16" Dream Astrograph - Filtered Air System Technology (FAST)

On the previous page we discussed the many benefits of Dream's FAST. We will go over a few of the reasons why Dream has developed such a system to deal with the thermal issues inside the Optical Support Structure (OSS).

Knocking down (but not eliminating) the boundary layer, that thermal gradient layer just above the optical surface, is proven to reduce mirror seeing. Unfortunately this merely acts as a Band-Aid, covering up the real problem. It is the internal heat within the optic that is causing the issues at the boundary layer. But internal temperature gradients within the optic itself are also causing a separate problem in non-zero-expansion glass types; Pyrex, Borofloat 33, etc. Internal temperature gradients distort the figure of the optic. For a 16" optic that is 2" thick, a 1C internal gradient will distort the figure of that optic by roughly 1/3rd wave (~183nm of distortion). This is why knocking down the boundary layer is not enough. The figure distortion will persist until the optic is approximately +0.1C or less from ambient temperatures.
Even a thin monolithic mirror, which is substantially more difficult to support without causing cell-induced astigmatism (yet another form of figure-robbing), takes a substantial amount of time to "equalize" when compared to Dream Cellular's engineered lightweight mirrors. Dream Cellular's mirrors have an independently tested CTE that is 23% lower than Pyrex, Borofloat 33, etc.

Dream has never masked the problem. We have always dealt with it directly.

Dream's use of FAST, since 2003, provides numerous benefits, especially when combined with Dream Cellular's engineered lightweight mirrors. This same system originated in a 10" f5 telescope. The extensive use of CF and CFSC to produce incredibly stiff, lightweight support structures that very closely match the Coefficient of Thermal Expansion (CTE) of the optics means that Dream's telescopes are at the pinnacle of performance.

Dream is the only company in the world utilizing FAST. Dream is also the only company in the world offering a standard optical instrument that utilizes engineered lightweight mirror blanks for both the primary and secondary mirrors. This combination produces unrivaled speed in equalization of the optics and ultimate performance.

Click either image to see examples of the quality inherent in Dream's telescopes.

Each instrument is fully tested under the stars prior to shipping.





pricing, availability and specifications subject to change without notice