ED120 put to the test

[MartinB]

I've posted a review before about this scope and have been very impressed with it. The problem I've had is not having much experience of high quality apos to use as a benchmark. Now I have an WO FLT 110 on loan from Steve that problem is solved. The FLT is a TMB designed triplet of very high quality and a perfect instrument to use for assessing the performance of the ED120 (I will be writing a full and detailed review of the FLT in the very near future).

The ED120 is 900mm f/l F7.5 compared with the FLT 770 F7

2 nights ago there was some scudding cloud but in between transparency was good. Seeing was variable - moderate to good. I had both scopes mounted side by site on an EM200 (now that was a good sight ). I was concentrating on the moon which was 2 days past full with the terminator nicely picking out the western edge of Mare Crisium and Cleomedes. EPs used were Moonfish 32mm UWA, 17mm Nagler T4, 7.5mm Pentax XL, 9 and 5mm Baader orthoscopics, 6 and 4mm Celestron plossls.

Looking through both the moonfish and the nagler there was a thin rim of colour along the edge of the moon when this was viewed out to the edge. To my eye this completely disappeared when the rim was moved into the centre of the FOV. Slightly out of focus the colour was slightly more pronounced with the ED120 but this difference was not apparent in focus. For such a full moon the contrast was excellent especially around the terminator but I needed to up the magnification to see what the scopes were capable of.

As the magnification was increased the views just became more and more impressive. Shadows were black with the shadows of the mountains on the edge of Mare Crisium being picked out with marvellous crispness. The tiny craters at the edge of the Mare were small but seen with a clarity that made you feel there was nothing between them and the eye - glass, atmosphere and 250 000 miles just dissolved away. Both scopes gave their best view with the Baader orthoscopic although the wider FOV of the Pentax might be preferred by some. I did try pushing the magnification up with a cheapo 4mm plossl and also by barlowing the Pentax but both scopes were running out of steam at this point. As could be expected, the ED120 was able to resolve a little more detail than the FLT thanks to it's extra aperture.

The point of an apo when viewing the moon is not really about not seeing any colour in the rim, it is that good colour correction reduces light dispersion and enhances contrast. The high power views in both scopes was immensely impressive - a tiny hint of colour along the rim in both scopes (more in the ED120 off focus but not in). I am sure the ED120 will show more colour than the FLT in poor seeing conditions. The 120 matched the FLT in terms of contrast and sharpness of detail.

There's no doubt the WO FLT is the superior scope - it is actually quite a bit heavier than the ED120 and looks chunkier, it has a nicer focusser which rotates as does the nose piece holder making it much easier to achieve comfortable viewing. The finish is altogether superior. It is the faster scope and can be fitted with a TMB flattener for very flat wide field imaging. So there is no doubt it is a much more of a package than the Skywatcher. What this has cleared up in my mind though is that optically, the ED120 is a mighty good performer and a true apochromat

[John]

Thanks for posting this review Martin, very interesting and well written. These are both scopes that I would like to own sometime and nothing you have said has made me cross one off my "wanted list"

The performance of your ED120 sounds very much like what I get with my Vixen ED102SS and my WO Megrez 90 before that - a very, very thin and faint ring false colour around the bright lunar limb which all but dissapears at sharp focus.

All credit to the Synta folks though - they have obviously managed to produce a quality, large aperture (for a refractor) apo doublet at a relatively short focal length and for a price that is at least affordable. That's no mean feat

John

[russ]

Martin, has the superior fit and finish, and the vastly superior focuser, of the WO tempted you to ditch the ED120? Or has this test increased your liking for the ED120? Especially seeing you can add that focuser to the ED120 anyway.

Russ

[Ant]

Thats a very interesting read Martin.

Certainly sounds like the ED120 is a very good scope. I do not know the difference in price between the two but would you say that it would be worth spending the extra money to get the WO?

I know that getting that little last bit of performance can be very costly indeed.

Thanks for taking the time to write the report,

Ant

[MartinB]

Rus, I'm happy with the basic Synta focusser both visual and imaging. It is plenty smooth enough and also takes a very heavy load (the previous owner had soap stoned the bearing surface to make it flat). Any upgrade to the focusser would be a motorised unit. I'm very happy with the ED120 and am looking forward to doing some more imaging with it. If a day ever comes when I can have a large format CCD camera then the FLT would come into the equation because of the wide flat field delivered by the TMB flattener.

I now know how well the FLT peforms as an imaging scope (outstanding), I've yet to image with the ED120 without being beset by unrelated technical problems. From what I've seen visually it should do well .

Ant - The ED120 should retail for around £1400 but there is the new Equinox on the way but don't know what that is priced at. The FLT 110 is around £1900. For the extra you get WO build quality and great design features and triplet optics which should outperform a doublet. What's more, for imaging you have a 4" draw tube so it can carry a mighty weight without risk of flexion plus the TMB flattener facillity.

