Focal Reducers / Correctors Archives - Modern Astronomy

TeleVue Paracorr Type 2

Bernard Karpinski — Mon, 18 Mar 2024 20:04:26 +0000

TeleVue Paracorr Type 2

An optical chain is only as good as its weakest link. With the development of 82 degree Nagler and 100+ degree Ethos eyepieces, Tele Vue offers the largest, flattest and best corrected visual fields in the industry. Combine the Nagler/Ethos revolution, Dobsonian revolution and Paracorr for the ideal mating for spectacular wide and sharp “spacewalk” observing.

Life without the TeleVue Paracorr Type 2

Coma makes stars look like blurry comets whose tails point out radially from the center of the field. The faster your scope’s speed, the worse the effect. All parabolic mirrors used in Newtonian reflecting telescopes are limited in field sharpness due to coma. Even a perfectly made 13″ f/4.5 parabola has only about 0.1 degree diffraction limited field.

Previous attempts to correct for coma have been limited in usefulness. Some correctors were designed mainly for astrophotography, some required difficult installation in the focuser’s draw tube. Dedicated coma correcting eyepieces were another approach. However, these were limited to 50 degree apparent fields and would orphan your existing eyepiece collection.

Life with the TeleVue Paracorr Type 2

Paracorr is a universal corrector that tightens and intensifies star images on all f-ratios down to f/3! (see spot size graphs: PDF or JPG) without adding any false color or spherical aberration! You no longer have to constantly shift a Dobsonian to keep objects centered for sharp viewing. Using a Tele Vue eyepiece, put M-13 at the edge of the field and enjoy fully resolving its beauty as it drifts across your view.

Paracorr is easy to use. It slips into your focuser, just like a Barlow. To minimize focuser in-travel, due to additional length, a mild 15% Barlow effect was designed into Paracorr to effectively push the focus out. Paracorr is recommended for use with all Tele Vue eyepieces because our Plössls, Delites, Panoptics, Naglers, Ethos and Delos eyepieces achieve higher levels of aberration correction than competitive models. However, Paracorr is also compatible with other eyepiece makes.

Try Paracorr on your “DobNewt.” We think you’ll agree that the revolution is complete.

Paracorr Eats Coma

Paracorr can be used with both 2″ and 1¼” eyepieces. For visual use, slip Paracorr Type-2 into your focuser like a Barlow lens, and your eyepiece into Paracorr. 1¼” eyepieces will make use of Paracorr’s special low profile 1¼” reducing adapter. Paracorr is threaded for 2″ filters.

SIPS

Note: The Paracorr Type 2 optical assembly is also available in a special adapter housing made by Starlight Instruments for their Feather Touch focusers. This unit avoids the need for a tunable top to optimize eyepiece position. Some Dobsonian manufacturers may also offer the Feather Touch focuser with integrated Paracorr type 2 as standard. Starlight Instruments offers Paracorr Type 2 integrated with Feather Touch focuser or as an add-on if you already have a Feather Touch focuser.

Astrophotography

Paracorr also works with DSLR and CCD cameras. Just unscrew the lens assembly from the Tunable Top and attach appropriate threaded accessory tubes and camera mounts. See 2″ Imaging (Paracorr Type-2), 3″ Imaging (3″ BIG Paracorr Type-2), and “is” adapter for 3″ (3″ BIG Paracorr Type-2) sections for more on Paracorr imaging.

History and How to Choose

Tele Vue’s two-part blog post on the Paracorr Type-2 is a must-read for any Dobsonian / Newtonian user!

In Part 1 they cover the history of the Newtonian reflector, its inherent aberrations, and how Tele Vue’s Paracorr enlarged the “sweet spot” of fast Newtonian / Dobsonians to cover the entire field. We also pitted the Paracorr — Newtonian combination against more “exotic” telescope designs for imaging.
The Part 2 post answers the follow-up question: Which Paracorr to Use? We focus on the three currently available versions of the Type-2 Paracorr: 2″ Photo/Visual, 2″ Starlight Instruments SIPS, and 3″ Paracorr Type-2 for imaging. They all have their own strengths. This post also has links to many sources to help you decide what Paracorr is best for your usage.

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0.77X REDUCER/FLATTENER FOR ESPRIT-120ED

Bernard Karpinski — Thu, 06 May 2021 12:16:05 +0000

0.77X Reducer/Flattener for Esprit-120ED

Designed specifically for the Sky-Watcher Esprit-120 ED Apo Refractor, the new three-lens 0.77X Reducer/Flattener for Esprit-120ED comes with a standard adaptor with M48 thread edge and 55mm back focus for use with Sky-Watcher’s M48 Canon EOS (code 20237) and Nikon (code 20238) adaptor rings. After removing the adaptor, an M71x1 internal thread with maximum 75mm back focus is available for self-made adaptor solutions. The Reducer/Flattener produces a fully illuminated and corrected image circle of 36mm diameter and is therefore perfectly suitable for image formats up to APS-C but can also be used for full format.

