Focusing in real time from laptop screen.

[avandonk]

After seeing this
http://www.intro2020.co.uk/pages/zigview.htm
This device does not work well at low light levels and is expensive.
It set me thinking. Why not mount a ToUcam on the Canon Angle Finder C and focus using the laptop screen without waiting for dark adaption to see the faint view in the Canon AFC.
First pic ToUcam on Canon AFC. Second pic of screen. View from behind camera.
I have tried this in a dark room and when looking through Canon AFC visually could barely make out anything. With the ToUcam (once the AGC cut in) clear and bright on the laptop screen and focus position was obvious and clear.
The ToUcam has it's original lens in, focused at infinity to take the place of the eye.
I will test it tonight on stars to see if its worthwhile making a more robust and accurate mounting device for the ToUcam.
Why should the 20Da guys be the only ones to have it easy.
Bert

[iceman]

Great idea Bert! Look forward to seeing the night time results!

[Striker]

Nice invention Bert......I do feal sorry for you guys who worry about focussing.....wait a minute.....no I dont...lol

[avandonk]

Screen shot of the bright central star in the second picture. The third picture is a full laptop screen of pic one.The exit pupil of the Canon AFC is much larger than the ToUcams lens. Will get a lens for the ToUcam with a larger diameter and focal length. It still looks promising.

Bert

[avandonk]

Got a better lens for the Toucam its just a CCTV lens from Jaycar. They come in focal lengths of 4,6 and 8 mm and are F2.0.
First pic shows the 8mm lens mounted on the Toucam with the original lens next to it to show the difference in aperture. Second a side view just superglued the lens to the Toucam after a bit of cutting with a scalpel. The lens is focusable. In fact the 4mm version screws straight in as the thread is the same as the Toucams original lens.
Here is the best bit a picture of the laptops screen in pic 3. Showing three stars at focus with the toucam mounted on the Canon Angle finder C.
Fourth a picture of the same area with the corresponding stars marked.
And last a screen shot with just the Toucam pointing at the sky. Guess the constellation.
The nearly 8mm diameter lens of the CCTV lens does wonders for the sensitivity of the Toucam.
I think this could be a goer. Does anyone know the magnitudes of these three stars.

Bert

[RAJAH235]

Bert, all relative info is here...> http://www.crystalinks.com/orion.html
HTH...:D L.

[RB]

What a wonderful idea Bert.
Were these taken with the Canon Angle Finder C on x1.25 or x2.5?
It will be a big help for people to be able to focus this way.

Although if people don't have a Canon Angle Finder C another good alternative is to buy the supurb DSLR Focus software to use with the laptop instead of buying the Canon Angle Finder C.

[avandonk]

It was taken at X2.5. Yes focus is accurate in real time, as long as the anglefinder C is adjusted correctly for either mag (1.25 or 2.5). My reason for doing this was to keep an eye on focus as the night gets colder and make an adjustment if needed while the camera is taking the 'dark' frame for in camera noise subtraction. This way you don't lose framing or guide star etc. I am thinking of trying a low light monochrome camera like this next if the ToUcam is not sensitive enough.
http://www.supercircuits.com/index.asp?PageAction=VIEWPROD&ProdID=4166

I have tried stepper motors for focus and taking test shots etc and it is all right to do once. But as the night gets colder focus changes and all you do all night is chase focus.
What I do at the moment is sit inside and watch the exposures as they come in over wireless network from the laptop controlling the Canon camera to my PC inside. It is obvious when focus is deteriorating. It would be nice to go out without dark adapting and simply adjust focus while the camera is taking the dark frame without disturbing the running setup.
Unless you are dark adapted to attain good focus with dim stars is impossible. I have also noticed if I am tired or had one or two beers I can never get good focus without long dark adaption. With a bright laptop screen there is no problem even when very tired and more beer and or coffee.
I do have DSLR focus but have not used it much.

The small attached picture shows how much an 8mm lens on the ToUcam sees of the viewfinder. The second is a view of the full viewfinder.

Bert