ED120 review

[MartinB]

I bought the ED120 to plug a large gap in the focal lengths I had available for imaging. I needed a scope that wasn't going to overwhelm my GPDX. The 900mm ED120 seemed to fit the bill perfectly.

There is really no competition around for this configuration of apochromatic refractor at this price point. William Optics now have a very competitively priced 110mm aperture scope but it's focal length is little more than my ED80 so wasn't what I was looking for. You are really looking at TMBs and Taks at 2 or 3 times the price. The closest competitor is the ED100. This has had some rave reviews but at F9 it is a little slow.

Having agreed a price via UKastrobuynsell I was a bit worried after reading a couple of threads on Cloudy Nights suggesting that the ED120 might show some colour which is the last thing you want when imaging since it makes it impossible to achieve focus. In fact I think those couple of threads did a lot of damage to the ED120 which just doesn't seem to have sold.

In appearance the scope is typical Synta, it is a big ED80 with standard fit and finish and comes with the usual Synta crayford focusser. It sports the champagne and white pro colour scheme. The dew shield is screw on which is an advance on the ED80. The scope has obviously been very well cared for without a blemish. Obviously the size comes as a bit of a shock after a ZS66 and ED80 but actually it is very manageable and quite light weight for this aperture.

My first look was on a cloudy day. Looking at some small distant twigs there was no colour when in focus. Appearances can be misleading though. The out of focus twigs did have a small colour fringe which can give a very false impression of poor colour correction. I then had a quick chance to view the moon at dusk during a 10 minute break in the cloud. The views were genuinely breathtaking. With a 6mm plossl giving x150 the terminator crators were crisp with superb contrast. There was absolutely no colour along the edge of the moon no matter how hard I looked.

Last night I managed a more prolonged look although unfortunately deep sky was out owing to the full moon. I was trying to get guiding sorted on the GPDX so didn't do as much as I would have liked. The seeing was good 7/10. I was using a range of budget plossls along with a 9mm Baader Genuine Orthoscopic EP. I checked collimation up to x450. It was perfect! Off focus there were sharp round diffraction rings, there was a faint blue outer halo. Looking at Plaeides the stars were sharp to the edges.

I algned using Aldeberan and Regulus. Again there was no colour when in focus up to x150

Finally I got onto Saturn which is what I had really been looking forward to. This was the first chance I have had to look through the 9mm Baader orthoscopic. The view didn't disappoint. There was some faint banding on the disc and Cassini stood out remarkably clearly, certainly a match for my 8" C8. I have just bought a 5mm orthoscopic from Steve ( http://www.firstlightoptics.co.uk/ ) but didn't have this available last night so used a budget 5mm celestron plossl instead. The view was astounding. Saturn was still bright at x180 and the detail on the disc was showing up more clearly. Cassini cleanly divided the rings being perfectly black. I barlowed the 9mm ortho but actually preferred the unbarlowed view with the 5mm plossl.

I am not planning using the ED120 for planetary imaging since I think my SCT with it's long focal length and larger aperture is more suitable but I had to have a go and this is what popped out of Registax. Using a £30 Tal x3 barlow

Given that this is a sub 5" F7.5 scope I was very pleased with the result.

Finally a word about the Synta focusser. It has come in for quite a bit of flack. The main problem has been that a lot of them have tended to slip under load despite having a tightening screw. I loaded it with an SXV H9, filter wheel and a full set of dangling wires and set it up for M81 which was pretty close to the Zenith. I was able to ease the tension screw so the the focusser moved smoothly with a little to spare. There was no problem with slipping andI was able to achieve a tight focus without any trouble. OK it doesn't have the lovely silky feel of some Crayfords but it does the job perfectly well.

My scope came with the 9x50 Skywatcher finder scope. This did it's job very well. The best thing about this is the very easy adjustment with one of the adjustment screws being replaced by a spring loaded jobby - must become the norm since it is a major improvement in ease of use.

Likes

Optical quality

Excellent control of chromatic aberration

Manageable size and weight

Finder scope adjustment

Price

Dislikes

None, I love it!!! However some might have issues with

Lack of Kudos compared with WO or higher - a lot of money to pay for a Skywatcher and a big jump from the ED100

Colour scheme (I only use the scope when it's dark though)

Focusser (OK for me)

Cool down time. You will struggle for grab and go if scope is kept inside in the warm.

Specs

# Objective Lens Diameter: 120mm

# Telescope Focal Length: 900mm (f/7.5)

# Dual-fit 1.25”/2” Crayford Focuser (Backlash-Free) With Brushed-Aluminium Hubs & rubber grip rings

# Fully Multi-Coated Doublet Objective Lens

# Single FPL-53 ED Fluorite Glass Objective Element

[FLO]

Good review Martin!

DislikesNone, I love it!!! However some might have issues with

Lack of Kudos compared with WO or higher - a lot of money to pay for a Skywatcher and a big jump from the ED100

Colour scheme (I only use the scope when it's dark though)

:silent:

[dazza1639]

Nice review, I'm glad your pleased with your new toy

Darren

[GazOC]

Great review Martin, your dislikes are pretty "managable".

Let us know how you get on with Jupiter, thats the acid test for apos visually.

[geppetto]

Don't beat about the bush Martin

Do you like it or not?

Hope you and the scope get lots of clear skies

[geoff_k]

Martin

Looks like you have made a good purchase there. Looking forward to seeing some more of your images, especially deep-sky ones.

I saw a really neat WO refractor (132mm I think) at Astrofest for a cool £2700. Very nice, I'm sure, but I think the Skywatchers are hard to beat for the price.

Geoff

[Kaptain Klevtsov]

Great review MB, made me want one! Sounds like its a keeper then?

Captain Chaos

[Alan D]

Sounds like a good-un to me

Alan

[Andrew]

Nice review - very useful for someone like me with an interest in, but no experience, of refractors

[Saso]

Thank you for this review. It is very helpful.

Saso