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Sad Sack SCT - Criterion Dynamax 8

catadioptric classic equipment SCT
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#826 highfnum

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Posted 11 March 2017 - 05:04 PM

Gil V"
"Realistically, there probably aren't more than a couple hundred left
"

? not sure what you mean few hundred total dy8 or just coated mgfl ones
or estimated good ones
?

#827 rolo

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Posted 11 March 2017 - 06:42 PM

I use it at least once a month. Probably the best deep sky scope I own.

 

Definitely my best DSO scope, so it will get used often when the Moon's not in the sky.  It'll go to the golf course, and across the river when I really want to see the fainter fuzzies.

Probably cause it's your largest scope.


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#828 rolo

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Posted 11 March 2017 - 06:54 PM

And it could just be that only the bad ones get sold...

 

Bill

If that's the case where are all the posts on the good ones? With my one good one out of seven and so many others that have said theirs is bad I think the ratio of good to bad is nowhere near 60/40. The only thing we can go on is actual documented test, everything else is speculation. This topic goes round and round like merry-go-round. We must face reality and accept the fact the the DX8 is responsible for its own reputation. Oh, I think global warming has distorted their correctors.


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#829 terraclarke

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Posted 11 March 2017 - 07:41 PM

 

And it could just be that only the bad ones get sold...

 

Bill

If that's the case where are all the posts on the good ones? With my one good one out of seven and so many others that have said theirs is bad I think the ratio of good to bad is nowhere near 60/40. The only thing we can go on is actual documented test, everything else is speculation. This topic goes round and round like merry-go-round. We must face reality and accept the fact the the DX8 is responsible for its own reputation. Oh, I think global warming has distorted their correctors.

 

 

Probably much closer to 100 to 1. :lol:


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#830 Bomber Bob

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Posted 15 March 2017 - 08:02 PM

FROM DAVE'S THREAD ON THE DX8 CORRECTOR

 

Starting with GilV --> https://www.cloudyni...16#entry7763669

 

Rolo, you have a knack for saying really irritating things.

The reason I discuss Criterion in the manner that I do is that I am a fan of telescopes, and to this day am grateful to have had the opportunity to build them for a living when I was 19-25 years old.

I also want to help any DX owner get the most they can get out of their scope - just like I did when I was there. I'm not an optician, never was.

There's plenty of animus expressed here about Criterion, which I sometimes take personally. You had to be there - that is the best way I can describe it. Sorry if that's not enough.

And I still profess that the S-C scopes we made were comparable to equivalent priced products made at the time. It's just fashionable to beat up the product in the threads here!

Had we never made the Dynamax, Criterion's reputation would be outstanding. And, they would have had to close their doors prior to moving to West Hartford, because the RV-6, while still very popular, did not generate enough revenue to support the business.

Creating the Dynamax was a simple business decision - nothing more, nothing less. I remain proud of the scopes we made there. It was a dream to work there. I hold no grudge against my associates who chose telescope making as their profession.

Go ahead and criticize the 40 year old product if you like. You all certainly seem to enjoy it.

Were you by my side in 1981, you might choose your words more carefully,

You can have the thread back now.

 

Terra

 

And I still profess that the S-C scopes we made were comparable to equivalent priced products made at the time. It's just fashionable to beat up the product in the threads here!

 

I highly doubt that if you selected ten C8s at random, all made within the same time period, and 10 Criterion DX8s, and subjected them all to routine optical testing that you would have anyway near the disastrous test results shown with the Celestrons as you would with the Dynamaxes. We have in effect done that in thse threads. The results are not the same. And the anecdotal testimony of respective owners in these threads certainly proves otherwise as well.

 

GilV

 

I respectfully disagree, Tara. I base my opinion on one simple fact - that I have looked through more of them than virtually anyone - by a factor of at least 500.

Like I said, I'm not an optician. But, I can certainly evaluate a set of optics, although not to the degree of David - whose expertise is a thing of beauty.

I understand the limitations of commercial telescopes from that period, because I worked in the industry.

We made a lot of decent scopes. We also made a lot of very poor scopes. Every once in a while, we made a great one.

The funny thing is, when they left my assembly bench, I knew which category that particular scope fell into.

I think David is onto something here - and I'm not surprised because the guy's an optical wizard. I anxiously await more updates. I am of the strong opinion that when he is done with polishing the flat, the performance of the scope will improve dramatically - so much so that no further work is required.

