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Originally Posted by xelasnave
One more question Paul if I may? Did you use the opportunity of installing baffles to add strenght to the tube? Thinking about mounting mine on an equatorial mount (sortta building a fork mount for it) but it occured to me that given the lenght of the tube it may flex.. have you encountered such a problem or taken action to head that one off?? and if you can try my "light tube extention approach.. doesnot have to be a baffled tube (much better) but you will appreciate the improvement with a flat black cardboard tube, tape a wire ring on the outside to give it support.. thanks for your informative reply
alex
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No. the baffles have nothing at all to do with OTA rigidity. In fact the baffles I made from a black foam I purchased from a nearby Clark Rubber shop.
As you can see from my images at
www.skylab.com.au/pmsa flexure is not a problem and has not been an issue at all.
With your light tube extension - i'm not exactly sure what you mean? do you mean a dew cap? and if you do, I certainly agree with you:- that an aperature extension (1.5x longer than tube dia.) is certainly a big contrast booster.
However, there's a slight problem with me, in particular, doing that. A dew cap makes the telescope exceed the roof height of the observatory and captures any wind blowing, which in turn really mucks up guiding. But when there is no wind, yes a must have.
I had a few goes a making ones from black cardboard, but I have found even with a wire for structural support, if dew if present they will quitely become saturared and the cardboard will begin to collapse (usually while I'm guiding).
However I have always successfully used one on my 400mm telephoto lens, but it's tube diameter is much smaller of course.
I tried making one from a thin sheet of Aluminium that I rolled into a tube extension, however it turned out to be simply too heavy and greatly upset the balance of the telescope. Even though it does not feel that heavy, it's offset weight is (in my case).
Clear Skies
Paul
