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Best choice for a used sct ?

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#1 rugby

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Posted 04 April 2019 - 08:53 PM

I am starting a search to buy a used sct to complement my large dobsonians. Apparenty some models are better than others. I am strictly a visual observer but need tracking for sketching. T he old orange c8 seemed perfect but there are references to bad optics in the mid 80's. I like the 9.25 or 10 inch models but dont want the goto optons..I am a star hopper needing good optics with a mount I can move quickly.  What should I avoid or consider buying?



#2 otocycle

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Posted 04 April 2019 - 09:15 PM

Hi -  newer optics with more modern light transmission coatings favor buying more recently manufactured "used" SCTs compared to more vintage instruments, all else being equal.   You can find some very good older equipment, but it is riskier unless you can test it before buying/owning.  

 

You don't need ACF/flatter field optics just for visual, so no need to pay for that premium unless it's still a great deal.

 

Like you, I have larger Dobs that I wanted to complement with an SCT on a driven or alt-az mount, so I settled for the C9.25 (big enough) and newer C6 (small enough).

 

I would avoid any of the Criterion/ B& L SCTs that went out of production many years ago.

 

A Takahashi TSC-225 would be worth considering, but they are rare and command a premium price.



#3 Spikey131

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Posted 04 April 2019 - 09:19 PM

I don’t know what your budget is, but I would advise getting the most recent SCT you can afford. New technology with optics and coatings have really improved these scopes.
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#4 MrRoberts

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Posted 04 April 2019 - 09:28 PM

I don't know much about this one but how about Celestron's Nexstar Evolution 6 or 8. I have the C-8/E on an Ioptron AZ Mount Pro (much more than you need or are thinking of). I'm on this site daily but don't recall seeing any Evo's for sale. Hopefully someone can chime in with thoughts/suggestions.


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#5 Gary Z

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Posted 04 April 2019 - 09:55 PM

One thing about the EVO mount is its versatility.  guess what, turn off the power, loosen the clutches and move the scope around as you see fit.  But I believe at some point, you'll enjoy the goto as well.The movement after loosening the clutches is quite smooth.

 

Gary


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#6 photomagica

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Posted 04 April 2019 - 09:56 PM

If you want or need a used one, buy the one that gives images you like when well collimated and used with a known star diagonal and eyepiece. If at all possible buy one conditional on satisfactory performance when tested or arrange to look through it first.

 

Why collimation and a known good star diagonal and eyepiece? I got a used older C-8 at one point. It was terrible. Collimation brought it up to fair. Then I got a new Celestron 2" dielectric diagonal and used it with Nagler eyepieces. That made a marked difference and brought it up to good. The diagonal was just pain awful so I threw it out! So you need collimation and good downstream optics for a fair test. Also let the 'scope come to temperature. There is sample variation among SCT's of any vintage so it is worth the effort to visually test if you possibly can.

 

BTW I have an Evolution 8 and it gives excellent images. I've heard good things about the Evo 8 from other users.

Bill



#7 rugby

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Posted 05 April 2019 - 06:34 AM

Thankyou all for some excellent advice. So far after reading different threads I could consider the 8 inch edge or 9.25 by celestron. What about the Meade products?



#8 otocycle

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Posted 05 April 2019 - 07:25 AM

Thankyou all for some excellent advice. So far after reading different threads I could consider the 8 inch edge or 9.25 by celestron. What about the Meade products?

 

De-forked Meade 8" SCT would be fine (LX90 or LX200GPS), but larger than that is 10" and the Meades tend to be heavier OTAs than the Celestrons.  Anecdotally, there also seems to be more used Celestron product offered for sale/auction.

 

Meade also had UHTC and non-UHTC coatings for a while, and UHTC is preferred for higher light transmission.



#9 MrRoberts

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Posted 05 April 2019 - 09:08 AM

How big is your DOB?

Just a reminder, but once one starts getting into SCT's larger than 8", weight and mount requirements start to be a more important concern. 



#10 photomagica

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Posted 05 April 2019 - 10:16 AM

When I bought my Evo 8 I debated getting the 9.25. I'm glad I got the 8 for portability reasons. If I had a permanent location or semi-permanent, then I'd go for the bigger aperture.

 

I haven't enough experience with Meade's to offer advice. I have seen samples of Celestron SCTs that do perform impressively well on the planets.  It was this experience that led me to get the Evo 8 and I was not disappointed.

Bill



#11 Nippon

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Posted 05 April 2019 - 02:18 PM

Thankyou all for some excellent advice. So far after reading different threads I could consider the 8 inch edge or 9.25 by celestron. What about the Meade products?

