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Making and Using a "Monocentric" Eyepiece from Commercial Parts

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#26 SteveC

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Posted 12 September 2014 - 08:54 AM

The Mojocentrics are my favorite eyepieces by far!!

Fixed my signature to reflect my new mojo.



#27 stevep

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Posted 12 September 2014 - 03:54 PM

 

I would suggest that if someone is as curious as I am, make the "Monocentric" eyepiece I describe and compare it to the new TMB "Super Monocentric", or a Zeiss "Monocentric" and tell us the results.  I think if the results were reported in an unbiased manner, they might be surprising.

 

 

Actually, monocentrics do not have to look like the pictured one at all.  All that a monocentric is, is one where the radii of all the curves of all the lens surfaces have a common central point.  So draw any three concentric circles with the same center point, then slice a cylindrical section out of it, and you have a monocentric design.  FWIW, I've seen lots of pictures that are incorrect, even in patent documents.  The drawings are illustrative only, the definition of the curves and glass types and indexes of refraction and spacings are definitive.  So just saying be careful about drawing any conclusions from any sketched representation.

 

 

Not according to the designer, from the 1907 catalogue, 2 designs of eyepiece sold by Steinheil both feature 3 cemented lenses but they only call one of them Monocentric, my guess would be that the one called Aplanatic is the original Steinheil design which he modified a few years later to create the Monocentric,

 

http://www.sil.si.ed...ges/image17.htm

 

Steve
 



#28 SandyHouTex

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Posted 12 September 2014 - 05:00 PM

 

I would suggest that if someone is as curious as I am, make the "Monocentric" eyepiece I describe and compare it to the new TMB "Super Monocentric", or a Zeiss "Monocentric" and tell us the results.  I think if the results were reported in an unbiased manner, they might be surprising.

 

 

Actually, monocentrics do not have to look like the pictured one at all.  All that a monocentric is, is one where the radii of all the curves of all the lens surfaces have a common central point.  So draw any three concentric circles with the same center point, then slice a cylindrical section out of it, and you have a monocentric design.  FWIW, I've seen lots of pictures that are incorrect, even in patent documents.  The drawings are illustrative only, the definition of the curves and glass types and indexes of refraction and spacings are definitive.  So just saying be careful about drawing any conclusions from any sketched representation.

 

Also, it is typical for monocentric designs to be highly curved and not flat.  Various aberrations are also present.  To give you an example, here's a quote from a research project where they used monocentric lenses for a 40 gigapixel imaging systems.  Here's what the researchers say about the monocentric design...

 

"The described monocentric objectives consist of a
spherical core of a crown glass (low index and high
Abbe number) surrounded by meniscus shells of flint
glasses (high index and low Abbe number) with the
shell surfaces concentric with the spherical core center.
A stop is placed at the center of curvature to limit
the f =#. Excluding the vignetting caused by the stop,
the lens is symmetric with the respective incoming
field angle. Unlike an ordinary lens,monocentric systems
have no tightly defined optical axis. This means
that no off-axis aberrations, e.g., lateral chromatic
aberration, astigmatism, or coma, are present. The
only aberrations present are axial chromatic aberration,
spherical aberration, and spherochromatism. In
addition, the image has field curvature because it is
formed on a spherical surface also concentric with
the core
.
"

 

To have a superb eyepiece really means a lot more than simply design.  IMO the engineering execution is more critical.  Who cares how well the paper design is if there is a lot of internal reflections, if the coatings are applied non-optimally causing ghosting and more scatter, and if the polish is typical meaning a fair amount of more scatter robbing contrast and degrading sharpness.  The Zeiss Abbe execution visually is the best I've encountered other than the Zeiss Monos.  Lowest scatter and highest definition of any eyepieces I have come across.  Superbly executed engineering.

 

FWIW, there is one view that I have seen that is better....but it was a 10 degree AFOV in the center of a spherical singlet "ball" eyepiece.  It was also a high specification lens so curves very precisely ground and polished.  No back scatter of course since only one lens so light had nothing to bounce around off of to come back to the optical axis.  Multi-element lenses, even cemented monocentrics will have backscatter between the lenses.  Single coating also helped keep scatter at absolute minimum since no multi-layers which can increase scatter if not executed very precisely. 

 

 

But you will concede BillP, that the Zeiss and TMBs are not Monocentrics based on the fact that just by looking at the pictures, the elements  in them do NOT have a common center.  Yes?

 

And before you criticize the "engineering drawings" I supplied for the Zeiss and TMBs, you should know that I've been a mechanical engineer all my life and been responsible for creating drawings like these.  They are always accurate representations of the actual product.  In other words, if the Zeiss and TMBs had lenses that were monocentric, that's how they would have been shown.

