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Opticstar ARC127 QUAD Optical Tube Assembly (OTA)
Quality Refractor Astrograph - Flat Filed of View
To order this item outside mainland Britain or Highlands, please contact us.
Opticstar ARC127 QUAD Optical Tube Assembly
Opticstar ARC127 QUAD Optical Tube Assembly (OTA).
  • 127mm Refractor Quadruplet
  • Corrected Flat Field
  • Focal length: 622mm
  • Focal ratio: F/4.9
  • 8x50mm Finder scope
  • Mounting tube rings and dovetail bar
  • 25mm Plossl eyepiece (1.25")
  • Star Diagonal (1.25")
Opticstar Visual
Opticstar Mount
CCD Cameras
Opticstar ARC127 QUAD Optical Tube Assembly (OTA)
Package includes:
  • Opticstar ARC127 QUAD refractor optical tube assembly.
  • Mounting tube rings and dovetail bar.
  • 8x50mm Finder Scope.
  • 1.25" 25mm Plossl Eyepiece.
  • 1.25" Star Diagonal.
  • Free options (please select one):
    • FREE: Opticstar 1.25" Moon Filter with 13% light transmission. Reduces the glare of the Moon. (R.R.P.: £9.95).
    • FREE: Red LED Torch made of aluminium alloy. Helps to preserve your night vision. (R.R.P.: £9.95).
  • OFFER: Please refer to the right hand column on this page.
Opticstar 1.25" Moon Filter 13% transmission. + £11.95
Red LED Torch (aluminium alloy construction). + £9.95
Opticstar 1.25" x5 XL TeleXtender. + £79.00
Opticstar 1.25" 15mm XS Super Wide Angle eyepiece. + £29.00
Opticstar 1.25" 10mm XS Super Wide Angle eyepiece. + £29.00
Opticstar 1.25" 9mm Wide Angle eyepiece. + £19.95
FREE Options & Offers (please select one)
Opticstar 1.25" Moon Filter 25% transmission. £0.00
Red LED Torch (aluminium alloy construction). £0.00
Order No. Price (inc_VAT) Shipping Delivery click button to purchase
OSRA12Q £ 395.00 £ 10.00
Opticstar ARC127 QUAD OTA
User Manual (PDF)
Opticstar CCD Cameras

The Opticstar ARC-127 QUAD is fast 127mm aperture F4.9 achromatic photo-visual refractor. The ARC-127 QUAD is ideal for both visual and imaging work.

The ARC-127 QUAD incorporates four lenses in two groups of two, Low-Dispersion (LD) Crown/Flint glass is used and lenses are broadband fully anti-reflection coated for increased contrast and sharpness. The design uses a F/10 doublet in combination with two additional near full aperture optical elements situated further down the optical path; these decrease the focal ratio to F/5 and also flatten the field offering very good off-axis performance.

Optical Design
The increased number of lens elements results to better correction of aberrations including coma and sphero-chromatism. This provides very good correction at F/4.9 and a wide field of view that makes the ARC-127 QUAD very well suited for wide field astro-imaging due to its fast focal ratio, flat field, higher contrast and markedly reduced false colour at F/4.9. In effect the secondary spectrum is reduced by nearly a 1/3 and allows a faster relative speed for the same degree of colour error. The telescope is also well suited for observation readily outperforming 2-element achromats of the same or similar focal ratios.

The lack of a central obstruction helps to increase image contrast and sharpness when compared to obstructed telescope designs including Newtonian reflectors, Maksutovs, and SCT telescopes among others. In general the obstruction means that all incoming light will reach the camera/eyepiece. In addition an un-obstructed optical instrument will reveal significantly more detail on brighter objects including planets, the Moon and the Sun when compared to obstructed designs. In practice the obstruction causes a significant loss in contrast and image sharpness.

The obstruction would not be of real concern if the diameter of the obstruction was less than around 10% the telescope aperture (diameter). It does however become a concern when the obstruction exceeds 20% of the diameter of the aperture; the vast majority of modern F/10 SCT's for example have obstructions between 35%-40% in diameter. A 35%-40% obstruction would also translate to a 12%-24% light loss in such cases.