0.77x Focal Reducer / Field Flattener
Effectively reduces Focal Ratio of Esprit-120ED to f/5.4
Three-Lens Fully Multi-Coated Optical Design
Image Circle 34mm
Full Frame Compatible
2-Inch Filter Compatible
75mm Back Focus or 55mm with supplied adaptor
M48 x 0.75 Adaptor
Weight 910g (with end caps)

The 0.77X REDUCER/FLATTENER FOR ESPRIT-150ED is also available here

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0.77X REDUCER/FLATTENER FOR ESPRIT-150ED

Bernard Karpinski — Thu, 06 May 2021 11:17:07 +0000

0.77X REDUCER/FLATTENER FOR ESPRIT-150ED

Designed specifically for the Sky-Watcher Esprit-150 ED Apo Refractor, the new three-lens 0.77X Reducer/Flattener for Esprit-150ED comes with a standard adaptor with M48 thread edge and 55mm back focus for use with Sky-Watcher’s M48 Canon EOS (code 20237) and Nikon (code 20238) adaptor rings. After removing the adaptor, an M71x1 internal thread with maximum 75mm back focus is available for self-made adaptor solutions. The Reducer/Flattener produces a fully illuminated and corrected image circle of 36mm diameter and is therefore perfectly suitable for image formats up to APS-C but can also be used effectively with full frame cameras.

0.77x Focal Reducer / Field Flattener
Effectively reduces Focal Ratio of Esprit-150ED to f/5.4
Three-Lens Fully Multi-Coated Optical Design
Image Circle 36mm
Full Frame Compatible
2-Inch Filter Compatible
75mm Back Focus or 55mm with supplied adaptor
M48 x 0.75 Adaptor
Weight 910g (with end caps)

The 0.77X REDUCER/FLATTENER FOR ESPRIT-120ED is available here

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SkyWatcher f4 Aplanatic Super Coma Corrector

Bernard Karpinski — Thu, 25 Jun 2020 12:00:55 +0000

The SkyWatcher f4 Aplanatic Super Coma Corrector is Optimised for f4 imaging Newtonians and delivers stunning wide-field views with pinpoint stars to the edge of the flat field. Magnification remains unaltered. Features a 4 x element design with one element made from FPL51 ED glass. Requires 55mm back focus. Image height 28mm. Outside diameter 50.8mm. A suitable M48 x 0.75mm adaptor is required to match your Canon or Nikon camera.

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Meade F6.3 Reducer

Bernard Karpinski — Fri, 25 Oct 2019 13:33:49 +0000

Meade F6.3 Reducer

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Revolution Imager 0.5x Reducer

Bernard Karpinski — Mon, 10 Dec 2018 13:09:17 +0000

Revolution Imager 0.5x Reducer, increases field of view and makes low surface brightness and extended objects much easier to find and view.
Works on any C/CS camera with a 1.25″ threaded nosepiece and accepts 1.25″ filters.
Exact reduction ratio varies with distance to sensor and can usually be optimised for the camera / scope combination in use – ask if unsure.

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SkyWatcher 2″ Field Flattener

Bernard Karpinski — Wed, 02 Nov 2016 22:37:01 +0000

The SkyWatcher 2″ Field Flattener is a superb quality, non-focal reducing Field Flattener optimised for DSLR imaging on refractor telescopes with focal ratios of between f/5.5 to f6.0.

Will also provide much improved results on refractors with focal lengths narrowly outside this optimised f/range. Integral T-Ring adaptor thread. High quality CNC machined body with gloss black anodised finish.

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TS Universal 2-Inch Field Flattener for Refractors

Bernard Karpinski — Sun, 16 Oct 2016 17:35:29 +0000

TS Universal 2-Inch Field Flattener for Refractors

The TS Universal 2-Inch Field Flattener for Refractors from f4 to f9 is a flat field imaging corrector for almost ALL refractors with a 2″ focuser, producing pinpoint stars from centre to edge!

The flattener has an optical diameter of 45.5 mm and offers reduced vignetting compared to narrower T2 types. Fitting is M48 at both ends.

For most refractors the optimum back focus distance is around 109mm from the M48 thread to the camera’s sensor.

Experience has shown that the flattener has a large tolerance for deviations from the ideal distance. A 5% deviation does not cause any deterioration of the image quality with an APS-sized sensor.

For smaller sensors somewhat larger deviations may be acceptable, but please bear in mind that for the best resolution the distance should be set as precisely as possible.

For refractors with a fast focal ratio we recommend a longer back focus distance of approximately 120-123mm.

Please ask if unsure about adaptation and spacing!

