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Meade 7" Mak

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#26 azure1961p

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Posted 04 September 2013 - 06:08 AM

Hi-

Yes - that was from my posting and my images. The images linked to above look different from my system - but they don't show the actual weight that was removed so it's hard to tell. In my case, when you removed the fan, you could see the weight inside completely blocking the opening - although there is a thin space between the weight and the back of the ota that would let some air through.

Frank


Here is the weight that I removed from my 7" Meade ex-LX50 Maksutov ;-

https://picasaweb.go...ovedFromMead...

Sorry but I have no pictures of the rear holes showing the weight still there before I started. As soon as I found the weight in the back of the OTA under the vent I went about removing it without a second thought to taking photo's of the weight still in place LOL. From memory there is about 1/4 inch of gap between the back of the weight and the inside of the rear cell casting, for air to circulate... and the black RTV Silicone which was holding the weight in took up this 1/4 inch gap, so the gap may vary from 'scope to 'scope.

Regards,

Alistair G.


Those pics are beyond words.

Pete

#27 orion61

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Posted 04 September 2013 - 10:52 AM



Quote:
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Optical quality varies, but can be good. IMHO, this telescope's biggest issue is cooldown, and then namely with LX200 variants. Compared to the cooldown performance of other 7" Maks with provisions for active cooling, it seems like the LX200 would never cool. On one side by side, we gave up after 4 hours. The comparo was with an MN76.

In another instance I compared the Meade (another LX200) to an I-M M715. It took the Russian MC quite a bit longer than the MN tested years before, but with the same end result. It seemed like the Meade would never cool enough to provide quality images.

I have seen early Meade 7's perform admirably, but that was during warmer months when most Maks will perform at their best.


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I don't understand. Are you saying that the Meade LX200 (LX200 Classic or GPS style) 7" Maksutov Cassegrain had no fan on it? Because the LX200 Mak did always have a fan on it (so "active" cooling), at least that's what it says in the LX200 Classic and LX200 GPS user manuals.

Or are you saying that the LX200 Classic Mak and LX200 GPS Mak both had fans, but the image took wayyyy longer to stabilise than other brands of 7" Mak that had fans in them, simply because of the cast iron disc in the back of the Meade Mak OTA was a thermal mass and air circulation problem which meant that cool down took a lot longer? In which case yeah that sounds likely. That cast iron weight in it is really bad.



I believe there's a reference to the Mak 7's cooling issues buried in the impossibly long thread (now locked) regarding Meade's impending sale. If memory serves, the cooling fan in the fork-mounted set-up serves no useful purpose, other than perhaps to act as a cosmetic ruse to stimulate sales. The sad truth is that the fan's airflow inside the scope is almost completely blocked by the notorious iron weight. On so many levels, adding that internal iron weight to balance the scope was a lousy and dishonest bit of "engineering."

Aiming a fan at a blank, impenetrable wall is never going to circulate cooling air through a room on the other side of that wall. So, remove the weight to allow the fan to operate properly, mount the Mak 7 on a competent GEM, and it should be good to go.

The early Meade tubes (EMC with the weight were nearly blocked, even so There was a definite benefit to havin the fan. The newer tubes with the Mirror lock had large holes bored in the weight to allow the air to flow. I have yet to observe through a 7" mak that was bad or even fair they have all been VG and one was EX. Seems the early ones hold a tiny edge in sharpness but not much. I have noticed the meniscus coatings on the earlier ones were a lot easier to scratch (personal experience on an LX50) Still among if not my favorite tubes. Only my Leo Henzl C8 ha come close to equaling them. The new 9.25's are better over all in shootouts. (so I have read).

#28 kingyo

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Posted 01 November 2013 - 09:06 PM

Seems that you all have a very good experience with this scope.
I am curious to know if there exists anyone who want to sell it, especially the ota version.

Regards,
KinGyo

#29 cavefrog

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Posted 02 November 2013 - 05:34 PM

I purchased a Meade 7 a while back. it is the only scope I have that has built in GPS. I like it enough to not sell it. (sorry). It is very good on planets, but not as good as the 10" or 12" SCTs. I wonder why. I had one odd night out with it. I was using another scope, and set the 7 out of the way , leaving the fan on. (purposefully) to get it to cool before I used it. it ended up to be about 2 hours. When I picked it up and put it on the mount, it was completely fogged inside! I was stunned to say the least. I
am gonna try a lymax 10" cooler on it tonight to see if it makes any difference.

If one puts a Dewshield on it, they need more than a heavy eyepiece or a pair of binos to balance. Right now with a dewshield, I have a pair of binos, two 2.5lb weights, and a one pound weight. The original weight is still in it. That is what it seems to take to balance. I worry more about the
motors than cooling. I need the dewshield and and heater strip to fend off mother nature around here. last night I
had both on my 12" with the Dewbuster turned on halfway. I was out until 13:00, and the dew was still just starting on the corrector when I started breaking down and coming inside.

