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Mewlon 250 focus with AP Maxbright

Started by cscappaticci, 08/23/2009 03:58PM
Posted 08/23/2009 03:58PM Opening Post
Hi, I just bought a used Mewlon 250, haven't gotten to first light yet but did set it up yesterday. I put my AP MaxBright 2" diagonal directly into the visual back but could almost but not quite reach focus with my 35mm Panoptic. Not enough "in" focus on the electric focuser, plenty of "out focus. The electric focuser is working correctly it seems as it moves the secondary and I can see a nice defocused circle on a tower light 10 miles away. The focus travel problem becomes worse with shorter focal length eyepieces. I'm sure some has dealt with this before. By the way, I do NOT have a cassegrain focuser on it, but would love to put on a FeatherTouch crayford eventually.

Thanks in advance,

Chuck
Posted 08/24/2009 01:17PM | Edited 08/24/2009 01:19PM #1
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