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I just realized that 10mm Plossls are usable.

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#1 stargazer193857

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Posted 21 January 2021 - 10:06 PM

I remember trying to look through a 10mm Plossl during the daytime, without glasses. No matter how I jmed my eye in there, I could not see the full field of view. I then made several posts saying that 10mm Plossls are junk. I even recall seeing blackouts in a 25mm during the daytime. Same for the 8.8mm Meade 82 deg.


But now that I think about it, I had no issues with these at night time. I had a good view with what I think was a 8-9mm Plossl. Maybe Kelner, but I think it said Plossl.

Very sharp views in the 8.8mm Meade 82 degree with no issues. Same with the 25mm Plossl.




I think the issue is spherical aberration of the eyepiece, which causes field distortion rather than star aberration, and results in tubes of light not intersecting at the same exit pupil. The small daytime pupil can't take in all the tubes, whereas the larger night time pupil can.


So, a 10mm Plossl is an economical and useful high power eyepiece, but only at night time.

I think a barlow would reduce the field distortion somewhat.



The downside to 52 degrees is it is harder to find planets. An Orion Expanse eyepiece might be the most economical option there. I read the 9mm has some blackout issues, though I've not bought one. I wonder how good the 6mm is.


How good is the 6mm Orion Expanse, and how much better is it than a 10mm Plossl and barlow? A 10mm Plossl costs less than half what the Expanse costs.

Edited by stargazer193857, 21 January 2021 - 10:12 PM.

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#2 vtornado

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Posted 21 January 2021 - 10:25 PM

Ha, I use an 8mm plossl because it gives me the sharpest planetary views of any other eyepiece I have but ...

 

The gso ED barlow class is a very good barlow for the money.  I don't really think it is the ED glass that makes it special,

I think it is made to a higher quality standard that the $30.00 barlow class.  I say class because there are various

similar barlows on the market that look a lot like the GSO ED.

 

I have black out issues with the Orion expanse 6.   You have to hold your head in the right place and steady.

They are sharp though.


Edited by vtornado, 21 January 2021 - 10:42 PM.


#3 Garyth64

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Posted 21 January 2021 - 10:26 PM

I think I know what you mean when you jam you eye into the eyepiece.  That is not how it works.

 

There is a little eye relief that the eyepiece has, there is a "sweet spot" for your eye to be placed.  If you put your eye against the eyepiece, you can get some darkening at the edges of the fov and it seems that the view gets narrow.

 

There is nothing wrong with the eyepieces.  I can get that effect with my ES 9mm 62*, in the house.  I can even start to notice it with a ES 20mm 68* eyepiece too.

 

It does not matter whether it is day or night.  You probably just don't notice it as much at night.

 

So, don't jam your eye up to the eyepiece, keep it away for the eye relief that the eyepiece has, and things will be fine.  That is simply all it is.



#4 stargazer193857

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Posted 21 January 2021 - 10:37 PM

I think I know what you mean when you jam you eye into the eyepiece. That is not how it works.

There is a little eye relief that the eyepiece has, there is a "sweet spot" for your eye to be placed. If you put your eye against the eyepiece, you can get some darkening at the edges of the fov and it seems that the view gets narrow.

There is nothing wrong with the eyepieces. I can get that effect with my ES 9mm 62*, in the house. I can even start to notice it with a ES 20mm 68* eyepiece too.

It does not matter whether it is day or night. You probably just don't notice it as much at night.

So, don't jam your eye up to the eyepiece, keep it away for the eye relief that the eyepiece has, and things will be fine. That is simply all it is.


I did not just jam my eye in there. I started far away and gradually got closer. I never found a sweet spot. I could only ever see the edge if I moved my eye to the side.

But now you got me wanting to try it again.

I do recall needing practice with ultrawide and megawide angle eyepieces. Now placement is easy.


45 deg Kelners are the easiest for beginners to learn. But they are even narrower for planets, and cramped, justifiable only in small monoculars.

#5 CrazyPanda

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Posted 21 January 2021 - 10:39 PM

I think it really depends on the shape of the housing of the Plossl. I had to give up trying to use my 11mm TV Plossl. Very hard to look through, even when I ripped the silly rubber eye guard off.

 

Conversely, my 9.6mm Meade Series 3000 Plossl is easier than the 11 TV Plossl was, but it doesn't have an eye guard and the lens is quite close to the surface. Still in striking distance of my eye lashes though...

