Posts Made By: Paul Gruener

Dear Greg,
The tube diameter for the FS-128 is 145mm. The cradle you have will also fit the FC-125 OTA.

The diameter of the TOA-130 and the FS-152 are the same, 155mm, so no, it will not work with the TOA-130.

Regards,
Paul

John.
I had an Intes Micro 715DX Maksutov. It was fantastic. Nice tight star images, stars showed wonderful color, very high contrast, and no (really no) image shift focusing.

I do not know about the Orion, but the I-M is one to consider.

Clear Skies,
Paul

JD,
I can not speak to the mounting part of your question, but as someone that has owned an FS-128 and FS-152, I can say the 6" is a wonderful step up. I loved my FS-128, but I love the FS-152 even more! I had mine out a few weeks ago after a long winter break. Gosh the view was wonderful. The comet with my 35mm Panoptic was just the best.

Best of luck with your plan, I think it is a good one. The more Taks the merrier.

Clear and steady skies,
Paul

Steven,
I have had an FS-128 and now have an FS-152. I find the 10 inch Mewlon to be a perfect complement to the refractor. I know your mount may not be up to weight of the larger scope, but stepping up to a larger GEM may be worth it for you in the long run. As one possible example, the Orion Atlas offered by Anacortes would provide excellent stability for both your refractor and the larger Mewlon.

I will echo many of Herb's comments on the M-250.

I have not used the smaller Mewlons, I can only tell you what I know about mine. Therefore my comments are through the myopic lens of an 10 inch Mewlon owner.

Killer optics - Razor sharp stars and planets.
Very high contrast images. This really helps bring out detail on deep sky objects.
Compact OTA. Overall it is easy to manage. The back has much of the weight, the front 3/4 of the OTA is very light weight.
The scope is practically dew proof. Where I live we get a lot of humidity in the summer. I have had it out on several foggy nights when everything except the inside of the Mewlon OTA and mirrors were dripping wet. The OTA acts as a very effective dew shield.
I can set my scope up on the mount at a medium height and sit comfortably in a small hunting chair to study objects for long periods of time.
I love the electric focuser. You do not need to touch the OTA, it is very smooth, and very precise. The benefit of the electric focuser can not be over stated. No mirror shift. Zero.
The collimation stays put.
It is a work of art.
Small central obstruction.
Again: killer optics

In the end it comes down to what you can see. The combination of the large mirror, exquisite construction, razor sharp optics, high contrast, and comfortable viewing position make observing a unique pleasure. The aperture difference between your refractor and the M250 would be a huge jump. This is why I think it is worth considering. To give you an idea, I call my Mewlon, the "Cluster Buster".

One more story. The last time Mars was close I was observing the planet with my Mewlon when a friend suggested we try some higher power EPs. I kept working through my case until I got to my 5mm Takahashi LE. At 600x we were awestruck while looking at the planet's volcano. No other scope out that night even came close to the Takahashi's performance.

Best of luck with your research and decision.
Paul

Louis,
Thank you for your thoughtful report. I have often wondered what it takes to set up and use a mount like this.

I have a question. You discussed going through a sync process with The Sky software. Is the goto pointing accuracy good even after the mount makes a meridian flip, or do you have to perform another synchronization?

Sincerely,
Paul

Hi,
If you are in the need of a more accurate alignment sometime in the future, another option is to have the computer help with the polar alignment. For example on my G-11 with Gemini I can roughly polar align the mount and then select 3-4 alignment stars on each side of the meridian. Then I run a routine with the computer and it helps me adjust the mount to set the polar alignment. I don’t have to see Polaris.

I know this same approach also works with the Argo Navis digital setting circle computer, but with a few more steps to set up and calculate the internal pointing model.

Other mounts may offer the same feature; I have only had first hand experience with the Gemini and the Argo Navis.

Clear skies,
Paul

Chuck,
Interesting. I have an M250, the standard visual back, an AP MaxBright and the 35mm Panoptic. It works just fine. I have two thoughts /guesses :-).
1) There is a person, that I think is in Germany, who makes a very short visual back for imagers. The distance from the retaining ring to the end of the back is only a few mm. Maybe you have one?
2) I am not sure if this is possible, but the previous owner may have adjusted the secondary during collimation such that the mirror it is now too far back in the secondary cell. This would push the focus too far out the back of the OTA.

One other comment: I know James has a thing for the Craford focuser on the Mewlon, but I will share with you, I honestly don't see why. For me one of the best features of the Mewlon is the ability to easily and very precisely focus the scope without touching the OTA. It is great when changing the EP and even better when you are sharing the views with friends. In both cases, it is so easy to zip the scope into exact focus. I get the nice precision feel of a FeatherTouch focuser, they are great on the right scope (I had one on my FS-128.) However, I suggest you give the standard Swiss motor driven focuser a good try before adding a second focuser. I am sure James loved his second focuser, but I have not found the need to add one to my scope.

Best of luck with your new Mewlon. I hope you enjoy yours as much as I love mine.

Clear and steady skies,
Paul

This photograph of the Moon was made on Friday night, August 31st, 2007. The Moon was 3 days past full. Raw files were captured with a Nikon D200 using a refractor at prime focus (1216mm). Image processing was done in Nikon Capture NX v. 1.2.

Andrew,
This is a good question. The Tangent devices (JMI, Televue, etc.) and Sky Commander both work off the same assumptions. The big ones are that the OTA and mount are mechanically and optically aligned. Also, as the OTA rotates about the mount it does so without variation (rotational wobble). So, if you are using a GEM or dob and your optics and mechanical alignment (and orthogonal) is solid, both types of DSC will work with the same level of performance of accuracy.

If you have some variance in the above, then as you move from your alignment stars you will find that your pointing accuracy will drop off.

As Greg mentions, the Argo Navis has the capability to do the same as the Tangent / Sky Commander, but also much more. The special advantage of the Argo Navis is its ability to take star sample positions and build a pointing model that takes into the account variations in the mechanical and optical system alignment. This process does take time to learn, but it is easy once you get the process.

So the AN can act like the simpler DSCs, or you can take advantage of the unique modeling feature and get very precise pointing across the entire sky. Finally, the AN can drive a goto system on a Dob.

Setup is the same no matter what you choose. The encoders need to be installed and working properly. Next, you need to tell the computer how many ticks the encoders generate and which way the mount moves. Finally, you need to tell the computer if you are using a Dob (alt / atz) or German Equatorial mount. You only need to do this once.

Clear skies,
Paul

Brad,
Every time I observe through mine I am amazed. I hope you have as much enjoyment with your beautiful M250 as I have had with mine. Your looks wonderul!!!

Clear skies. Welcome to the "club!"

Sincerely,
Paul