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Gettting a good Meade 7" ED?

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#26 starman876

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Posted 12 May 2019 - 08:58 AM

It’s my understanding that Meade’s answer to the cell problem was not to machine a tighter cell but to take the less expensive road and to add radial “lens element adjustment screws” to the cell. These screws do not collimate the complete cell to the tube but adjust “one of the lens elements” in relation to the other.

 

To get good color correction in a doublet of this size Meade used a lens design with elements that are more steeply curved. Although an exaggeration, think of 2 clear marbles as lens elements and what kind of cell tolerances would be needed to keep them aligned.

 

Send the scope back to Meade and they will adjust it and say it was perfect when it left our factory. Of course in shipping the screws may or may not be enough to keep the elements aligned. Also, if you transport the scope, the same issue may or may not arise. Also, large temperature swings over time may or may not cause an issue. In all of the above you might have to realign the lens elements in respect to each other.

 

If you have a scope with the old cell you will have problems. If you have a new cell with the screws you may or may not have problems depending on shipping and how the scope was used in the past and how and where you intend to use the scope going forward.

 

Bob

There are other scope builders that have this kind of adjustment.  So it is not uncommon to have the radial lens adjustments.  Therefore, I would presume that others when not being gentle with their scopes might have issues with their lenses being out of alignment.



#27 bobhen

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Posted 12 May 2019 - 09:48 AM

There are other scope builders that have this kind of adjustment.  So it is not uncommon to have the radial lens adjustments.  Therefore, I would presume that others when not being gentle with their scopes might have issues with their lenses being out of alignment.

The first shipments of SW 150ED scopes did have alignment issues. SW had to beef up their shipping containers.

 

The Meade 178 is also a larger lens and a much heavier OTA than the SW 150. Heavier lens elements means more issues. A heavier OTA also means harder impacts when shipping/traveling. More weight = more issues.

 

Bob



#28 CHASLX200

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Posted 12 May 2019 - 10:35 AM

The first shipments of SW 150ED scopes did have alignment issues. SW had to beef up their shipping containers.

 

The Meade 178 is also a larger lens and a much heavier OTA than the SW 150. Heavier lens elements means more issues. A heavier OTA also means harder impacts when shipping/traveling. More weight = more issues.

 

Bob

Plus the Meade has steeper curves.



#29 starman876

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Posted 12 May 2019 - 11:01 AM

It is interesting when testing the lens in DPAC you can adjust the screws and see the effect instantly how the screws effect the collimation of the two lenses.   I would strongly suggest anyone wanting one of these scopes to have a DPAC set up to adjust the radial alan screws.   You just take the lens cell off the scope put it in the DPAC setup and adjust.   Much easier than doing it on the mount and on a star.  



#30 25585

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Posted 12 May 2019 - 01:57 PM

I never leave the house with any scopes. Last Star party marty was in 2003. As long as the lens stays centered i should be fine. But i have never collimated a refractor.  A older AP 7" would be nice, but not paying 20k for one.  As far the 826 goes, i would like to find a light weight made 10" F/6 Newt with no heavy rotating rings to use on the AP800.

My Orion Optics UK is a 10" F6. Solid but aluminium tube, which is light compared to steel. They also do carbon fibre. I expect there are US equivalents.



#31 CHASLX200

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Posted 12 May 2019 - 02:28 PM

My Orion Optics UK is a 10" F6. Solid but aluminium tube, which is light compared to steel. They also do carbon fibre. I expect there are US equivalents.

Pop a Zambuto and better 2ndary in there and then it could be a great scope.



#32 SteveG

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Posted 12 May 2019 - 05:36 PM

If you find one, do what this guy did, provided the optics are good:

 

https://www.cloudyni...iewfirst-light/



#33 starman876

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Posted 12 May 2019 - 08:01 PM

My Orion Optics UK is a 10" F6. Solid but aluminium tube, which is light compared to steel. They also do carbon fibre. I expect there are US equivalents.

Those UK Orion optics are very good.  Did you get a test report with it?  They Zygo all their stuff.  Some believe they are the equal of Zambuto optics.



#34 starman876

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Posted 12 May 2019 - 08:09 PM

If you find one, do what this guy did, provided the optics are good:

 

https://www.cloudyni...iewfirst-light/

Amazing report.  Does show they are out there.



#35 mitsos68

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Posted 13 May 2019 - 12:54 AM

Hi,

APM tested adjusted and modified my 8 inch f/9 lens. Radial adjustment added. The lens in conbination with a Chromacor II performs amazingly.

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#36 CHASLX200

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Posted 13 May 2019 - 05:33 AM

Guess i will see who wants to sell a 7" ED.  I am sure none are in FL. So shipping would be scary.



#37 Illinois

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Posted 13 May 2019 - 06:15 AM

Guess i will see who wants to sell a 7" ED.  I am sure none are in FL. So shipping would be scary.


You might drive 1000 miles to pick up if you really want it so badly!

#38 CHASLX200

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Posted 13 May 2019 - 06:25 AM

You might drive 1000 miles to pick up if you really want it so badly!

I can't go a anywhere with my sis going to hosptial every week.  Things are getting worse fast.



#39 t.r.

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Posted 13 May 2019 - 07:37 AM

I think many are floating around with the bad cells. And some are floating around with the cell fix. I want one soon and will place a ad.