 

I seem to recall that you have some TMBs and that you're not against taking eyepieces apart.  Why don't you check and see what's inside your TMB?



#29 BillP

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Posted 12 September 2014 - 05:11 PM

 

Not according to the designer, from the 1907 catalogue, 2 designs of eyepiece sold by Steinheil both feature 3 cemented lenses but they only call one of them Monocentric, my guess would be that the one called Aplanatic is the original Steinheil design which he modified a few years later to create the Monocentric,

 

http://www.sil.si.ed...ges/image17.htm

 

 

Just to illustrate, the "monocentric: in Fig 6 of your link, which they *say* has all the radii struck from common center, does not by their illustration.  Taking that pic and importing into Photoshop and placing circles whose circumferences coincide with what is pictured shows no common center.  So these pics are really illustrative only.  If one builds the monocentric design, the spherical surfaces of all lenses need to have that common center.  Only thing I am pointing out is don't make any inferences by the pictures, it's the wording of the specification that is the truth of the matter.

 

ps - I cannot superimpose the image of the Monocentric from that figure 6 since that would be altering an original pic and against TOS, so I removed the pic I worked from and left only the yellow circles to show how non-monocentric the illustration is.  So if the eyepiece was built per the specifications illustrated by the picture...I image it would perform horribly!!

Attached Thumbnails

  • temp.jpg

Edited by BillP, 12 September 2014 - 05:13 PM.


#30 BillP

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Posted 12 September 2014 - 05:17 PM

 

But you will concede BillP, that the Zeiss and TMBs are not Monocentrics based on the fact that just by looking at the pictures, the elements  in them do NOT have a common center.  Yes?

 

 

 

Oh...absolutely!  Looking at various drawings whoever has done or was contracted to do in a patent application, does not fit the parameters.  Of course, even the old pic of a real monocentric does not per my previous post with pic.  I would love to take them apart, and de-cement them, but someone would have to donate them to me to destroy in that process....I'm not going to destroy my $350+ 4mm TMB Supermono or my $600 ZAO or purchase a Zeiss Mono for $1500 just to satisfy that curiosity.  :lol:

 

And besides...the curiosity will not alter the fact that they perform better than anything out there.  So the design together with the attention to the engineering makes the top most on-axis planetary performers in the field today (by my personal direct observations).  And frankly, there are so many eyepieces out there whose internals do not match the design they are claiming, we should really be used to this (e.g., mondified symmetricals called Plossls, 5 element things called Plossls, things labeled MAs that are Symmetricals, things labeled Erfles that are some other design, etc.).

 

ps - Glad your engineering diagrams are accurate...but given what I see from others in the eyepiece realm your good work would be something they should really try to follow!


Edited by BillP, 12 September 2014 - 05:28 PM.

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#31 stevep

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Posted 12 September 2014 - 07:35 PM

 

 

Not according to the designer, from the 1907 catalogue, 2 designs of eyepiece sold by Steinheil both feature 3 cemented lenses but they only call one of them Monocentric, my guess would be that the one called Aplanatic is the original Steinheil design which he modified a few years later to create the Monocentric,

 

http://www.sil.si.ed...ges/image17.htm

 

 

Just to illustrate, the "monocentric: in Fig 6 of your link, which they *say*

 

 

They say !,,,,,,,,,,,,,,,,,,,,,,,,,,

this is not ''they say'' this is Steinheil, they invented the design !, this is just an illustration from a 1907 catalogue !!, not an engineering drawing, let alone an optical perscription,

in my opinion the term '' monocentric'' has just been ''coined'' first by Zeiss and then by TMB, both designs are just triplets, based on the first Steinheil design, if Steinheil only called his his triplet Aplanatic, then why did he call the other design Monocentric, this design bears no resemblance to any other design,
if I recall when Mr Back was asked what would be the ultimate ep, he replied an original Steinheil monocentric with either Zeiss coatings or Pentax smc coatings,

but he did not choose to make one !, I would guess that the true Steinheil monocentric would be very difficult to manaufacture commerical basis,

just my thoughts,

Steve


Edited by stevep, 13 September 2014 - 04:16 AM.


