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Long story shortened - need help with Vintage Orange Tube C8

Celestron classic optics
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#1 Drive-In

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Posted 23 May 2019 - 09:42 PM

Hi all,

 

Working my way back in to using my Vintage Orange Tube C8. Had started to prep the optics for shipping out to re-coat but my son was diagnosed with brain cancer and the C8 gathered dust. Dropped it at Celestron and they said they don't re-coat and I couldn't afford the XLT Star Bright optics so I told them I'd be by to pick it up.

 

Picked it up to discover they'd re-assembled the scope and put a new set of Star Bright XLT optics in - at no charge. I was so floored - I'm still floored. And as I start to put the scope to use, I have some questions.

 

1. They replaced the secondary - taking the serial # with it. I may have registered the scope here some years ago, but searching my posts only goes back to 2016. I believe the scope was produced in 1980.

 

2. What is the XLT Starbright Optical system? Having a hard time finding specs. f/10? Focal length still 2000mm? Does it matter what the mirror is made of or just the coatings are important? Is XLT coating industry-standard?

 

As I said, I'm starting back up and need time to work through getting familiar with the scope, discovery of any issues (ie focuser, backlash etc) I still even need some eyepieces so any help coming this way is a big deal for me and thanks in advance.

 

Oh, and I live in a rural, desert area and the viewing is spectacular (when the planes aren't leaving trails that spread into thick cover smile.gif

 

Mike

 

 


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#2 DreamWeaver

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Posted 23 May 2019 - 10:13 PM

Here's the old post you were looking for Mike... https://www.cloudyni...cope/?p=3254041   To search for older posts, you need to click on the little gear looking symbol next to the search field.  Then select "archive" towards the bottom of the search page.

 

Sorry to hear about your son.  

 

That was pretty awesome of Celestron to do that!


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#3 Drive-In

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Posted 23 May 2019 - 10:32 PM

Here's the old post you were looking for Mike... https://www.cloudyni...cope/?p=3254041   To search for older posts, you need to click on the little gear looking symbol next to the search field.  Then select "archive" towards the bottom of the search page.

 

Sorry to hear about your son.  

 

That was pretty awesome of Celestron to do that!

Thanks Keith - good to have the number again. And for your condolences - Interesting "coincidence", the day we picked up the Cate - my son and I had just come from his ophthalmologist who said his seriously diminished eyesight is "slightly" better (huge tumor also crushed his optic nerve - lost all of his peripheral vision and some central) - so Celestron's gift of far distant seeing was/is way too meaningful to take lightly - you know? :)

 

Looking forward to reacquainting myself with this scope's power and versatility.


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#4 Littlegreenman

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Posted 24 May 2019 - 02:21 AM

Hi all,

 

Working my way back in to using my Vintage Orange Tube C8.... [Post shortened by Littlegreenman]

 

2. What is the XLT Starbright Optical system? Having a hard time finding specs. f/10? Focal length still 2000mm? Does it matter what the mirror is made of or just the coatings are important? Is XLT coating industry-standard?

 

As I said, I'm starting back up and need time to work through getting familiar with the scope, discovery of any issues (ie focuser, backlash etc) I still even need some eyepieces so any help coming this way is a big deal for me and thanks in advance.

 

Oh, and I live in a rural, desert area and the viewing is spectacular (when the planes aren't leaving trails that spread into thick cover smile.gif

 

Mike

My wishes for your son.

XLT Starbright is or was Celestron's advanced coatings.  They were introduced in the late 1990's ? or there abouts. I don't know if they have come up with anything newer since then. I forget the details, but vaguely remember they may involve either more precise deposition of layers, and pretty sure it involves an element in addition to fluorite. Hafnium? Neodymium? The benefits would be more light transmission and less light reflected off the optical surfaces, with a resulting brighter image, and with less reflected light bouncing around inside the optics resulting in increased contrast. Compared to uncoated optics, the difference would be visible, but not uber-dramatic. It is still an f/10 system.

 

Eyepieces: let us know what you have. People will recommend what would be nice to have that you don't. A starter set would be 3 eyepieces or 2 eyepieces and a Barlow to give you high, medium and low magnification. Modern eyepieces also give us more selection of wide FOV, to see wider patches of sky. You can also ask about eyepieces on the CAT forum her on CN. With an F/10 you do not 'need' premium eyepieces like Naglers, although if you can afford them, they are nice.

