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How common is pinched optics in the winter on Esprit APOs?


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Hi all,

I'm keen to understand how common it is to see pinched optics on the Sky-Watcher Esprit APOs in cold weather during the winter. I get hexagonal stars with my Esprit 120 when the temperature dips close to 0C outside, even with a dew heater strap. The effect becomes less noticeable as the ambient temperature increases, so that by around 5C I have nice round stars again. You can see the effect clearly on the image of M106 below (particularly the brighter stars towards the top left hand corner of the image). The temperature outside for this image was getting on for -2C.

I know that this is caused by the six collimation screws holding the objective in place, which pinch the lens cell a bit too much when the temperatures get cold. Do most Esprit owners see this effect to some degree in cold temperatures or is it only in some isolated cases like mine? If the latter, then this suggests it should be possible to fix this by loosening these screws ever so slightly so there is no pinching in cold weather, but secure enough to maintain collimation of the scope. Certainly not a procedure I would want to do myself, but I presume someone like Es Reid would be able to fix this easily enough. I'm generally very happy with the scope I have, but I would be happier if I could have clean round stars in my images all year round.

Would welcome some thoughts/opinions on this.

Charles

M106-test2-mod-lpc-cbg-csc-mod-St.JPG

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My Esprit 100 suffered terribly from this issue, and was even serviced by Es Reid to try and reduce the problem. However, even after having the lens retaining screws loosened, the pinching was still bad. The scope also developed a focuser fault, so I ended up returning it. The pinching was visible from temperatures as high as 15 degrees C (I never imaged warmer than this), but got much worse in the cold. The lowest temperature I ever used the scope in was -4.5 degrees C and almost every single star was hexagonal. The issue was also exasperated by me switching to a camera with smaller pixels early this year, and thus having a better sampling rate. 

Some examples (all at 1:1 except the first which is at 2:1):

15 degrees C ambient (Canon 6D):

image.png.1f94b5b22ecb98b4ed9708fc42316e17.png

8 degrees C ambient (Canon 6D):

image.png.c173555a0655bdc8478fee92d8792102.png

7 degrees C ambient (Canon 6D):

image.png.d7f99af22c0bf1240460fea1c59c3025.png

5 degrees C ambient (Canon 6D):

image.png.f92f92b53e0a823f17218b4512e558f9.png

5 degrees C ambient (QHY268M and 3nm Ha filter):

image.png.f026e58bd3a2294dd9c0a104fc7205ef.png

-2 degrees C ambient (QHY268M and 3nm Ha filter):

image.png.b501e406a56869c54c5e3933cfe5aeaf.png

-4.5 degrees ambient (QHY268M and 3nm Sii filter):

image.png.638275a7fc68d5ea64bc7e18484fe555.png

After this the scope was adjusted by Es Reid. The focuser subsequently packed up and I only got one night of imaging out of it, but here is an example of post adjustment pinching at 5 degrees C ambient (QHY268M and 3nm Ha filter):

image.png.a6db9d32f6b6c5a0150008c92168033c.png

 I feel like I certainly got a bad sample of the Esprit 100, as almost everyone else I've seen using it has excellent round stars. Rather than take the risk with a new copy though, I decided to go for another scope and see if that is any better (Askar FRA600).

Sorry for the long post but I hope this helps :)

Cheers

Edited by Spongey
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Thank you, this is helpful and I’m sorry to hear about your experience. It certainly looks like your issues are much worse than mine, and it is a shame they could not be resolved. Your story does not fill me with confidence that an easy fix will be possible, so maybe a replacement is a safer option, though it’s a real pain with availability of telescopes being so poor at the moment. I bought mine from Widescreen Centre, so I’m hoping that if I approach them about this they will be as understanding as doubtless FLO would be based on my experience with them so far and from what I see on this forum. I’m also keen to hear from other owners to see how common this issue is, because this will influence what decision I eventually make.

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Same thing with my Esprit 80 which I returned for that reason.  Haven't found any replacements but there are so many problems with them I'd only consider buying them if able to test myself.  The downfall of Esprit QA over the last year or two is a mystery but I'll let them sort it before I touch them again.

IC434.thumb.jpg.917b06604b65b3d9dfa5f4b57ae3f9cf.jpg

Edited by licho52
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I ordered an Esprit 100ed a few days back from Flo. I have to say this I the first time I have read anything negative on the Esprits and as mentioned other images I have seen on here and other places have been flawless.

Perhaps a faulty batch/couple of scopes?

My confidence has been ever so slightly rattled but when mine arrives and has had its first light I will report back!

Edited by Jonny_H
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7 minutes ago, Jonny_H said:

I ordered an Esprit 100ed a few days back from Flo. I have to say this I the first time I have read anything negative on the Esprits and as mentioned other images I have seen on here and other places have been flawless.

Perhaps a faulty batch/couple of scopes?

My confidence has been ever so slightly rattled but when mine arrives and has had its first light I will report back!

If you're not lucky and request a replacement it might just turn out to be worse than original.

My story.  Wasted 2 months and tons of aggravation.  Sky Watcher point blank refused to fix it.

