10-20mm focus help

[daveangie0110]

Hi All

Please help!

The other night i set up my Staradventurer polar aligned it attached my DSLR with my 10-20mm lens set at 10mm and set the focus to infinity, started up BYEOS on my laptop, i then tried to focus on the milkyway, but i could not see anything on the laptop screen, i then rasied the iso up to 6400 but i still could not see anything on the screen ! i then tried setting the lens to 20mm but still i could not see anything on the screen.

Can anyone give me some advise on how to focus a 10-20mm lens using BYEOS.

Thanks

[ronin]

Not sure I can help but this is what I have found, and I am NOT using BYEOS, do not have it and not even sure if it will operate on my camera. Sony A350.

I cannot see anything, the "picture" is too low and all I "see" is noise. What I have to do is in effect take an exposure of the duration intended, then display this picture on the screen, possibly on/in BYEOS (?). Then things start to appear, either in or out of focus. Usually out. So adjust and try again. Means a number of attempts to get it right. 6400 will likely just boost the noise. ISO is not the right word to use as in my thinking it does not 100% correlate to the original ISO on film, and that is what I initially played with.

Have found that a distant tree helps, focus manually on that the move nothing and direct to the skies. One possibly odd bit I found is if I set manual focus then manually focus on something like a tree the camera still gives me an indication that focus is right, a couple of green pointers are displayed. So even manually the camera is still functioning WRT focus a bit.

I do not think you will get focus on the Milkiy Way specific, or at least not easily, it is a big fuzzy patch and so nothing to really specific focus on. When I did this first I was "lucky" I had a very small cresent moon low and behind me, I used that to focus on. That was when I found out about the "in focus" indication even when set to manual focus.

[Star Struck]

Whilst not an expert in this, I have been trying to do some astrophotography this week using a Canon camera and variety of lenses.

Trying to focus with Live View (and by implication a computer), you can see absolutely nothing to help you focus.

I have had to manually focus the camera using trial and errior, keep shooting a test frame and alter focus until acceptable.

If you turn the focus ring all the way, you will likely focus beyond infinity and get lovely test pictures of star donuts.

Try manually focusiing on a distant object during daylight, remember the focus position and experiment from there.

Not an exact answer to your question, but it worked for me.

 

Tony

 

[Steve Ward]

Focusing the 10-20 is no easy task at night , the focus ring does not operate conventionally to a stop.

I use tethered to the laptop via EOS Utilities which has remote focus controls built in allowing you to take long exposure test shots while monitoring the focus and adjusting as required without touching the lens.

Guessing focus with such a wide fov is just frustrating so eliminate the guesswork.

 

[geordie85]

Try pointing your camera at the brightest star you can see ( vega is good of you have a flip screen, Arcturis if you haven't) put the ISO to the highest it will go, set the f ration to the lowest number it will go and set exposure time to the longest you can. Now in the top right hand corner of you DSLR there will be a button that will zoom in on your screen. Press it twice to zoom in to x10 then start moving your focus ring. 

You should be able to see the brightest stars this way

 

Edit: just remember to return the setting back to what you want before shooting