Reduce Effective Apeture

Is there a way to reduce the apeture of a commercial refractor (such that of the new cheap Meade LXD 55 telescope) to reduce false color? I have heard that it was an old way ATMers could make semi-apo scopes back in the day. Then I guess a minus violet filter could be used to reduce the remaining color. Is it possible, because a solid 3.5 inch sharp unobstructed refactor with go-to would be grand.

Sure that works. Get a 6" f/8 refrector cut a 4" hole in the lens cap and you have a 4" f/12 refractor. You will probably have less color and since you are using the center of the objective, sharper images. BUT, you are still mounting and dealing with the weight and size of a 6" refractor. Thereby requiring a large and more expensive mount. The money saved for a cheap 6" is used for the heavier duty mount. You can get some very nice 4" refractors at a reasonable price and get good color correction, fine images and light weight. The light weight lets you mount your scope on a less expensive mount. The size difference between a 6" f/8 and a 4" f/6 is huge. I'm attaching a photo of my 6" Meade and 4" Borg on a Giro mount to give you some idea of the difference. Yes the Meade gains some size by being closer to the camera, but you can see that the diameter and tube lenghts are massively different with only a 2" diameter difference in objective. Think about it. Clear skies,
Tom

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Here's another photo with the 4" Borg and 5" Orion RFT opposite the 6" Meade. Here there is less perspective distortion but you can see that the size difference is still large.
Tom

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