Optical Reports

Discussion of optical systems and their characteristics.
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Lady Fraktor Slovakia
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Optical Reports

#1

Post by Lady Fraktor »


I was looking around a different astro site when I read a conversation about someone not being able to get a Zygo report for his refractor so was no longer going to trust any of their product. This company is well known worldwide for their high quality products.

I have had multiple refractors over the years but have never been that concerned about having a zygo report.
In fact, of all the refractors I have owned only two companies have ever offered a report, TMB and Stellarvue.
To me learning how to star test an optic is better than the piece of paper anyway.
With my last refractor I was told I could bring a couple of my current refractors to test alongside the new one.

Now the reason why I do not put a lot of interest in these reports.
When I arrived my refractors were placed on the test bench then we went for a long lunch while my telescopes acclimated to the test room.
That is right, the Zygo tests and DPAC are done in a temperature and humidity controlled room. 20°C @ 45% humidity.
Conditions that you will not match outside. 1° warmer/ cooler and different humidity will show different numbers.

My completely unprofessional advice is not to worry about posted numbers, if the telescope is from a well known manufacturer then you are likely to recieve exactly what they have promised/ guaranteed.
Learn how to evaluate your own optics be it a refractor, newtonian or compound or your eyepieces.

Any opinions on the value of reports?
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
Eyepieces: Antares to Zeiss
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Bigzmey United States of America
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Re: Optical Reports

#2

Post by Bigzmey »


Completely agree, Gabby! The report is a nice thing to have and shows that the vendor goes extra mile to satisfy the customer, however I would not base my buying decision just on that.

As yourself, out of many scopes I have owned I only have a test report just for one (or rather a pair :)) - APM 100-90 binocular telescope. I would still trust APM even without the report.

For me the ultimate test is how the scopes perform on tough targets. Since I tend to push them to the limits I find soon enough how good is optic in a newly-acquired scope.
Scopes: Stellarvue: SV102ED; Celestron: 9.25" EdgeHD, 8" SCT, 150ST, Onyx 80ED; iOptron: Hankmeister 6" Mak; SW: 7" Mak; Meade: 80ST.
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.

Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2382, Comets: 34, Asteroids: 255
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OzEclipse Australia
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Re: Optical Reports

#3

Post by OzEclipse »


I agree, proof of the pudding is in the eating.
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Amateur astronomer since 1978...................Web site : http://joe-cali.com/
Scopes: ATM 18" Dob, Vixen VC200L, ATM 6"f7, Stellarvue 102ED, Saxon ED80, WO M70 ED, Orion 102 Maksutov, ST80.
Mounts: Takahashi EM-200, iOptron iEQ45, Push dobsonian with Nexus DSC, three homemade EQ's.
Eyepieces: TV Naglers 31, 17, 12, 7; Denkmeier D21 & D14; Pentax XW10, XW5, Unitron 40mm Kellner, Meade Or 25,12
Cameras : Pentax K1, K5, K01, K10D / VIDEO CAMS : TacosBD, Lihmsec.
Cam/guider/controllers: Lacerta MGEN 3, SW Synguider, Simulation Curriculum SkyFi 3+Sky safari
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Don Pensack United States of America
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Re: Optical Reports

#4

Post by Don Pensack »


The two best scopes I've owned (out of 31) are telescopes for which no test report was available.
Both have yielded perfect star images at a 0.5mm exit pupil level (one at 0.4mm) when the atmosphere allowed.
And if you see perfect star images even once, if you never see them again in the same scope, you know it is not the fault of the optics.
I learned to star test scopes many years ago, so a quick star test in superb seeing can reveal optical problems.
I also have a Ronchi eyepiece and know how to use it.
And my frequented observing site often has 0.5" seeing or better, allowing a good 16" to resolve star patterns in the cores of small globular clusters at 600-800x.

Near-perfect optics seem to go deeper than average optics due to a superior contrast. I have seen that in several truly excellent telescopes over the years, only a couple owned by me.
Those near-perfect optics performed incredibly with just about every eyepiece. The difference with average optics is not subtle.

Interferograms don't tell the whole story. They certainly are revealing, like the Lyot test (which REALLY reveals the truth about the surface), Ronchi, Foucault, et.al.
But the use in the field is the most revealing.
I get so tired of seeing mirrors that have interferograms of the optics that crow about a 0.96 Strehl ratio where the mirror is so rough it scatters light everywhere and yields poor contrast.
Carl Zambuto talks about what is really important here:
https://zambutomirrors.com/zambutoopticalca.html

What matters is not the testing, but the maker. And most of the world-class makers of optics don't provide interferometry.
Astronomer since 1963
Currently using a 12.5" dob and a 4" apo refractor
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John Baars Netherlands
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Re: Optical Reports

#5

Post by John Baars »


I agree with Lady Fraktor. One should learn to do his/her own testing if necessary. Most of the time it isn't, one can recognize quality when one sees through it. I'll make an exception on the Lyot test though, on the other hand...... micro-ripple is easily recognized.
Enjoying the universe is more important than knowing one has a 0.95 ( or better / worse) Strehl refractor.
Refractors in frequency of use : *SW Evostar 120ED F/7.5 (all round ), * Vixen 102ED F/9 (vintage), both on Vixen GPDX.
GrabnGo on Alt/AZ : *SW Startravel 102 F/5 refractor( widefield, Sun, push-to), *OMC140 Maksutov F/14.3 ( planets).
Most used Eyepieces: *Panoptic 24, *Morpheus 14, *Leica ASPH zoom, *Zeiss barlow, *Pentax XO5.
Commonly used bino's : *Jena 10X50 , * Canon 10X30 IS, *Swarovski Habicht 7X42, * Celestron 15X70, *Kasai 2.3X40
Rijswijk Public Observatory: * Astro-Physics Starfire 130 f/8, * 6 inch Newton, * C9.25, * Meade 14 inch LX600 ACF, *Lunt.
Amateur astronomer since 1970.
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