#32 jtaylor996

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Posted 12 September 2014 - 07:50 PM

Look here for more accurate info on the supermonocentric origins, especially relating to that (erroneous) pic: http://www.brayebroo...w_critique.html



#33 SteveC

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Posted 12 September 2014 - 08:54 PM

Look here for more accurate info on the supermonocentric origins, especially relating to that (erroneous) pic: http://www.brayebroo...w_critique.html

I remember that article and harsh criticism. The 8" Newt was the cream of the crop, but it had it's limitations, especially with the Supermonos. The 85mm Apo and the 90mm Mak, not my idea for great testbeds for planetary viewing. Nevertheless, the reviewer gave the Supermonos 5 out of 5 possible stars for on axis performance.  That says a lot, and was what I was looking for when I bought the Supermonos. At the time I was viewing with a 7" f15 Mak on a G-11 which worked wonderfully with the Supermonos. The Mak had cooling issues, but that's another story. If you can't find differences in on axis performance between Supermonos, plossls, and generic orthos, then something is wrong with the test. I can't comment on Brandons and 

RKE's, I've never observed with those eyepieces.

 

I really don't understand the controversy over names and designs,  it's the results that count.


Edited by SteveC, 12 September 2014 - 08:56 PM.


#34 BillP

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Posted 12 September 2014 - 08:58 PM

 

I really don't understand the controversy over names and designs,  it's the results that count.

 

 

So very true :bow:



#35 leonard

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Posted 12 September 2014 - 09:22 PM

Ball 001.jpg

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                         Ball-O-Centric

 

 

 

 



#36 SteveC

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Posted 12 September 2014 - 11:23 PM

lol, are we considering the marbles in the tray, or your eyepiece? There's conflicting evidence in that photo.



#37 leonard

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Posted 12 September 2014 - 11:45 PM

Hi Steve ,

 

 

 

               You know I missed that , I left that dang eyepiece in the shot of the marbles in a circle around the bottom of the candle holder !



#38 Sarkikos

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Posted 12 September 2014 - 11:50 PM

The finger that points to the Moon is not the Moon.

 

:meditate:

Mike


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#39 SandyHouTex

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Posted 13 September 2014 - 05:48 PM

 

 

But you will concede BillP, that the Zeiss and TMBs are not Monocentrics based on the fact that just by looking at the pictures, the elements  in them do NOT have a common center.  Yes?

 

 

 

Oh...absolutely!  Looking at various drawings whoever has done or was contracted to do in a patent application, does not fit the parameters.  Of course, even the old pic of a real monocentric does not per my previous post with pic.  I would love to take them apart, and de-cement them, but someone would have to donate them to me to destroy in that process....I'm not going to destroy my $350+ 4mm TMB Supermono or my $600 ZAO or purchase a Zeiss Mono for $1500 just to satisfy that curiosity.  :lol:

 

And besides...the curiosity will not alter the fact that they perform better than anything out there.  So the design together with the attention to the engineering makes the top most on-axis planetary performers in the field today (by my personal direct observations).  And frankly, there are so many eyepieces out there whose internals do not match the design they are claiming, we should really be used to this (e.g., mondified symmetricals called Plossls, 5 element things called Plossls, things labeled MAs that are Symmetricals, things labeled Erfles that are some other design, etc.).

 

ps - Glad your engineering diagrams are accurate...but given what I see from others in the eyepiece realm your good work would be something they should really try to follow!

 

 

ZAOs?

 

Anyway, I wasn't asking you to do any destructive testing.  I know you frequently take eyepieces apart and I thought it would be cool to just open up the TMB you have and see what was inside.  If it has really thick lens elements running the length of the eyepiece like the first image, I posted or if it looks like a Hastings triplet.

 

And I think you know that I am totally with you on the misnamed eyepieces.  Unfortunately I think that's what we have here.



#40 SandyHouTex

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Posted 13 September 2014 - 05:54 PM

Look here for more accurate info on the supermonocentric origins, especially relating to that (erroneous) pic: http://www.brayebroo...w_critique.html

 

I personally find that article disingenuous.  Showing the actual Steinheil Monocentric picture (that I used by the way) and saying that the TMBs have a triplet with thin elements is just wrong.  It leads the casual reader to believe he's getting the actual Steinheil design.  The Steinheil design is a thick lens eyepiece design.



