Ray Trace..... where can I find info???

Started by Bruce N., 05/08/2002 10:08PM
Posted 05/08/2002 10:08PM Opening Post
Yikes...... I am in the process of changing the old single stalk secondary out to a spider on my 6" f8 Edmund white tube.

I ordered a spider and holder from Sky Instruments (very nice by the way and $20!!). I had decided to change the mirror to a 1.1" MA after recent posts regarding that.

Question: After talking with the folks at Sky Inst. he talked about a ray trace to determine optimum secondary placement. Is there a place on the web that can walk me thru this??

He said that going to a 1.1" may not work out as the light cone may move the secondary out quite a bit and reduce focusor travel???

I obviously need to do some reading on this.

Thanks

Bruce
Posted 05/08/2002 11:37PM #1
Bruce,

I presume what he's talking about is a program like Dale Keller's NEWT
http://home.att.net/~dale.keller/atm/newtonians/newtsoft/newtsoft.htm

However, unless you're thinking about changing or moving the existing focuser, I don't see the point. Once the focuser is placed, the secondary gets lined up with it, and the focus travel is not affected by the size of the secondary, only illumination levels.

Sounds to me like he was just speaking in general terms wrt placing a focuser and secondary. Now, if you are going to change the focuser or moving it, then we can talk about where to put it. I can't remember, did you ever report a measured lateral dimension, i.e. how far the from the center axis of the scope the tip of the focuser is when you have it in focus on an astronomical object? Should be about 6" or so, but if it is substantially greater, we probably should run the numbers again, and of course you can put all your measurements into Keller's NEWT program and see what is going to happen.
--
Mike