But David will polish it anyway, because he can. And the scope will be even better. If we're lucky, we'll all get to read about it here. Maybe someday, I'll get a chance to look through it!


Edited by Bomber Bob, 15 March 2017 - 08:32 PM.


#831 starman876

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Posted 15 March 2017 - 08:30 PM

I think it is time for all of us to stop bashing the DX8 or 6.  We have had our fun and enough is enough. I apologize for any bashing I have done.  I would hate to use this as an example of how our kids or anybody else to behave. 


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#832 Bomber Bob

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Posted 15 March 2017 - 08:31 PM

Whew!

 

First, Gil, you're not a Defendant in a Cloudy Nights vs. Criterion lawsuit.  The criticisms & bashing is of the DX8 (mostly), and of Criterion's business / management decisions regarding their product.  If we've made you feel culpable, then we're off base.  But I can tell you honestly, I don't know what they were thinking / doing...  Have you seen my non-circular corrector?

 

Second, my tentative opinion of my 1974 DX8 is that it's a limited-purpose scope.  BUT, I haven't had enough 8+ seeing & trouble-free sessions to have a final opinion on it.  Why?  Cause the tube kept pulling away from the base, and wrecking the collimation.  I think that problem is fixed.  I'm actually looking forward to systematically sky testing my DX8.  If it can deliver sharp views at 40x per inch, I'll call it a Good Scope.  IIRC, so far it's maxed-out at about 180x, which is unsatisfactory -- just 23x / inch.

 

I have a large collection of Jupiter digital imagery made with most of my scopes.  Next chance I get, I'll image Jupiter with the DX8, and see how it compares.  Here's the rub:  If the images are satisfactory, all I'll have shown is that one Dynamax out of many is an acceptable SCT.  I agree with Terra that the majority of posts by Dynamax owners trend negative.


Edited by Bomber Bob, 15 March 2017 - 08:35 PM.

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#833 terraclarke

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Posted 16 March 2017 - 09:13 AM

I think it is time for all of us to stop bashing the DX8 or 6.  We have had our fun and enough is enough. I apologize for any bashing I have done.  I would hate to use this as an example of how our kids or anybody else to behave. 

Maybe you need to be a moderator Johann. I have noticed you too as a participant observer in these little debacles. You like to subtly get things going, then sit on the sidelines and add just a little jab here or there; and after the fact pontificate on the everyone else's 'bad' behavior.  There is a saying that goes something like: 'The person who stirs the sxxx gets to lick the spoon! 


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#834 deepwoods1

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Posted 16 March 2017 - 09:21 AM

Ewwwwwww……..


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#835 starman876

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Posted 16 March 2017 - 09:30 AM

Ditto, Terra must be going trough some kind of withdraw.



#836 terraclarke

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Posted 16 March 2017 - 09:31 AM

A little self reflection and projection going on J? :lol:


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#837 starman876

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Posted 16 March 2017 - 10:14 AM

A little self reflection and projection going on J? lol.gif

a bit lovingly defensive Terra


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#838 tim53

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Posted 16 March 2017 - 10:35 AM

I dunno, folks.  I can understand some of Gil's defense of Criterion.  

 

My story is somewhat different, but I think there might be some points that are similar:

 

I started out as a child.  Got my first tasco 4vte when I was 7.  Used it and my tasco 60mm (forget what that was called, but another variable power gizmoid) until 1972, when I couldn't stand not having a "real telescope".  Got addicted to reading Cave and Optical Craftsmen ads in S&T (been a subscriber since Feb 1969, started reading them in the library in fall 1965 - when I was 12 years old).  And when my parents saw how serious I was about upgrading, actually paid half of the $464 for the 8" f/6 OC Discoverer I ordered in Fall, 1972.  ...the purchase experience is another, long story that involved developing more than a little animosity toward Dick Nelson that essentially vanished the first night I got the scope home and looked at Saturn with it...  I loved that scope and did all kinds of things with it that would make me reluctant to even plug it in now.  So I used it a lot for about 8 years, at which time I put the optics in my Springfield (where they still live today).

 

I went from reading magazines and showing stuff to luke-warm interested friends in the early 70s (I even dragged them to star parties from time to time), attending John Sanford's Astrophotography classes at Orange Coast College, and eventually joining and making a herd of life-long friends in the Orange County Amateur Astronomical Association (now just the OCA).  