 

Concerning the 6mm Orion Expanse, the Expanse version is overpriced IMO. The generic brand for $30 is a better value: https://www.amazon.c...e/dp/B07H8YZHFT

 

Or if you look around on Ebay or AliExpress, it can be had for $20 or less.

I did a mini shootout on the Moon last night between my 6 Ethos and 6 "gold line" (generic Expanse). A few things I noted:

 

1. The 6 "gold line" was surprisingly sharp. I had to try pretty hard to see things in the Ethos that I could not in the gold line. It mainly boiled down to subtle texturing rather than any macro features. I had a similar experience with a 12 Nagler and 2x Powermate. That combo was sharper, but not by much.

2. The gold line suffers from poor contrast and veiling glare. There are specific eye positions you can get into where the glare goes away, but they're so specific that for all intents and purposes, there is an omnipresent veiling glare in the 6 "gold line".

3. Kidney beaning is bad in the 9mm version (which I also own), but it's worse in the 6. Often you end up with competing problems - you have to position your eye one way to avoid the kidney beaning, but then you get veiling glare. Trying to position your eye to avoid veiling glare, you get kidney beaning. For the price it's something one could learn to live with, but it's definitely challenging.

 

I have little doubt that a 10mm + Barlow (lets' assume for the sake of argument that you get 6mm out of the combo) would have easier eye placement and fewer contrast issues than the 6 gold line/expanse. Whether it's *sharper* or not, hard to say.

 

What would no doubt be sharper is the 10mm Baader Classic Ortho + Nikon 1.6 barlow. But that's a lot more expensive than the 6 "gold line".


Edited by CrazyPanda, 21 January 2021 - 10:41 PM.

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#6 stargazer193857

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Posted 21 January 2021 - 10:44 PM

I wonder what eyepiece I should recommend to a beginner on a very tight budget and lacking skill, and still impress him/her on planetary views.


Is there a decent glass achromat coated 2x or 1.6x barlow on eBay for under $15? Plenty of $10 ones on eBay, but I don't know how bad their quality is. I've looked through a few plastic ones that come with cheap scopes and decided they reduced total detail.

I wonder if 32mm Plossl, 10mm Plossl, 2x barlow is a good suggested combo, or if something else is better.

I see 32mm Plossls on eBay for $22, sold by SVBony. I wonder if they are good. Now I'm going off topic a bit.

#7 izar187

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Posted 22 January 2021 - 01:57 AM

A 32mm(+/-) plus a 10mm(+/-) plossl were at one time common ep's that came with a new scope.

Because they work, and pretty well with a little experience.

 

My 9mm GSO plossl was noticeably better on axis on planets than my 9mm Expanse.

No not the equal in fov, nor off axis correction at f/5, nor as easy on eye relief.

But better planets.


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#8 Jon Isaacs

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Posted 22 January 2021 - 05:04 AM

I am able to see the entire field of view in a Celestron 4mm Plossl.  The eye relief is about 2.5mm, not comfortable but it's straight forward.

 

I doubt there is SAEP, it's too small to have much curvature.  The difficulty during the day with short focal length eyepieces is that your pupil is very small and the exit pupil is very small so aligning the eyepiece laterally is more difficult.  At night, your dark adapted pupil is a big target for the exit pupil, during the day, they both might be 2mm or even less so alignment is critical and not so easy.

 

As far as the 9mm Expanse, some of my best planetary views were with the 9mm Expanse with a 2X Barlow, 423x in the 12.5 inch F/6 Meade Research Grade.  In my experience, excellent planetary views start with excellent seeing and a telescope with sufficient aperture and optics to take advantage of the excellent seeing.  The eyepiece is of lesser importance.  

 

Jon


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#9 Rick-T137

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Posted 22 January 2021 - 07:09 AM

I wonder if there's a personal and/or physiological aspect to this. Perhaps some people's eyes are just more "compatible" with certain eyepiece designs (ie: Kellners, Plössls, Orthos) than others.

 

For example, @CrazyPanda above mentions that the 11mm TV Plössl was very hard to look through. I also have that eyepiece, and it is one of my favourites to use. I also have no trouble using it or the more restrictive (eye relief wise) 8mm version.

 

Just a thought.

 

Clear skies! 

