SonnyE Loc: Communist California, USA

Hi Matthew!

1X puts me out of the running. :cry:

All I want is the Hubble.... :roll: :lol:

John_F Loc: Minneapolis, MN

In my copy of "Theoretical and Experimental Optics" by J. Valasek there are derived formulas for the near tolerable focus distance and the far tolerable focus distance based on the derived hyperfocal distance. The later is calculated from the focal length, the numerical aperture, and the 'circle of confusion.' In film the later is the silver halide grain size. In digital it might be the areal size of a pixel. When the the focal distance is set the hyperfocal distance, objects will be in tolerable focus over the span of 1/2 the hyperfocal distance to Infinity. Might that work?

SonnyE Loc: Communist California, USA

'Circle of confusion'
Yeah, that sounds like where I fit... :?

http://youtu.be/5RmHSbTNudk?t=43s

I feel good knowing I won't fall off a corner... :lol: :lol: :lol:

JimH123 Loc: Morgan Hill, CA

I'm sure that is true for terrestrial objects. But not stars. They have to be in PERFECT focus. The dim stars just dissappear if focus is off even a tiny amount. And brighter stars become fat.

Stars are not extended objects. They are point sources. The point does does move around due to the effect of the atmosphere. Trying to find the hyperfocal point with stars will have you end up with only a few fat stars and no dim stars.

SonnyE Loc: Communist California, USA

Except in Hollywood, CA.

rbartz Loc: Arizona / Missouri

Focus is an interesting and complex subject. I downloaded an app that helps with Depth of Field and near and far focus distances. HOWEVER, it seems like the good old trial and error method is easier when it is dark and the stars are bright and even the light from a smart phone screen seems to irritate someone nearby. The live view magnified screen does help a lot.

The app is Photo Tools and it has a lot of stuff that ought to be helpful as I get into this. I like that it does the DoF calcs based on Camera model so ti probably (!) compensates for sensor size and number of pixels. I did not see the settings for the "circle of confusion" but they are no doubt considered....!

SonnyE Loc: Communist California, USA

Oh, there's an app for smart phone irritation, too.
It's called a pellet gun. :shock:
Gotcha! :lol:

Oknoder Loc: Western North Dakota

The best focusing technique is to use a Bahtinov focusing mask. Not only will it show if your focus needs tweaking but it will show in which direction your focus is off. Not too sure how this thread became focused on focus, lol. But I must say it looks like your initial image's focus was spot on. Considering your first image is the only one not contaminated by clouds I will only offer tips on it, even though I like the composition of the third image the best. When submitting images it is best to select the store original so we can look at the image with a higher resolution than typically allowed.

Your focus looks good, from what I can tell, with no trailing, even to the point you might be able to extend the length of exposure. I would image that with a FL of 35mm, 10-15 second exposures would show little to no trailing and increase your signal, which will bring out more color and detail in the night sky. If using your camera on a fixed tripod raise your exposure time until trailing is observed at 100% zoomed, then increase your ISO till noise becomes an issue. The ISO and noise is are subjective terms but use your best discretion.

If time was not an issue, waiting a couple more hours in image one, would have brought Pleiades and Orion into view, which would have produced a much more impressive image.

All in all great images and welcome to the forum,
Matthew