LGM


Edited by Littlegreenman, 24 May 2019 - 02:43 AM.

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#5 Mike W.

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Posted 24 May 2019 - 07:45 AM

Good morning Mike, my son went through a year at Children's Hospital here in Seattle when he was 11, 

My long story short, the long days and nights while he was there is what got me into the hobby, that was 20yr's ago.

 

People were more than generous, unlike Blue Cross, still paying on that, anyway I have a few X-Cels lx's, an 18mm, a 25mm, & the matching X Cel  Barlow which will give nice high and low mag views.

 

PM me your address and they'll be shipped tomorrow.

 

Hope the best for your son's recovery, family is more important than anything else on this planet, or other planets as well cool.gif    


Edited by Mike W., 24 May 2019 - 08:16 AM.

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#6 Drive-In

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Posted 24 May 2019 - 12:40 PM

My wishes for your son.

XLT Starbright is or was Celestron's advanced coatings.  They were introduced in the late 1990's ? or there abouts. I don't know if they have come up with anything newer since then. I forget the details, but vaguely remember they may involve either more precise deposition of layers, and pretty sure it involves an element in addition to fluorite. Hafnium? Neodymium? The benefits would be more light transmission and less light reflected off the optical surfaces, with a resulting brighter image, and with less reflected light bouncing around inside the optics resulting in increased contrast. Compared to uncoated optics, the difference would be visible, but not uber-dramatic. It is still an f/10 system.

 

Eyepieces: let us know what you have. People will recommend what would be nice to have that you don't. A starter set would be 3 eyepieces or 2 eyepieces and a Barlow to give you high, medium and low magnification. Modern eyepieces also give us more selection of wide FOV, to see wider patches of sky. You can also ask about eyepieces on the CAT forum her on CN. With an F/10 you do not 'need' premium eyepieces like Naglers, although if you can afford them, they are nice.

LGM

Thanks LGM :) The only 1.25 I have is a Celestron 40mm Plossl. Works pretty well but planets are too bright with no detail. Without goto, I need to learn how to manually locate before I can drill down to higher mags. Had some trouble aligning the 6x30 finder - not sure if the mount is bent or the finder or what - still getting warmed up.

Mike



#7 Drive-In

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Posted 24 May 2019 - 12:48 PM

Good morning Mike, my son went through a year at Children's Hospital here in Seattle when he was 11, 

My long story short, the long days and nights while he was there is what got me into the hobby, that was 20yr's ago.

 

People were more than generous, unlike Blue Cross, still paying on that, anyway I have a few X-Cels lx's, an 18mm, a 25mm, & the matching X Cel  Barlow which will give nice high and low mag views.

 

PM me your address and they'll be shipped tomorrow.

 

Hope the best for your son's recovery, family is more important than anything else on this planet, or other planets as well cool.gif    

Hi Mike - I sent a pm this morning and thanks. Has your son made a full recovery? Do hope so. These things can really take a long time. We spent 18 days in ICU, 14 in acute rehab and got dumped. No referrals, no follow up - just sent me home with a deathly ill and unstable young man. Took 8 months for someone to finally tell me a University Hospital was the only option. We drive 300 miles rt for each appointment but Sean is so much better now. Lots of places to fall through the cracks in stuff like this but as I said, hope all is well for you and your family now. Insurance has been/is (surprisingly) the most stable thing of all so far. Huge Godsend, that.

 

Bet other planets don't have anything close to the joy that family is... probably all growing their children in creches! :)

 

Mike and Sean


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#8 Littlegreenman

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Posted 24 May 2019 - 12:53 PM

Mike,

A 40mm eyepiece with that scope will not resolve planets to a disc very well. They will look more like stars. Higher power eyepieces in the 8mm to 20mm range will show planets as a disc, and Saturn's rings will pop out. Even higher mag with up to 5 or 6mm will show more, but only on nights with very still air. Atmospheric conditions often limit higher magnifications. Vangard's eyepiece offer above is will get you closer. The Barlow will increase the magnification of any eyepiece by the Barlow X -factor: a 2x Barlow will double the mag, a 3x will triple it, etc.

 

The finder might have one or two sets of three screws around the tube. These help adjust the aim of the finder.

