XT10 endcap/dustcover continued

Thanks everyone for the showercap ideas! I was hoping to get another endcap such that I could make a really nice off-axis apeture stop. I experimented using poster board and noticed some remarkable viewing characteristics. The moon and Saturn were dramatically sharper and had much greater contrast - beyond what I think could be gained by the apeture reduction with less than ideal seeeing. I know there are different opinions regarding this concept of stopping down and clearly a larger apeture wins if the optics are immpecable but this is not a premium mirror! By stopping down the apeture, however, I have 4-5" of UNOBSTRUCTED optics that are probably on par with a premium mirror. I'm assuming that sampling a small portion of an average or better than average mirror will show that the given area has less aberations etc. Another added benefit was that I noted that my 40mm Optilux 2" eyepiece (not great on fast scopes) performed REMARKABLY better with the apeture stopped down.

I'm surprised we don't see off-axis stops on more dobs. Medium and big dob owners could essentially have big APO's for practically pennies. I guess I'll make a nice apeture mask out of some thin plywood and finish it nicely with paint and hardware.

Does anyone else have experience with "slowing down" the optics on the dob with an off-axis mask? Comments/Suggestions welcome.

thanks,
david

Most big dob owners I know have fabricated an off-axis stopdown mask of some sort. Some nights it just pays to have it, no matter how good your mirror is.

I used black foamcore. Light, durable, and nonreflective. Cut it with a razor knife insert on a regular compass, and have a nice 6 inch unobstructed scope working at f 13.5 when I use it.

Jim Mahon

Well I have experience doing my own fixes to my used scopes, because they are all Meades and Orion is not the only co. who won't exactly sell you a spare lens like Tele Vue just did for my broken 35mm Panoptic :-) Al Nagler is a nice guy to talk to on the phone. The value brands just don't do things like the companies who are in the telescope optics business for love of the hobby rather than profit.

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