Does the Celestron f/6.3 reducer fit an EdgeHD?

No. Celestron lists it as not compatible with EdgeHD tubes: each EdgeHD has a field flattener in its baffle tube and needs the 0.7x reducer matched to its aperture.

What spacing does it need?

Celestron gives a working distance of 105 mm from the rear, camera-side threads. The generic 0.63x reducer on my C5 reached only 0.80x at the spacing I used, so plan the distance to your sensor.

Celestron or the generic 0.63x reducer?

I have used both. Celestron's was the first reducer I ever used, on my C8, and I think it is really good; a generic one gave me the Needle Galaxy, the Pinwheel and M 13 on my C5. I lean to the generic ones because they are cheaper, though Celestron's own states the working distance and weight that the generic listing leaves out.

How much does the Celestron f/6.3 reducer cost?

The prices I recorded: £165 at First Light Optics (UK), awaiting stock; $200 at Agena Astro (US), in stock; $113 at AliExpress (STARRYSEA Official Store), Global, listed.

What have I not tested on the f/6.3 Reducer-Corrector?

I have not measured the reduction Celestron's reducer gave me, and none of my images through it is on this page.

Celestron f/6.3 Reducer-Corrector review: my first reducer

Where does it rank on our leaderboard

Nine of the 46 accessories on my board, against price
Rank	Accessory	Stars for Your Buck	Recorded UK price
1	GEMINI EAF	100 out of 100	£42
2	Generic Dew Heater	93 out of 100	£9
12	Celestron 8-24mm Eyepiece	82 out of 100	£99
13	ASIAIR Plus 256GB	81 out of 100	£399
30	Celestron 0.63x Reducer	62 out of 100	£165
33	ZWO EAF	51 out of 100	£199
35	PowerMate 5x Barlow	47 out of 100	£255
45	SKY ROVER 2x54 Binoculars	28 out of 100	£139
46	365 Solar Telescope Cover	5 out of 100	£73

Contents

01 Where does it rank on our leaderboard
02 Specifications and features
03 Should you buy it?
04 Questions and more about this review

In 30 seconds

Stars for Your Buck 62/100

Written 26 Sep 2026 Updated 26 Sep 2026

Rank: #30 of 46 accessories
Verdict: Worth a look

Written by Damon Scotting 2 min read

Buy it if

You own a standard Celestron SCT (C5, C6, C8, C9.25, C11 or C14) and want Celestron's own reducer with a stated working distance.
You would rather buy from a UK or US dealer than wait on an AliExpress delivery.

Skip it if

You own an EdgeHD: Celestron lists this reducer as not compatible.
You want the lowest price: a generic f/6.3 reducer costs well under half as much.

It was the first reducer I ever used on my Celestron C8, and I think it's really good.

Specifications and features

Celestron 0.63x Reducer reviewed #30 of 46
Recorded UK price	£165
Type	Reducer-corrector for Schmidt-Cassegrain telescopes
Model	94175
Reduction	0.63x: focal length and focal ratio cut by 37% (f/10 to f/6.3)
Fits	Celestron C5, C6, C8, C9.25, C11 and C14
Not for	EdgeHD optical tubes
Working distance	105 mm from the rear, camera-side threads
Size	56 mm across, 34 mm long
Weight	122 g (4.3 oz)
Coatings	Fully multi-coated
Housing	Machined aluminium

Should you buy it?

62/100 Stars for Your Buck

Pros

I have used it on a lot of my earlier setups.
Celestron states it cuts the focal length and focal ratio of its SCTs by 37%, from f/10 to f/6.3.
Fits the Celestron C5, C6, C8, C9.25, C11 and C14.
A stated working distance: 105 mm from the rear, camera-side threads, so the spacing is not guesswork.
Small and light: 56 mm across, 34 mm long and 122 g.

Cons

Not compatible with EdgeHD optical tubes.
£165 at First Light Optics, about two and a half times a generic 0.63x reducer: the reason I lean to the generic ones.
The full 0.63x holds at its working distance only: the generic reducer on my C5 reached 0.80x at the spacing I used.

I'm a big fan of the generic reducers over the Celestron or Meade ones, simply because they're cheaper.

Three alternatives I have reviewed

Questions and more about this review

Reviewed by

Damon Scotting

The Telescope Man Verified

BSc (Hons) Physics with Astrophysics and Cosmology, Loughborough University PGCE / QTS, University of Nottingham

About Damon About Damon Damon Scotting is The Telescope Man. He holds a BSc (Hons) in Physics with Astrophysics and Cosmology from Loughborough University and a PGCE with QTS from the University of Nottingham, and taught physics in secondary schools before becoming an astronomy creator. He is a contributing writer for BBC Sky at Night Magazine and the author of 42 Wonders of Our Night Sky, and his photograph of the galaxy M100 with the dwarf planet Ceres was Highly Commended in the Astronomy Photographer of the Year 2024 competition run by Royal Observatory Greenwich. He has appeared on the BBC's Blue Peter. More than 750,000 people follow his astronomy channels on YouTube, Instagram and TikTok, and he has reviewed more than 140 telescopes, mounts, cameras, filters and accessories hands-on for this site. More about Damon · How I test · Damon's book

I review all kinds of gear: most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way. How this site is funded

Five questions, answered

Questions about the Celestron 0.63x Reducer

Written 26 September 2026 ·Updated 26 September 2026

I review all kinds of gear. Most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way: no company sees or approves a review before it is published. Some shop links are affiliate links: I earn a commission when you buy through them, at no extra cost to you. How this site is funded

Does the Celestron f/6.3 reducer fit an EdgeHD? No. Celestron lists it as not compatible with EdgeHD tubes: each EdgeHD has a field flattener in its baffle tube and needs the 0.7x reducer matched to its aperture. The specifications ↓
What spacing does it need? Celestron gives a working distance of 105 mm from the rear, camera-side threads. The generic 0.63x reducer on my C5 reached only 0.80x at the spacing I used, so plan the distance to your sensor. The specifications ↓
Celestron or the generic 0.63x reducer? I have used both. Celestron's was the first reducer I ever used, on my C8, and I think it is really good; a generic one gave me the Needle Galaxy, the Pinwheel and M 13 on my C5. I lean to the generic ones because they are cheaper, though Celestron's own states the working distance and weight that the generic listing leaves out. The specifications ↓
How much does the Celestron f/6.3 reducer cost? The prices I recorded: £165 at First Light Optics (UK), awaiting stock; $200 at Agena Astro (US), in stock; $113 at AliExpress (STARRYSEA Official Store), Global, listed. A record, not a live price The verdict, the readers and the sellers ↓
What have I not tested on the f/6.3 Reducer-Corrector? I have not measured the reduction Celestron's reducer gave me, and none of my images through it is on this page.