Very confused wet-darkroom photographer

Dave - *now* I see...

The way I focus is completely for the camera. Since I don't have a flip mirror for the C8, I can only focus using the Laptop (albeit you rightly point out that an LCD is not as good as a CRT). And so far anyway, the focus I get via the laptop comes through as good focused images, especially on stars.

Certainly, I have read about the technique you describe - image, check focus, refocus if necessary, image etc. As I get better, quicker and more accurate, I can spend more time on focusing but I suspect you are much further up the learning curve than I am! I'd hope to catch you up, especially with you giving out the tips!

I now understand what you meant about focusing the image with your eye, rather than the focuser - I never really thought about that before but its a very good point.

Do you usually image with a flip mirror and an eyepiece that's parfocal with your camera?

Now, off to make that 8" Hartman. I don't envy you making a 12" version :shock:

All the best and cheers for the advice - much appreciated!

Dave

No probs Dave,
I made up a hartman mask a year ago out of cardboard, but its not rigid enough and is pretty much useless, so I'm going to have to make one using somethingrigid and very light like balsa wood.
Infact, I'll make 2, one using 3 circles and another using 3 triangles.

The flip mirror is an invaluable piece of gear, it makes life so much easier, not only can you focus with it but its great for centering objects in the FOV of the 300D, whose viewer is poor for faint deep sky objects.
It takes abit of effort to get things parafocal, but its worth the effort.
You're also not swapping adapters/cameras/eyepieces around if you have one of these.
Go for the 2" version if you can, you'll get vignetting with the 1.25 inch version for 35mm and some DSLR cameras.

As for laptops, between and cold and dew, I blew a laptop out in the backgarden about 5 years ago, luckly I had a way of getting it fixed for nothing at the time
The lidl laptop I have now generates so much heat, it keeps itself warm :lol:

Ummm! whats a Hartman mask? :oops:
Bill H.

Bill - its an aid to reaching focus. BAsically a cap over your OTA which has some kind of holes cut in it. I use two triangles for the ETX70.

You put the mask on (the scope), point at a bright star then view - you will see two images if you are out of focus. As you near focus, the two images get closer - this is actually the bright star. As the image becomes one, you are at focus. Remove the mask and start imaging.

Here's one for an 8" SCT

rao.150m.com/Focusaid.html

Cheers

Dave

Dave,
I had a look at the link above, in it he had a circle cut out for the central mirror, this way the mask could sit on it.
I do not like this idea as there is a possability of contact with the corrector plate, be it your fingers or the mask itself.
I prefer to make it like the end cap, which is supported around the outer edge of the tube/cell, this seems abit safer to me.

anyway, have fun.

I thought it looked a bit dodgy when I first saw it... Well spotted! Bill - don't make a mask this way. Make a 'cap' style mask - fits around the end of OTA.

Cheers
Dave