Folded / Flexed Reflector designs

Hi all,

I am new to this group and I live about 1 hr north of Sydney Australia. I have a couple of questions regarding exotic reflector design which I am hoping someone can help me with.

I attach two web pages below and if you click on the thumbnail on each page it gives you a schematic of the design of each telescope. I have a couple of questions regarding these designs:-

http://www.kitgear.com/25%20inch%20plans.htm

http://www.kitgear.com/flex/Flex_Project.htm

1. I have on order from Willman Bell, two books, these are coming by surface mail and should arrive in the next 2 or 3 weeks, The Dobsonian Telescope by Kreige and Berry and How to Make a Telescope by Texereau. My question is do either of these books have any mention of these exotic design dobsonians. If not, is there a book that does
talk about these designs?

2. Obviously there is no free lunch so to speak, and these designs have some advantages / disadvantages over the standard newtonian.

With regard to the 25" folded reflector design I assume the disadvantages are a large obstruction in the light path, with an additional obstruction in the secondary light path and an additional reflective surface to suffer light loss and to keep collimated. Are my assumptions correct ? Are there additional disadvantages that I have missed? What are the disadvantages / difficulties of the flexed mirror design.

Ideally I would love to be able to build a 15 or 16 inch long focus dob and get the focuser close to the ground, I would like my wife to be able to use the telescope without a ladder. I dont think either design is the answer. Maybe there is another option, other than building the telescope at f5 or have the eyepiece 8ft in the air.

Clear Skies and thanks for any help in advance

John Bambury

The 3rd reflection will turn things around from the normal orientation of east-west & north-south as seen in a newtonian reflector. Something to consider; it may even present a correct orientation as seen with the un-aided eye, or perhaps right side up but reversed left to right- the exact orientation I'm not sure of, but so informed of the change you can search out the new orientation. One advantage of flexed mirrors is that they can be tweaked to perfection in response to temperature changes during the observing period. Ron

John, Your goals that have led you to your folded reflector remind me of my son's project whose goals were EXACTLY the same as yours. He decided on a folded Dall-Kirkham Newt. that would fit in his Honda CRX. It is a 10.5" with a 2" convex secondary and a 1.83" flat. It is an F/10 system with an F/5 primary. All the best on your project.