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

[Spongey]

1 minute ago, cfinn said:

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.

I agree that it is a terrible shame. The optics on my Esprit 100 were fantastic if it weren't for the pinching issue; I measured the Strehl ratio as 0.976. Interestingly enough the effects of minor pinching can be seen in the intra and extra focal images here. I don't recall the ambient temperature but it was not very cold, I'd guess ~10 degrees.

 

[cfinn]

14 minutes ago, Spongey said:

I agree that it is a terrible shame. The optics on my Esprit 100 were fantastic if it weren't for the pinching issue; I measured the Strehl ratio as 0.976. Interestingly enough the effects of minor pinching can be seen in the intra and extra focal images here. I don't recall the ambient temperature but it was not very cold, I'd guess ~10 degrees.

 

Yep, superb. This is what sold me in the first place. You have to pay 2-3 times the price for this performance elsewhere. Hopefully Sky-Watcher can learn from these examples and improve their QC and/or lens cell design.

[SamAndrew]

No issues with my Esprit 100, I'm very happy with how it performs. Not sure how many people owned it before me or how old it is however.

Happens to premium scopes as well, see this thread and Olly's comments about 2 x FSQ 106 that had this issue.

 

[Spongey]

3 minutes ago, SamAndrew said:

No issues with my Esprit 100, I'm very happy with how it performs. Not sure how many people owned it before me or how old it is however.

Happens to premium scopes as well, see this thread and Olly's comments about 2 x FSQ 106 that had this issue.

It's worth noting that this effect is very different to what we are discussing here and is caused by aperture masking. This has been modelled and explained by Mark Shelly in the following thread.

 

[Adam J]

13 minutes ago, SamAndrew said:

No issues with my Esprit 100, I'm very happy with how it performs. Not sure how many people owned it before me or how old it is however.

Happens to premium scopes as well, see this thread and Olly's comments about 2 x FSQ 106 that had this issue.

 

The first two number of the lens serial number are the year of manufacture. 

[SamAndrew]

17 minutes ago, Adam J said:

The first two number of the lens serial number are the year of manufacture. 

Thanks, 2017 in that case! not as old as I thought.

[cfinn]

Just thought I would share that Sky-Watcher UK have agreed to send a replacement. Fingers crossed this one turns out better and I was just unlucky.

[wimvb]

On 09/03/2021 at 19:35, Sunshine said:

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

Alloy?

[Spongey]

53 minutes ago, cfinn said:

Just thought I would share that Sky-Watcher UK have agreed to send a replacement. Fingers crossed this one turns out better and I was just unlucky.

Glad to hear it! Do let us know if the new scope performs any better

[tomato]

I have access to two 150s, one purchased new in 2018 with the ES Reid inspection, the other second hand (but as new) in 2019 without the inspection. To my untrained eye they look Ok even at sub zero temperatures, the scopes are housed in an unheated observatory, not sure if this is a factor.

Hope your replacement performs, I could only dream of a dual APO rig of this aperture without these SW scopes.

[inFINNity Deck]

35 minutes ago, tomato said:

I have access to two 150s, one purchased new in 2018 with the ES Reid inspection, the other second hand (but as new) in 2019 without the inspection. To my untrained eye they look Ok even at sub zero temperatures, the scopes are housed in an unheated observatory, not sure if this is a factor.

Hope your replacement performs, I could only dream of a dual APO rig of this aperture without these SW scopes.

Same for me, I have one ED150 which resides in an unheated observatory and have so far not seen any issue of this kind, even near freezing point.

Nicolàs

[cfinn]

Thank you, this is encouraging to hear. I’ll report back once the new one arrives (end of this month supposedly) and I’ve had chance to test it. It will of course be warmer so I may not know for sure if the problem is still there until next winter...!

Edited March 11, 2021 by cfinn

[Ken82]

Yep I had this issue with 120 esprit. 
 

Ken 

[david_taurus83]

This is a bit of a damning report for the Esprit range! Are these issues apparent with new scopes or is it a collection of experiences since the Esprit was released? I've seen a thread where recent Esprit 80s had issues.

[cfinn]

21 hours ago, Ken82 said:

Yep I had this issue with 120 esprit. 
 

Ken 

What did you do about yours in the end? Did you get a replacement or go for something else?

[Adam J]

I think that it's important to remember that thousands of Esprit 100's have been sold so if you ask people for problems your immediately not going to get a balanced audience and it's inevitable there will be some bad examples. 

[Ken82]

58 minutes ago, cfinn said:

What did you do about yours in the end? Did you get a replacement or go for something else?

To be honest I sent it back but for something else. I had been using a certain camera and filters without any halo issues, but when I started with the 120 esprit I suddenly had halos. So logically I thought this was the issue but as it turned out the filter was causing the problem and not the scope, so I stand corrected on that! 
 

Sorry back on topic - 
 

I do believe Steve has said FLO have also seen this issue on some takahashi scopes. 
 

I’ve not seen this issue since and I’ve used a few different scopes. But perhaps adding an additional dew shield and heater may keep it warm enough ??

Something like this perhaps ?

 

[cfinn]

2 hours ago, Adam J said:

I think that it's important to remember that thousands of Esprit 100's have been sold so if you ask people for problems your immediately not going to get a balanced audience and it's inevitable there will be some bad examples. 

Yes, you’re absolutely right, I’m quite sure the replacement will be fine. I should emphasise that I’ve not set out in any way to rubbish the reputation of these telescopes. It was just helpful to me to verify that replacing the scope was the right course of action.

[cfinn]

2 hours ago, Ken82 said:

To be honest I sent it back but for something else. I had been using a certain camera and filters without any halo issues, but when I started with the 120 esprit I suddenly had halos. So logically I thought this was the issue but as it turned out the filter was causing the problem and not the scope, so I stand corrected on that! 
 

Sorry back on topic - 
 

I do believe Steve has said FLO have also seen this issue on some takahashi scopes. 
 

I’ve not seen this issue since and I’ve used a few different scopes. But perhaps adding an additional dew shield and heater may keep it warm enough ??

Something like this perhaps ?

 

Ok, thank you for the clarification. Your suggestion is a reasonable one, but of course should not really be necessary. Sky-Watcher have been good enough to recognise that in offering me a replacement.

[Spongey]

It is worth noting that I used a dew heater on 100% for every single example I posted above, and it's hard to know for sure how much it really helped.

I definitely think that my sample was an outlier in this regard as I've seen hundreds of images made with the esprit 100 that didn't suffer from this issue in the slightest.

[BallistaSlim]

Yup, got this issue as well with a E100. Received the scope in October from FLO. It varies by temperature, and maybe where I put my dewheater.

In all other aspects it is fantastic, so I'm not sure if I want to exchange it.

[Adam J]

6 hours ago, BallistaSlim said:

Yup, got this issue as well with a E100. Received the scope in October from FLO. It varies by temperature, and maybe where I put my dewheater.

In all other aspects it is fantastic, so I'm not sure if I want to exchange it.

That's a mild case at least. 

[BallistaSlim]

14 hours ago, Adam J said:

That's a mild case at least. 

Yes, and this is when it is most pronounced. Some pictures I cant notice it at all. I would think it is really hard to design the scope to prevent this altogether. If I send it in and they loosen the collimation screws who knows how it will work in higher temperatures?  

[Adam J]

comment removed. 

 

Edited March 23, 2021 by Adam J

[cfinn]

Does anyone know what metal/alloy the Esprit lens cell is constructed of? Steel is supposed to be the best because it has very similar thermal properties as the glass, which minimises the risk of this happening.