The Skywatcher Evostar ED150 DS Pro Is Here !

[Stub Mandrel]

It's not unusual for machine tools to be checked (or not) by importers for basic setup/accuracy. Those who do check, charge more for the product.

My inclination would be to offer either checked scopes (or not) at present, but not both. Even if this put a premium on the scope's costs (and £50 seems a bit blight to me for a £1500 scope) it only needs the invoice to include proof of testing for the scope to retain premium value.

[John]

I ought to point out that I don't have anywhere near the level of skills that Es Reid has. The optical issues with the 2 scopes that I had (especially the 2nd one) could have been spotted by most observers with using basic collimation and star tests I think. I showed my wife (pretty much zero interest in, and experience with optics) the star tests in the ED150's and my ED120 and even she could see clear differences.

Diagnosing the cause of the issues and putting them right calls for much more skill and experience of course.

 

[DRT]

I've just read this whole thread from start to finish for the first time. What a disappointing outcome!

Whilst the first issue is entirely understandable given what we all know sometimes happens to big boxes handled by couriers, the issue with the second scope is just shoddy QC that simply should not happen. No one would need to do a star test to see that the ring hasn't been inserted correctly, including the person who put the two blobs of cement on it. That lens cell should never have left the factory in that state.

With all due respect to Es Reid, a junior member of staff at any reputable astro retailer could be trusted to remove the dew shield and look for this problem before any of these scopes are shipped.

Let's hope Synta get their act together soon.

The silver lining on all of this is John's report on the control of CA and the performance of the focuser on the first scope, both of which are very encouraging if the other problems can be fixed.

[CHASLX200]

Reminds me of the Meade 7" ED nitemare i had back in 1999.  It went back to Meade 4 times and woudldalways come back out of collimation. This was before the cell fix.  I got my money on that load of junk.

[Stub Mandrel]

I get the feeling we are a long way from the 'outcome'.

Even assuming out-of whack samples are scarce, the fact John saw two suggests others will be turning up.

There's an 'emperors new clothes  ' effect that means some purchasers may convince themselves their scopes are OK, but I am sure if there are others about some of these will surface. If this starts hurting the big US market, Skywatcher will have to get the QC sorted very quickly.

 

[Macavity]

Quite strange... Looks almost like a crossed thread. But I'm reminded of
the "no-meddle" rule, which I should often have observed in the past! ?

I found real interest in articles re. "fixing" Apochromatic (Triplet) cells!
Optical bench + Genuine Expertise - Both fascinating & terrifying? NOT
one for the uninitiated though! On the plus side, the lens elements did
seemed capable of significantly better things... One lives in hope etc. ?

Edited August 8, 2018 by Macavity
Confused my Achros and Apos! <ashamed>

[FLO]

16 hours ago, FLO said:

We will endeavour to put a good example in John’s hands but I think we should consult with Sky-Watcher’s UK distributor before deciding the next move. Not least because this is a new model so we are not sure what the current stock situation is like. 

We have spoken with the UK distributor.

Unfortunately it will take us longer than normal to source and dispatch another to John because stock here in the UK is very low. But as soon as we can, we will ? 

HTH, 

Steve 

[gorann]

4 hours ago, wimvb said:

Maybe Skywatcher should hire Es as a consultant for quality control, just as they hired Pal Gyulai for the optical design of Esprit.

Fortunately my Esprit 150 was checked by Es, so I feel relaxed. By the way Wim, what you say may only be half true?. I just read this on Cloudy Nights:

"Esprit 120 and 150 have f/7 optics designed by Hugo Ruland of Lichtenknecker Belgium, while the faster Esprit 100 and 80 have been designed by Gyulai Pal in Hungary.

So these are different optical designs." (https://www.cloudynights.com/topic/535789-sky-watcher-esprit-150ed-fpl-53-triplet/)

By the way, does anyone know who designed the 150ED, and why is the glass composition a secret?

[Stub Mandrel]

1 hour ago, gorann said:

why is the glass composition a secret?

In order to generate massive on-line speculation and discussion, generating massive free publicity ?

[John]

5 hours ago, Macavity said:

Quite strange... Looks almost like a crossed thread. But I'm reminded of
the "no-meddle" rule, which I should often have observed in the past! ?

I found real interest in articles re. "fixing" Apochromatic (Triplet) cells!
Optical bench + Genuine Expertise - Both fascinating & terrifying? NOT
one for the uninitiated though! On the plus side, the lens elements did
seemed capable of significantly better things... One lives in hope etc. ?

