Image of the day

Captured by
John Popiel

Lunar in IR

My Account

New to Astromart?

Register an account...

Need Help?

Meade 7” Maksutov, …Updated 5-18-09

Posted by Steve Hollenbach   05/18/2009 07:00AM

Meade 7” Maksutov, …Updated 5-18-09
In the articles I’ve written on the Meade 7” Maksutov you might get the impression I’ve become so obsessed with this one OTA, that I put too much into it. Maybe so, but I have the luxury to do so, and that means other owners of this scope need not waste time and money on things that don’t work.

The drawbacks of the scope can be listed in descending order of importance. To address these I have summarized the cures:

1. Long cool-down> Cured by removing the counterweight. This is effective only for equatorial mounted OTA’s but one gentleman is installing external lead weights for use on an LX90 mount.
2. Image shift> Please see the explanation below.
3. Fan vibration> reduced by improved cool-down times.
4. Heavy OTA> Reduced by counterweight removal.
5. Awkward balance point on a GE mount> Cured by counterweight removal.

I considered adding a second fan to draw air out of the OTA while the stock fan blows air in. Equalization times are so good now that I no longer consider a second fan necessary.

I also considered flocking the interior of the OTA. Contrast is already very good. To reduce stray light from entering the OTA, I added a Meade dew shield. I no longer consider the effort of adding flocking material worth the small gain you might expect. It would require the complete disassembly of the scope and introduce fabric with lots of stray fibers.

Another plus is the red grease from Peterson Engineering. That’s a non-petroleum product with excellent lubrication and self cohesive properties.

There were two other drawbacks to the 7” MAK that deal more with telescope selection than this OTA. They are:
1. Limited Aperture> Take a road trip to get away from cities.
2. Long Focal Length> make or buy a focal reducer. The oversized mirror can handle it.

Image shift was the last difficult problem to overcome. My OTA came with a mirror lock. This can be found on the GPS and in some of the last run of LX200 models. For these telescopes image shift can be eliminated by adding a Crayford Focuser. On LX50 and LX200 models without the mirror lock the affects of image shift can be greatly reduced.

For an opinion of Moonlight’s CS focuser, please read my recent review. Suffice to say it worked very well indeed. The model I bought was Moonlight’s CS dual rate focuser with a 1.15 inch travel on a rotating base. It threads directly onto 7 inch Maksutov. They make it with a blue anodized finish which complements the Meade blue paint job.

The price was $345, but much lower than the comparable Feather-touch.
The focuser was in collimation and has adjustments for that if needed.

I hung my TeleVue 2 inch diagonal, my homemade focal reducer and a 27mm Panoptic off the end at high declinations and nothing drifted. That was about two and a half pounds of optics with nothing but friction holding it in place. It was all rock solid.

The Moonlight CS’s rotation was very smooth, and the thumb screw set it easily without any sign of slippage. This is not a clutch like the Virtual-View and so requires the rotational axis to be set rather than left with some friction to hold it still or let drift. It took about five seconds to get used to. In use; there is absolutely no backlash, vibration, looseness or run-out play. It enabled me to place the eyepiece at any rotational angle.

Focusing was excellent as anticipated. You just set the mirror close to the focal length needed, set the lock on the OTA and the Crayford action does the rest.

An unexpected plus was that the Feather-touch focuser I installed in the body of the scope two years ago became obsolete. It and the Virtual View back will be for sale soon. Both are excellent devices.

This completely solved the image shift problems on that OTA. The next big step will be a home built observatory.

Now that the Meade 7” Maksutov topic has been pretty much exhausted, I must get out there. Saturday night I delighted the neighbors with views of the moons of Saturn, and M13. A backyard observatory will make impromptu sessions easier, but I must get out where the stars can overwhelm the sky.

If anyone has a comment please don’t be shy!
Thanks once again,