#41 SandyHouTex

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Posted 13 September 2014 - 05:58 PM

 

 

 

Not according to the designer, from the 1907 catalogue, 2 designs of eyepiece sold by Steinheil both feature 3 cemented lenses but they only call one of them Monocentric, my guess would be that the one called Aplanatic is the original Steinheil design which he modified a few years later to create the Monocentric,

 

http://www.sil.si.ed...ges/image17.htm

 

 

Just to illustrate, the "monocentric: in Fig 6 of your link, which they *say*

 

 

They say !,,,,,,,,,,,,,,,,,,,,,,,,,,

this is not ''they say'' this is Steinheil, they invented the design !, this is just an illustration from a 1907 catalogue !!, not an engineering drawing, let alone an optical perscription,

in my opinion the term '' monocentric'' has just been ''coined'' first by Zeiss and then by TMB, both designs are just triplets, based on the first Steinheil design, if Steinheil only called his his triplet Aplanatic, then why did he call the other design Monocentric, this design bears no resemblance to any other design,
if I recall when Mr Back was asked what would be the ultimate ep, he replied an original Steinheil monocentric with either Zeiss coatings or Pentax smc coatings,

but he did not choose to make one !, I would guess that the true Steinheil monocentric would be very difficult to manaufacture commerical basis,

just my thoughts,

Steve

 

 

Bingo!  For someone to try and manufacture the actual thick lens Steinheil design would probably be prohibitively expensive.  I would love to look through one though!  And of course compare it to my "Monocentric".   :lol:



#42 stevep

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Posted 13 September 2014 - 07:54 PM

 

 

Not according to the designer, from the 1907 catalogue, 2 designs of eyepiece sold by Steinheil both feature 3 cemented lenses but they only call one of them Monocentric, my guess would be that the one called Aplanatic is the original Steinheil design which he modified a few years later to create the Monocentric,

 

http://www.sil.si.ed...ges/image17.htm

 

 

Just to illustrate, the "monocentric: in Fig 6 of your link, which they *say* has all the radii struck from common center, does not by their illustration.  Taking that pic and importing into Photoshop and placing circles whose circumferences coincide with what is pictured shows no common center.  So these pics are really illustrative only.  If one builds the monocentric design, the spherical surfaces of all lenses need to have that common center.  Only thing I am pointing out is don't make any inferences by the pictures, it's the wording of the specification that is the truth of the matter.

 

ps - I cannot superimpose the image of the Monocentric from that figure 6 since that would be altering an original pic and against TOS, so I removed the pic I worked from and left only the yellow circles to show how non-monocentric the illustration is.  So if the eyepiece was built per the specifications illustrated by the picture...I image it would perform horribly!!

 

 

Bill,

 

I'm still not sure I understand your reply post,

 

As said in my previous post ''they say'' is Steinheil, the designer and inventor of this eyepiece,

are you stating that the illustration in fig 6 is incorrect,

 

IE: that the design and the production eyepieces  did not look like this,

 

Steve

Attached Thumbnails

  • Steinheil_Monocentric_1880_Eyepiece_Konkoly_Thege_1890.jpg


#43 leonard

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Posted 14 September 2014 - 10:05 AM

Hello Steve ,

 

 

 

                 Yes thats correct , the production TMB Supermonocentric eyepiece does not look anything like that .

 When asked Tom Back stated that the eyepiece in your image was never produced . I can only take his word for it

as no one has ever produced an example of it for all to see.



#44 leonard

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Posted 14 September 2014 - 10:29 AM

Hello

 

 

          Well a lot of gas has been expelled about who's name goes with what and is the glass thick or thin and who struck john . :lol: 

Back to the OP # 1 . Roger said he would like to see what all the hub-bub was about and purchased some commercial optics to find out .

From what I can understand from his report was his experiment was a success . To say that his BGO's and Brandons were just as good

markes that success . 90.00$ commercial optic , 200.00$  Brandon equal on axis , what more is there to say ?

But I know there will be something . :flowerred: 

 

              BTW : Because of all the different designs on eyepieces with the same name its only speculation to call the TMB Supermonocentric a Hasting triplet.

                                                    I always felt the name should have been TMB Planetary Triplet .

 

                                                                                       Leonard



#45 stevep

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Posted 14 September 2014 - 10:38 AM

Hello Steve ,

 

 

 

                 Yes thats correct , the production TMB Supermonocentric eyepiece does not look anything like that .

 When asked Tom Back stated that the eyepiece in your image was never produced . I can only take his word for it

as no one has ever produced an example of it for all to see.

 

Hmm !

 

If you check my earlier post futher up this page, there is a link to the Steinhiel catalogue of 1907, it shows them for sale, along with all the other

eyepiece designs, IE: Kellners, Orthos etc, there is also an earlier version of the catalogue on the web late 1890's that is in French they are also

shown for sale in there,

 

Steve



#46 BillP

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Posted 14 September 2014 - 11:19 AM

 

I'm still not sure I understand your reply post,

 

As said in my previous post ''they say'' is Steinheil, the designer and inventor of this eyepiece,

are you stating that the illustration in fig 6 is incorrect,

 

IE: that the design and the production eyepieces  did not look like this,

 

Steve

 

 

