Instructions for Ordering Secondary Mounts
(for both Newtonian and Cassegrain secondary mounts)
In general, there are four pieces of information we need in order to make your secondary mounting. There are three basic dimensions you need to supply, plus any optional features you want to add. If you have any questions, or are unsure how to take these measurements, feel free to call us before placing your order.
1. Provide basic dimensions
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Dimensions to provide for a
solid tube telescope
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Dimensions to provide for a
truss-style telescope
(upper cage shown)
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Dimensions to provide for a
curved secondary mount in a
solid tube telescope
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A = The actual inside diameter of your tube or upper cage. Provide the actual inside diameter of your tube or cage. We will make your spider slightly smaller (about 1/4" smaller) than this so it can be properly tensioned and centered. A measurement accuracy of +/- 1/16" (+/- 1.5 mm) is sufficient.
B = The size of your secondary mirror (minor axis). You can install any size secondary mirror even if it is not one of our "standard" sizes. Non-standard sizes can be adhesively mounted to the holder face instead of using the metal shroud. If you will be doing this, order the next smallest size holder.
C = The tube wall thickness. If it is a truss-style scope, please provide the strut diameter (the strut is what the spider will attach to). This dimension is not important for making your spider, but it does let us put the proper length mounting screws into your kit.
2. Optional features
ProtoStar straight-vane secondary mounts can be ordered with two options; wireless antidew heaters, and spider offset. Both of these options must be specified at the time you order your mounting, since they cannot be retrofitted later. Read the options page for more information.
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