I have an Edge 8 I use on a Losmandy GM8. I'm picky about optics and own two high end 4" apo refractors and the Edge 8 optics still impress me. As far as used buy either pre Haley comet era scopes or models produced in the 90s and beyond. Celestron scopes got pretty bad during the mad rush of production for the anticipated demand as the great comet approached



#12 JohnnyBGood

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Posted 19 April 2019 - 08:04 AM

It's hard to find SCTs without GOTO or even the ability to use them manually if the battery/computer/drive motor goes out. I'm 98% visual and wanted a non-GOTO SCT that could be used manually. For me the 8" LX-10 ended up being the ideal scope. Good optics (same OTA as the LX-200), no frills, low price. It's pretty much the last of the manually operable SCTs.


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#13 gnowellsct

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Posted 20 April 2019 - 06:33 AM

It's hard to find SCTs without GOTO or even the ability to use them manually if the battery/computer/drive motor goes out. I'm 98% visual and wanted a non-GOTO SCT that could be used manually. For me the 8" LX-10 ended up being the ideal scope. Good optics (same OTA as the LX-200), no frills, low price. It's pretty much the last of the manually operable SCTs.


That's not really true. You just buy an OTA and put it on a non go to mount.

It is true that COMPLETE SYSTEMS are sold mostly go to. I'll grant that.

But I haven't used a complete system in 17 years. Why bother with Meade or celestron mounts when the G11 is available or the Mach 1s.

I'm on the board of an outreach organization and three directors of local observatories noted they get a lot of offers of donated scopes and they're always Meades and always don't work. In fact I have one of those in my basement right now. The goal is to fix it up for sale and put the funds for outreach. Often the first step in rehabbing these older systems is to take them off the fork. The ten inch lx200 is a monster. I don't know how people solo observe with those.

A c8 or 9.25 are both good choices. The requirement above for tracking for sketching makes sense. But tracking and moving the rig around the yard are contrary requirements. There's the power supply, the wires, alignment protocol for alt az, and power supply and wires for a GEM. I guess if approximate tracking is ok you can just use a compass for polar alignment. It's what I do for solar.

The need to move around the yard gives the nod to the c8. Less weight and a larger field of view for reacquiring objects.

#14 Jon Isaacs

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Posted 20 April 2019 - 07:15 AM

I don’t know what your budget is, but I would advise getting the most recent SCT you can afford. New technology with optics and coatings have really improved these scopes.

:waytogo:

 

The Celestron White Paper on the Starbright XLT coatings is a good read.

 

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

 

According to the white paper, Starbright XLT coatings have an average transmission of 84% across the visual band.  That was an increase of 16% over older Starbright coatings, that's about 71% transmission.  And many older scopes do not even have Starbright coatings.  This does not include the loss due to the secondary shadow but all SCTs have that.  It also does not include any degradation the older mirror coating might have suffered. 

 

Jon


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#15 wrnchhead

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Posted 20 April 2019 - 08:32 AM

If I needed a scope, I would jump on Agustus' listed C8 Ultima OTA in the classefieds. I have an identical one and it's great. Wish I'd have went with sct over my dob originally! Only weighs 11 lbs. It would need a mount so that's a consideration. 

 

Plus if someone buys it, I will quit feeling so tempted to get it myself!! 


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#16 MalVeauX

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Posted 20 April 2019 - 05:20 PM

I am starting a search to buy a used sct to complement my large dobsonians. Apparenty some models are better than others. I am strictly a visual observer but need tracking for sketching. T he old orange c8 seemed perfect but there are references to bad optics in the mid 80's. I like the 9.25 or 10 inch models but dont want the goto optons..I am a star hopper needing good optics with a mount I can move quickly.  What should I avoid or consider buying?

There's generally nothing wrong with 30~40 year old SCT mirrors. The older 70's Celestrons are actually quite good and still sought after. I would avoid older Meades (they're heavier and cost a lot less for a reason... those optics seems to be variable and the coatings are not great after 30+ years, especially those old `silvered' ones).

 

Unless you're on an extreme budget, I would recommend you look at used SCT's that are recent with modern coatings.

 

OPT cycles through used gear often and have great deals. I got my used C8 Edge HD + feather touch focuser for $1k there.

 

Very best,


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#17 Stargazer3236

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Posted 22 May 2019 - 11:15 AM

De-forked Meade 8" SCT would be fine (LX90 or LX200GPS), but larger than that is 10" and the Meades tend to be heavier OTAs than the Celestrons.  Anecdotally, there also seems to be more used Celestron product offered for sale/auction.