 

Rick


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#10 Jon Isaacs

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Posted 22 January 2021 - 07:38 AM

I wonder if there's a personal and/or physiological aspect to this. Perhaps some people's eyes are just more "compatible" with certain eyepiece designs (ie: Kellners, Plössls, Orthos) than others.

 

For example, @CrazyPanda above mentions that the 11mm TV Plössl was very hard to look through. I also have that eyepiece, and it is one of my favourites to use. I also have no trouble using it or the more restrictive (eye relief wise) 8mm version.

 

Just a thought.

 

Clear skies! 

 

Rick

 

I think there are definitely both physiological differences in individuals as well as personal preferences.  And experience is a big player.  

 

My first decent eyepieces were Plossls, a 10mm, 17mm, 25mm and 32mm plus a 2x Barlow in a C-8.  They were and are all possible to view through. I had a lot of fun.  But the short eye relief of a 10mm is not as pleasant as the 17mm and up and once one becomes accustomed to more eye relief as well as a wide field of view, a short focal length Plossl is less satisfying 

 

Jon


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#11 Garyth64

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Posted 22 January 2021 - 08:25 AM

Stargazer said:   "No matter how I jmed my eye in there, I could not see the full field of view."

 

I had an older set of eyepieces that really didn't have any eye relief at all.  At outreach events, people had no problems with viewing.  They would just get their eye as close to the eyepiece as they could.

 

Since I got eyepieces that have good eye relief, I've noticed that many people have trouble in getting their eye in the correct position, the sweet spot.  Many still want to get their eye as close as possible to the eyepiece, which is wrong. I tell them to move their eye back away from the eyepiece and that seems to work for them.  But some have difficulty in keeping their eye in that spot because they can't hold their head steady.

 

 


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#12 MartinPond

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Posted 22 January 2021 - 08:56 AM

Adustable eyecups help a lot with long eye relief eyepieces.

The distance is set and the x-y placement is 'suggested'.

If that isn't available, short-cut length of piping or bicycle 

   innertube sliced lengths are often mentioned.

 

I find that even eyepieces without special blackout issues

   can be hard to place, if their FL is very long.  A spacer is

    very helpful.



#13 epee

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Posted 22 January 2021 - 10:19 AM

This past Fall, I rediscovered Plossls for planetary viewing. I have to remove my glasses, but darn if the view isn't crisp and with higher contrast than more complex EPs. Without glasses I can use down to a 6mm.


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#14 BillP

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Posted 22 January 2021 - 12:47 PM

How good is the 6mm Orion Expanse, and how much better is it than a 10mm Plossl and barlow? A 10mm Plossl costs less than half what the Expanse costs.

I've used the 6 and 9 Expanse (a rebrand actually) and while they are fantastic for the money, IMO on planetary they are a little soft in their on-axis presentation.  IMO a good simple Kellner, RKE, Abbe, or Plossl in 12mm with a 2x Barlow will provide a crisper planetary view than the 6 Expanse.  Using longer focal length simpler designs with a good Barlow has always provided some of the best performance on planetary on-axis, better than the complex designs with their internal Smyth/Barlow elements.


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#15 Jon Isaacs

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Posted 22 January 2021 - 01:25 PM

I've used the 6 and 9 Expanse (a rebrand actually) and while they are fantastic for the money, IMO on planetary they are a little soft in their on-axis presentation.  IMO a good simple Kellner, RKE, Abbe, or Plossl in 12mm with a 2x Barlow will provide a crisper planetary view than the 6 Expanse.  Using longer focal length simpler designs with a good Barlow has always provided some of the best performance on planetary on-axis, better than the complex designs with their internal Smyth/Barlow elements.

 

I've owned a number of Expanses including 3 or 4 each of the 6 mm and 9 mm. The 9mm was a good performer but the 6mm always seemed soft.  The 9mm was a workhorse as this photo suggests. An eyepiece doesn't have it's paint worn off and it's barrel battered with nicks and scratches unless it spends a lot of time in the focuser.. 

 

4474639-Synta Widefield 9mm.jpg
 
At the time, my main scope was my 12.5 inch F/4.06 and it sat between a 7 mm Type 1 Nagler and a 12 mm Type 2 so it was up against some very good eyepieces for fast scopes.
 
Jon

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#16 Kutno

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Posted 22 January 2021 - 01:45 PM

I remember trying to look through a 10mm Plossl during the daytime, without glasses. No matter how I jmed my eye in there, I could not see the full field of view. I then made several posts saying that 10mm Plossls are junk.

