190mm f/6 StarFire CS (190CS)
Brand : Astro-Physics
Price TBA
- SKU:
- 190CS
- Availability:
- Refer to Availability tab below
Description and Design Goals
Introducing the 190mm f/6 StarFire Christen Superachromat (190CS). Starting with a clean sheet of paper, we researched back to the 1800s looking at the brilliant formulations Carl Friedrich Gauss developed to eliminate spherochromatism - the last frontier to achieving optical perfection. After years of development and testing, the result is the new CS Christen Superachromat; optimized as a high resolution, high contrast imaging platform that can only be achieved with a refractor. This new design combines near-perfectly corrected optics in a compact, fast aperture, large diameter instrument.
FEATURES
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Diffraction-limited polychromat telescope. Exceptional sharpness and contrast for both imaging and visual use.
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Highly light efficient multi-layer coatings. >93% strehl across the entire photo-visual spectrum, peak strehl 99.8%, approximately 1/30th wave.
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f/6 focal ratio is the ideal aperture for the small pixel CMOS chips, delivering the best combination of resolution and imaging speed.
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Compact, lightweight tube assembly is a delight to handle and manage.
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Silky smooth 3.5” Astro-Physics Focuser with a greaseless drawtube and Starlight Instruments Feather Touch 9:1 Micro dual-speed mechanism. Compatible with autofocus systems from Starlight Instruments, Optec, and others.
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Rotating Doveloc circular dovetail system enables you to easily frame your photos for optimal artistic composition.
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Fully retractable, felt-lined dew shield with thumbscrew fastener.
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Field Flattener included.
Imaging Performance at f/6 with Flattener, 60mm Image Circle
Polychromatic Strehl Ratio for Imaging Wavelengths
Strehl Ratio measures the lens correction on-axis to show how well the colors of the visual spectrum are focused across the wavelength range. Best correction occurs at 555nm to match the peak visual acuity of the human eye. Eye response falls off to 2% in the deep red and violet ends of the spectrum. The correction level of the 190 lens design exceeds 1/10 wave for all colors in the visual wavelengths.
RMS Spot Radius Over a 60mm Diameter Field
Theoretical Ray Trace Performance over 60mm Image Circle
Actual Diffraction Performance over 60mm Image Circle
Although the spot sizes are usually given for performance comparisons, the actual smallest spot diameter will be limited by diffraction. The Airy Disc size for an F6 lens is approximately 8 microns as shown below.
This diagram shows the expected star shapes over the field as well as for 0.1 and 0.2mm defocus.
Longitudinal Spherical Correction
This graph shows the color correction as well as the spherical correction of all the wavelengths in the visual range. The closer together the color curves are the lower will be the chromatic aberration of the lens. The straighter the lines are from the on-axis point (0% Pupil Radius) to the outer diameter of the lens (100% Pupil Radius) the higher will be the spherical correction for each color.
The 190CS f/6 uses a Gauss derived optical design where each color from deep red to deep violet has less than 1/40 wave P-V of spherical error. To get that kind of correction in a normal triplet lens, even with a Fluorite element, requires a much greater focal ratio in a 190mm aperture. Wide airspaced triplets can be made to have very high polychromatic spherical correction at faster focal ratios, but the large air spaces can cause thermal cool-down issues. The 190CS f/6 has relatively small air spaces and comes to thermal equilibrium in a normal manner.
Specifications
| Lens Design | 3 element Christen Superachromat |
| Target Application | Optimized for high-resolution medium-field imaging, can also be used visually |
| Color Correction | Extends from near IR to the violet edge of the visible spectrum |
| Clear Aperture | 190mm |
| Focal Length | 1140mm (Backfocus 180mm) |
| Focal Ratio | f/6.0 |
| Image Circle | 3 element f/6 field flattener covers 64mm image circle |
| Theoretical Resolution | 0.59 arc seconds |
| Coatings | Multi-layer, broadband, overall transmission greater than 93% across all visible wavelengths, greater than 99.8% at peak |
| Magnification Range | 30x to 700x |
| Tube Assembly | Cream white, 8” diameter, machined aluminum tube, fully baffled, flat black interior, engraved retaining ring. |
| Focuser Type | 3.5” I.D. Focuser, rack and pinion, 9:1 dual-speed reduction, 4.5” (114mm) travel, 7.3" (185mm) backfocus. Focuser drawtube features millimeter focusing scale. 2.7", 2” and 1.25” adapters included. |
| Telescope Length | ~1016mm (50") with dew shield fully retracted and adapters removed. Add 1.5" with visual adapters in focuser drawtube. |
| Diameter of Dew Shield | 8.99" (228.3) O.D, retractable. Internal thread of 8.916 x 28 |
| Weight with Dew Shield | ~39 lbs. (17.7 kg) |
| Carrying case | TBA |
| Production |
Each telescope is individually produced, assembled, |
Specifications subject to change without notice as details are finalized. The pictured scope is the prototype.
What's Included?
- Tube Assembly with Astro-Physics 3.5" Focuser, Dew Shield and Dustcap
- Flat Field Corrector
- 2.7", 2" and 1.25" Adapters
- Carrying Case
Items That You Will Need For Your Scope
- 8.0" Mounting Rings (80RING)
Accessories to Consider
- 10 x 60 Vario-Finder/Guidescope with Quick Release Guider Bracket (1060GUIDE)
- Handle with Dovetail Slot for Guidescope and Finder Brackets, PICQRM2 & STARFMD (QRHANDLE)
- MaxBright 2" Mirror Diagonal (PMDMAX)
- 2" Advanced Convertible Barlow (BARADV)
- Baader Mark V Binocular Viewer (BPMARKVS)
- Baader Cool-Ceramic Safety Herschel Prism (BPHERP)
- Kendrick Dew Remover Premier Heater (KDR006)
- Solar Filter options, all feature Baader Planetarium AstroSolar SafetyFilm, Density 5-Visual
- Baader AstroSolar Filters (ASTF-180), Diameter of filter material: 180mm
- Baader AstroSolar Film (AS50A4). 200mm x 290mm (7.9"x11.4") sheet to make your own filter. Instructions included.
- Baader AstroSolar Film (AS50HM). 500mm x 1000mm (19.7" x 39.4") sheet to make multiple filters, Instructions included.
Availability
Spring 2025 Update
The 190mmCS is not available for ordering and there is currently no available notification list.
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