Steven


Edited by Littlegreenman, 24 May 2019 - 01:18 PM.

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#9 Drive-In

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Posted 24 May 2019 - 01:05 PM

Mike,

A 40mm eyepiece with that scope will not resolve planets to a disc very well. They will look more like stars. Higher power eyepieces in the 8mm to 20mm range will show planets as a disc, and Saturn's rings will pop out. Even higher mag with up to 5 or 6mm will show more, but only on nights with very still air. Atmospheric conditions often limit higher magnifications. Vangard's eyepiece offer above is will get you closer. The Barlow will increase the magnification of any eyepiece by the Barlow X -factor: a 2x Barlow will double the mag, a #x will triple it, etc.

 

The finder might have one or two sets of three screws around the tube. These help adjust the aim of the finder.

Steven

Hi Steven and thanks. I did use the set screws - focused on the top of a telephone pole 1/2 mile away and used that to center the finder. The finder is angled inside the mount, corner to corner, so to speak - so, it's turned as far as possible and I'm still some degrees away from what the primary is centered on - if that makes sense. I shimmed the finder mount between the OTA and the finder mount base, but it only helped a little. Also missing the O-ring but not sure replacing that is going to get me closer. Still working on it.



#10 DreamWeaver

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Posted 24 May 2019 - 03:49 PM

...but Sean is so much better now....

That's great to hear Mike.  I pray you and Sean get to enjoy this scope together for many many years to come!


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#11 Jon Isaacs

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Posted 24 May 2019 - 04:48 PM

Mike:

 

Sorry to hear about your son. My thoughts and prayers are with you.

 

I am quite sure the Starbright XLT are the most recent coating and quite a bit better than the original coatings. You can read about them here.

 

https://www.celestro...ptical-coatings

 

Jon


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#12 Drive-In

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Posted 24 May 2019 - 06:58 PM

Mike:

 

Sorry to hear about your son. My thoughts and prayers are with you.

 

I am quite sure the Starbright XLT are the most recent coating and quite a bit better than the original coatings. You can read about them here.

 

https://www.celestro...ptical-coatings

 

Jon

Thanks so much Jon. And for the link too - I'd read somewhere that Celestron's original aluminum coatings were exceptional for the time and were still operating at near-peak performance all these years later. Interested in what advances they've made since the heyday.

 

Mike



#13 Drive-In

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Posted 24 May 2019 - 06:59 PM

That's great to hear Mike.  I pray you and Sean get to enjoy this scope together for many many years to come!

Thank you Keith - and for you and yours too. Little things are starting to come together and snowballing. Looking forward to clear skies and clearer sailing. :)


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#14 Mike W.

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Posted 25 May 2019 - 08:02 AM

Morning Mike, was reading here that you're having an issue with your finder, most hardware stores carry "O" rings of varying sizes.

I'd remove the finder bracket and take it with the finder OTA to the store with you and start stretching "O" rings until you find one that does the job, the "O" ring is critical to the way the finder bracket & OTA function together, using tape in place of the "O":ring isn't the real solution.

 

A nice polarize or neutral density filter will be what you'll want for those really bright objects in the eyepiece, they reduce the glare enough to bring out the detail.

 

As far as finders go, a Telrad would be the ideal replacement for the stock finder, the 6 X 30 finders just don't have the light gathering ability you need.

 

Maybe someone here has a spare one kicking around they could offer up?

 

 

 

Until you've been there you'll really never understand the anxiety of the day to day of it,,,,,,,,,

 

Also,while digging though the stuff this morning I ran across a stock "Moon" filter that comes with many starter scopes, it's about an ND. 13 the optics are okay but after a while a few quality filters are fun to have to experiment with.

 

 

Astronomy is a lot like fishing, sometimes we just sit for very long times staring at nothing really, just thinking,,,,,,,,,,,waytogo.gif


Edited by Mike W., 25 May 2019 - 09:36 AM.

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#15 Drive-In

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Posted 25 May 2019 - 11:15 AM

Morning Mike, was reading here that you're having an issue with your finder, most hardware stores carry "O" rings of varying sizes.

I'd remove the finder bracket and take it with the finder OTA to the store with you and start stretching "O" rings until you find one that does the job, the "O" ring is critical to the way the finder bracket & OTA function together, using tape in place of the "O":ring isn't the real solution.