...

But now that I think about it, I had no issues with these at night time. I had a good view with what I think was a 8-9mm Plossl. Maybe Kelner, but I think it said Plossl.
...

So, a 10mm Plossl is an economical and useful high power eyepiece, but only at night time.

I think a barlow would reduce the field distortion somewhat.

...

 

When I bought an Orion XT6i Dob years ago, one of the two eyepieces that came with it was a 10mm Orion Sirius Plossl.  I was not impressed with its outer-third field of view.  After I matched it with a 2x Orion Shorty Barlow, the Plossl turned into a tiger in the Dob, at 240 power; making it a bona fide challenger to a 5mm UO Ortho in the same scope; especially, on Jupiter!


Edited by Kutno, 22 January 2021 - 01:49 PM.

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#17 stargazer193857

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Posted 22 January 2021 - 02:04 PM

The scope would be f5.5. In case that matters.

Everyone has talked me out of the 6mm expanse.

Now there is competition between a 9.6mm Plossl and 9mm gold line, the gold line costing $10 more, having a little more power, but being reviewed by some here as less crisp than the Plossl. I wonder if they used a $10 Plossl or a more expensive one.


Sounds like the gold line is at least as sharp off axis as the Plossl is.



I think a 2x barlow still might beat a 6mm Plossl. It costs more, and might be of worse quality if low price, but it can be used with the low power eyepiece too.



As for low power eyepiece, I wonder if the 25mm it 32mm is better for a beginner. The 32mm is $5 more, frames and finds stuff better, but also has different eye relief. It has a richer view but can antagonize eye astigmatism. It is a good match with a 2x barlow, whereas a barlowed 25mm would be redundant to the 9mm.


I think providing only a 9mm and no barlow, 134x, would disappoint on the planets. A 6mm Plossl would cost less than the barlow.


A barlow also allows more out focus for looking at trees during the daytime.

#18 stargazer193857

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Posted 22 January 2021 - 02:09 PM

It is starting to sound like the best combo for the beginner is also the most expensive one:

32mm Plossl, 2x barlow, 9mm gold line. Well worth it though. I just wonder if that can be beaten, and which ebay 2x barlow is good enough quality.

Anyone used this barlow?
https://www.ebay.com...1gAAOSwIwpf5GMM

SVBony is a reasonable brand that cares about its reputation. That barlow dies not look like one of the really bad ones I used.


This looks like the best deal on the 9mm:
https://www.ebay.com...r0AAOSwjqFf~m45


Still a little question left as to 25mm vs 32mm, but I'm thinking the wider view of the 32mm is better for finding and framing stuff, and coupled with the 2x barlow allows a lower powered view with enough back focus for daytime viewing.

Total cost for the 3 is $60. Not bad at all for a grab n go set that fits in your pocket and does not break the bank if you lose one.

Edited by stargazer193857, 22 January 2021 - 02:24 PM.


#19 csrlice12

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Posted 22 January 2021 - 02:13 PM

If nothing else they're good dust plugs that you can look thru....my 10mm Sirius plossl was originally relegated the duty as my finder alignment eyepiece till I gave it away.....then I got a 10mm Orthostar ortho, it's a keeper.



#20 stargazer193857

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Posted 22 January 2021 - 02:26 PM

I am concerned about some Plossls having poor off axis performance. The ones I looked through were sharp at f5 and a bit below. Now I wonder if it matters where I buy, and if these low prices ones will hold up.

#21 Thomas_M44

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Posted 22 January 2021 - 03:01 PM

I remember trying to look through a 10mm Plossl during the daytime, without glasses. No matter how I jmed my eye in there, I could not see the full field of view. I then made several posts saying that 10mm Plossls are junk. I even recall seeing blackouts in a 25mm during the daytime. Same for the 8.8mm Meade 82 deg.


But now that I think about it, I had no issues with these at night time. I had a good view with what I think was a 8-9mm Plossl. Maybe Kelner, but I think it said Plossl.

Very sharp views in the 8.8mm Meade 82 degree with no issues. Same with the 25mm Plossl.




I think the issue is spherical aberration of the eyepiece, which causes field distortion rather than star aberration, and results in tubes of light not intersecting at the same exit pupil. The small daytime pupil can't take in all the tubes, whereas the larger night time pupil can.