Just a point of detail, the ED150 DS Pro is a doublet rather than a triplet. The objective cell design is simple compared with a triplet but does need to be accurately machined and accurately put together of course. The lens elements in a 150mm are reasonably heavy chunks of glass so the lens cell needs to be able to hold them firmly in place, accurately centrered and spaced in relation to each other and the whole objective purpendicular to the optical axis of the focuser. This needs to be maintained when the scope is in transit but the glass elements should not be held so tightly that they are pinched when the scope is being used at a wide range of temperatures. It's all quite a subtle business. Skywatcher can do this though.

 

[Macavity]

16 minutes ago, John said:

Just a point of detail, the ED150 DS Pro is a doublet rather than a triplet. 

Yes, sorry to muddy the waters on that one. Relative simplicity of ED doublets,
knowledge of my limitations (+price!), a clincher re. my small non-Achromats. ?

Edited August 8, 2018 by Macavity

[DRT]

22 hours ago, John said:

These reflections should overlap each other completely if things are OK . Things were definitely not OK with this ED150 objective lens collimation.

Here is an illustration of the project image of the cheshire eyepiece. Not what you want to see:

The retaining ring on the second scope was not only tilted but had been cemented in place using two blobs of cement (often normal practice) so I can only conclude that it left the manufacturer this way.

Here are some photos of the retaining ring in the cell from the side (top, bottom and the whole thing) which I hope show it’s tilted position:

@John's post edited by @DRT to only include the bits I wanted to comment on

This has just reminded me of a similar experience with my SW ED120 - caused by me but as a result of something I suspect the ED120 and the ED150 will have in common.

A couple of years ago I unscrewed the lens cell of my ED120 in order to clean some paint flakes off the inside surface of the objective. After screwing the lens cell back on I did a similar test to that described by @John and the pattern I saw was identical to the sketch in the above post with two completely separate circles. I removed the cell again and re-fitted it. The next test showed two concentric circles in perfect alignment. 

The problem had been caused by me screwing the objective cell onto the OTA with the threads crossed so the objective was tilted to one side. Neither thread was damaged and it was a simple task to refit the cell with the threads properly engaged and the lens in the correct alignment.

My conclusion was that the tolerances used in the manufacture of the OTA and the cell are relatively coarse, thereby allowing this mis-alignment to occur. Tighter tolerances of highly accurately machined threads would have prevented me from screwing the cell onto the OTA with the threads misaligned, or would have caused me to use so much force that the threads would have been damaged. 

I suspect the threads on the lens cell and its retaining ring are machined to a similarly slack tolerance to those on my ED120.

A compromise in the manufacturing process when trying to keep cost down?

Edited August 8, 2018 by DRT

[John]

18 minutes ago, DRT said:

This has just reminded me of a similar experience with my SW ED120 - caused by me but as a result of something I suspect the ED120 and the ED150 will have in common.

A couple of years ago I unscrewed the lens cell of my ED120 in order to clean some paint flakes off the inside surface of the objective. After screwing the lens cell back on I did a similar test to that described by @John and the pattern I saw was identical to the sketch in the above post with two completely separate circles. I removed the cell again and re-fitted it. The next test showed two concentric circles in perfect alignment. 

The problem had been caused by me screwing the objective cell onto the OTA with the threads crossed so the objective was tilted to one side. Neither thread was damaged and it was a simple task to refit the cell with the threads properly engaged and the lens in the correct alignment.

My conclusion was that the tolerances used in the manufacture of the OTA and the cell are relatively coarse, thereby allowing this mis-alignment to occur. Tighter tolerances of highly accurately machined threads would have prevented me from screwing the cell onto the OTA with the threads misaligned, or would have caused me to use so much force that the threads would have been damaged. 

I suspect the threads on the lens cell and its retaining ring are machined to a similarly slack tolerances to those on my ED120.

A compromise in the manufacturing process when trying to keep cost down?

I have experienced exactly the same with Evostar 120 and 150 achromats Derek. It's so easy to put the objective cell back on the tube a little tilted.

After doing the 1st set of tests I did actually remove the ED150 objective cell from the scope tube (very carefully) and then re-seated it again (again carefully) on the tube threads. No change to the cheshire test, unfortunately. 

Our experiences also demonstrate that it does not take much of an error in objective tilt to produce a really noticable collimation problem. Worth noting by those with push-pull tilt collimatable objective cells - small adjustments are all that is required !

I have had couple of scopes where adjusting the tilt of the objective secured a good cheshire test but still a less than ideal star test, particularly at focus (rather like the 1st ED150 example). I never did get to what exactly would cause this but culprits could include de-centered optical elements, lens spacing errors, lens objective "wedge" or simply poor quality figuring of a lens. I hope the latter two would be unlikely with todays optical stanards but I guess the odd "dog" gets though. 