 

A nice polarize or neutral density filter will be what you'll want for those really bright objects in the eyepiece, they reduce the glare enough to bring out the detail.

 

As far as finders go, a Telrad would be the ideal replacement for the stock finder, the 6 X 30 finders just don't have the light gathering ability you need.

 

Maybe someone here has a spare one kicking around they could offer up?

 

 

 

Until you've been there you'll really never understand the anxiety of the day to day of it,,,,,,,,,

 

Also,while digging though the stuff this morning I ran across a stock "Moon" filter that comes with many starter scopes, it's about an ND. 13 the optics are okay but after a while a few quality filters are fun to have to experiment with.

 

 

Astronomy is a lot like fishing, sometimes we just sit for very long times staring at nothing really, just thinking,,,,,,,,,,,waytogo.gif

Sometimes I sit and think... sometimes I just sit. :)

 

Lovely post Mike and thanks. I'll get right on the O-ring for starters but a good finder is going to be crucial, I think. Need to develop a knack for locating and... what's it called - stepping up magnification but still keeping an object centered? Sure there's a word for it (no coffee yet. :) )

 

When we viewed Jupiter the other night, a filter was just what I thought of. But then the Plossl (for me at least) being the only eyepiece I have, is just an unknown. It's like getting to go fishing after a long drought - a real scramble first remember, and then to just bring with me every single piece of gear I could possibly need to "catch the big one!" Or prospecting for gold. "I know I'm gonna need that and that and that :)

 

I don't know if it's an issue yet or not but I see there's play in the (declination?) control. (slews the scope side to side) Not sure if it was there before but it sort of scares me with respect to locating, zooming in on and tracking DSOs. Would an oversize knob compensate for the play in it?

 

I'd forgotten how nice people on this forum were. Someone named Jon said if he does bring his gear out, maybe we could meet up somewhere near Joshua Tree (not far from here). I can't tell you how nice it is to talk to people about something else for a change. And people stepping up to help out... for me it's like Gilligan seeing a ship on the horizon - imagine his excitement! :)

 

Thanks Mike



#16 Geo.

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Posted 25 May 2019 - 01:38 PM

In the beginning CATs had no anti-reflective coatings. Thus thruput averaged about 74-78% of the light that struck the corrector. Each surface of an uncoated optic reflects about 4% of the light striking it. A SCT has 2 surfaces on the corrector, 1 each on the primary and secondary and generally 2 on the diagonal. So...

The corrector passes 92% to the primary which passes 88.3% to the secondary which passes 84.8% to the prism diagonal which passes 78% to the eyepiece.

 

In 1980 Meade began selling the 2080 in competition with Celestron's C8. They soon introduced their EMC coatings. Celestron responded with an option called "Special Coatings." Like EMC his involved coating the corrector with Magnesium fluoride. This reduces the reflected light per surface from 4 to 1%. So now the numbers look like this: 100% in 98% out at corrector, 94% at primary (98 * 96), 90% at secondary (94 * .96) and 83% at the diagonal (90 * 92).

 

In 1984 Celestron introduced its "StarBright Coatings." Meade later responded with UHTC. Both technologies involved Magnesium fluoride coatings on all the optical surfaces. Each were paired with coated prism diagonals. Thus the 100% of entering light only 12% was lost to reflection and we have 88.3% reaching the eyepiece. Enter the 99% diagonal and we get 89% thruput.

 

XLT StarBright Coatings are not much different than good old StarBright Coatings. What is new is that about 2000 Celestron changed the glass used in its corrector to water glass from crown glass, crown contains iron that gives it that green tint. Some users complain that XLT has a yellow tint. Actually, this is just the lack of the green filtering effect. This also makes XLT "look" brighter, but the actual thruput is only slightly higher. This probably due to more precision in the coating disposition process rather than the materials used.

 

In spite of what the marketing folks would have you believe, getting the reflectivity of an optical surface below 1% runs afoul of the laws of physics. CATs will always operate at a disadvantage to a Newtonian with its minimal 2 optical surfaces between the light and the eyepiece. A Newt with uncoated optics gets 92% of the light to the eyepiece.


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#17 Mike W.

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Posted 25 May 2019 - 04:05 PM

Afternoon Mike, if it's the Jon I'm thinking about break your neck to be there, he's good people.

