Astrophotography forum > ATM, Optics and DIY Forum

Dimensions for 8" f6 reflector

(1/5) > >>

Michael Postle:
I plan to build a Newtonian Reflector with an 8" f6 mirror and 1 1/2" diagonal.
I would appreciate any advice as to optomizing the design.
I have attached the results from the "Newt" design tool.
Can this design be improved?
Attached Thumbnails



Owen Khan:
I would use a larger secondary and/or a low-profile focuser, otherwise you're going to get some field illumination loss.

Clyde Duke:

--- Quote ---I plan to build a Newtonian Reflector with an 8" f6 mirror and 1 1/2" diagonal.
I would appreciate any advice as to optomizing the design.
I have attached the results from the "Newt" design tool.
Can this design be improved?


--- End quote ---
Yes, the very minimum size secondary for an 8" f/6 with conventional 2" focuser is 2.14".
If you plan to use 1.25" eyepieces only and use an extremely low-profile 1.25" focuser, like a Kine-Optic, you can possibly get by with a 1.83".
But if you plan to use large 2" eyepieces with large field stops, go for 2.14".
For normal use in general viewing, 100% illuminate a 0.4-0.5" field and illuminate to the 75% level a field 1.5" wide.

Jacob Cota:
I would use a 1.83in 2ndry

moonlite focuserif you want to minimize the 2ndry to focal plane reduce tube dia.

.25 wall thk is sturdy but a 10in tube will be heavy.

if you use a fan you can get away with a 9 something tube.

also make the tube longer or build and attachment so the spider won't be right at the edge of the tube.

stancacoho:
I use a Kineoptics HC-2 focuser on my 200mm F/6.16 Dobsonian.
It allow me a 15mm fully illuminated field for a 46mm or 1.8'' secondary and focal plane at 182mm or seven inch from optical axis.
End of tube is at 182mm from focuser hole axis.
My tube is 250mm diameter , I'm not using and not plan to use any fans.

Your tube is too short, diameter is good.
As suggested , use a bigger secondary , 0.15'' fully illuminated field is way too small,it should be at least 7mm or 1/3''.
0.5'' for extra travel is too much.
Keep in mind ''Newt for the Web'' don't add the extra travel to ''focuser minimum height''.
I suggest to you to use a focuser baffle and don't disregard ''front aperture diameter''.
In the two weeks since I'm using this telescope I saw NGC 6196 galaxy of 13mv and split 16 Vulpeculae double star of 0.735''.

Good luck ,Ziridava

Navigation

[0] Message Index

[#] Next page

Go to full version