Why can I not get high magnification photos through my 8 inch Dobsonian?
Hi Spaceboy,
Thank you for taking the time to gets photographs, each is worth a thousand words. The news is not good, I'm afraid.
At a glance I can tell that you are too far inside focus. The shorty Barlow is defeating its purpose by a, being too short in tube length, b, pushed too far into the focuser. With your short Barlow set up as it is, you cannot rack it out far enough to come to focus.
Also, if you use a 9.0mm EP in the Barlow, the camera needs to be a lot farther away from the EP to the point that the whole thing becomes unwieldy. You would need the same weight stuck out the opposite side of the focuser as well as more weight added to the mirror end.
What you are attempting to do will not work with a Newtonian telescope on a Dobson mount. The resulting image will be so highly magnified and very dim, which even if you could get it in the field & focused, would be out of the field in the blink of an eye, due to the stationary mount. The exposure needed would be too long and end up being a blur.
I have a friend with a reasonable level of photo experience, with an 11" SCT whole is struggling with a web cam, which produces a much bigger image of Saturn than your 8" Newtonian, so the task is not an easy one, even with the right size EQ driven telescope.
The next Moon is coming along next few days, please do the little experiment with just the Barlow lens and the tissue/tracing paper - it will show you just how far away the camera needs to be. Don't push the Barlow all the way in to the focuser as long as it is secure, and rack the focuser out and leave enough travel to focus.
Please let me know how your Moon experiment goes.
Regards
Shevill
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