This large format field flattener is designed to work with the Altair Astro 102mm, 115mm and 130mm F7 EDT Triplet APOs, and has an M48 rear conical adapter for connecting your DSLR or CCD camera. It is compatible with 35mm format CCD chips, utilising about 95% of the field. The flattener works best at F7 with about a half F stop tolerance. The flattener screws into the rear focuser rotator of your Altair EDT APO, converting it into an astrograph with a flatter photographic field.
Focuser compatibility for direct-threaded attachment:
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Fits the new 2014 2.5" Rack 'n Pinion focuser on the 2014 Altair Wave Series refractors by means of an adapter (Product code: PLANOS-3-1.0-M48-RP25-ADAPT) which is ordered in the dropdown menu opposite. Simply remove the self-centering adapter and screw the adapter into the focuser body, then screw the flattener into the adapter.
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Fits the standard 3" Crayford Focuser on the pre-2014 Altair Wave Series refractors directly - remove the 2" pushfit assembly and screw it in.
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Fits the standard 3" Crayford Focuser on the Starwave 80, 102 and 110mm ED Doublet refractors - remove the 2" pushfit assembly and screw it in.
All triplet APOs (and arguably all telescopes) have some amount of field curvature. The field curvature of the Altair Wave Series refractors is amongst the lowes on the market however for larger DSLR camera sensors, some correction is required for the flattest possible field. To see the benefit, we've uploaded an Altair Planostar field flattener test image taken with a 35mm full frame DSLR by UK professional photographer Francis Milsom - you can also click on the product gallery to see this and more images showing flattener performance.
Altair PlanoStar Field Flattener specification:
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The 3" PlanoStar field flattener corrects for field curvature without altering the focal length of the telescope.
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2x FMC lens elements when combined with the front triplet lens system, produce a 5-element optical system with excellent colour correction.
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High quality multi-coatings on all surfaces ensure maximum transmission and almost zero reflections. These coatings are so efficient, the flattener lenses are almost invisible at first glance.
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The flattener is threaded directly to your focuser (or via an adapter) for optimum rigidity. Simply remove the 2" pushfit assembly from your focuser, and screw the flattener into the rear of the focuser.
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For 35mm DSLR chips, the conical adapter with M48 rear aperture reduces Vignetting to almost undetectable levels - compared to a T-Thread connection which causes some vignetting.
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The optimum distance from the rear flat shoulder (excluding the m48 thread) of the flattener to the CCD chip in your camera is 51.5mm, however tests indicate that the flattener is very tolerant either side of this distance and you can probably work with a 5mm tolerance, if not more. The smaller your CCD chip, the more tolerance you have to work with and some customers with small chips are working 10mm outwards with no issues.
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DSLR cameras and spacers: To connect a DSLR you need the Canon/Nikon M48 DSLR Adapter (available separately in the associated products below). The DSLR adapter adds about 10mm to the light path. The ideal distance to CCD sensor from the rear of the conical adapter flat shoulder excluding the M48 thread is 51.5mm. Here are two examples:
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Example Canon EOS DSLR with M48 adapter: The Special Altair DSLR adapter adds 7mm to the light path, the EOS backfocus is 44mm. That's 54mm total minus the 51.5 ideal spacing which leaves 2.5mm. This is within 5mm tolerance.
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Example Nikon F mount DSLR with M48 adapter: The generic Skywatcher Nikon DSLR adapter adds 8.5mm to the light path, and the Nikon backfocus is 46.5mm. That's 56.5mm total. 51.5mm ideal spacing minus 55mm = 3.5mm so this is within 5mm tolerance.
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CCD cameras and spacers: It's possible to fine tune the spacing between your CCD camera or DSLR chip by using the Altair variable M48 and fixed M48 spacers. We recommend buying the Altair M48 spacers as a set to use in various combinations to get the ideal backfocus when you use your CCD equipment. If you subtract the light path distance taken up by your camera from the ideal spacing of 51.5mm from the rear thread shoulder of the conical adapter.