Yet another "My First Pics"

[FNQ_View (Mick)]

Taken 20/06/05 at about 2150 from Cairns in Far North QLD using a handheld Pentax Optio in Macro Mode through a 20mm Plossl on a Celestron Nextar GT4

If I sound like a new father it's because I'm stunned at result of my first astrophotography attempt.

http://members.ozemail.com.au/~micknsal/IMGP2073.JPG

At about the 10:00 position on the image is the start of a shadow effect in the image. At its worst it seemed there was the shadow of the secondary in the image. Is this likely to be the cause? How do I prevent it?

A t-mount is already on my shopping list

Mick

[[1ponders] (Paul)]

Another good pic Mick. It probably is the secondary. If you hold the camera further back from the eyepiece than the focal length of the eyepiece, then you start to get the secondary appearing in the image. It also can become a problem when imaging very bright objects, ie the moon. Try getting in closer to the lens and using your zoom on the camera (Zoom out first before moving in to the lens ). That might help.

[RAJAH235]

Hi Mick. In my very limited time, ie; 1 day, as an 'Astrophotographer'?, I can only say that, when I was taking images last night & experimenting with aperture/shutter settings, I had the same 'shadow' effect when I didn't have enough aperture. I could actually see the 'shadow' disappearing when the shutter button was pressed 1/2 way, with diff. aperture settings.
When I got down to around 5.6/4?? etc, the 'shadow' was gone, & I got clear shots.
Does this sound right, Paul/Mike anyone? L.

[[1ponders] (Paul)]

Alot of things can affect it Laurie. By stopping down the aperture your restricting the amount of light thereby reducing the brightness. I was actually reading something about this particular problem today at work. Unfortunately I can't remember where it was or what my google search parameters were. I'll have a look at my history at work tomorrow and post the link for the site. Had a great deal of information about afocal work.

[RAJAH235]

Paul, Thanks. If I remember correctly, when I was changing the Ap. & watching the screen, I could actually see the image area brighten & that shadow effect disappear. At f8 it was very dark with a great big black spot in the centre.(moved around with camera movement). Is this like you say, the 2ndary or small Ap. setting? L.

[[1ponders] (Paul)]

I'll find that site tomorrow. It explained it really well.