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Hi Peter,
I read your thread asking about spiders and holders. What I'm not clear about is do you want to purchase a unit or make your own.
Purchasing an off the shelf unit is just like any instrument - you get what you pay for. You've experienced this with the list of disappointments you've noted. But more expensive units can come with their own baggage too. Sure they are more stable and predictable, but usually they are heavy, long in profile, and not often suited to the scope we are trying to fit them into.
I ran into this problem for the scopes I build. The mass production spiders and holders are just not up to the task, and the better quality ones are just totally too large for the low profile I require. The only option I had was to make my own. And what I came up with is everything the better quality expensive units are, but lighter in weight and very low profile, and allows for an integrated dew heating system to be added to the secondary.
Such a holder and spider is not the easiest to make; it is time consuming (especially the designing), a lot of care is needed, and some screws and inserts need to be modified. While I had some components specially made for me, for a one-off this is not necessary. You need to design the spider and holder assembly for the scope. This is why the instruments I make are not inexpensive - I design and build the whole thing (other than the focuser) because this is the only way I can produce the scope I want. Everything is custom/hand made. Use someone else's components, and the entire instrument is a compromise to other people's components. Make it yourself, and you get what you want.
This is not intended as a sales pitch. It is meant as a pep-talk to show you YOU are in control of your scope, not someone else. Select the correct materials, a clever, well thought out design, and you are the master. Clever design can also mean cannibalizing bits and pieces from other spiders/holder if these give you what you want.
The better quality, more expensive units will work the way you want a spider & holder to work, don't get me wrong. They are marvels of engineering. But they are expensive as the spider-holder unit is actually a complex little machine.
So, make it yourself or buy a compromise? Both options are as valid as the other, and it is best to consider both.
Alex.
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