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Nichol Optical 18" F/4 1/8th wave mirror


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  • 4 years later...
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455mm diameter 1838mm focal length Hilux coating This is not a first light report. I’ve had a couple of those while building the telescope earlier this year. I’ll post those in a separate post below.

Here are the first light reports from April. First Light Proper Here we go. Was out the moment Jupiter was visible. The scope had been cooling for a couple of hours. I settled down with a list of obje

Great report John, really glad you are enjoying the scope now. I was at herstmenceux star camp last month with my scope observing and this guy comes over and ask to have a look through the eyepiece. H

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  • 4 weeks later...
On 17/10/2019 at 21:14, Johnthefrench said:

Hello everybody,

Did someone already test john's Nichols mirrors ? I mean with Foucault test.etc

There are few comments of french who are not happy with these mirrors but No reports since 2010...

I Hope to try one 18for my dobson.

Someone ?

Thanks

 

Perhaps you could start a new thread - you may get more responses

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A good mirror needs high magnification and good seeing to test its true precision.
Thermal issues will confuse matters if the blank is cooling or warming. It usually is!
Unless, of course, it is thin and made of something expensive & exotic.

A Foucault test needs practice, patience AND personal interpretation.
While a Ronchi screen in the empty focuser should show straight lines.
As will a humble straight edge. I "tested" every telescope I looked though that way.
It will tell you something about support and the optical figure at a quick glance.
Always assuming it is not cooling or warming. It usually is!

Judging any telescope mirror at the eyepiece is not easy without practice and experience.
It assumes perfect collimation and proper support for the mirror blank.
With larger mirrors the subject of proper support is a steadily advancing science.
What works in a Dobsonian altazimuth will probably not work in an equatorial.

Is the mirror properly supported in a well thought out, thermally efficient cell?
Inevitably high, thermal mass and tight enclosure, without forced ventilation, just won't do.
How is the mirror blank supposed to adapt to constantly changing temperature and inclination?
Is it being pinched at the edges? Or being bent into a pretzel by gravity?

A fine mirror [or lens] must be judged with great care.
Professional reputations [and livelihoods] depend upon it.
Judge the critic's skills and experience before you judge the mirror.
Demanding a Foucault test is not a sign of very much experience at all. IMHO.

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On 09/11/2019 at 20:15, Peter Drew said:

I think most of us would confirm John Nichol's integrity and optical excellence so I'm surprised that, allegedly, there have been unhappy customers.    🤨

I am certainly happy with a second hand mirror that was re-figured for me by John Nichol. Before John re-figured the mirror, it exhibited zonal errors in the star test and John confirmed this when he sent me a picture of the mirror under an autocollimator test before he worked on it. Now the mirror is very good and the cost was reasonable; I am just glad the used scope was cheap to buy.

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I have one of John's mirrors...don't have any information on it....don't need any.

Experienced observers have looked at many objects with my scope , all say its excellent...Mapstar, swamp thing have mirrors that have been touched by the hand of John.

Daniel-K said it was one of the best hes used. No reports needed, john doesn't make bad mirrors and certainly wouldn't let one leave his workshop. Not only is he a great craftsman but also a gentleman. 

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On 17/10/2019 at 21:14, Johnthefrench said:

Hello everybody,

Did someone already test john's Nichols mirrors ? I mean with Foucault test.etc

There are few comments of french who are not happy with these mirrors but No reports since 2010...

I Hope to try one 18for my dobson.

Someone ?

Thanks

 

9 years ago?

I've never heard of a displeased customer myself.

John gave up his time, hospitality and experience to help me finish my 22" F3.4.  Not sure how many other mirror makers would do that.

Easy I guess to post (2 posts!!!!) on a forum and Question an individual's reputation. You could always question the reputation of Zambuto, Lockwood and Bartels if you're thinking about their optics too? I'm sure there are various French mirror makers to consider as well as GSO.

There are plenty of comments to read in this thread so I'm sure you will draw your own opinion and order accordingly. 

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I have met John, he is a genuine person who spends a fair amount of his time promoting astronomy. I also asked him to give a talk at our local Astronomy branch in South Shields. He did it without any cost to us, purely because I asked. His talks always show his enthusiasm, which he seems to effortlessly pass on to others. If I was in the market for a DOB he would be my one and only call.  Have met several of his customers and all give glowing reports on his service and mirrors. 

I suggest reading around the subject, a lot, then talk to lots of real astronomy amateurs before coming to your own conclusions. I am sure you will find no complaints here.

Derek

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