Theo

#30 cavefrog

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Posted 02 November 2013 - 06:49 PM

I have heard that these scopes have a steel plate , a weight behind the main mirror that is the reason for the S-L-O-W , cool down times and there are a few web sites that show how to remove it , and then cool down is a reasnable 1 hour or so .
Great scopes , do a google on the plate removal .
Brian.

Bob,
Brian is correct about the 11 or 13? lb internal iron counter weight behind the primary mirror. Pros and cons:
counter weight keeps the dec motor balanced to prevent burnout but slows cooling time.
Removing the weight (if not done correctly) can damage the primary mirror and expose you to potential motor failure if you do not use an external weight on the back of the scope.
So, If you buy one with the weight removed, be sure the dec motor is working well and use an external weight at all times (note internal 11-13lb weight would probably equal a 6-8 lb weight on the back of the scope, some of which could be in the form of heavy binos, eyepieces and a small counter weight on the back of the ota.
like this one
web page
Rex


That counterweight made by Peterson will not work on the 7. It is for 10" and up. reason being on the 10" and up, there is a removable visual back. the visual back on the 7 is not removable, it is in the cast. the Peterson weight is held on with the removable visual back.

Theo

#31 cavefrog

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Posted 02 November 2013 - 06:58 PM

I purchased a Meade 7 a while back. it is the only scope I have that has built in GPS. I like it enough to not sell it. (sorry). It is very good on planets, but not as good as the 10" or 12" SCTs. I wonder why. I had one odd night out with it. I was using another scope, and set the 7 out of the way , leaving the fan on. (purposefully) to get it to cool before I used it. it ended up to be about 2 hours. When I picked it up and put it on the mount, it was completely fogged inside! I was stunned to say the least. I
am gonna try a lymax 10" cooler on it tonight to see if it makes any difference.

If one puts a Dewshield on it, they need more than a heavy eyepiece or a pair of binos to balance. Right now with a dewshield, I have a pair of binos, two 2.5lb weights, and a one pound weight. The original weight is still in it. That is what it seems to take to balance. I worry more about the
motors than cooling. I need the dewshield and and heater strip to fend off mother nature around here. last night I
had both on my 12" with the Dewbuster turned on halfway. I was out until 13:00, and the dew was still just starting on the corrector when I started breaking down and coming inside.

Theo

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#32 Live_Steam_Mad

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Posted 02 November 2013 - 08:54 PM

I would love to hear what difference that Lymax cooler makes on your LX200 Mak with the weight still in it when taking the 'scope out of an e.g. 18 degrees Celcius house and putting it into the outside environment at e.g. 7 degrees Celcius, then trying it on Jupiter after allowing the planet to rise to say 40 degrees above the horizon, and making sure you have no bad Jetsteam above you (can be checked easily on the Web), so the seeing is good. I'd be interested to hear how long it takes for the Star Test to be excellent and for the views to be stable at high power with the Lymax cooler.

I can't hardly wait to try my OTA with no weight and do some tests and see how long it takes for my 7" Meade Mak to cool for use at high magnification. I turned my fan around in it's housing so that the fan now sucks air IN to the tube with tip positive on my 12V power supply.

Cheers,

Alistair G.

#33 cavefrog

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Posted 03 November 2013 - 01:37 AM

It was about 8 degrees in and out when I put it outside tonight. at about 13:00 it was 11. it will be a few days before it drops to 7 around here at night. but I did not see any real difference. I put the scope out just before sundown so it would not get heated by the sun. Then I have to wait for it to get dark, and for the bloodsuckers to get too cold to eat. that makes it about 8pm and cooling for 1.5 hrs. after 1 hr. I went out and turned the Lymax off and left the internal fan on. I don't think the Lymax was worth it yet. not cold enough to make any difference. I sure had a good night with a couple of odd EPs though. A 32mm Vernonscope and a 40mm XL Pentax were my faves tonight. as for the jet stream... I think it is pretty close, but not over me. viewing Uranus was fun. I tried to see how strong I could go on it, and 381X was way too much, 267X was still too soft, 190X seemed too round it out nicely though.

Theo

#34 cavefrog

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Posted 03 November 2013 - 01:40 AM

I was wrong... jet stream is nowhere near me.

#35 Binomania.it

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Posted 03 November 2013 - 03:44 AM

Dear friends, thank you all for the comments! My specimen of OTA Meade 7 has arrived two days ago. In my C8 and C9.25 I inserted the black velvet. Now I have a doubt: the velvet might slow down the cooling of the tube. I want to know what is your opinion.
Best Regards from Italy
Piergiovanni

#36 jjack's

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Posted 04 November 2013 - 05:26 PM

Sorry guys, i had one. Nothing magic is this mak. Yes it is a good quality optic. But with 38% obstruction and F/15...
I sold it after seeing less contrasty d├ętails on planets and the moon, than a GSO newtonian 8"f5. my old 1990's C8 (f 10 and f6.3)was as good on planets and gather more light on deep sky objects.






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