Also at an aperture of under 7-inches atmospheric turbulence has a limited effect unlike apertures of 8-inches and above. This is important during long exposures and mostly when imaging deep sky objects.

Opticstar ARC127 QUAD Optical Tube Assembly
Opticstar ARC127 QUAD.

The ARC-127 QUAD offers a fitting solution when imaging even under not ideal conditions since the scope offers everything the imager would need in such cases i.e. good aperture, flat imaging field, fast focal ratio, reduced false colour at F/4.9 and no obstruction.

Most important the ARC-127 QUAD would be ideal for narrow band imaging with any size sensor and without the need for a flattener when considering that false colour would no longer be an issue. For the same reasons and in conjunction with a short focal length the ARC-127 QUAD is ideal for imaging or viewing the Sun in H-alpha with an appropriate filter.

Imaging and Viewing the Sun
Being a flat-field, air-spaced refractor with metal knife edge baffles the ARC-127 QUAD is also ideal for imaging and viewing the Sun when used with a specialist (H—alpha) Solar filter at the eyepiece end and in conjunction with a full aperture Solar heat rejection filter that is required due to the large size of the telescope’s objective lens and optical design.

Please note that suppliers of specialist, at the eyepiece, H-alpha filters recommend that the telescope’s aperture should not exceed a given size and/or a full aperture heat rejection filter should also be used in conjunction with a particular H-alpha eyepiece. Please contact the supplier of such equipment for advice.

Otherwise refractor telescopes with cemented or oil spaced objectives are not recommended for Solar work unless they are always used with a full aperture Solar filter. Newtonian and catadioptric designs in general are also not suited for use with specialist H-alpha eyepieces alone as the heat from the Sun will have an adverse effect on the small secondary mirror over time unless a full aperture Solar filter is used. White light full aperture Solar filters are inefficient in such cases as they also proportionally reduce the amount of H-alpha entering the telescope and reaching the H-alpha eyepiece.

Finally make certain that the Solar Filter you intend to use is safe, never use cheap eyepiece type Solar filters as they can crack under the heat and seriously damage your eyes.

Field of View
The ARC-127 QUAD is relatively portable due to its shorter focal length which in turn offers unusually wide fields of view for the aperture.

For example the ARC-127 F/4.9 QUAD will show a 4.2 degrees field of view with an Opticstar XS 38mm 70 degrees AFOV (apparent field of view) eyepiece. This will easily fit in the field of view particularly large objects like the Andromeda Galaxy. Eyepieces with larger AFOV will offer even wider fields of view.

A high quality optical tube keeps the optics precisely aligned allowing for heavier optical equipment to be attached at the focuser end. The optical tube greatly benefits from anti-reflection coatings and knife-edge baffles that prevent stray light from reaching the focal plane thus increasing image contrast and sharpness further. The optical tube assembly has a dew shield that also protects the lenses from condensation forming on the objective when the telescope is used in unfavourable conditions.

The focuser's 2" rack & pinion focuser draw tube has an etched millimetre scale to aid with focusing and repositioning, in addition the focuser has brass compression rings to securely support and not scratch accessories. It comes with a 1.25" eyepiece adapter so it will accommodate both 2" and 1.25" eyepieces and other accessories.

A single–piece cradle with a carry-handle is used to lift and support the telescope on its mount. The telescope has a Vixen/Skywatcher type dovetail and will mount on most astronomical mounts including the Opticstar EQ1300 GOTO. The carry-handle has been designed so as to enable the user to attach a DSLR, guide-scope or other accessories without the need of side by side platforms or similar, thus reducing costs, the total weight and the need for a heavier mount.

The ARC-127 QUAD comes collimated from the factory. If there was a need the objective could be collimated by an experienced user, three sets of easily accessible screws allow for precise collimation. Collimation can take place on a star under good atmospheric conditions or with the use of an artificial star like the Opticstar Artificial Star XL.

The ARC-127 QUAD comes with a 8x50mm finder scope and bracket. A 1.25" diagonal, and 25mm Plossl eyepieces are also included. An optional 13% transparency Moon filter is recommended as is a 2.3mm-3mm eyepiece for high power viewing.