 

Then I worked for Meade from summer 1978 through Fall 1979 (and for a few months from fall 1981 through Spring 1982).  This is where my experiences may be most similar to Gil's at Criterion (though I hope I'm not being too presumptuous).  When I first started working there, I thought I'd died and gone to heaven - all these cool toys and an employee's discount on all of them!  I even drooled over the 4" refractor that I'd seen in the showroom for months (years?) prior to going to work there.  But a lot of the stuff was too expensive for the salary I was pulling down at the time.  So I mostly dreamed a lot, and I built a lot of telescopes.  I even made some suggestions to improve efficiency in making parts (the machined-off bare aluminum band around the base of the pier cap on the RGs was my idea - before that, they put a strip of aluminum tape around the base, which was hard to do without some waviness.)

 

A couple things:  At the time, Meade didn't make any of their own optics.  Coulter made all the Newt optics.  And when they started selling the first SCTs, they were made by Mizar (though I didn't know the brand until several years ago - because Meade was careful not to have it discoverable pretty much anywhere).  And to my knowledge, they never made any of the 4" SCTs in house.

 

In any hobby I've been deeply involved in, I find I have to be somewhat careful not to set my fantasies too far beyond reality.  So when I got the chance to take an 826 home to try planetary astrophotography for potential use in a catalog, I jumped at the chance.  Remember, I already had an 8" f/6 OC that I'd been using for 6 years by then.  So when I couldn't get the sharp planetary views I was accustomed to with the OC, I set them up side by each one night when the seeing was really good, and gee-whizzed Saturn with them.  Simply stated, the OC optics were a lot better than the Coulters.  So that experience (I never did get any good planetary images with it, but after that night I admit that I didn't try, either), coupled with the realities of making a living from my hobby, took a lot of the wonder out of commercial telescopes for me that's never really come back (except for the nostalgia aspect, of course).

 

One of the things that also came from that time was my defense of Cave, and even Celestron.  Not because they were run by saints who always made perfect telescopes, but because Meade was so vicious in putting Cave out of business (and trying to put Celestron out of business).  Heck, I even had horror stories of Cave sending scopes out the door with obvious defects, told to me by his former employees (hired away from Cave to help Meade put them out of business).  

 

So now I have what I would like to think is a much more realistic set of expectations and recognition of limitations of these old scopes I find myself still collecting (when I probably shouldn't!).  I try to pay a good enough price that I'm not risking too much if the optics aren't up to snuff.  So far, most of the Caves I've bought seem to be pretty good.  One notable exception appears to be the 1963 8" f/6 with the undercorrected primary.  And I've learned not to expect a lot from the two 10" DKs I have.  Fortunately, I got the second one for a ridiculously low price.  So even if I end up having to refigure the optics, it'll still be a good deal.  

 

I still haven't had the opportunity (and currently lack the space) to purchase a DX8.  But when the time is right, I expect I'll probably be willing to give it a shot, PROVIDED I have a pretty good expectation that I'll know how to refigure the corrector (or make a new one).  Because they're still pretty cool bits of history in this hobby.  And having one that's also excellent optically - a possibility with some work - would be particularly cool.

 

-Tim.


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#839 Bomber Bob

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Posted 16 March 2017 - 10:48 AM

Tim, thanks for sharing your experiences!



#840 Bomber Bob

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Posted 16 March 2017 - 11:17 AM

I've said before that I admire the folks who made & sold telescopes back then -- the profit margins had to be thin.  Criterion was gutsy to take on Celestron in the SCT market.

 

At times I sound completely disgusted with my Dynamax 8.  But that's almost always temporary frustration with some issue that's popped up.  From all the negative posts, I didn't expect much from it.  Yet, I bought one anyway.  And, bought a GP & wedge for it.  And, I've spent whole days working on it.  Why?  Because I see potential; and, as you say, it's a part of Classic Scope history.  

 

Now, Dave is showing us that the corrector problems can may be solved.  No offense Dave, but you're a mixed blessing!  If I choose not to tackle the project, I'll have  "... but, it could do so much better ..."  in mind every time I use the scope.  And if I do try polishing the corrector, and mess it up... it really will be a static display.  At least right now it's usable.  Only for DSOs, but no scope is perfect for every target type.  Luckily, I'm a Southerner - a member of the What's the rush? culture.  I can postpone making that Big Decision for months / years.

