Sky-Watcher Esprit ED-100 quintuplet

[cybermystic]

Kieron of SCS Astro sent me one of the above scopes to review. I must admit when it arrived and I opened the box I was totally bowled over.
The scope came in a fully-padded aluminium case - and this case was suspended by 8 strong springs from an outer metal frame, and the lot was in a tough cardboard box. No cries of "the collimation must have got lost in the shipping" with packing like that - other telescope manufacturers please take note.
The silky smooth 11:1 ultra-beefy focuser was a real joy to use and you could suspend a tank off that focuser with no focus creep - superb job.
So now the big question - do the 5 pieces of glass perform? The short answer is with the scope I had - no. I also believe someone else had one of these and returned it to the vendor - blast, what a huge let down.
No chromatic aberration from what I could see, covered an APS size chip with no vignetting and good uniformity, so what was wrong? Well I can't tell you what the proper optical term is for what I saw but basically I don't think it focuses too well. All the stars no matter what size or brightness are "fuzzy" there is a clear ring (halo) around a core for each star and the bright central core is also off-centre. Now I'm not sure why this is so as I got good collimation and reasonable focus numbers with CCDInspector - but the stars simply weren't good. The real shocker was looking at the star image as Robofocus brought it into best focus. As it came into focus it went through all sorts of funny shapes with lines across the star (forgot to mention there was a clear "cross" across very bright stars indicative of pinched optics). In the Sky 90 you get a big round nice uniform circle coming down to a small nice uniform circle as the Robofocus does its job.
So - after what looked like a brilliant start it was let down by the optics. Here's my guess at what's wrong.
I don't believe they've got the optical design wrong, I do know it's really tough getting the lens alignment right with short focal length low f# optics. It's a pig collimating the Sky 90 doublet - and in the Sky-Watcher we have 5 pieces of glass, not 2. My bet is that the manufacturers had not thought it through (cost wise) in that I reckon it would take a skilled person a day (at least) to optically align a 5 lens system. If the cell and the adjusters haven't been properly designed, then you'll never get there. There will be precision gaps between the lenses to sort as well as the X-Y position in plane. And did I mention there are 5 lenses?
Well that's my guess for what it's worth. What I can say is that if Sky-Watcher can sort out the optical issues then they have a most brilliant imaging product here - effectively an FSQ-106 at half price. Get the optics sorted and they have a real winner on their hands. But can it be sorted??
Greg

[Gasman]

Interesting review Greg. I have been very interested in trying to find a 120 to look through so its a bit disappointing to hear about the optics of the 100 they sent you. I think after your review I`ll hang fire as I`ve also heard of someone else`s dealings testing a 100!!
Regards
Steve

[Harry Page]

Hi

Yes a real shame , something I was looking at myself

Harry

[Gasman]

Hi again Greg
I had a look at your review on your NFO site on the 100 and notice on March 12th you mention "Good star shapes across the chip" and "perfect collimation" so has the problem with the optics just occurred ?
Regards
Steve

[cybermystic]

CCDInspector did indeed give a perfect collimation number (I think I mentioned that in the above review, something I didn't understand). The star shapes IN FOCUS were perfect across the chip - problem was they were fuzzy with halos when I magnified the image and looked in close. So what changed was that I had a close in look. The whole image however did appear "soft" (without looking in close) - far softer than anything I'd ever seen with the Sky 90s.
Greg

[DaveS]

Hmm!! , disappointing indeed Greg, and given the cost, even more so.

It would seem that Skywatcher/Synta's attempt to get into the 'high end scope' market, has failed at the 'first hurdle'.

The likes of Takahashi, Astro-Physics, TMB, and Tele-Vue etc, must have a smile on their face.

Dave

[Gasman]

It is frustrating looking for another decent scope. Like most other things you buy these days it does still seem to be potluck whether you get a dummy or not regardless of the cost!!. I was shortlisting WO scopes but then hear of someone in the states complaining of pinched optics ;-(
Steve

[cybermystic]

It's a very tough one guys - and I was only looking at these Sky-Watchers as I was having trouble with collimating a Sky 90, something which has now fortunately been solved And as for Takahashi et al having a laugh - probably not! When I was having collimation trouble a friend lent me his Sky 90 so I could get on with the mini-WASP. I was well-pleased. He had only used it visually and was very happy with it. First night with the camera on - strange notches in the side of stars??? Camera on the blink now? Nope - pinched optics!! So I think you can even have pot luck with the big boys. Given the cost of these instruments this is simply not acceptable and I would like to know what level of quality control allows them to leave the factory in this condition. Unless of course it all happened in the shipping
Greg

[MikeMillan]

FWIW, of all the scopes in the Takahashi line, I believe the Sky 90 has had the most issues. I've been reading of optical issues with this one for years in various forums. None of the others in their line have had this issue that I recall.

