What focal length does the C11 EdgeHD reach with the 0.7x reducer?

Celestron states 2,800 mm at f/10 and one full f-stop faster with the reducer. My frames through it plate-solve at 1,952 mm, 0.397 arcsec per pixel on 3.76 micron pixels, which is 0.70x and close to f/7.

What sat behind it in my imaging train?

A T-adapter, ZWO's camera angle adjuster, a 7 x 2 inch filter wheel and the ZWO ASI2600MM Air, with the C11 EdgeHD on the ZWO AM7 (1:36 in the video). Celestron gives 146 mm of back focus, and my frames solved at 0.70x.

What did I capture through it?

With the C11 EdgeHD on the ZWO AM7: the Dumbbell Nebula in 12 hours, the Elephant's Trunk in 8 hours, Thor's Helmet and the Crab in 3 hours each and the Horsehead in 2 hours 15 minutes. My short in the videos shows them.

How much does the EdgeHD 1100 0.7x reducer cost?

The prices I recorded: £855 at First Light Optics (UK), awaiting stock; $849 at Agena Astro (US), in stock; $849 at Celestron (Global), in stock.

What have I not tested on the 11″ EdgeHD 0.7x Reducer?

I have not tested it with a full-frame sensor or at other spacings.

Celestron EdgeHD 1100 0.7x Reducer review: f/7 on my C11

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
22	Flat Panel 150mm	73 out of 100	£50
26	Altair EAF	70 out of 100	£139
39	Celestron 8″ EdgeHD 0.7x Reducer	44 out of 100	£429
41	Celestron 11″ EdgeHD 0.7x Reducer	42 out of 100	£855
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 In use
04 What I captured through it on my C11 EdgeHD
05 Raw against finished
06 Watch it in my videos
07 Should you buy it?
08 Questions and more about this review

In 30 seconds

Stars for Your Buck 42/100

Reviewed 4 May 2026 Updated 25 Sep 2026

Rank: #41 of 46 accessories
Verdict: With reservations

Written by Damon Scotting 4 min read

Buy it if

You image deep-sky targets with a Celestron C11 EdgeHD and want f/7 with the flat field kept.
You use an APS-C or full-frame camera, or an off-axis guider: Celestron gives it a 42 mm image circle.

Skip it if

Your telescope is not an EdgeHD 1100: every EdgeHD aperture has its own reducer, and standard SCTs need the f/6.3.
Your mount is near its limit: it adds 1.47 kg to the back of a 13 kg tube.

My C11 EdgeHD deep-sky images, from the Dumbbell to the Horsehead, went through this reducer: it takes the C11 from f/10 to f/7, and my frames plate-solve at 1,952 mm.

Specifications and features

Celestron 11″ EdgeHD 0.7x Reducer reviewed #41 of 46
Recorded UK price	£855
Type	0.7x reducer for the Celestron EdgeHD 1100
Model	94241
Reduction	0.7x: one full f-stop faster than f/10
Focal length I measured	1,952 mm on my C11 EdgeHD (0.70x of 2,800 mm), plate-solved
Lens elements	5
Back focus	146 mm (5.75 in), the same as at f/10
Image circle	42 mm (full frame)
Clear aperture	60 mm
Weight	1.47 kg (3.25 lb)
Coatings	Fully multi-coated
Fits	EdgeHD 1100 only, on its 3.25 inch rear thread

In use

On the back of my C11 EdgeHD

Pointing out the reducer

Reducer, filter wheel and camera

The C11 EdgeHD rig on the ZWO AM7

What I captured through it on my C11 EdgeHD

Ten targets

M 27, ASI2600MM, Scorpio 3 nm HSO

Integration: 12 h
Field: 0.64 x 0.43 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MM
Mount: ZWO AM7
Target: M 27 Dumbbell Nebula
Type: Planetary nebula
Location: Bortle 6.8 (in my garden)

