SCT Corrector II - 0.63x Reducer/Coma Corrector (SCTCORR-II)


SCT Corrector II - 0.63x Reducer/Coma Corrector (SCTCORR-II)

Regular price
$ 399.00
Sale price
$ 399.00
Unit price

This item is out of stock but you can place an order now and we’ll ship when it becomes available.


We have updated our popular SCT Corrector! By modifying the optical design of the SCT Corrector based on the 4-element design of our large-format SCT Corrector LF model, we were able to increase the focal reduction from f/7.5 to f/6.3 while preserving the optical performance and keeping the available backfocus the same.

The new SCT Corrector II has the same mechanical backfocus as the original SCT Corrector, which means it uses the same camera adapters. If you already own the original SCT Corrector, you won't need any new adapters if you upgrade to the SCT Corrector II. (Yes, we know it's almost mean to make it that easy....)


The diagram above shows how the SCT Corrector II improves the off-axis spot size on a Celestron 11" SCT. Performance is similar on other size telescopes.

Focal Length

The exact focal length of the reducer/telescope combo depends slightly on where in the optical path the SCT Corrector lens is placed. Nominally it will be within a few mm of the rear threads on the telescope. Changing this distance should only affect the focal length, not the optical quality. Listed below are the nominal focal lengths for the various sizes of Celestron SCTs*. The SCT Corrector works great on standard f/10 Meade SCTs as well, we just didn't have exact data for the nominal designs of those telescopes.

Telescope Focal Length Focal Ratio
C6 1220mm f/8
C8 1380mm f/6.8
C9.25 1490mm f/6.3
C11 1760mm f/6.3
C14 2365mm f/6.7

* The reduction ratio is different for the C6 and C8 because the nominal backfocus at f/10 of those telescopes is less than that for the larger scopes, so there is slightly less reduction. The C14 is slightly slower because it is natively f/11.

Camera Adapters

The SCT Corrector II has a nominal image circle of 27mm, accommodating most popular CCDs and DSLRs. For larger format cameras, check out our SCT Corrector LF.

Because the back focus of the SCT Corrector II is fairly critical, for best performance Starizona makes a variety of camera adapters, and custom adapters are also easy to make for less-common camera setups.

The nominal back focus is 90.3mm from the base of the threads on the camera side of the SCT Corrector II. For the largest compatible cameras, this should be kept within +/-2mm, while smaller format cameras may work fine at slightly larger tolerances. If we do not have the correct length or style adapter you need, we can gladly make the correct part to get the best performance from your setup. Please contact with any questions on making your camera configuration work.

Telescope Adapters

The SCT Corrector II, like the original SCT Corrector, has a 2" barrel that allows it to fit into a 2" visual back or 2" focuser. If your telescope does not have such an adapter, we recommend our Virtual View rotating visual back, which allows for easily changing the camera orientation without loosening any lock screws.


The front (telescope side) of the SCT Corrector II is threaded to accept standard 2" (48mm) filters.


  • 0.63x focal reduction factor
  • 2.5x faster than SCT's native f/10
  • 1.4x faster than original f/7.5 SCT Corrector design
  • 27mm image circle
  • 2" barrel
  • Threaded for 48mm filters
  • Black anodized, machined aluminum housing
  • Fully multi-coated optics
  • Improved 4-element optical design
  • Made in USA

Personal Upgrade Path

Buy risk-free: When it’s time to trade up you’ll get the most value for your used gear.