tube length

[tesla2002]

guys , I wanna build a 6 inch refractor and I've got 2 problems and I was wishing that someone would have solutions , the first one is what should be the length of the tube and the second one is that I will get a diagonal mirror and I will install a focuser , if I use a focuser do  I need a second lens also if I can only use one tube how to install the diagonal

, THANK YOU

 

[Cornelius Varley]

The length of the tube will depend on the focal length of the objective lens.

[tesla2002]

the focal length is 1200 mm

 

 

[Willie]

Hi , Have a look here.

https://stellafane.org/tm/newt-web/newt-web.html

 

John

[hughgilhespie]

Hi Tesla2002,

Do you really mean you want to make a 6 inch refractor? If you do, it would be a very unusual design to use a secondary mirror. With a refractor you would normally have the objective lens at one end of the tube and a focusser at the other. You will need a second lens in the form of an eyepiece if you want to use the telescope for visual astronomy. 

If you actually meant a 6 inch reflector then you would use a secondary mirror, positioned near the open end of the tube. This mirror would reflect the light through a hole in the side of the tube and into your focusser. Again, you will also need an eyepiece to actually see anything in detail.

The post from Willie points you to a very good site for designing your reflector telescope.

Regards, Hugh

 

[tesla2002]

no there's the diagonal mirror , it reverses the image