With a simple doublet refractor requiring 4 accurately figured lens surfaces, triplets 6 etc, etc I guess it's clear why the refractor is more expensive to produce , inch for inch, compared to the single optical surface of the primary mirror.

 

[DRT]

5 minutes ago, John said:

I have experienced exactly the same with Evostar 120 and 150 achromats Derek. It's so easy to put the objective cell back on the tube a little tilted.

After doing the 1st set of tests I did actually remove the ED150 objective cell from the scope tube (very carefully) and then re-seated it again (again carefully) on the tube threads. No change to the cheshire test, unfortunately. 

 

Maybe you should put it back on tilted and see if it compensates for the misaligned retaining ring?  

 

Just to be clear - this is a joke!!!

[John]

3 minutes ago, DRT said:

Maybe you should put it back on tilted and see if it compensates for the misaligned retaining ring?  

 

Just to be clear - this is a joke!!!

I have hit it several times with a lump hammer to see if that helps. I felt much better about things but the scope did not, alas

FLO - don't panic - this is also a joke !!!!

The scope is in perfect order, of course.

[DRT]

Just now, John said:

The scope is in perfect order, of course.

If only that were true ?

[Alan White]

Shame it has run this way so far John, but let's face it it;

One scope damaged in transit, couriers are not anyone's friends when it comes to anything delicate.
One scope with a manufacturing fault and missed on QC, its an anomaly, not a proven trend as its 1 in XXXX with a problem to date.

I await fresh stock and your update, but based on months of delay on imports to SW fear we may a bit a a wait in store.

But a big thank you to John for the dedicated testing and also all at FLO for being prepared to publicly do this test, good on you all.
 

[John]

5 minutes ago, DRT said:

If only that were true ?

Good point. The scope is in exactly the same order that it was delivered ....

[DRT]

1 minute ago, Alan White said:

But a big thank you to John for the dedicated testing and also all at FLO for being prepared to publicly do this test, good on you all.

Well said, Alan - great to see this happening in real time and credit to FLO and John for sharing the information so openly.

[Tim]

8 hours ago, wimvb said:

In the mean time, an Es Reid test can provide the quality control that should be SOP in China. The scope just became £ 75 (which I believe is the price FLO  usually adds for a test) more expensive than its list price.

The list price for the 150ED is £1699 on OVL's website IIRC. So actually, a buyer would still be 4 quid better off

[Tim]

4 hours ago, gorann said:

 why is the glass composition a secret?

Perhaps  not so much a secret as  much as irrelevant to most purchasers? I also have no idea what type of glass is used in my Televue eyepieces, but I know that they work well

[Owmuchonomy]

8 hours ago, John said:

From reports elsewhere, it appears that Synta (who of course make the scope) had a problem with the 1st batch of glass used for the objective and had to scrap the lot and start again. The release of the scope was delayed but this could well have put pressure on other parts of the manufacturing chain perhaps ?

We must also remember that Skywatcher are far from alone in experiencing problems of this nature with a new design. Many brands including some very prestigious names, have experienced such issues. Lets hope that the very substantial organisation behind the ED150 can quickly iron out the problems and allow the design to shine, as it deserves to

Oh indeed John. I could name and shame another ‘quality’ brand but there is nothing to be gained from that.

[Moonshane]

My concern with this sort of cell is that misalignment can recur if everything you knock the scope slightly or sometimes even with cool temperatures. I am though referring to my experience with a Meade triplet

[John]

6 minutes ago, Moonshane said:

My concern with this sort of cell is that misalignment can recur if everything you knock the scope slightly or sometimes even with cool temperatures. I am though referring to my experience with a Meade triplet

Fair point Shane. We probably need winter and summer tests. Either that or I need to get a very capacious fridge !

 

[DRT]

9 minutes ago, Moonshane said:

My concern with this sort of cell is that misalignment can recur if everything you knock the scope slightly or sometimes even with cool temperatures. I am though referring to my experience with a Meade triplet

Without wanting to cast doubt on the work of Es Reid and others like him, I do think this is a very real problem.

If FLO send an ordered scope to Es to have the alignment checked, and perhaps tweaked to make it perfect,  that scope then goes back in a box and potentially gets chucked around a few vans and warehouses before reaching the customer. Even if handled carefully (in courier terminology) I doubt very much that everything will be as it was when it left Es Reid's hands by the time it arrives at the customer's address, particularly if the lens is held in a relatively inexpensive cell.

I think if I wanted to pay for someone like Es to optimise the alignment of some expensive optics I would then want to be in complete control of the onward transport to wherever I wanted the scope to live. DHL, DPD and their kin are very efficient at getting big boxes from A to B quickly, but they do not do it with kid gloves ?