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Stadius
member
Reged: 06/15/08
Posts: 27
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OK. I have taken delivery of the scope but to my dismay it incured some damage during delivery. Nothing I can't fix, but still a pain in the *BLEEP*.
I have some information about the mirror. I would like to post it here to get a better understanding of the quality of the optics... so here it goes.
PV - peak to valley = .105 (this is illustrated with a sketch of a single sin wave where the peak is at 1.0 and the trough is at 0.0) Any commments? is this good/bad?
RMS - Root Mean Square = .024 wave Any comments? is this good/bad?
PTS - Number of points used in the scan = 28177
There is also a note that says "Figure of overall optic 0.0 best 1.0 worst"
There is also a hand drawn figure of a circle with a solid band thru the middle (like a billiard ball) and it says "Figure Across the strip scanned"
The only other info on the test print out is "Zygo MkIVxp" and APT%.
I have the invoice for the optics. They were made by Galaxy Optics of Beuna Vista Colorado. The invoice is as follows:
Date 3/9/93
12.5" X F5.6 X 2.0" optic for testing and optical figuring. ($250)
3.1" EDF for optical testing , optic N/G ($00)
3.1" EDF, C-2 replacement optic ($135)
ALSIO OPTICAL COATING FOR ITEM #1 ABOVE. ($45)
I have one concern about the optics and I have attempted to attach a picture of it. First of all it is very dusty. The entire scope needs to be cleaned. The real problem is that there seems to be a black scar on the centre of the main mirror. It is visible in the photo. What could this possibly be? Will it affect viewing? Will the mirror have to be refinished and recoated? (I am considering refinishing and coating anyway, especially if what I have posted here turns out to have *BLEEP* optics)
PLEASE tell me everything you know. I will continue to search the forums for additional info...
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Stadius
member
Reged: 06/15/08
Posts: 27
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Here is a link to a better image of the mirror.
http://s280.photobucket.com/albums/kk191/Stadius/?action=view¤t=P8110001.jpg
The spot in the middle appears to be an adhesive ring, like the ones you use to repair the holes in a 3 holed piece of paper. Any idea why someone might have put it there?
As you can see, this mirror needs to be cleaned very badly. How should I do this? What is the best way to clean this mirror. The accessories that came with the scope included a sheepskin chamois. Should I use this to clean the mirror? What type of cleaning agent should I use (if any)
Thanks!
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Jarad
Post Laureate
Reged: 04/28/03
Posts: 3850
Loc: Atlanta, GA
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Quote:
RMS - Root Mean Square = .024 wave Any comments? is this good/bad?
Diffraction limited is ~1/13 wave RMS (~0.075 wave). This one is significantly better than that.
The ring is a center mark. It is used to help collimate the mirror. Collimation means getting the focuser, secondary, and primary all properly aligned.
Any marks near the center of the mirror will likely be in he shadow of the secondary, and not affect the image at all.
Galaxy is considered one of the better mirror makers, it should be a good mirror.
Be very careful cleaning the mirror - there are some sticky threads near the top of the Reflector forum with good advice on how to clean without damaging the mirror. Essentially, you want to avoid touching the surface as much as possible.
Jarad
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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 10441
Loc: Amargosa Valley, NV, USA
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Do NOT use the chamois on the mirror. It will almost certainly scratch it. Use the threads Jarad mentioned for advice on how to clean the mirror. It's not difficult to do, but does require some care.
The optics appear to be excellent from the description -- and the coating doesn't look bad from the photo. It will be easier to tell whether the mirror needs to be recoated after it's been cleaned.
There looks to be other work that's needed on the rest of the telescope. Is that flocking that's peeling off the interior?
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"S.O.E." (Sauron's Other Eye) 16" Royce conical mirror: A permanent work in progress.
10" Homebuilt dob, old Coulter mirror
Next Project: The "Eye of Sauron" Observatory!
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BluewaterObserva
Post Laureate
Reged: 05/18/04
Posts: 4763
Loc: Zuni Mtns, NM
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Galaxy mirror? Looks to be in good shape? With some doccumentation even?
Nice score for sure. 
Great scores on optics don't get much better than that in all honesty.
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Stadius
member
Reged: 06/15/08
Posts: 27
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Thats good news, but what about the coatings.
1. Were those score taken with or without the coatings?
2. If I have the mirror recoated but not resurfaced should I expect similar scores?
3. If the mirror needs recoating will it also need to be resurfaced? I assume that resurfacing the mirror will totally change the test scores.
I have not properly cleaned the mirror yet. I will do this after the remove the secondary and clean the inside of the tube. It will be the last thing I do before fix everything and put it back together. I fixed the leg that was broken today so thats one thing out of the way.
Thanks for any answers.
Cheers
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pstarr
scholastic sledgehammer
Reged: 09/17/04
Posts: 870
Loc: NE Ohio
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The mirror being re-coated will not change the surface accuracy. It will not need resurfacing either. Send it to a reputable coater, like Spectrum or Nova optical and you won't have any worries.
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Paul
10" Home built F-6 Eq planetary Newt. w/Zambuto mirror
fully flocked aluminum tube
curved spider, Antares 1/30 wave secondary
12'x12' roll-off roof observatory
6" Home built f-6 Newt. w/Parks mirror on CG-5 Eq. mount w/Digital setting circles
4.5" Orion Starblast on Eq. mount
TV Radians 5,6,8,10,12mm
Pentax XL 10.5mm
Baader Hyperion 17mm
3.2mm TMB planetary
13mm Ethos
TV 2.5x barlow, TV 1.8x barlow
My equipment philosophy... If it ain't broke, fix it anyway.
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Stadius
member
Reged: 06/15/08
Posts: 27
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so i have an excellent mirror and if recoated will only become even more excellent? Thats good news.
Once I have this mirror cleaned what should I be looking for to determine if it needs to be resurfaced?
Thanks
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Don W
Postmaster
Reged: 05/19/03
Posts: 13178
Loc: Wisconsin, USA
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It shouldn't need it.
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Don Wyman
Obsession 18" f/4.5 #1166
W/Argo Navis DSC and Torus Primary
William Optics Megrez 90
Coronado PST
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pstarr
scholastic sledgehammer
Reged: 09/17/04
Posts: 870
Loc: NE Ohio
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Look through the back of the mirror while holding it up to a light. If there are allot of pin holes, or you can see allot of light through the coating, it probably need a recoat. Here is some info. web page Some info on cleaning. web page
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Paul
10" Home built F-6 Eq planetary Newt. w/Zambuto mirror
fully flocked aluminum tube
curved spider, Antares 1/30 wave secondary
12'x12' roll-off roof observatory
6" Home built f-6 Newt. w/Parks mirror on CG-5 Eq. mount w/Digital setting circles
4.5" Orion Starblast on Eq. mount
TV Radians 5,6,8,10,12mm
Pentax XL 10.5mm
Baader Hyperion 17mm
3.2mm TMB planetary
13mm Ethos
TV 2.5x barlow, TV 1.8x barlow
My equipment philosophy... If it ain't broke, fix it anyway.
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