 

Meade also had UHTC and non-UHTC coatings for a while, and UHTC is preferred for higher light transmission.

Meade 10" ota weighs in at 26 lbs, Celestron 9.25 weighs 20lbs, Celestron 11" weighs 27.5 lbs. So Saying Meade weighs more is incorrect.



#18 Richard Whalen

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Posted 22 May 2019 - 12:00 PM

Meade 10" ota weighs in at 26 lbs, Celestron 9.25 weighs 20lbs, Celestron 11" weighs 27.5 lbs. So Saying Meade weighs more is incorrect.

Not really, you are comparing different size scopes. From your numbers per inch of aperture the 10" Meade weighs more.

 

Meade 2.6#

Celestron 9.25 = 2.16#

Celestron 11 = 2.5# per inch of aperture.



#19 Stargazer3236

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Posted 22 May 2019 - 12:24 PM

Not really, you are comparing different size scopes. From your numbers per inch of aperture the 10" Meade weighs more.

 

Meade 2.6#

Celestron 9.25 = 2.16#

Celestron 11 = 2.5# per inch of aperture.

Check retailers sites. Celestron doesn't have a 10" , only 9.25 or 11" .



#20 SeattleScott

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Posted 22 May 2019 - 03:32 PM

The issue with Celestron is the newer models have a tendency to fog up inside, requiring taking the corrector out to clean it every couple years. Not saying this is the case with all of them, but it happened to a buddy who bought a used one. Previous owner probably discovered the issue, cleaned it once so he could sell it, and within a couple years of my friend buying it, it clouds up again. Not a huge deal if working on scopes is a labor of love but a turnoff for some. That thin corrector can crack if you aren’t careful in the operation. Another buddy got an older C8 (late ‘90’s?) and it has been fine.

Mount can be tricky. Evo mounts aren’t normally sold separately and they don’t have the adjustable tension on the clutch from what I understand that you would want for accommodating eyepieces of different weight. iOptron mounts are designed for GoTo and aren’t really suitable for starhopping in my experience. So maybe a lighter weight GEM. Vixen SX2 has tracking and is very stable with an 8” SCT. If that is too pricey you might consider a CG4 or Skyview Pro with motors. If you want something classy a Great Polaris with motors could do the trick. Just finishing fixing one up, those motors are built to last. Mount isn’t overly heavy. I can certainly pick it up and move it around with a 4” F10 achro on it. If you want the specifics like weight just let me know.

Scott

#21 Bean614

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Posted 22 May 2019 - 03:58 PM

The issue with Celestron is the newer models have a tendency to fog up inside, requiring taking the corrector out to clean it every couple years. Not saying this is the case with all of them, but it happened to a buddy who bought a used one. Previous owner probably discovered the issue, cleaned it once so he could sell it, and within a couple years of my friend buying it, it clouds up again. Not a huge deal if working on scopes is a labor of love but a turnoff for some. That thin corrector can crack if you aren’t careful in the operation. Another buddy got an older C8 (late ‘90’s?) and it has been fine.

Mount can be tricky. Evo mounts aren’t normally sold separately and they don’t have the adjustable tension on the clutch from what I understand that you would want for accommodating eyepieces of different weight. iOptron mounts are designed for GoTo and aren’t really suitable for starhopping in my experience. So maybe a lighter weight GEM. Vixen SX2 has tracking and is very stable with an 8” SCT. If that is too pricey you might consider a CG4 or Skyview Pro with motors. If you want something classy a Great Polaris with motors could do the trick. Just finishing fixing one up, those motors are built to last. Mount isn’t overly heavy. I can certainly pick it up and move it around with a 4” F10 achro on it. If you want the specifics like weight just let me know.

Scott

"The issue with Celestron is the newer models have a tendency to fog up inside, requiring taking the corrector out to clean it every couple years. Not saying this is the case with all of them, but it happened to a buddy who bought a used one."....??????

 

You have given an example of ONE model that fogged up, and you got this info second hand.  Please..... Give us another verified example of the new ones "fogging up".

 

Next, you wrote "Mount can be tricky. Evo mounts aren’t normally sold separately and they don’t have the adjustable tension on the clutch from what I understand".....???????

 

Why even write Anything about an item if you have NO hands on experience with it?!  All you are doing is spreading misinformation, which helps no one.

  The Evolution mounts most certainly DO have Adjustable Tension Clutches on BOTH Alt and Az Axis.



