First Imaging issues

[Kerrp30]

Finally got everything I need to do some night time imaging. My set up is as follows

1. Canon 500d DSLR

2. Celestron T ring to 1.25" adaptor and Canon T ring.

3. x 2 Orion Stumpy barlow

4. CPC800 8" scope SCT.

5. Celestron Focal Reducer.

Decided to give this a try during the day in the comfort of my home.

Scenario 1

Canon DSLR to the scope back via the adaptor and t ring. Set the camera to live view focused something that was 600 metres away and took the picture it came out looking fine.

Decided to add the x2 barlow, took the picture and ended up with a very dark image, you could make out what was there but it was not clear. Decided to change to bulb setting on the camera and ended up with all white pictures with everything from 10 seconds to 4 and even one. Decided to change the bulb setting to an sixth of a second and it came out good enough.

Anyone tell me why the same setting with the x 2 barlow showed a very dull image?

Also why all the whiteness on the longer exposures, is this just overexposure?

will not bother with the focal reducer and DSO stuff till I have got the moon and planets stuff sussed.

Also the camera does HD video can I use this for stacking images?

Thanks in advance for your help

Paul

[jgs001]

Paul, when you use a barlow, you effectively double the focal ratio of the scope, so instead of f/10, you're running at f/20, this is the same effect as stopping a camera lens from f/10 to f/20 (try it with the DOF Preview active, you'll see what I mean). Basically, you're spreading the light from the centre of the image over a larger area, so the image dims. When you went to bulb, you overexposed, thus the white image. If you use the DISP button on the preview screen, you should be able to get to a display, which is the pic in a small box, with the histogram. Any overexposed highlights will blink at you, you'll see the entire image is flashing. When you're shooting daytime with the scope, the camera's light meter will be fine, leave it in matrix metering, the default.

In theory the video could be stacked, I've not tried it so can't comment specifically.

[Kerrp30]

jgs001,

Can I clarify the DOF answer:

Put the camera on the liveview PC control, had the depth of field preview switched on, when I zoomed in it got darker and when I zoomed out it got lighter. Is this correct? Just trying to understand it.

So the higher the F number the darker the image, think I am getting it now amd therefore the longer you need to keep the shutter open to get a decent image.

When I press the DISP button on my camera using live mode, I get a full picture with a small box and if I press it again I get a histogram up. I get nothing flashing at me with the supplied camera lens, will this only happen when hooked up to the scope?

Anyways will need to wait tll the middle of the month for the moon to make an apperance and some bloomin leaf blower to get rid of these damn clouds.

Thanks for your input to make me understand things a bit clearer.

paul