Why can I not get high magnification photos through my 8 inch Dobsonian?
Hi,
I have to say this does not make sense to me somehow, when you put a Barlow into the focuser - it extends the focal plane away from the focuser outwards and with a camera attached, one normally would have to rack the focuser out, especially if the camera is dome distance from the Barlow lens. Without seeing how it is all set up I am shooting in the dark.
I can understand it if you were trying to do prime focus with your camera, then you do need in-travel.
Try the following: Insert your long tube Barlow (2x telenegative lens) (not a shorty) into the focuser attach your camera say 4" away from the lens if you can (no eyepiece) and you should get an image in focus, start all the way racked in then rack out and you should get an image at some point (racked out - not in).
The Barlow lens produces a diverging virtual image which you cannot see with your eye but it will be seen if you hold a piece of frosted glass or thin greaseproof paper over the end and adjust the focuser. The farther away from the lens - the larger the image gets, also much dimmer. This is well worth doing with the Moon which has heaps of light which makes it an easy experiment.
Let me know what happens before going any further.
If you can post some quick pics of your set up, it will help.
Regards
Shevill
|