 

Sad Sack?  Naw!  If you buy one thinking you're gonna get tack-sharp 800x views, with a space-probe detailed Jupiter the size of a beach ball... you're not gonna be a happy camper.  But I don't think anyone in this hobby is that uninformed about the Dynamax.  Google:  "Dynamax 8" + "optical quality"  and you'll see a whole bunch of CN threads & posts to educate you before you buy!  Check out this comment from 2008 --> https://www.cloudyni...n/#entry2271910  It's pretty typical for the whole thread -->  https://www.cloudyni...cope-criterion/     This thread is the #4 hit, and it's already at 34 pages, and I've only had one decent session with the scope!  It's interesting to me that the Criterion SCTs and much rarer Tinsley Cassegrains generate so much interest - and negative comments - when I have both, and Rolo is shopping for his 8th DX8...

 

One of the things that also came from that time was my defense of Cave, and even Celestron.

 

I'll add Criterion to that list.  This same company made the Dynascope.  For the price, you got a lot of capability.  I still think that all the good will the company built with those economy scopes was squandered with the Dynamax.  You'd have to be totally heartless not to have some sympathy for Criterion -- unless you plunked down $1000's on a brand new DX8 back then.  In that case, your cussing & fussing is 100% appropriate.  My feelings are shaped from buying a near-mint but used DX8 for $400.  Totally different situation.


Edited by Bomber Bob, 16 March 2017 - 11:21 AM.

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#841 rolo

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Posted 16 March 2017 - 11:25 AM

Tim, enjoyed your post! Brought back lots of memories!



#842 tim53

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Posted 16 March 2017 - 11:52 AM

 

 

One of the things that also came from that time was my defense of Cave, and even Celestron.

 

I'll add Criterion to that list.  This same company made the Dynascope.  For the price, you got a lot of capability.  I still think that all the good will the company built with those economy scopes was squandered with the Dynamax.  You'd have to be totally heartless not to have some sympathy for Criterion -- unless you plunked down $1000's on a brand new DX8 back then.  In that case, your cussing & fussing is 100% appropriate.  My feelings are shaped from buying a near-mint but used DX8 for $400.  Totally different situation.

This further reminded me...  when I first started working at Meade, they had an RV-6 in the shop that they'd just put back together to sell on the used market.  Diebel had bought it anonymously to see what he could copy in designing the 1" shaft 6 and 8" Newtonians.  That particular RV-6 had a flaw that was pretty glaring - the RA housing must have been machined with a dull boring bar, because it was galled and oversized.  What they did was to take a punch and punch around the shaft to take up play caused by the oversized borehole, when they should probably have just replaced the RA casting.

 

I don't remember that level of goober being allowed or sent out while I was working for Meade, but have no doubt that sometimes it occurred. I remember one time when Ron brought out a customer's scope for a will-call.  The spider mounting bolts were too long, so he put like 6 washers under the acorn nuts.  It looked really stupid!  And the customer thought so too.  But Ron just said "that's the way they're supposed to be" and left the guy alone in the front room with the scope.  He was probably some newbie like I was when I picked up my OC from Dick Nelson, and probably made the decision that it was better to just deal with it than to return it and have to come back later.

 

I wonder when the Deluxe Dynascopes were made, in relation to the RVs and the Dynamaxes?  Those were obvious classics from the get go, but it was probably also pretty obvious that they wouldn't be able to compete in the market that was taking shape by the 1980s.  

 

-Tim.


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#843 GreyDay

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Posted 16 March 2017 - 03:28 PM


At times I sound completely disgusted with my Dynamax 8.  But that's almost always temporary frustration with some issue that's popped up.  From all the negative posts, I didn't expect much from it.  Yet, I bought one anyway.  And, bought a GP & wedge for it. And, I've spent whole days working on it.  Why?  Because I see potential; and, as you say, it's a part of Classic Scope history.  

 

It's interesting to me that the Criterion SCTs and much rarer Tinsley Cassegrains generate so much interest - and negative comments - when I have both, and Rolo is shopping for his 8th DX8...

