My apologies to resurrect a very aged post, but 1) I couldn't find Christian's contact anywhere else and 2) my experience is similar to Ezra's.

I have an Astromechanics Focuser and a Rokinon AF 85mm (for Canon EF) and I'm using the latest KStars with Astroberry server.

What I've noticed is that the Index range is 0-22 and that seems to be underlying one or two issues I'm having:
1) I have 22 possible apertures on this 85mm lens, where Index of 0 would map to f/1.4 and Index of 21 would map to f/16. To be clear, the available apertures for this 85mm lens I'm using are: 1)1.4, 2)1.6, 3)1.8, 4)2, 5)2.2, 6)2.5, 7)2.8, 8)3.2, 9)3.5, 10)4, 11)4.5, 12)5, 13)5.6, 14)6.3, 15)7.1, 16)8, 17)9, 18)10, 19)11, 20)13, 21)14, 22)16. If the Index Range was 0-21, I could rule out the lack of a 23rd aperture setting being the problem.

and/or

2) I've stepped from 0-22 at the INDI control panel while watching the iris in the lens. 0 is always wide open at 1.4. Moving to 1, the iris closes somewhat. Moving to 2, the iris opens wide then close further than 1. All seems fine until about 15. At 15-22, the iris opens wide and closes to the same tight aperture- what I can only assume is minimum aperture of the 85mm at f/16. That is to say, my apparent Index range for this lens is 0-15 whereas my technical range should be 0-21, and I certainly am missing many aperture settings by using astromech_foc as is.

I'll say bluntly that I will probably be able to find a sweet spot with the current 0-22 Index, but if this problem with my 85mm lens can be solved, what could the issue be? My coding experience is in statistical programming, so reading the .h and .cpp driver files is no use to me- I can't even fathom how the Index maps to another integer to be sent over USB to trigger the iris movement. Maybe I could change <code>IUFillNumber(&AppertureN[0], "LENS_APP", "Index", "%.f", 0, 22, 1, 0)</code>; to 21 just for my own use, but that does nothing for others who might experience my issue. I thought maybe <code>IUFillNumber(&MinAppertureN[0], "MIN_APP", "Min", "%.1f", 1, 64, 0.1, 16); IUFillNumber(&MaxAppertureN[0], "MAX_APP", "Max", "%.1f", 1, 64, 0.1, 64)</code> and from a list of common aperture setting for lenses (1 1.2 1.4 1.6 1.8 2 2.2 2.5 2.8 3.2 3.5 4 4.5 5 5.6 6.3 7.1 8 9 10 11 13 14 16 18 20 22 25 28 32 36 40 45 51 57 64) determine the number of values in the range of Min and Max aperture and use it to replace the "22", while also displaying the current aperture for the user. Of course I see many problems with this, the least of which not being that not every lens will fall on this range of apertures, and I honestly don't even know if decreasing or increasing the 0-22 range will work at all, let alone improve anything.

I'll stop there! It's a great driver that let's me control a camera lens without a camera- I'm very happy to have it over a manual focus 85mm without a doubt! Just wanted to share my experience in case there was an easy solution, but hopefully to also learn a thing or two about the driver itself. C++ doesn't look to intimidating, I just don't know where to start.

Thanks for the driver, and I was glad to find one instance where somebody else also had a similar confusion regarding the driver.

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