#22 carolinaskies

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Posted 22 May 2019 - 05:28 PM

For star hopping without having to go buy an extra mount the old Meade 8" LX10, LX50, LX200 classic or the Ulitima 8, Celestar 8.   Stick with late 90s, early 2000s for best deals.  Basic tracking, actual ability to move the RA/Dec axis with semi-fine controls.  UHTC and XLT coatings are easy enough to come by in this time period.  Prices should range from 300-600 for these units, available alt-az or often with wedges.   Performance is pretty similar, not enough to worry over for your usage. 

For visual SKIP GEM mounts.  I don't care what GEM lovers say, a fork is the EASIEST ERGONOMIC visual piece of equipment.  No meridian flip, no crouching on the ground, just rotate around the OTA at a pleasant distance and enjoy.  

All the newer fork and single arm mounts are worthless for star hopping as you have to loosen clutches and hold OTAs, and have no fine RA/DEC manual controls.  For star hopping you want manual controls for minute movements without having to find which button on the hand control goes which direction. 

I had many hours on my LX10 before I gave it up for the LX200 so I could do some serious photography.   They are simple, light, effective, and fun.  The Celestar 8 is similar.    

I sold my LX10 to a good friend 20 years ago and he just sold it last year for $450 as he was getting into asto imaging and has access to a big planetarium scope for visual.   

A word on coatings, when brand new the coatings are as spec'd but over time the degrade to a certain reflectivity level, but 9 times out of 10 most people aren't going to notice the minor loss in an 8" or larger scope for the typical targets.   And final effective reflectivity is a combination of scope mirrors plus diagonal used anyway, so optimal performance is often less than 'advertised' anyway.  Not enough to truly worry about.  More important is to look at the coatings on primary and secondary to see if they are flaking or have pin-points in the coating... if they do, move on to another scope, the cost for recoating isn't extreme but for what these telescopes cost on the market it's better just to move on to another choice. 

Most old scopes probably haven't had their colimation checked so figure on doing that on any one you buy, just the nature of the market.  Don't discount a scope directly if it seem just a tad off, if you can check that colimation and you may find it just needs a tweak. 



#23 SeattleScott

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Posted 22 May 2019 - 05:54 PM

"The issue with Celestron is the newer models have a tendency to fog up inside, requiring taking the corrector out to clean it every couple years. Not saying this is the case with all of them, but it happened to a buddy who bought a used one."....??????

You have given an example of ONE model that fogged up, and you got this info second hand. Please..... Give us another verified example of the new ones "fogging up".

Next, you wrote "Mount can be tricky. Evo mounts aren’t normally sold separately and they don’t have the adjustable tension on the clutch from what I understand".....???????

Why even write Anything about an item if you have NO hands on experience with it?! All you are doing is spreading misinformation, which helps no one.
The Evolution mounts most certainly DO have Adjustable Tension Clutches on BOTH Alt and Az Axis.

Thanks for the clarification on the Evo clutches. I must have misunderstood that from my prior research. Good to know! I did at least say “as I understand” since I haven’t personally seen an Evo mount, but good to have an experienced user chime in. So Evo sounds like it might be a good option, other than requiring a one star alignment for tracking each time it is moved around.

As for the Celestron SCTs fogging up, this has been well documented in long threads on CN, in addition to my personal experience (even if it isn’t my personal scope). Again it is more the newer models. Not sure what the year cutoff is. Eddgy I think was the first to report it so he would know more.

Scott

Edited by SeattleScott, 22 May 2019 - 05:56 PM.


#24 SeattleScott

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Posted 22 May 2019 - 06:12 PM

For star hopping without having to go buy an extra mount the old Meade 8" LX10, LX50, LX200 classic or the Ulitima 8, Celestar 8. Stick with late 90s, early 2000s for best deals. Basic tracking, actual ability to move the RA/Dec axis with semi-fine controls. UHTC and XLT coatings are easy enough to come by in this time period. Prices should range from 300-600 for these units, available alt-az or often with wedges. Performance is pretty similar, not enough to worry over for your usage.

For visual SKIP GEM mounts. I don't care what GEM lovers say, a fork is the EASIEST ERGONOMIC visual piece of equipment. No meridian flip, no crouching on the ground, just rotate around the OTA at a pleasant distance and enjoy.

All the newer fork and single arm mounts are worthless for star hopping as you have to loosen clutches and hold OTAs, and have no fine RA/DEC manual controls. For star hopping you want manual controls for minute movements without having to find which button on the hand control goes which direction.

I had many hours on my LX10 before I gave it up for the LX200 so I could do some serious photography. They are simple, light, effective, and fun. The Celestar 8 is similar.

I sold my LX10 to a good friend 20 years ago and he just sold it last year for $450 as he was getting into asto imaging and has access to a big planetarium scope for visual.