So, a 10mm Plossl is an economical and useful high power eyepiece, but only at night time.

I think a barlow would reduce the field distortion somewhat.



The downside to 52 degrees is it is harder to find planets. An Orion Expanse eyepiece might be the most economical option there. I read the 9mm has some blackout issues, though I've not bought one. I wonder how good the 6mm is.


How good is the 6mm Orion Expanse, and how much better is it than a 10mm Plossl and barlow? A 10mm Plossl costs less than half what the Expanse costs.

I have a full set of current TeleVue Plossls.

 

Very good optical quality, but progressively more uncomfortable eye-relief as one goes below 20mm FL.

 

A few months ago, however, I had an epiphany:

 

With use of a 2.5X and 5X Powermate, I will never have to suffer the cramped eye-relief of shorter FL eyepieces again.

 

I *might* use my 15mm TV Plossl on some occasions, but likely never again use the 11mm or 8mm. I most likely will sell the 11mm and 8mm and never miss them.

 

Same goes for my 7mm and 6mm KK Fujiyama orthos --just not needed.

 

With the very high quality magnification afforded by the 2.5X and 5X Powermates, 1.25-inch eyepieces between 32mm and 15mm can be used to fulfill all of my higher-magnifications needs cool.gif


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#22 BillP

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Posted 22 January 2021 - 04:05 PM

 

I've owned a number of Expanses including 3 or 4 each of the 6 mm and 9 mm. The 9mm was a good performer but the 6mm always seemed soft. 

 

My experience as well.  I never Barlowed them that I recall FWIW.  They are definitely excellent eyepieces though for those wanting to keep costs down.


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#23 epee

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Posted 22 January 2021 - 06:41 PM

I have a full set of current TeleVue Plossls.

Very good optical quality, but progressively more uncomfortable eye-relief as one goes below 20mm FL.

A few months ago, however, I had an epiphany:

With use of a 2.5X and 5X Powermate, I will never have to suffer the cramped eye-relief of shorter FL eyepieces again.

I *might* use my 15mm TV Plossl on some occasions, but likely never again use the 11mm or 8mm. I most likely will sell the 11mm and 8mm and never miss them.

Same goes for my 7mm and 6mm KK Fujiyama orthos --just not needed.

With the very high quality magnification afforded by the 2.5X and 5X Powermates, 1.25-inch eyepieces between 32mm and 15mm can be used to fulfill all of my higher-magnifications needs cool.gif


I collected a set of Barlows, x2, x3, & x5 for much the same reason. Then I gravitated to longer eye-relief eyepieces. Now I'm back to stuffing Plossl sitting on Barlows, into my eye socket.
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#24 doug mc

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Posted 22 January 2021 - 07:04 PM

I have the 25, 20 and 10mm versions of these in pairs for binoviewing. Sort of like plossl volcano tops. The 10mm is comfortable to use.

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#25 Kutno

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Posted 22 January 2021 - 07:46 PM

 

I've owned a number of Expanses including 3 or 4 each of the 6 mm and 9 mm. The 9mm was a good performer but the 6mm always seemed soft.  The 9mm was a workhorse as this photo suggests. An eyepiece doesn't have it's paint worn off and it's barrel battered with nicks and scratches unless it spends a lot of time in the focuser.. 

 

 
 
At the time, my main scope was my 12.5 inch F/4.06 and it sat between a 7 mm Type 1 Nagler and a 12 mm Type 2 so it was up against some very good eyepieces for fast scopes.
 
Jon

 

 

I am not surprised by the condition of the bottom of your 9mm Expanse.  I've always wondered what material is used to make the 1.25" end of the barrels of those eyepieces.  A 6mm version of the Expanse, purchased from Owl, possessing the same gold ring and sickly soft eye guard, with lettering around the lower end of the upper barrel, has a lower barrel that is incredibly easy to dent with a set screw.  It resides in the stable for newbies, who profit from its eye relief, which is a lot more than similar focal length Plossls or Orthos would have.  Don't get me wrong.  Its cost and performance make it fine for someone who cannot afford the high-priced spread and wants to see the night sky without eye strain.  I must add, though, that it does get soft towards the edge of its published 66° AFOV and the performance of the remainder of that field of view, while good, is not Orthoscopic.       


Edited by Kutno, 22 January 2021 - 07:49 PM.



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