Seeing "potential" has been a large part of my scope buying experience, 60mm scopes aren't that popular in the UK with the exception of maybe Unitron, Zeiss and Pentax which sell themselves. It's only through spending time on here and other forums that i realized that maybe they aren't all made equal, but they all have potential. The Dynamax may not be the best performer but it does look great, and that great look will keep people buying them in the hope that they get one that performs as good as it looks. (whoever gets DavidG's will)

 

Spending time renovating and repairing isn't wasted, it just means the scope is at it's best even if its best aint that good :)


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#844 Bomber Bob

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Posted 16 March 2017 - 03:44 PM

even if its best aint that good

 

That could've been Criterion's corporate motto...  just kidding!  Y'all lighten up:  It's almost Friday!


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#845 Bomber Bob

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Posted 16 March 2017 - 10:31 PM

Sky Testing Between the Scud

 

The annoying low-level river scud started clearing out at 2110 local.  I took out the Mizar P-100 first, verified the seeing at 9/10, with calm upper level air.  Checked the DX8's collimation -- and tube joint! -- and brought it out...

 

Castor -- clean split in both scopes at 40x.  Nice views in the P-100, and awesome views in the DX8, both at 100x.  

 

M35 -- pretty but kinda sparse in the 100mm, but rich as a loose globular in the DX8, both at 40x -- and NGC 2158 is a roundish cloud in the SCT that I don't see in the Newt.

 

SCUD returned -- dang it.  I got a quick look at Jupiter in both scopes as it cleared the oaks, but I'm looking over the roofs of both the shed and the house, which gives it the waterfall rippling.  Gonna go back out in a bit when Jupiter gets above these heat islands.  Both scopes are set up on the NE corner of our concrete pool deck.  Got the laptop ready for imaging.  Probably won't attempt that until 0100 local.  Temps are dropping about 2* per hour, so both scopes are staying dry and thermal-free.

 

P-100 is a good crosscheck:  1/2 the aperture & focal length of the Dynamax.  And, it's views are very close to refractor quality.

 

Red-Eye Update --> Clouds at 12K MSL from The Gulf.  Base Weather Sq says they'll evaporate over the next hour.  Uh-huh -- pull the other one!   I'm hoping they're right, as Jupiter will be on the meridian at 0230 local.  I just love sessions like this.  I could pack everything up, but my next shot won't be until Sunday night, and that'll be after a cold front, which makes the air volatile.


Edited by Bomber Bob, 17 March 2017 - 01:39 AM.

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#846 starman876

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Posted 16 March 2017 - 11:04 PM

awesome. Hope the DX8 performs well



#847 Bomber Bob

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Posted 16 March 2017 - 11:18 PM

So far, so good.  Never realized Castor A&B were that bright!  No matter what, I already like the DX8:  It really makes pretty deep sky views with the 3 spectros Big Kellners (50, 40, & 30mm) -- 40x, 50x, and 67x -- with black space and zero glare.  The fork mount makes sweeping a breeze, and the drive has kept Jupiter near COF for almost an hour now.  The P-100 is no slouch, either.


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#848 Bomber Bob

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Posted 17 March 2017 - 09:52 AM

Well... phooey!   The mid-level clouds did not evaporate.  They got thin, and Jupiter popped out infrequently in gaps, but at 0215 I'd had enough.  It took me < 10 minutes to move both scopes to the shed, button them up, and put the other stuff back up.  Not too bad for an old guy doddering around in the dark.

 

The tube joint is no longer a problem.  Both scopes hold collimation very well, even after multiple moves during a session.  The DX8 mount & drive system are worth at least $300, no matter what scope you decide to use with it.


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#849 terraclarke

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Posted 17 March 2017 - 10:23 AM

So far, so good.  Never realized Castor A&B were that bright!


8" of aperture tends to do that! lol.gif
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#850 Karl Fabian

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Posted 17 March 2017 - 10:09 PM

 

My RV8 must be parabolic since its f/6. 

 

attachicon.gifRV-8 004.JPG

attachicon.gifRV-8 007.JPG

 Are you sure you have the original mirror in yours ? All the RV-8 I have seen were all F/7 and when I tested the mirrors they were all spheres.

 

                              - Dave 

 

Dave, are you sure they were all spherical?  That would be a 1 wave rated mirror at F7 if spherical. An 8 inch spherical would need to be F11 to be rated 1/4 wave. 


Edited by Karl Fabian, 17 March 2017 - 10:42 PM.



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