Let's see if I can do better...  I am not saying that the production and design did not look like this.  What I am saying is that the design picture of the monocentric, is not monocentric because the curves of the elements as pictured, do *not* follow the language they provide which says that it is: "Consisting of three cemented lenses...of which the radii are all struck from a common centre."  The picture is incorrect in that none of those elements show a common center of radii.  So it is not technically accurate and just for illustrative purposes only to give you a general idea and nothing more...it's a pretty picture and not an accurate and scaled representation of the device. That being the case, you really can't make any assumptions about the accuracy of the even the shapes of the lens elements A, B, and C.  Given that the curves do not even match the criteria, can't trust anything else.  In addition, shapes of the lenses, cylindrical or cone shaped, I'm sure are not necessary to be as shown.  Bottom line is that one really can't tell much of anything from a picture.  You need the glass types, the indexes of refraction, the curve radii, and the spacings.  Once you have all that, then you can begin to make some good deductions.


Edited by BillP, 14 September 2014 - 11:23 AM.


#47 BillP

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Posted 14 September 2014 - 12:43 PM

 

Anyway, I wasn't asking you to do any destructive testing.  I know you frequently take eyepieces apart and I thought it would be cool to just open up the TMB you have and see what was inside.

 

 

OK Roger!  Do you know what a p.i.t.a. it is to futz with 4mm lens sets :bigshock:  Anyway, decided to give it a try for youall...OMG was it unnerving!

 

Anyway, attached is the pic.  The 4mm Supermono is all I have.  Interesting to note that the lenses are not blackened.  Also interesting to note, although not pictured, is that there was a mark on one side indicating the eye lens, so they obviously have an orientation (others have said they can be flipped and are omnidirectional).  So here is the pic.  Not sure if any conclusions can be drawn from this given can't see any curves between elements and have no idea of the glass types or indexes, all of which change what a design visually looks like,  It was a microscopic lens so had all kinds of extensions on my camera lens to get to this image scale.  Right side is the field lens.  The entire lens is about 1/10th" in diameter!!  Have fun :grin:

Attached Thumbnails

  • 4mm TMB Supermono Lens.jpg

Edited by BillP, 14 September 2014 - 12:44 PM.

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#48 SandyHouTex

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Posted 14 September 2014 - 01:43 PM

 

 

Anyway, I wasn't asking you to do any destructive testing.  I know you frequently take eyepieces apart and I thought it would be cool to just open up the TMB you have and see what was inside.

 

 

OK Roger!  Do you know what a p.i.t.a. it is to futz with 4mm lens sets :bigshock:  Anyway, decided to give it a try for youall...OMG was it unnerving!

 

Anyway, attached is the pic.  The 4mm Supermono is all I have.  Interesting to note that the lenses are not blackened.  Also interesting to note, although not pictured, is that there was a mark on one side indicating the eye lens, so they obviously have an orientation (others have said they can be flipped and are omnidirectional).  So here is the pic.  Not sure if any conclusions can be drawn from this given can't see any curves between elements and have no idea of the glass types or indexes, all of which change what a design visually looks like,  It was a microscopic lens so had all kinds of extensions on my camera lens to get to this image scale.  Right side is the field lens.  The entire lens is about 1/10th" in diameter!!  Have fun :grin:

 

 

That is awesome Bill.  It does look on the outside  like a Hastings triplet.  But you are right in that we don't know R2 and R3 or R4 and R5s curvature, although R2 and R3 are probably equal, along with R4 and R5 being equal.  We also are unsure of whether there are 2 or 3 glass types as you say.

 

I guess one of my pet peeves is manufacturers mislabeling their eyepieces or claiming they're something they're not.  I broke your book out because I was reading that "Erfle" thread and opined that the OP could get some Antares "Erfles".  Much to my chagrin, the 30 mm. is not an Erfle.  8 elements in 5 groups does not resemble any Erfle design I've seen.  But because of the mislabeling, the manufacturer got my $160.

 

Oh and someone must have made the thick lens Steihneil Monocentric.  Otherwise Chris Lord's comments on it would be disingenuous.  (Is that a nice way to put it?)


Edited by RodgerHouTex, 14 September 2014 - 01:46 PM.


#49 BillP

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Posted 14 September 2014 - 03:25 PM

I did an examination in Photoshop of the curves of the eye and field lens using appropriately sized circles, and they do look the same as best can be determined by that method.  btw, the cloth it is on is a microfiber cloth...it case anyone was wondering what the microfibers looked like too :lol:


Edited by BillP, 14 September 2014 - 03:26 PM.


#50 JustaBoy

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Posted 14 September 2014 - 04:26 PM

I thought it was on your New Shag Carpet:-)




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