albert_barmettler1

Hi Andy,

The question "is prime focusing preferred over eyepiece projection" ist actually the wrong one.

Prime focussing means, you attach the camera directly to the telescope (usually using a T2 adapter), without any other gear in between them (hence the term "prime focus"). Doing so, you are using the scope's focal length (lets say 700mm like a consumer newton telescope, approx. 100.- or 150 Euro's).

Using eyepiece projection, there is an eypiece between telescope and the camera. It's purpose is to >>extend<< the focal length of the whole system. Using EPP you'll get equivalent focal length of several meters, depending on the focal length of the telescope, the eyepiece and the distance between camera and eypiece.

You wil have to choose... as usual...

Prime focus means:

- Higher image quality (because of no eyepiece)

- brighter image (and therefore shorter shutter speed)

EPP means: Depending on the eyepiece..

- darker image (due to the focal ratio)

- worse image quality especially at the outer edges

- often only a small area in the center of the image

gets really sharp, because the usual eyepiece is not optimized

for yielding a flat field (they are optimized for the human eye)

BUT: EPP allows to pfotograph details (on the moon) at high magnification.

So generally speaking: Prime focussing is usually used for "deep sky" images, EPP usually for details of the moon and the planets of our solar system.

Im sure the magnification of the system is too low to photograph planets [in a reasnonable size].

I recommend to have a look at the astrophotography pages in the internet, usually they describe the settings and used gear. Use this as a starting point!

Have fun!

Albert

I know, we are young, and we need the money :-) but wouldn't it be great to own an old Canon camera of the first days (perhaps inherited from our grand-grand-grand-pa)? Or have a look at an old Canon F-1.. an amazing piece of mechanic perfection. Perhaps the EOS-3 will stand for perfection in many ways in 30 years or so.

So I go along with Joe:

Keep it. Love it. Give it to your children one day.

Sorry, I can't share your concerns about "correct exposure" settings. You are shooting digital - use spot metering and click-di-click. You can see immediately the result on the screen. I am shooting astro photos for years now, all on slide film. Mainly deep sky objects, but I started with moon (as all astro photographers do, because it's very easy compared to other astronomical objects). Digital makes life a lot easier in astro photography, just give it a try.

albert

Hi,

The AF sytem will only be disabled, if the teleconverter tells the camera about the real aperture (yes, the Canon TC's do). I've used a Tamron 2x TC for some time, the camera's AF was NOT affected by the TC. Of course, in poor light conditions the AF failed, but most of the time it worked pretty well.

One more thing I've to tell you about the Tamron TC: The image quality drops rapidly in the edges. But in the center it's ok.

Hi,

Yes, there is no problem focussing the RB67 in "standard" light conditions. But I must admit, it was quite a challange even to compose the picture when I shot some star trail images.

regards

Hi matt,

Perhaps your focussing is not entirely correct? - Try the DOF Scale of the lens, it tell's you which distance to focus in order to achieve the desired DOF. By the way, I do not often use the DOF preview lever, the image in the finder get's too dark for me.

regards

albert

Hi,

I know, it's the "wrong" answer for your question... The Pro-SD back can be used on the Pro-S without problems (I'm using both, the Pro-S back and the Pro-SD back on my Pro-S camera).

ciao

albert

I've made similar observations. The fogged area is very small, about 1..2 millimeters into the frame. The bigger problem is the hole in the pressure plate. You can overcome this problem in some cases by rotating the camera in the right way, so that the hole in the pressure plate is depicted in an rather turbulent part of the picture (let's say trees, grass etc.).

But in general I do not use my EOS 3 for shooting IR anymore. I've found an used Canon F1 (built in the 1970ties). My F1 has no holes or dimples in the pressure plate. But be careful, there are several versions of the F1 around (also AE-1), some of them with different pressure plates.