# Thread: Martin's formula for tilt and calc issue

1. ## Martin's formula for tilt and calc issue

I am studying Martin's formula of tilt. I believe I understand it fine, but my calculator doesn't. This is rather embarassing to even admit, but my error most likely lies in how I am entering things in my calculator. Before I go absolutely insane from frustration, I just want to know if I at least have the mathematical concepts correct. every time I put this in my calculator in any sequence, I get an error message.

The example question is what is the effect ofa -10.00 D sph lens that has 10 degrees of excess panto....

Would it be 1+sin^2(10-the amount of excess tilt)/3 multiplied by 10.00 ( the power of the lens)??
I realize that some my scoff at the idea of someone dealing with this formula with out having control of thier calculator..but I don't care. I'm frustrated and I frankly am at my wit's end.:hammer:

Thank you in advance for any light you can shed on this for me!

Thank you  Reply With Quote

2. Assuming a 1.5 index.

1. s'=(-10.00)(1+[sin10]^2/2[1.5])
2. s'=(-10.00)(1+0.0301536896/3)
3. s'=(-10.00)(1+0.0100512299)
4. s'=(-10.00)(1.0100512299)
5. s'=-10.10D

1. You want to take the sine of the angle then square that number
2. Divide the number from above by the number you get when you multiply 2 times the refractive index
3. Add that number to one
4. Multiply sphere power times the number from above.  Reply With Quote

3. And don't forget to calculate the cylinder- with the final result of -10.10 -.31 x 180.

My dirt cheap TI-30xa doesn't accept formulas so I can't offer much advice except that it probably has to do with the notation- check the instruction manual for details.

Regards,  Reply With Quote

4. Do yourself a favor and get a TI calculator then perform the equations that you use in steps. The calculator even has an ANS key to help with performing complex equations in steps and allows you to store multiple answers into variables for longer calculations.

I have also written some programs for the TI-83 and I think I may have a martins formula calculator that I can send you.  Reply With Quote

5. A basic calculator will work fine, you just need to know the order to enter stuff in to get the right answer (or, you could use the "Memory" buttons to store intermediate calculations; every calculator has at least two or three).

For instance, for Martin's formula, the order would be:

Enter "10" (tilt) -> Sine Button -> Square Button -> Divide Button -> Enter "3" (2 * index) -> Equal Button -> Add Button -> Enter "1" -> Equal Button -> Multiply Button -> Enter "10" (power) -> Equal Button -> Answer  Reply With Quote

6. Grab a regular calc as well, but if you plan on messing with any advanced calculations you would be really doing yourself an injustice not having a TI  Reply With Quote

7. A good programmable graphing calculator would certainly be a good investment. And, as Harry indicated, you can write small "programs" for it, including lens tilt and even thickness calculations/graphs.

But, honestly, I do most of my own calculations using MS Excel.  Reply With Quote

8. MS Excel, is actually becoming a great place to create these small calcs as Darryl does. It has 3 big advantages:

1) It is very easy to learn the language and create some nice looking graphs and calculators.

2) Some of the newer cell phones have a mobile version of ms excel making these small calcs portable and allowing you to have them where ever you roam. Now if that isn't convientient I don't know what is.

3) It is very easy to add another sheet in a excell book which means it is very easy to create a document that uses the results of a previous calculation in a new calculation with very little effort.

I personally like the TI because it is usefull in many areas and has many functions that make life easier.  Reply With Quote

There are currently 1 users browsing this thread. (0 members and 1 guests)

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•