 

I'm not familiar with the mount you have so I can't help with the questions about it, if I see a couple of pic's of it that helps, and pics of the ota w/finder might give me a few idea's that might help.


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#18 terraclarke

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Posted 25 May 2019 - 04:24 PM

In the beginning CATs had no anti-reflective coatings. Thus thruput averaged about 74-78% of the light that struck the corrector. Each surface of an uncoated optic reflects about 4% of the light striking it. A SCT has 2 surfaces on the corrector, 1 each on the primary and secondary and generally 2 on the diagonal. So...
The corrector passes 92% to the primary which passes 88.3% to the secondary which passes 84.8% to the prism diagonal which passes 78% to the eyepiece.
 
In 1980 Meade began selling the 2080 in competition with Celestron's C8. They soon introduced their EMC coatings. Celestron responded with an option called "Special Coatings." Like EMC his involved coating the corrector with Magnesium fluoride. This reduces the reflected light per surface from 4 to 1%. So now the numbers look like this: 100% in 98% out at corrector, 94% at primary (98 * 96), 90% at secondary (94 * .96) and 83% at the diagonal (90 * 92).
 
In 1984 Celestron introduced its "StarBright Coatings." Meade later responded with UHTC. Both technologies involved Magnesium fluoride coatings on all the optical surfaces. Each were paired with coated prism diagonals. Thus the 100% of entering light only 12% was lost to reflection and we have 88.3% reaching the eyepiece. Enter the 99% diagonal and we get 89% thruput.


I have a 2nd Qtr 1977 Orange C8 and I had a 2nd Qtr 1977 Orange C5. Both with “Special Coatings.
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#19 Drive-In

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Posted 25 May 2019 - 07:02 PM

Afternoon Mike, if it's the Jon I'm thinking about break your neck to be there, he's good people.

 

I'm not familiar with the mount you have so I can't help with the questions about it, if I see a couple of pic's of it that helps, and pics of the ota w/finder might give me a few idea's that might help.

He might well be - he seems like a wonderful guy. Must have a truck tho - road he suggested we meet on eats sedans!

 

Think I figured out the image upload reqs - hope they're clear enough.

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#20 Don W

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Posted 25 May 2019 - 07:24 PM

The finder mount is mounted backwards. The rubber ring goes in the groove in front of the eyepiece.


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#21 Drive-In

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Posted 25 May 2019 - 08:24 PM

The finder mount is mounted backwards. The rubber ring goes in the groove in front of the eyepiece.

Thanks Don. I only find one groove in the barrel and it's toward the rear of the finder. Turning the mount around puts the set screws onto the front of the finder with the O-ring likely (it's missing for now) fitting into the rear mount. Does that sound right? Without an O-ring, I can't align for now so I can't tell if it's centering better in the mounting rings.



#22 Don W

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Posted 25 May 2019 - 08:50 PM

yes flip the mount around and reverse the finder.


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#23 Mike W.

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Posted 25 May 2019 - 09:40 PM

Mike, i don't know if your familiar with the Telrad, here's a link

 

https://www.youtube....h?v=NH33pXGkNF8


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#24 Steve Allison

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Posted 26 May 2019 - 02:16 AM

Drive-In

 

I disagree that the finder mount is backwards. Mine is the same as yours, and the grove in the finderscope is to locate the three set screws- like on just about every other finder that uses three adjustment screws. Including my Takahashi 6X30 finderscope and bracket.

 

I have my original 1970's manual in front of me and the picture shows the pillar of the bracket facing forward and the three screws closest to the eyepiece of the finder. All just like yours in the picture. The O-ring just goes around the finder with no grove for it.


Edited by Steve Allison, 26 May 2019 - 02:33 AM.

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#25 Mike W.

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Posted 26 May 2019 - 10:49 AM

I have the Tasco newer version ota & mount, Tasco has a small second groove for the "O" ring plus the wide and squared grove for the alignment screws.

When you receive the ")O" ring just press it under the front ring of the mount and shift the ota forward until the alignment screws are in the groove.

 

That will also allow for a greater arch of adjustment when aligning and may be the issue you're having with your finder.

 

What again was the issue with the scopes mount? Free play in one of the locks?


Edited by Mike W., 26 May 2019 - 10:51 AM.

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