The replacement had the following feature:

Capture_00001.png.3ec9ca8e6d0ee21bca33eff4814d5315.png

Edited by licho52
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2 minutes ago, licho52 said:

If you're not lucky and request a replacement it might just turn out to be worse than original.

My story.  Wasted 2 months and tons of aggravation.  Sky Watcher point blank refused to fix it.

What was their rationale for not fixing it? Surely they didn't say it was 'normal'?

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It was tremendous: "we test all telescopes to perform optimally and seal them in box from factory"

It is probably a bit better in the U.S. but in E.U. they don't care.

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These reports are not good. The Esprit range are not £100 Startravels or their equivalent.
You are all paying a lot money and the scope should be right - from delivery.
Skywatcher will only get their act together if a number of users & retailers start returning product.

Given the number of problems that are reported, I would take a lot of persuading to upgrade in the Esprit direction.
Actually if Skywatcher are sending shoddy products from their supposedly premium range, what can we expect from their more affordable ranges?
I will stick with what I have already, thank you Mr. Skywatcher.

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2 hours ago, Spongey said:

I feel like I certainly got a bad sample of the Esprit 100, as almost everyone else I've seen using it has excellent round stars. Rather than take the risk with a new copy though, I decided to go for another scope and see if that is any better (Askar FRA600).

The Askar is made by Sharpstar.  I have one of their 90mm APO FPL-53 triplets under the TS Optics brand.  Hopefully, your FRA600 works out better for you than the Esprit did.  I can say that I have spiky stars in my Sharpstar triplet until it acclimates, but I'm just a visual observer.

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 Were these scopes made recently? could it be that maybe they’ve had to change lens cell material due to certain metals being difficult to source due to Covid? All it would take is an increase or decrease  in one particular metal mixture and expansion/contraction rate can change.

Forgot the word to describe an impure metal, one made of a mixture of metals.

Edited by Sunshine
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1 hour ago, Jonny_H said:

I ordered an Esprit 100ed a few days back from Flo. I have to say this I the first time I have read anything negative on the Esprits and as mentioned other images I have seen on here and other places have been flawless.

Perhaps a faulty batch/couple of scopes?

My confidence has been ever so slightly rattled but when mine arrives and has had its first light I will report back!

I'm in the same boat - ordered a few weeks ago, and partly based the decision on the strength of the reputation of the esprit range. Thankfully bought through FLO, so have every confidence any issues with it will be rectified appropriately.

If it turns out to be a bad one though, might just exchange for that new triplet from Williams Optics...

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8 minutes ago, cfinn said:

I ordered mine in August and it arrived in November.

My response was just speculation but, all it takes is for one metal to skyrocket in price and the higher ups decide to use a percentage less of one metal and a percentage more of another in the mix and it can drastically change how a metal behaves under different temps.

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1 minute ago, The Lazy Astronomer said:

I'm in the same boat - ordered a few weeks ago, and partly based the decision on the strength of the reputation of the esprit range. Thankfully bought through FLO, so have every confidence any issues with it will be rectified appropriately.

If it turns out to be a bad one though, might just exchange for that new triplet from Williams Optics...

Well let's hope we are one of the lucky ones! :)

As you mentioned we have ordered from FLO so any issue will be promptly addressed.

My only concern is that by the time the scope arrives it will possibly be warmer weather (perhaps optimistic for the UK 😂) so the issue may not be as apparent for a while.

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1 minute ago, ballisticbrian said:

What is pinching for the resident noob?

When the lens cell is over tightened and it distorts the image.

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4 minutes ago, ballisticbrian said:

What is pinching for the resident noob?

When the lens cell which is made of some type of metal has contracted under low temperatures therefore applied stress to the glass, slightly deforming it on a particular axis causing light rays to travel at different paths than what they should.

Edited by Sunshine
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13 minutes ago, Sunshine said:

My response was just speculation but, all it takes is for one metal to skyrocket in price and the higher ups decide to use a percentage less of one metal and a percentage more of another in the mix and it can drastically change how a metal behaves under different temps.

That’s interesting. You could well be right.

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16 minutes ago, ballisticbrian said:

  Lockheed Martin on "The Hubble Telescope", 😆😆😆

Yeah blimey, you’re not wrong! I’ve emailed Widescreen Centre to report the issue and explore what my options are. Let’s see what they say.

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2 hours ago, licho52 said:

My story.  Wasted 2 months and tons of aggravation.  Sky Watcher point blank refused to fix it.

Working as designed.  Never mind that the design (or implementation) is flawed.

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Hope you get this sorted and don't put you off these excellent scopes

If you don't have any luck there's a chap in France that,  cleans and gets them up to scratch, probably better than factory spec.. but at a price

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5 minutes ago, newbie alert said:

Hope you get this sorted and don't put you off these excellent scopes

If you don't have any luck there's a chap in France that,  cleans and gets them up to scratch, probably better than factory spec.. but at a price

Thank you. That is good to know, but of course it shouldn’t have to come to that. It’s a shame, because when I first got the scope it gave an excellent star test (in warmer temperatures). The optics are first class and this is essentially just an assembly/design issue.

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