[cybermystic]

The Sky 90 has had its collimation problems which have now been sorted and apparently they now ship (and arrive) in good collimation. I don't know about problems with any other Taks as I only have Sky 90s (3 of them )
Greg

[Darth-Takahashi]

I feel like I must defend the honour of the Sky90 a little here. I owned the Sky90 MKII SV version made for the US market. Bought it directly in Japan and imported it myself, hand carried and never bumped etc. I have never had any trouble with it mechanically or optically and I have never collimated it.

Now the main issue with the Sky90 is admittedly first it price and secondly its expected performance as an astrograph!. These short tube flourite doublets are little mini wonders but they definitely suffer from coma at the edge of the FOV. So on an APS size sensor you are definitely going to notice it. When using the reducer there is also little back focus and room for error, so its also quite difficult to use correctly as an astrograph also.

In the end, I returned it back home to Japan where I traded it in for the BabyQ FSQ85EDX which suits my purposes much better than the Sky90 did. Still, I have to say that I enjoyed owning and using the Sky90 and wouldn't hesitate to recommend it, especially if you can pick one up used on the second-hand marketplace, this is when it becomes a bargain; but please understand its limitations.

No telescope is free of optical aberration, not even the famous RC (Ritche Chritein). The real question is how noticeable is the aberration?

The Sky90 is an excellent compact, light-weight and quality flourite doublet but coma is present in the last 10-15% of the FOV, along with high contrast sharp views of the universe.

Can Sky Watcher match the quality of the big names suppliers - NO. Can they get close enough that no one will care about the difference, PROBABLY. Its already happening, GSO are now making affordable RC up to 12" in diameter, something that was thought to be too difficult to do?

We are all privileged to live in these times of affordable quality optics.

Regards


Neil.

[NadeemShah]

Typical of skywatcher, how about getting the quality control of the basic scopes correct first, let alone trying to produce high end 5 element jobs....

Nadeem.

[Coco]

I see the Skywatcher dealers are going ahead with selling this Skywatcher Esprit 100 f/5 scope despite rumours of its poor performance now abound, I have sent several emails for clarification to one well known box shifter and after 3 none replies gave up.

I personally take great comfort in reports such as yours Greg, I feel you genuinely wanted/expected to find an affordable gem in the Esprit, I feel sorry for those who will get suckered into buying it.

[cybermystic]

I see the Skywatcher dealers are going ahead with selling this Skywatcher Esprit 100 f/5 scope despite rumours of its poor performance now abound, I have sent several emails for clarification to one well known box shifter and after 3 none replies gave up.

I personally take great comfort in reports such as yours Greg, I feel you genuinely wanted/expected to find an affordable gem in the Esprit, I feel sorry for those who will get suckered into buying it.

Believe me I was (and still am) totally gutted.
Greg

[cybermystic]

I feel like I must defend the honour of the Sky90 a little here. I owned the Sky90 MKII SV version made for the US market. Bought it directly in Japan and imported it myself, hand carried and never bumped etc. I have never had any trouble with it mechanically or optically and I have never collimated it.

Now the main issue with the Sky90 is admittedly first it price and secondly its expected performance as an astrograph!. These short tube flourite doublets are little mini wonders but they definitely suffer from coma at the edge of the FOV. So on an APS size sensor you are definitely going to notice it. When using the reducer there is also little back focus and room for error, so its also quite difficult to use correctly as an astrograph also.

In the end, I returned it back home to Japan where I traded it in for the BabyQ FSQ85EDX which suits my purposes much better than the Sky90 did. Still, I have to say that I enjoyed owning and using the Sky90 and wouldn't hesitate to recommend it, especially if you can pick one up used on the second-hand marketplace, this is when it becomes a bargain; but please understand its limitations.

No telescope is free of optical aberration, not even the famous RC (Ritche Chritein). The real question is how noticeable is the aberration?

The Sky90 is an excellent compact, light-weight and quality flourite doublet but coma is present in the last 10-15% of the FOV, along with high contrast sharp views of the universe.

Can Sky Watcher match the quality of the big names suppliers - NO. Can they get close enough that no one will care about the difference, PROBABLY. Its already happening, GSO are now making affordable RC up to 12" in diameter, something that was thought to be too difficult to do?

We are all privileged to live in these times of affordable quality optics.

Regards


Neil.

You're onto a loser even trying to defend the Sky 90 a little. Look at the specification sheet and you will see that the quoted imaging circle with the reducer flattener is given as 45mm which will adequately cover an APS size chip. So why do you say it's expected to have coma at the edge of the field with an APS size chip? Is is reasonable that an "imaging circle" means something that has an image in it, even if the image is grotty round the edges? Or is it sharp advertising practice?
Greg