformly around Airy disk and much far from it.
In other words in these two cases we see two different pictures:

1. Standard apochromat shows an Airy disk with relative (to ideal) brightness of 0.85, surrounded by diffraction rings of increased (in compare to ideal case) brightness.

2. APO-D shows an Airy disk with relative (to ideal) brightness of 0.92, surrounded by diffraction rings of almost normal (to ideal case) brightness and very wide circle of scattered light which consists 0.03 of energy.

Second one is better for resolution and planetary details detectability. First one is aesthetically more pleasant and more habitually looking.

We saw these both cases in the laboratory (on a very bright lamp string), but nobody seen real stars and planets in such a way.

Now we need to make a working sell for objective, finish the tube, install the objective in the tube and see how the objects on a real sky look through such a telescope - APO-D.