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Easiest way to de-weight a Meade Mak 7

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#1 laixiaolue

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Posted 23 September 2019 - 12:37 AM

I remember last time I de-weight a Meade Mak 7, It was a big project. I spent one hour to de-fork the OTA and remove the primary, and two hours to pry the weight off the rear cell. The glue residual created a mess, so I spent one hour to clean it up, and one more hour to put the OTA back to the mount.

 

I received my second Meade Mak 7 last week. This time I decided to do the work with a much easier way. I left the OTA on the mount, I removed the primary and applied a big woodworking clamp to one of the fan port (fans were removed). I used a hair dryer to heat up the rear cell for about 5 minutes. When the glue got weaken by the heat, I gently tightened the clamp. I heard "click" sounds, that means the glue got split from the cell. I did the same thing on the other fan port, and then I could simply take the weight  out of the tube. The whole process took about 30 minutes. There has no glue residual on the rear cell.

 

 

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#2 dweller25

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Posted 23 September 2019 - 01:23 AM

Good procedure waytogo.gif

 

Whats the purpose of the fans - it looks like they just cool the metal weight down ?


Edited by dweller25, 23 September 2019 - 01:23 AM.


#3 laixiaolue

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Posted 23 September 2019 - 01:48 AM

If you don't remove the weight, the fan just cools down the weight;)

 

Good procedure waytogo.gif

 

Whats the purpose of the fans - it looks like they just cool the metal weight down ?



#4 freestar8n

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Posted 23 September 2019 - 02:46 AM

Good procedure waytogo.gif

 

Whats the purpose of the fans - it looks like they just cool the metal weight down ?

This is a really nice technique by the OP.  I removed the weight from mine just by sticking a big screwdriver in the back and prying for a while.  It didn't take too long but it risks warping the back of the OTA.

 

As for the purpose of the fans - well of course it is to cool down and equilibrate the OTA for better viewing - as so many people strive to do these days.  As for what they actually do - they just blow a trickle of air on a giant mass of iron.  And in the process - pretty much nothing gets cooled down...

 

I used that scope happily on many nights and made sure to have the fan on.  (There is only one fan - the other hole just acts as a vent).  If someone had told me that if you remove the fan you will see it is blowing air on a giant hunk of iron - boy would I have been surprised.  And more.

 

And as long as the OTA is attached to the fork, you can't really tell the OTA is heavier than it should be.  But once you defork it you realize.  And then when you remove the weight and see how light it is - it's a nice scope.

 

Frank



#5 aeajr

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Posted 23 September 2019 - 06:35 AM

Why are the weights there.  I would think they are there for balance.  No?


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#6 mclewis1

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Posted 23 September 2019 - 07:13 AM

Yes, the weight is there to help balance the ota. I believe that Meade used the same fork arms as the 8" SCT version (which has different balance points) so a little counterbalance was needed with the MCT ota.

 

Without the internal weight you can add your own externally or use heavier optical accessories (2" eyepiece/diagonal, camera, OAG, etc. etc.) ... but since most folks are also de forking the ota any extra counterweight is no longer necessary at all.

 

The optics of the Meade MCT cool down quite a bit faster without the internal weight (less thermal mass, and more air flow around the primary mirror).


Edited by mclewis1, 23 September 2019 - 07:14 AM.


#7 laixiaolue

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Posted 23 September 2019 - 10:44 AM

Actually the telescope balances well without the weight if you use 2" visual back and diagonal. And it is very back-heavy if you don't remove the weight. The weight really makes no sense at all.


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#8 Skywatchr

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Posted 23 September 2019 - 10:54 AM

Why are the weights there.  I would think they are there for balance.  No?

The front meniscus is much heavier than the corrector plate on an SCT. The weight is necessary to balance the scope. And since the tube is longer, it doesn't swing through the forks as it is so the side axis couldn't be moved to help compensate for balance. They just should have used longer forks, but alas, the bean counters wouldn't let it happen.



#9 jgraham

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Posted 23 September 2019 - 12:13 PM

BTW... with the weight removed the scope balances fine on an LX90. :)
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#10 Brollen

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Posted 23 September 2019 - 12:22 PM

How much does this scope OTA weigh with and then without the rear weight?


Edited by Brollen, 23 September 2019 - 12:25 PM.


#11 laixiaolue

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Posted 23 September 2019 - 12:25 PM

The weight is about 8lb.

 

How much does this scope weigh with and then without the rear weight?



#12 Brollen

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Posted 23 September 2019 - 12:44 PM

The "piece of iron" is 8 lbs? That is a lot of weight!

 

That can't be the weight of the OTA, as that is lighter than the 6" MCT and about the same as the 5" MCT.


Edited by Brollen, 23 September 2019 - 12:44 PM.


#13 laixiaolue

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Posted 23 September 2019 - 01:04 PM

Yes, the weight of the cast iron is 8lb. Now I have two, I can put them together to make a counterweight form my CGE mount;)


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#14 The Ardent

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Posted 23 September 2019 - 01:08 PM

I have a Meade LX200 7” and need to remove the weight. Thanks for the info.

#15 gfstallin

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Posted 23 September 2019 - 02:25 PM

Yes, the weight of the cast iron is 8lb. Now I have two, I can put them together to make a counterweight form my CGE mount;)

When you finish doing that, you should add this to the forum "non-astronomy equipment adapted for astronomy." grin.gif 

There is no reason an 8 lbs. hunk of metal should be used in astronomy except for a counterweight, or in a lathe that is being used to make precision parts for something that has business being under night skies. 

 

George



#16 jgraham

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Posted 23 September 2019 - 04:11 PM

I have a pair of de-weighted Mak 7s and without the weight it cools _fast_ with the fan. Love it!


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