Reducer problem: increase or decrease distance?

[vlaiv]

I'm not sure that you can fit meaningful curve to above table. Here is excerpt from Telescope Optics .net piece on field curvature

Different scopes have different lens surfaces - there is difference between doublet and triplet, F/ratio will play a part as will focal length. Glass type will also play part (note indices of refraction in expression).

[Adam J]

2 hours ago, vlaiv said:

I'm not sure that you can fit meaningful curve to above table. Here is excerpt from Telescope Optics .net piece on field curvature

Different scopes have different lens surfaces - there is difference between doublet and triplet, F/ratio will play a part as will focal length. Glass type will also play part (note indices of refraction in expression).

Yes already noted that there are other factors and that its just a starting point earlier in the thread.  

[gorann]

2 hours ago, Adam J said:

Yes already noted that there are other factors and that its just a starting point earlier in the thread.  

As soon as it clears, which may not be soon, I will start experimenting, starting at 52.9 cm. As far as I know this is only one of two reducers that will work on Esprit 150 (the other one being the Riccardi) so it could be useful for others to hear of the best distance.

[wimvb]

15 hours ago, vlaiv said:

I'm not sure that you can fit meaningful curve to above table.

With all due respect, it doesn't have to be meaningfull, it just has to work. 

Göran, try a shorter distance next time and see if that either solves the problem or gives star shapes as in the other image. If it does, you know in what interval to look. 53 mm seems as good a value as any to start.