Understanding Zygo report

[Robindonne]

Although its probably not that important (due to not really knowing the report belongs to a particularly scope), i can’t seem to find a well explained explanation or info on how to read these diagrams and numbers.  
 

I received this report as a “screenshot” with the purchase of a used scope. No further details about the scope are shown.  I have my doubts about this report and therefore want to ask someone who can read it.  
 

Can someone, based on the info given in the report, tell the possible mirror size which is tested? 

many thanks. 

Edited July 15, 2021 by Robindonne

[vlaiv]

I'm not sure that you'll read off anything meaningful from that.

Is this scope reflector?

This should be the most important bit:

Which says that wavefront aberration is about 1/13.5th PV wave or 1/66.66th RMS wave

Both are exceptionally good results. 1/4th wave is diffraction limited optics, 1/6th is considered good, 1/8th very good and 1/10th excellent.

Problem is - that we don't know anything about how these numbers were derived. Is this system performance? What wavelength? Is it just main mirror in case of Newtonian. How was it measured? What wavefront components were removed?

I honestly doubt accuracy of this report as is.

[Robindonne]

26 minutes ago, vlaiv said:

honestly doubt accuracy of this report as is.

thanks.  indeed a questionable piece of paper with ink.  I have far too little knowledge to get anything meaningful from this report other than that it comes from Zygo.  The only thing I can deduce from other reports is that sometimes the size of the measured object is indicated.  see even reports with a clear mention of the telescope.  in this case, a fraction of a certain size appears to be readable.  half hidden behind a diagram.  I doubt whether these are millimeters or pixels or something else.  My mirror is round and has a hole in the middle 🙂.  Based on that resemblance alone, I cannot assume that this report is actually correct.  There seems to be far too easy to cheat on me.  And completely suspicious if the size of the mirror does not match.

[rl]

This looks superficially like an OO zygo test certificate. All of theirs I have seen have a few extra details though...telling the data and time of the test, and the size and focal length of the mirror, and its serial number, and the wavelength at which the test was done, and the operative (usually R Rogers) The numbers on yours are typical of an OO 1/10 wave mirror. On wavelength, OO use a 632nm HeNe laser so 1/10 wave is more like 1/8 wave at 550nm where the eye is most sensitive. 

Attached is the one for my VX14 for comparison.

Without full details tying the report to a particular mirror, there is no traceability. I would be a bit suspicious...

[Robindonne]

16 minutes ago, rl said:

would be a bit suspicious...

metoo.

 you guessed the telescope's origin correctly.  And while my untrained eye is far from being able to detect differences in qualities when using a telescope, let alone ever request a report for a telescope myself, it should give the end user some confidence.  And I am really open to a value judgment based on professional measurements.  unless the mirror dimensions do not match.

 

something tells me the text is trying to tell its a report of a 17?mm telescope.  Possible a 7”.  And that’s  not corresponding.  
the only thing I doubt is that some reports indicate mirror diameter in measured pixels.  That could be the only thing that would make this report more credible

Edited July 15, 2021 by Robindonne

[jetstream]

42 minutes ago, vlaiv said:

I honestly doubt accuracy of this report as is.

Me too.

[vlaiv]

21 minutes ago, rl said:

Attached is the one for my VX14 for comparison.

Do OO give mirror surface or wavefront figures?

[rl]

It's the wavefront. They make the point about the 2:1 ratio on their website somewhere. They also miss out the secondary shadow zone which is fair enough. I don't think the test includes the secondary but I might be wrong on that one.