A word on coatings, when brand new the coatings are as spec'd but over time the degrade to a certain reflectivity level, but 9 times out of 10 most people aren't going to notice the minor loss in an 8" or larger scope for the typical targets. And final effective reflectivity is a combination of scope mirrors plus diagonal used anyway, so optimal performance is often less than 'advertised' anyway. Not enough to truly worry about. More important is to look at the coatings on primary and secondary to see if they are flaking or have pin-points in the coating... if they do, move on to another scope, the cost for recoating isn't extreme but for what these telescopes cost on the market it's better just to move on to another choice.

Most old scopes probably haven't had their colimation checked so figure on doing that on any one you buy, just the nature of the market. Don't discount a scope directly if it seem just a tad off, if you can check that colimation and you may find it just needs a tweak.

I had a new 10” reflector with 97% reflectivity coatings out next to an old Coulter 10” Dob. The difference in brightness was obvious. The owner of the Coulter couldn’t believe how much brighter the views in my scope were. Granted SCTs are closed tubes so coatings should stay cleaner and not degrade as quickly. But when you are comparing new enhanced coatings against decades old, degraded standard coatings, there will be a considerable difference. It may not be as dramatic as my experience but it will be noticeable. Another time I had my 8” with 96% reflectivity coatings (several years old) alongside a buddies 8” SCT from probably the late ‘90’s with the standard Starbright coatings. My reflector clearly provided brighter views. Not night and day difference but we could both easily see it was brighter. And my reflector has about the same CO as his SCT so you can’t attribute the difference to secondary size. I’m not saying non-XLT scopes are obsolete and worthless, but the difference between them and the scopes with newer, enhanced coatings is significant.

Scott

#25 carolinaskies

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Posted 22 May 2019 - 06:51 PM

I had a new 10” reflector with 97% reflectivity coatings out next to an old Coulter 10” Dob. The difference in brightness was obvious. The owner of the Coulter couldn’t believe how much brighter the views in my scope were. Granted SCTs are closed tubes so coatings should stay cleaner and not degrade as quickly. But when you are comparing new enhanced coatings against decades old, degraded standard coatings, there will be a considerable difference. It may not be as dramatic as my experience but it will be noticeable. Another time I had my 8” with 96% reflectivity coatings (several years old) alongside a buddies 8” SCT from probably the late ‘90’s with the standard Starbright coatings. My reflector clearly provided brighter views. Not night and day difference but we could both easily see it was brighter. And my reflector has about the same CO as his SCT so you can’t attribute the difference to secondary size. I’m not saying non-XLT scopes are obsolete and worthless, but the difference between them and the scopes with newer, enhanced coatings is significant.

Scott

LOL, comparing an old Coulter to anything is not a viable comparison since they had a standard aluminum coating typically with no protective layer like the UHTC or XLT coating systems.  The curve of reflectivity reduction is kind of like depreciation on cars, the first few months it's pretty good, within a couple years that 97% coating (which in reality is effectively less btw) will be down several percent. Depending on storage, weather, humidity the coatings are affected.   

Aluminized coatings on the Coulter would be expected to need recoating in about every 5 years on average, of course back then coatings werent' extremely expensive and you could opt for standard or highly reflective acknowledging degredation factors. So comparing any Coulter from then to a modern (last 20 years) telescope is going to be a significant improvement.  Once Meade and Celestron introduced a system to improve reflectivity and longevity the expectation of recoating an SCT dropped significantly. It did so in such a respect that after the early 2000s Meade dropped it's standard coating altogether offering UHTC as the baseline.

To reiterate my former post for the benefit of individuals concerned about coating longevity and effectiveness, you should actually be more concerned about the diagonal you use and it's light transmission characteristics, whether prism or coated mirror.  Expect to replace a mirror diagonal which is regularly exposed to night conditions, humidity, storage in various states every few years.  You'll find that makes far more difference than the actual coatings in the SCT.  FWIW in a large newtonian replacing a standard first surface secondary mirror with a high reflective coated version is far more efficient.  This again is because the secondary mirror tends to be exposed to more humidity/temp variation due to much less protection than a primary mirror located inside the rocker box.  

Since the OP was questioning used SCTs it can also be expected that some degredation has occurred to the typical used SCT.  The drop-off of reflectivity after 5 vs 10 vs 20 years is far less intra-compared vs brand new to any one of these given the same standardization of coating that has been around for 20 years.  I'd have to go digging around for the details on this, but I recall reading up about it two years ago when a discussion ensued about recoating mirrors and life expectancy.  




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