Quote:
Originally Posted by ausastronomer
Hi,
It's unlikely this modification will give you enough additional in travel.
The easiest way to modify your scope for imaging purposes is to remove the primary mirror cell and shorten the tube by about 35mm. This should allow the scope to reach focus with your DSLR camera attached to the focuser, as is. When you plan to use the scope for visual observing you just insert a standard extension tube into the focuser if you have insufficient out travel to reach focus with any eyepiece. Try all your eyepieces before you buy the extension tube.
In some cases, depending on your scope, the existing secondary size and other parameters, the secondary mirror may vignette slightly. However, the Synta scopes as they come off the rack generally have an "oversized" secondary if anything and this shouldn't be a problem.
In all probability shortening the tube a tad shouldn't cost anything, except for an extension tube, if you need one.
Cheers,
John B
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I have heard some folks say rather than cut the OTA tube, a simpler way is to replace the mirror hold-down screws with longer ones, then move it further up the tube and re-collimate after seeing if you can gain focus. I've never done this myself, but it seems a more elegant way than attacking the tube with a saw, as you can at least go back if you're not happy.
Would like to hear results if you proceed.