Bundled accessories.
Bundled accessories.
Model Opticstar ARC127 QUAD
Aperture 127mm
Focal ratio F/4.9
Focal length 622mm
Objective 4 achromatic lenses in two groups of 2, can be collimated
Optical coatings Anti-reflection coated
Optical tube Internally anti-reflection coated with metal knife-edge baffles
Dew shield Yes
Finderscope saddle Yes
Focuser type Rack & Pinion with lock
Focuser 2" with 1.25" adapter (T-threaded for camera use)
Tube rings Dual rings with carrying handle and dovetail platform
Tube weight 7.2kg (inc. rings)
Tube length 970mm
Eyepieces Plossl 1.25" 25mm
Magnification With bundled eyepiece:
  • w/25mm eyepiece x25.
With optional eyepieces and barlow lenses:
  • w/15mm eyepiece x41;
  • w/10mm eyepiece x62;
  • w/10mm eyepiece and x3 barlow lens x188;
  • w/9mm eyepiece and x3 barlow lens x207; (maximum practical magnification)
  • w/15mm eyepiece and x5 barlow lens x207; (maximum practical magnification)
Star diagonal 1.25"; 90°
Finderscope 8x50mm with bracket

Opticstar ARC Series Refractor Optical Tube Assemblies
Model Aperture Focal Ratio Focal Length Optical
User Manual
Opticstar ARC127 Optical Tube Assembly ARC127 127mm F/9.5 1,200mm Achromatic doublet ARC127 OTA (PDF)
Opticstar ARC152 Optical Tube Assembly ARC152 152mm F/7.9 1,200mm Achromatic doublet ARC152 OTA (PDF)
Opticstar ARC Series Refractor Optical Tube Assemblies

Opticstar ARC QUAD Series Astrograph Refractor Optical Tube Assemblies
Model Aperture Focal Ratio Focal Length Optical
User Manual
Opticstar ARC127 Optical Tube Assembly ARC127 QUAD 127mm F/4.9 622mm Achromatic quadruplet ARC127 QUAD OTA (PDF)
Opticstar ARC152 Optical Tube Assembly ARC152 QUAD 152mm F/5 760mm Achromatic quadruplet ARC152 QUAD OTA (PDF)
Opticstar ARC QUAD Series Astrograph Refractor Optical Tube Assemblies

We are constantly checking the accuracy of the technical data. We are prepared to provide more detailed information on request. Technical data is subject to change without notice.

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Promotional Offer
Cash Back on Opticstar
Imaging Products
updated: 8th September 2017
Opticstar cashback offer.

Customers who purchase any Opticstar telescopes, Opticstar optical tubes or Opticstar mounts listed on this page qualify for a 10% cash back on any Opticstar astronomy cameras purchased at the same time or at a later date.

This offer is valid for 1 year commencing on the date that the Opticstar product is purchased from the Opticstar website or the Opticstar showroom.

Any additional purchases at a later date of Opticstar products that qualify for this offer will renew the cash back period to 1 full year.

Opticstar astronomy cameras that qualify for this offer include the following: Once an Opticstar CCD or CMOS camera has been purchased within a year of the qualifying Opticstar purchase, the cash back can be claimed by contacting Opticstar by email or over the phone quoting the receipt number(s). Please allow up to 14 days to process the payment.

Sample Images
Opticstar DS-145M ICE
posted: 13th March 2009
Sample image.
The NGC7293 shot by John Haunton with the Opticstar DS-145M ICE.
We want to hear your comments.
Sample Images
Opticstar DS-335C ICE
updated: 20th August 2010
Sample image.
The Trifid nebula shot by John Haunton with the Opticstar DS-335C ICE.
Opticstar Imaging
posted: 26th February 2013
Opticstar telescopes for imaging.
High quality refractor telescopes, bundled with CCD cameras for deepd sky imaging, planetary video imaging and auto-guiding.
A&M 80mm f/6 Review
"Best Of Breed"
updated: 25th March 2009
A&M 80mm f/6 A&M/TMB.
The A&M 80mm f/6 A&M/TMB has been reviewed in Cloudy Nights and it has been hailed as the "best of breed". The review concludes by saying "offers stunning performance while standing out from the crowd, look no further".
Willmann Bell
Books for Astronomy
updated: 20th September 2019
Willman Bell books.
Acclaimed books from Willmann Bell...
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