Item Code – TSFlat2

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Celestron 0.7x Focal Reducer for 8″ EdgeHD

Bernard Karpinski — Fri, 16 Sep 2016 14:05:21 +0000

The Celestron 0.7x Focal Reducer for 8″ EdgeHD features a custom 4 element optical design engineered to maintain the flat-field performance of our award winning EdgeHD optical system. Unlike generic reducers, our premium reducers provide substantial back focus to accommodate an assortment of imaging accessories.

The Celestron 0.7x Focal Reducer for 8″ EdgeHD offers high index optical elements, including extra low dispersion, exotic Lanthanum elements, which provide high contrast viewing while minimizing chromatic aberration. All air to glass lens surfaces feature multiple layers of coating for maximum light transmission and color correction and contain blacken edges to minimize internal reflection and maximize image contrast.

Incorporating computer assisted CNC machined aluminum housing, for precise spacing and alignment of optical elements, and threaded metal covers on the lens assembly to protect your investment from dust and scratches, our reducers offer you an outstanding mechanical design.

With the Fastar option on all EdgeHD optical systems, coupled with the .7x reducer, your telescope becomes the most complete imaging system available in its price range today.

Performance

Design: 4-element optical layout designed specifically for the EdgeHD 8″ to maintain the flat-field performance of the Edge HD optical design
105mm of back focus: Provides generous back focus to accommodate additional accessories and a wide variety of cameras. Also allows use of existing T-adapters for EdgeHD 800 and other Celestron imaging accessories
One full F-Stop faster than f/10: Reduces the exposure time by one-half to capture the same brightness of object
Increase field of view by 43%: Better for capturing wide field images of larger galaxies and nebulae

Glass

Lanthanum Glass Elements: EdgeHD reducer uses “rare earth” Lanthanum glass elements for clear, high contrast viewing while minimizing chromatic aberration
Fully multi-coated lens elements: All air-to-glass surfaces have multiple layers of coating for maximum light transmission and color correction
Blacken edges: All lens elements have blacken edges to minimize internal reflection and maximize contrast

Large Illuminated Field

Optimized for APS-C sized sensors: Including most DSLR cameras and Nightscape CCD cameras

Mechanical Design

Machined aluminum housing: Computer assisted CNC machined aluminum housing for precise spacing and alignment of the optical elements.
Threaded metal covers for both ends of the lens assembly: To protect your investment from unwanted dust and scratches

Versatility

Provides and intermediate focal length between EdgeHD’s native f/10 (or f/11) and the optional Hyperstar accessory at f/2, making the EdgeHD the most complete imaging system in its price range

FEATURES

The EdgeHD .7x Focal Reducer Lens makes your EdgeHD 800 one full f-stop faster than f/10, doubling the equivalent exposure at f/10
4-element lens design
Maintains similar flat-field performance as native EdgeHD optical design
Increases field of view by 43% (double by area) to better capture wide field images
Optimized for APS-C sized sensors, including most DSLR cameras and Nightscape CCD cameras
Provides generous 105mm back focus to accomodate additional accessories and a wide variety of cameras
Compatible with EdgeHD 800 T-adapter

SPECIFICATIONS

Optical Coatings: Fully multi-coated
Weight (lbs): 0.8 lbs (0.36 kg)
Compression Factor: .7 x
Lens Elements: 4-Element
Optimal Back Focus (mm): 105 mm (4.13 in)

Please Note: The optimum photographic back focus of the EdgeHD 8” is 105 mm when used with #94242 Reducer Lens at f/7.
Our #93648 Off-Axis Guider, when used with the reducer #94242 and a DSLR, reaches appx 120mm.
Therefore because the 105mm distance is so critical, the Off-Axis Guider is not typically compatible for use with the EdgeHD 8″ and Reducer lens combination.
The EdgeHD 11″ and 14″ all keep the same 146mm back focus with or without the reducer so are not affected.

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Baader MPCC Mark III

Bernard Karpinski — Fri, 20 Nov 2015 22:38:49 +0000

The Baader MPCC Mark III now improves image quality in reflectors down to F3.5.

Fits 2″ focusers and has rear 48mm and T threads, covers up to 35mm format.

Available in Photo and Photo / Visual versions.

MPCC Mark III properties…

no change in focal length or field size
newly calculated lens system – designed for an unvignetted field down to f3.5
maximum sharpness across the field – without center soft spot (as reported of other makes)
accepts T-2(M42x0.75) and/or 2″(M48x0.75) threaded photographic- or visual-adapters
2″ stopping collar removable for increase in backfocus
For photographic and visual use
easy to use
exceptional price/performance ratio
Optional adapter for direct coupling of the MPCC III directly onto the Baader CANON EOS protective T-ring
44mm clear aperture when using the M48(2″) filter-tread or the Protective T-ring with optional adapter

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