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Dust and speck of paper inside a new triplet

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#1 Palmito

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Posted 25 February 2020 - 02:06 AM

Hi everybody,

 

 

I recently purchased a new refractor. And I noticed that on the rear of the lens (inside the refractor) there is dust and what seems to be small pieces of paper.

 

 

The seller tells me he believes I have never used a telescope before and that my expectations are too high. That it is perfectly normal to be dust inside and outside of a brand new OTA.

 

I am expecting it to be pristine.

 

 

What do you guys think?

 

 

Cheers

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#2 sg6

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Posted 25 February 2020 - 03:17 AM

Should be "pristine" if new. Say "if new" as the post reads that you may have purchased used from someone and it is "new" to you.

 

Lens like these are assembled in clean rooms. Personel hooded and in a coat with air filtered. Basically at assembly nothing in the room to cause a possible problem.

 

Since the lens cell is almost completely sealed then usually difficult for anything to get in at all. Fine dust maybe due to warming and cooling effect of expansion and movement ofair in and out. But someting of any size it should be almost totally impossible.

 

So guess someone has hauled the lens cell out and maybe tried to adjust things that require freeing up the lens - thinking thoughts along "I can check/change/better the collimation if I play with this".

 

If it is/was a used item then unsure. Should be clean, would expect some fine dust as over time it tends to get everywhere. Still think that big bits mean someone has been making adjustments. But those lens are in a cell with retaining rings that prevent crud getting in. So someone has been sloppy.

 

I am fortunate here, know someone 12 miles away that will check and adjust scope lens. Sort of semi retired optics engineer and he does it for one of the retailers. Have taken an ED doublet to him for us to "play" with. I wanted it checked as I had a little bump with it.


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#3 Palmito

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Posted 25 February 2020 - 04:19 AM

My thought exactly. There are other signs of the lens being hauled out, like the strip around the lens that has not been completely attached, the white nail mark at that exact position.

 

It is a SkyWatcher Esprit 150ED that was sold to me as brand new by a shop.

 

It has already been sent back once at the beginning of the month because the lens was really really dirty. To be honest I didn't find it to look new. The shop said it was new and not refurbished.

 

I was told a brand new replacement was sent to me. I was also given a printed quality analysis report.

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#4 ngc7319_20

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Posted 25 February 2020 - 07:17 AM

Stuff can move around during shipping. Maybe a speck of dust starts out on the focuser plug, and is on the back of the glass when it arrives. Maybe if the focuser is not air-tight, it can start out in the packing material. 

 

If the scope and views are otherwise ok, I'd forget about it. The speck of dust will affect absolutely nothing.

 

In the old days, manufacturers would sometimes put sticky glue everywhere inside optical instruments to capture loose dust.  This is why.


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#5 Blueox4

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Posted 25 February 2020 - 07:21 AM

If it’s between elements I would not be happy either but if only on the rear element facing the focuser it could have moved during shipping. Try blowing it off with a bulb blower and long plastic tube. 


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#6 Palmito

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Posted 25 February 2020 - 07:55 AM

Many thanks for your inputs!

 

Ok, so to follow-up, the shop said I should remove the focuser and blow from behind.

 

Upon further inspection I noticed the paper piece fell. But found some cleaning marks inside. Trying to take a picture of it I found huge scratches inside!

 

That was my fear, they cleaned it with dust remaining, that meant it was very badly done. Dust is abrasive and causes scratches....

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Edited by Palmito, 25 February 2020 - 07:57 AM.


#7 starryhtx

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Posted 25 February 2020 - 08:13 AM

I'd send it back


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#8 Alan French

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Posted 25 February 2020 - 08:27 AM

Many thanks for your inputs!

 

Ok, so to follow-up, the shop said I should remove the focuser and blow from behind.

 

Upon further inspection I noticed the paper piece fell. But found some cleaning marks inside. Trying to take a picture of it I found huge scratches inside!

 

That was my fear, they cleaned it with dust remaining, that meant it was very badly done. Dust is abrasive and causes scratches....

They look more like the streaks that are often left after cleaning a lens than scratches.

 

Clear skies, Alan


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#9 Palmito

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Posted 25 February 2020 - 08:36 AM

Thanks starryhtx, yes I really feel like sending it back. But at the moment the shop says they could replace it 10 times, it will always be the same, that this is normal.

I am waiting for an answer after my last emails about the cleaning marks and what I believed was scratches.

 

Thanks Alan, I really hope so.



#10 Alan French

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Posted 25 February 2020 - 08:54 AM

Me too. 

 

Clear skies, Alan



#11 Palmito

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Posted 25 February 2020 - 09:02 AM

Me too. 

 

Clear skies, Alan

Clear skies!



#12 ngc7319_20

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Posted 25 February 2020 - 10:14 AM

Some amount of scratches and pits on optics is normal.  I would say what you have there is in the normal range. There is no such thing as a "perfect" optical surface.  There are just specifications and measurement methods.

 

Optics comes in different surface grades, etc. Probably these mass-produced China lenses are the lowest grade called 80/50.  If the seller promised 2/1 grade and you paid $2,000,000, then you probably have a legitimate beef.  

 

https://www.edmundop...specifications/

 

https://wp.optics.ar...ig_Tutorial.pdf

 

https://www.newport....ptical-surfaces


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#13 Bill Barlow

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Posted 25 February 2020 - 10:57 AM

Who did you buy it from?



