occulting bar

[Trevor]

Just wondering if anyone has made an occulting bar to fit a CCD camera?

I made one for an eyepiece with a tinfoil strip fixed to the field stop now that worked quite well, but having trouble getting the correct distance between chip on the CCD and the focus spot any ideas?

It’s a bit like micro surgery cutting the dam foil

[blinky]

Erm...What's an occulting bar?

[MikeP]

It is either a place where devil worshippers go for a drink or perhaps more likely in this case ....

An obstruction to mask a bright object to make dimmer objects visible. The reference I Googled was related to viewing Phobos and Deimos by "hiding" Mars behind the occulting bar.

I'm sure someone more knowledgable will correct or add to this.

Mike

[Trevor]

Mike’s got it correct, just spent a couple of hours trying to get one to work with the DMK but it’s proving difficult to find the correct thickness of foil and distance from the CCD chip to achieve a sharp focus of the foil on screen before attached to the scope.

However I did find out that I can get 3200 frames in one minute with a file size of 950 MB.

Will be doing some imaging tomorrow evening and was hoping to try for phobos and deimos.

[Kaptain Klevtsov]

With an eyepiece the image is focussed in front of the eyepiece lens, the eyepiece is then used as a microscope to view the aerial image. The occulting bar goes at the focus point in mid air. With the CCD, the image is focussed on the chip, so the bar has to go on the chip surface. I don't think this is a good idea.

Kaptain Klevtsov

[Trevor]

Thank’s KK no wonder I was having problems, will have to think about an alternative.

[winfij]

With an eyepiece the image is focussed in front of the eyepiece lens, the eyepiece is then used as a microscope to view the aerial image. The occulting bar goes at the focus point in mid air. With the CCD, the image is focussed on the chip, so the bar has to go on the chip surface. I don't think this is a good idea.

Indeed - the common way to achieve the same effect with a CCD is to position the bright object just off the chip.

It's a problem when the thing you're trying to image is closely surrounded by brighter things, you can try putting it in the corner of the chip for example, although halos from filter reflections can still cause trouble.

You'll also need a system with low off-axis aberrations to make this practical.

John