What is wrong with mathematically setting up the equations and solving them? Agreed that it isn't sexy but it will give you all the degrees of freedom for a general case and thus every thinkable way.

...What i want to test for is:1-secondary big enough to capture the entire primary light cone, and at what distance ?2-where do i need to position both secondary and Focuser for the two secondary sizes ?3-how will this all play out in a LR newt at radically different mounting angles ofsecondary and focuser ?

QuoteWhat is wrong with mathematically setting up the equations and solving them? Agreed that it isn't sexy but it will give you all the degrees of freedom for a general case and thus every thinkable way.Tos etup and align the lasers correctly to trace out the edges of the field will require several alignment aids and accompanying calculations such that the effort and or costs involved greatly exceed the cost of a few sheets of paper that would be required for a graphical solution accompanied by a few calculations.

Bruce and I are on the same side so it seems. Honestly: of you can set up and solve a first degree equation you are already there for a good guesstimation for a Newtonian.

Quote...What i want to test for is:1-secondary big enough to capture the entire primary light cone, and at what distance ?2-where do i need to position both secondary and Focuser for the two secondary sizes ?3-how will this all play out in a LR newt at radically different mounting angles ofsecondary and focuser ?Already done by Jason K (reverse of your experiment):https://www.cloudyni...-3#entry4116531Where to place the laser "pupil":http://www.vicmenard...rspectives.html (scroll down to: "Notes on matching a sight tube to your 'scope's focal length")

...I am confident in my ability to set it up to the required degree of precision, I see the critical parts being only a perpendicular beam striking the edge , a properly offset 45* sec mirror, in line with the focuser. All of that is easily measureable, therefore physically verifiable...

QuoteQuoteWhat is wrong with mathematically setting up the equations and solving them? Agreed that it isn't sexy but it will give you all the degrees of freedom for a general case and thus every thinkable way.Tos etup and align the lasers correctly to trace out the edges of the field will require several alignment aids and accompanying calculations such that the effort and or costs involved greatly exceed the cost of a few sheets of paper that would be required for a graphical solution accompanied by a few calculations.Thanks for your comments. Certainly nothing is wrong with the mathematical solution approach. I have done that much using newt for web. What I am looking for is physical verification before I start cutting pieces for the new scope.Especially when I move on to the LR layout. So what I am hearing is that something like this would work if set up correctly ??I am confident in my ability to set it up to the required degree of precision, I see the critical parts being only a perpendicular beam striking the edge , a properly offset 45* sec mirror, in line with the focuser. All of that is easily measureable, therefore physically verifiable..Bob

Quote<p class="citation">BGRE, on 19 Nov 2017 - 12:29 PM, said:<a href="https://www.cloudynights.com/index.php?app=forums&module=forums&section=findpost&pid=8221924" rel="citation">[/url]<blockquote class="ipsBlockquote built" data-author="BGRE" data-cid="8221924" data-time="1511087397"><p class="citation">Benach, on 19 Nov 2017 - 12:08 PM, said:<a href="https://www.cloudynights.com/index.php?app=forums&module=forums&section=findpost&pid=8221915" rel="citation">[/url]<blockquote class="ipsBlockquote built" data-author="Benach" data-cid="8221915" data-time="1511086108">What is wrong with mathematically setting up the equations and solving them? Agreed that it isn't sexy but it will give you all the degrees of freedom for a general case and thus every thinkable way.Tos etup and align the lasers correctly to trace out the edges of the field will require several alignment aids and accompanying calculations such that the effort and or costs involved greatly exceed the cost of a few sheets of paper that would be required for a graphical solution accompanied by a few calculations.

<p class="citation">BGRE, on 19 Nov 2017 - 12:29 PM, said:<a href="https://www.cloudynights.com/index.php?app=forums&module=forums&section=findpost&pid=8221924" rel="citation">[/url]<blockquote class="ipsBlockquote built" data-author="BGRE" data-cid="8221924" data-time="1511087397"><p class="citation">Benach, on 19 Nov 2017 - 12:08 PM, said:<a href="https://www.cloudynights.com/index.php?app=forums&module=forums&section=findpost&pid=8221915" rel="citation">[/url]<blockquote class="ipsBlockquote built" data-author="Benach" data-cid="8221915" data-time="1511086108">What is wrong with mathematically setting up the equations and solving them? Agreed that it isn't sexy but it will give you all the degrees of freedom for a general case and thus every thinkable way.

Honestly: even if you're interested in rigging something up, make a simple rig in which you can place the secondary and the primary and determine where you can see where the focal plane is (by focusing an object at infinity).Look at the primary from the point where the primary fills the secondary completely, and by placing templates at the focal plane (cardboard pieces with circular holes) you'll be able to see the size of the fully illuminated field (it's the template through which you can still just see both the secondary and primary).Using lasers isn't going to be very helpful, except perhaps in determining the axis to which the focal plane is square (but for this experiment extreme precision is not really needed).