IC 1396, ASI2600MM, HSO

Integration: 8 h
Field: 0.67 x 0.45 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MM
Mount: ZWO AM7
Target: IC 1396 Elephant's Trunk Nebula
Type: Emission nebula with a dark globule
Location: Bortle 6.8 (in my garden)

NGC 2359, ASI2600MM, HSO

Integration: 3 h
Field: 0.64 x 0.43 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MM
Mount: ZWO AM7
Target: NGC 2359 Thor's Helmet
Type: Emission nebula around a Wolf-Rayet star
Location: Bortle 6.8 (in my garden)

IC 434, ASI2600MM Pro, HSO

Integration: 2 h 15 min
Field: 0.66 x 0.45 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MM Pro
Mount: ZWO AM7
Target: IC 434 Horsehead Nebula
Type: Dark nebula
Location: Bortle 6.8 (in my garden)

M 1, ASI2600MM Pro, LRGB

Integration: 3 h
Field: 0.44 x 0.28 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MM Pro
Mount: ZWO AM7
Target: M 1 Crab Nebula
Type: Supernova remnant
Location: Bortle 6.8 (in my garden)

NGC 2237, ASI2600MM, HSO

Integration: 1 h
Field: 0.69 x 0.46 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MM
Mount: ZWO AM7
Target: NGC 2237 Rosette Nebula (core)
Type: Emission nebula
Location: Bortle 6.8 (in my garden)

M 13, ASI2600MC

Integration: 1 h
Field: 0.69 x 0.46 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MC
Mount: ZWO AM7
Target: M 13 Hercules Globular Cluster
Type: Globular cluster
Location: Bortle 6.8 (in my garden)

NGC 6960, ASI2600MC

Integration: 1 h
Field: 0.69 x 0.46 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: ZWO ASI2600MC
Mount: ZWO AM7
Target: NGC 6960 Western Veil Nebula
Type: Supernova remnant
Location: Bortle 6.8 (in my garden)

M 31 core, LRGB

Integration: 1 h
Field: 0.63 x 0.35 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: Unknown
Mount: ZWO AM7
Target: M 31 Andromeda Galaxy (core)
Type: Spiral galaxy
Location: Bortle 6.8 (in my garden)

M 51

Integration: Unknown
Field: 0.23 x 0.13 degrees
Telescope: Celestron C11 EdgeHD with the 0.7x reducer
Camera: Unknown
Mount: ZWO AM7
Target: M 51 Whirlpool Galaxy
Type: Spiral galaxy
Location: Bortle 6.8 (in my garden)

Raw against finished

Watch it in my videos

The 4 targets, the raw combined stack against my finished image, each with its integration, the camera and the palette:

M 27 Dumbbell Nebula: 12 h of light, ASI2600MM, Scorpio 3 nm HSO, the raw combined stack with one automatic stretch
IC 1396 Elephant's Trunk Nebula: 8 h of light, ASI2600MM, HSO narrowband, the raw combined stack with one automatic stretch
NGC 2359 Thor's Helmet: 3 h of light, ASI2600MM, HSO narrowband, the raw combined stack with one automatic stretch
IC 434 Horsehead Nebula: 2 h 15 min (45 x 180 s) of light, ASI2600MM Pro, HSO narrowband, the raw combined stack with one automatic stretch

One of the BEST Mounts in the WORLD or Underwhelming...? (AM7 Review) · published 4 May 2026 · 8:21 · Watch on YouTube · 12,503 views, 423 likes on 2 Oct 2026

Jump to

1:28 The C11 EdgeHD on the ZWO AM7
1:36 The 0.7x reducer and the imaging train
1:39 The back end, up close
1:55 Images through the C11 EdgeHD
2:09 Guiding at this focal length

Transcript of the video 268 words · 4 chapters · searchable

Press a time stamp to play from there.

1:30 The C11 EdgeHD on the ZWO AM7

1:30 So, of course, we have the Celestron 11-in Edge HD telescope. 1:30 It is a beast. 1:33 But, down the back end over here, I'm going to spin it around. 1:35 Connected to the telescope, we have a 0.7 times reducer as well as a T-adapter, camera angle adjuster from ZWO as well, as well as a 7 by 2-in filter wheel, and then the ASI 2600 monochrome air camera.

