The 'Black Chrome' Ronchi Screen 

 

 

The Series IV 'Stiletto'  Professional Edition and Deluxe Model .incorporate a very specialized laboratory-grade ronchi grating to achieve high resolution focusing while minimizing  loss of light from the source.  The result is that the photographer is able to focus directly on much dimmer stars than with  standard ronchi gratings.  The ultra high resolution of the 'Black Chrome' screen also compensates for changes in depth of field at very low f/ratios guaranteeing perfect focus even for very fast refractors and CCD imagers with f/3.3 focal reducers.    This is accomplished by etching the ronchi screen directly on photo-quality soda lime float glass that is .5mm thick. The ruling pattern itself is vacuum deposited Low Reflection  Black Chrome with a minimum 3%-R at 600 nm light.  This computerized chemical process results in extremely crisp bar edges and bars that appear darker and  more highly visible when focusing.  The ronchi ruling itself is 300 lines per inch consisting of line/space widths of .00167" +/- 0.00010" .  The 'Black Chrome' screen is truly a state-of-the-art component  and the heart of the Series IV Professional Edition.  It is well worth the small additional investment for those serious about astrophotography.

 

"I finally had a few clear nights here for some imaging, so I went on a tear and got quite a few nice images. It was easy to focus with the Stiletto IV and the new screen, even at 3.3. I tested the Stiletto against diffraction spikes and are far as I can tell, you calibrated it perfectly! " - Rob Bensko    ( MX7 )