Celestron EdgeHD 11"

Worth knowing before you buy

How long does the EdgeHD 11 take to cool down and reach thermal equilibrium?

The EdgeHD takes significantly longer to cool than standard SCTs due to its sealed baffle tube with optical elements at both ends. Multiple owners report 3-4 hours for full thermal equilibrium in winter conditions, compared to about 1-2 hours for non-Edge SCTs.

Why do my star images look fuzzy or mushy even with good collimation?

Thermal issues from the sealed tube design are the primary culprit—trapped heat inside the baffle creates distortion for hours even after cooling time. Atmospheric seeing conditions also mask optical quality; you may be seeing the atmosphere rather than diffraction limits.

Is the EdgeHD really better than a standard C8 or C11 for visual observing?

The EdgeHD delivers sharper stars across the entire field of view due to its coma-corrected design, particularly at the edge of the field where standard SCTs degrade significantly. However, this advantage only manifests under good seeing conditions and proper thermal equilibrium; on poor nights the difference disappears.

Should I use the 1.25" or 2" visual back for visual observing?

Back focus distance is less critical for visual than for imaging, so both work acceptably. However, using a 2" shorty diagonal with the 1.

Can I fix thermal and cooling issues with active cooling fans?

Aftermarket fans like the TEMPest system from Deep Space Products are available and help somewhat by moving trapped air in the rear cell, but they do not dramatically solve the fundamental thermal lag of the sealed baffle design. Wrapping with multiple layers of Reflectix bubble wrap and simply allowing longer cool-down time are more effective strategies than active cooling alone.

Will the EdgeHD outperform my refractor on planets and the Moon?

Yes—under good seeing and proper thermal equilibrium, the EdgeHD delivers superior planetary and lunar views compared to similarly sized apochromatic refractors due to higher contrast, better splitting of doubles, and more light-gathering. However, this requires patience for cooling and favorable atmospheric conditions; on typical nights the advantage may not be obvious.