Ian Turner and Chuck Pizza from Wolf Cam ended up with my scope after i forced the seller to refund my money. They did adjust it and said it had a good lens. But it did end up going to Meade in 2000 for a new cell. The new owner destroyed the scope by placing it on the mount with no counter weight and it slammed into the tripod, not once, but he did it twice. Talk about dumb.

I was so happy when i first got the scope, but 20 secs later looking at a star i said, Huston we got a prob. So the 3 times it went back to Meade they fixed it and shipping bumped it out of center each time. I don't think the end user should have to adjust a scope that cost him over 6k. I was glad to get rid of it.

Now i want a second chance and got the cash ready.


“Fool me once shame on you...Fool me twice...” comes to mind! Why would you want the headaches of taking a chance again? Been there done that...I wouldn’t look back...YMMV and Good luck with it.
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#40 Jeff B

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Posted 13 May 2019 - 08:49 AM

I can't go a anywhere with my sis going to hosptial every week.  Things are getting worse fast.

I'm sorry to hear that Charles.

 

Take care.

 

Jeff



#41 Jeff B

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Posted 13 May 2019 - 08:52 AM

Hi,

APM tested adjusted and modified my 8 inch f/9 lens. Radial adjustment added. The lens in conbination with a Chromacor II performs amazingly.

Curious as to what optical "symptoms" you detected before the adjustments.  Astigmatism and/or coma, lateral color?

 

Beautiful lens by the way.  waytogo.gif

 

Jeff



#42 mitsos68

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Posted 13 May 2019 - 11:02 AM

Curious as to what optical "symptoms" you detected before the adjustments. Astigmatism and/or coma, lateral color?

Beautiful lens by the way. waytogo.gif

Jeff

Hi Jeff. Astigmatism mainly. Modification works well. The optical expert Wellenform suggested to proceed with the radial adjustment. APM modified the cell. Lens checked, adjusted, and tested by Wellenform.

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Edited by mitsos68, 13 May 2019 - 11:54 AM.

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#43 starman876

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Posted 13 May 2019 - 12:38 PM

That is a big scope, Should provide wonderful images.



#44 Mitrovarr

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Posted 13 May 2019 - 01:25 PM

Hopefully the inexpensive new 6" ED doublets will free up chromacors for people to use them on really big achros.
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#45 Steve Allison

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Posted 13 May 2019 - 02:16 PM

I, too, am sorry to hear about your sister, Charles. I hope everything turns out okay.

 

Sincerely,

 

Steve


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#46 SteveGR

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Posted 13 May 2019 - 03:19 PM

I would need a monster mount for a 14" Newt, Unless a 14.5" Starmaster pops up for sale cheap local..  I always wanted a good Meade 7" since i got cheated out of the one i had. The seller did not tell me the truth when i bought it. He said it was at Meade and Was fixed and still sitting in the box when i traded 6k worth of Televue eyepieces and a nice 10" LX200.  It went back to Meade 3 time when i had it and each time  when i got it back it was bad each time.  This was before the cell fix.

 

So i need to have my second chance with this scope.

Stuff like that is why I don't buy used. mad.gif  People, to a large degree, are horrible.



#47 Jeff B

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Posted 13 May 2019 - 03:20 PM

Hi Jeff. Astigmatism mainly. Modification works well. The optical expert Wellenform suggested to proceed with the radial adjustment. APM modified the cell. Lens checked, adjusted, and tested by Wellenform.

Very good mitsos.  You can see the mild astigmatism in the computer generated interferogram as the mild "S" shape to the fringe lines towards the bottom.  Low coma and SA really, has a good edge too.

 

A nice fast achromat.

 

Jeff



#48 PowerM3

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Posted 13 May 2019 - 05:27 PM

I love threads about the 178ed. Most people that post about it make it sounds like it's a plague that you should avoid at all cost. I have owned 2 127ed's in the past witch where 100'% problem free. I have always wanted the 178ed and about a year ago I  finally found one after looking for years. It took me placing a wanted ad at least 5 times over a period of at least 5 years to find one. Even after looking for so long did I get a perfect scope??? No. I did have to re-glue the baffles and the centering although very close to perfect after shipping coast to coast does need some work. 

 

When I first received the scope I took the scope to a star party with the lose baffles in the light path, with the centering not perfect and it still produced by far the best view of m45 that I have ever seen. The extent of the nebulocity was amazing and close to photo like. The view of Jupiter with the Binotron was absolutly crazy. 

 

These threads make you feel that every owner of one is just waiting to unload this OTA. If you do decide to place a wanted ad you find that this is very far from true.  What other option do you have for a 7" refractor that's not even an ED in the $3k price range????? Its the best bargain in the frac used market as far as I'm concerned as long as you are willing to show it a bit of love. 


Edited by PowerM3, 13 May 2019 - 05:37 PM.

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#49 CHASLX200

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Posted 13 May 2019 - 05:45 PM

“Fool me once shame on you...Fool me twice...” comes to mind! Why would you want the headaches of taking a chance again? Been there done that...I wouldn’t look back...YMMV and Good luck with it.

I think i can trust a few here to tell me the truth ruth.  If they say it is good i may jump, but will it take the shipping bumbs and jumps?



#50 CHASLX200

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Posted 13 May 2019 - 05:46 PM

I'm sorry to hear that Charles.

 

Take care.

 

Jeff

Not sure what is going to happen.

 

Thanks.




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