1:39 The back end, up close

1:46 So, with this setup, I'm hoping to take some really nice quality narrow band images of our night sky at a very long focal length.

1:55 Images through the C11 EdgeHD

1:56 Just for entertainment purposes, here are a few images I captured with the C11 Edge HD. 1:59 But the truth is, for the rest of the video, I'm using the exact same camera setup at the back end, but now with a much sharper telescope in the Askar SQA106.

2:09 Guiding at this focal length

2:09 And this is for the simple reason that I was really struggling to guide with the C11 Edge HD. 2:12 So, I think the next question I'm going to answer is how well does this mount guide, and is it the best value mount on the market currently available? 2:20 So, the key thing to note here is that I'm not using a separate guide scope and camera. 2:23 I'm using the ASI 2600 mm Air, which comes with an inbuilt guiding sensor. 2:28 So, the issue is when imaging in narrow band using the C11 Edge HD telescope, it's such a large focal length that the guiding camera really suffers. 2:36 So, instead, here is almost 20 minutes worth of 1 second guiding whilst tracking the Whirlpool Galaxy with the Askar SQA106.

Check out more videos on the Celestron 11″ EdgeHD 0.7x Reducer

The Night Sky through my 11-INCH Telescope!

12 Feb 2026

Should you buy it?

42/100 Stars for Your Buck

Pros

Takes the C11 EdgeHD from f/10 to f/7: my frames through it plate-solve at 1,952 mm, 0.70x of 2,800 mm.
A 42 mm image circle and 60 mm clear aperture: Celestron rates it for full-frame sensors and off-axis guiders.
Threads straight onto the EdgeHD 1100's 3.25 inch rear thread and keeps the same 146 mm back focus as at f/10.
My C11 EdgeHD images went through it: the Dumbbell, the Elephant's Trunk, Thor's Helmet, the Crab and the Horsehead.

Cons

Expensive: £855 at First Light Optics.
Heavy: 1.47 kg at the back of an already heavy tube.
Made for the EdgeHD 1100 only: every EdgeHD aperture has its own matched reducer.
Even at f/7 the C11 EdgeHD works at about 1,950 mm, and guiding at that focal length is demanding.

With this setup, I'm hoping to take some really nice quality narrow band images of our night sky at a very long focal length.

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 11″ EdgeHD 0.7x Reducer

Reviewed 4 May 2026 ·Updated 25 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. Shop links marked Ad are affiliate links: I earn a commission when you buy through them, at no extra cost to you. How this site is funded

What focal length does the C11 EdgeHD reach with the 0.7x reducer? Celestron states 2,800 mm at f/10 and one full f-stop faster with the reducer. My frames through it plate-solve at 1,952 mm, 0.397 arcsec per pixel on 3.76 micron pixels, which is 0.70x and close to f/7. The specifications ↓
What sat behind it in my imaging train? A T-adapter, ZWO's camera angle adjuster, a 7 x 2 inch filter wheel and the ZWO ASI2600MM Air, with the C11 EdgeHD on the ZWO AM7 (1:36 in the video). Celestron gives 146 mm of back focus, and my frames solved at 0.70x. In use ↓
What did I capture through it? With the C11 EdgeHD on the ZWO AM7: the Dumbbell Nebula in 12 hours, the Elephant's Trunk in 8 hours, Thor's Helmet and the Crab in 3 hours each and the Horsehead in 2 hours 15 minutes. My short in the videos shows them. Watch it in my videos ↓
How much does the EdgeHD 1100 0.7x reducer cost? The prices I recorded: £855 at First Light Optics (UK), awaiting stock; $849 at Agena Astro (US), in stock; $849 at Celestron (Global), in stock. A record, not a live price The verdict, the readers and the sellers ↓
What have I not tested on the 11″ EdgeHD 0.7x Reducer? I have not tested it with a full-frame sensor or at other spacings.