The ED120 is a fantastic buy second hand - I paid £650 for mine. If I was buying new I would get the WO FLT - slightly faster scope, ability to upgrade to large format CCD, rock solid 4" draw tube and the comfort of knowing you have triplet optics. I also suspect it will hold it's value better.

Edit - just to add, if I had the scope primarily for visual I would go for the ED120 - the optics are close enough to the FLT to make the extra aperture count.

How's that for sitting on the fence!!

[Gordon G]

Nice review enjoyed reading that !

got a little 80mm WO and often thought of an upgrade, cleared a few things up there. Thanks

[barkis]

I thoroughly enjoyed reading your report Martin. Now, all I need is the money for the triplet. It would be worth half it's value just to look at it.

[russ]

Martin,

Did you know that Orion USA have upgraded their motor focus unit, Accufocus, to fit the Synta Crayford. And it's cheap.

Regards

Russ

[anthony]

Nice report Martin,

As you know i have the FLT110 and agree with it being a great scope. I also have an ed100, 900mm FL.

I appreciate that I lose out by 20mm against your ed120 - but as a budget apo - it fares superbly. Despite the longer focal length it has done me very well on DSO's - and had good stars to the edge on my SXV H9.

I have threatened to sell it several times following the arrival of the FLT110. However, I am consitently pleased that i have not. As a second hand purchase the ed100 is great.

For visual work - both are great though I see a clear difference between the FLT110 and the ed100, particularly at higher mag on bright objects, (FLT does better).

So, I concur - FLT 110 Very good. The synta ed scope fantastic value. Mine is better still for the lovely WO 2 speed focuser.

Anthony

[GordonCopestake]

Great stuff Martin, I would love to have seen (and owned!) the FLT 110 on the EM200 hehe, a dream setup almost! I'm sure I have an ST120 somewhere that has more aperture than the FLT110 and is faster at f/5..... want to swap?

[MartinB]

I would happily swap Gordon, seems a very fair deal, but unfortunately the FLT belongs to Steve, not me

[jcm]

This thread makes interesting reading.

Several reports I have read says that the 100 ED produces better images than the 120ED and this is the reason why many have bought the cheaper scope. From what you say the 120ED is a good scope and there have been some bargins because people have found it difficult to sell the 120ED.

John

[FLO]

I'm sure I have an ST120 somewhere that has more aperture than the FLT110 and is faster at f/5..... want to swap?

... unfortunately the FLT belongs to Steve, not me

I think I'll pass

[GordonCopestake]

Spoil sports

[MartinB]

This thread makes interesting reading.

Several reports I have read says that the 100 ED produces better images than the 120ED and this is the reason why many have bought the cheaper scope. From what you say the 120ED is a good scope and there have been some bargins because people have found it difficult to sell the 120ED.

John

The ED120 has had a troubled life. It all started on the Cloudy Nights forum when some people postulated that the colour wouldn't be well corrected because they had dropped the F ratio compared to the ED100. People in the same post also made the comment that it was too expensive. This was without anyone ever having looked through the scope :shock: Then one chap got to have a look through it and said it was superb, then changed his mind and decided that colour correction wasn't that good. After this people started describing it as a well corrected achromat - again without ever having looked through it. After those threads the ED120 was doomed really, which is great news for those of us on the look out for a second hand bargain.

I've only done 2 images with the scope - one was M51 in a near gale http://www.astropixels.co.uk/M51_March07_reedit.jpg and and the other was M101 when I couldn't get my GPDX to behave itself with the guiding http://www.astropixels.co.uk/M101_LHaRGB_March07.jpg Not happy with either image but not the scopes fault. I'm hoping to have another go with it again soon and think it will be capable of producing some cracking images (by my standards anyway)

[MartinB]

Did you know that Orion USA have upgraded their motor focus unit, Accufocus, to fit the Synta Crayford. And it's cheap.

Sounds interesting Rus. I wonder if it's controllable from Maxim using focus max. I want something that can do that so that the focus can be replicated and automatically adjusted during a long imaging session. Trouble is that the units I've seen so, such as robo focus are horribly expensive.

[GazOC]

That refractor forum on Cloudynights can really kill a scopes reputation....

[The Warthog]

Sounds like it may be a worthy upgrade to my excellent Vixen/Antares 105mm, one day. Thanks for that review, Martin.

[Whippy]

Good one Martin, I believe the WO ZS110 is the same optically as the FLT but in a ZS tube and costs the same as the ED120 new, but I also believe WO have discontinued the ZS and just keeping the lens cells for the FLT. That would have been an interesting match up! Saying that, if you can get a 120mm ED refractor for less than £700 second hand, bargain!!

Tony..

[FLO]

That's right Tony, your ZS110 has the same triplet lens cell as the flt110 8)

Unfortunately, you are also right that WO no longer offer the ZS option