#14 Heywood

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Posted 25 February 2020 - 11:25 AM

The Esprits are expensive. I would send it back for a refund.

#15 BillP

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Posted 25 February 2020 - 11:36 AM

Thanks starryhtx, yes I really feel like sending it back. But at the moment the shop says they could replace it 10 times, it will always be the same, that this is normal.

I am waiting for an answer after my last emails about the cleaning marks and what I believed was scratches.

I would not buy from that shop again.  They are wrong.  Can you imagine buying a camera lens and have issues like this!!  I have purchased so many camera lenses in my life and never a spec on any of them.  Given the price of an OTA, stuff like this is unacceptable IMO.  Send it back and ask for a full refund.  That is just marketing B.S. they are giving you about 10 others would be all the same.  If they emailed you saying that then find out who is the owner or franchise owner of the shop and let them know.  Unacceptable!


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#16 BillP

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Posted 25 February 2020 - 11:36 AM

Who did you buy it from?

Yes.  Please PM those of us that want to know so we cross that shop off our list. 

 

The moment the consumer lets the market know they will accept poorly attended optics like this and still pay the price, then this sort of unacceptable quality will be come the normal for high price wares.  Don't give up the demand for quality from the marketplace!


Edited by BillP, 25 February 2020 - 11:40 AM.

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#17 Palmito

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Posted 25 February 2020 - 01:30 PM

Many many thanks for your inputs. I understand perfect optics is impossible and that the price is raising exponentially with quality. But my 80mm guide scope looks much better and it is worth only $150, it has no scratches, no cleaning marks and not dozens of pieces of paper inside the tube.

 

 

Meanwhile I have received an answer from the shop. They said that the refractor is brand new and has never been cleaned by the shop. I am being told it is absolutely normal that any refractor will show cleaning marks under a flashlight.

They don't think it is scratches as it would have shown on the star test and the ronchi test.

That I should look into the skies instead of looking for problem because of a single particle of dust.

 

 

Please understand I won't communicate the name of the shop as at this point I have looked into legal advise.

I will only say it is not a shop in the US for those of you who are worried ;-)


Edited by Palmito, 25 February 2020 - 01:40 PM.


#18 peleuba

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Posted 25 February 2020 - 01:39 PM

They don't think it is scratches as it would have shown on the star test and the ronchi test.

That I should ok into the skies instead of looking for problem because of a single particle of dust.

 

 

No.  Scratches will NOT show up in single pass Ronchi or star test.  Scratches won't show up in double pass either unless they are particularly wide/deep and/or affect the figure of the lens.  



#19 Palmito

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Posted 25 February 2020 - 01:45 PM

No.  Scratches will NOT show up in single pass Ronchi or star test.  Scratches won't show up in double pass either unless they are particularly wide/deep and/or affect the figure of the lens.  

They are long but do not seem wide or deep.

 

Will double pass ronchi show it?

 

Is there a way to test if it is a scratch by myself?



#20 peleuba

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Posted 25 February 2020 - 02:17 PM

They are long but do not seem wide or deep.

 

Will double pass ronchi show it?

 

Is there a way to test if it is a scratch by myself?

 

The scratches in the photos above will not show up in DPAC or in the star test. 


Edited by peleuba, 25 February 2020 - 02:17 PM.


#21 sunnyday

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Posted 25 February 2020 - 02:29 PM

 

 

Please understand I won't communicate the name of the shop as at this point I have looked into legal advise.

I will only say it is not a shop in the US for those of you who are worried ;-)

nothing can happen if you just give the company name.
I don't know in which country you live, but if the company is outside your country even less to worry about legal problems.
you could give it as a private message to people who request it.
but on the other hand I can understand your hesitation to do so.
ps. too bad for you that this telescope is not up to your expectations.


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#22 SeattleScott

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Posted 25 February 2020 - 02:34 PM

If it is a scratch, and deep enough to matter, you should see light scatter looking at a bright object.

Personally the new scopes I have purchased had pristine lenses, although I never was compelled to examine them with a flashlight. I did buy a refractor with a speck of paper like that stuck on the rear of the lens, but that scope was a couple decades old and purchased for a very reasonable price off CL.

If the lens looks perfect in normal room lighting then I would be tempted to give it a shot and see how it performs. But I would track a bright star across the view where these suspected scratches are and see if there is any distortion. If the scope performs great, no distortion detectable from the scratches, and you can only see any defect with a flashlight, then you might as well keep it. If you do see some distortion from the suspected scratches, now you can go back to the vendor with confirmation that the defects are affecting the view. If you are going to pursue legal action, a judge would want to know if these defects are just superficial or if they actually impact performance. So far you have no proof. You might argue it impacts value, or resale value, but even that could be hard to prove if it takes a flashlight to see the defects.

Scott

#23 Blueox4

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Posted 25 February 2020 - 03:42 PM

No way would I keep that. A dust speck is one thing. Looks like dew marks too. The scratches are a deal breaker. If you paid by credit card dispute the charges if they won’t replace it. Please tell us who this seller is also and help the community avoid them. 


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#24 helpwanted

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Posted 25 February 2020 - 03:48 PM

credit card dispute the charges

 

YES, i forgot about that, there is your best path to get this resolved



#25 Kunama

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Posted 25 February 2020 - 04:32 PM

Not sure what country the OP is in but if it was my scope it would be going back for a replacement or refund......  


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