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Old 18-02-2010, 05:55 PM
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floyd_2 (Dean)
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Focusing DSI II Pro Camera Through a Ha CCD Filter

I was outside last night wondering why I couldn't focus my LX200GPS SCT using a Bahtinov mask. I have focused many times before this way. It took me a while to realise that I was using my new Astronomik Ha CCD filter for the first time on my DSI II Pro filter slide.

I switched to my IR filter, and Bingo, focusing was a doddle.

I realised that I had to look VERY closely at the screen to see any spikes at all using the Ha filter (der...it's blocking the light). In fact, the spikes were represented by three very tiny dots. As I shifted focus, the middle dot moved left or right.

Does anyone have any tips for focusing using a Bahtinov mask and an Ha CCD filter by any chance?


Last edited by floyd_2; 18-02-2010 at 05:57 PM. Reason: Learn how to spell focusing, Dean :^/
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Old 18-02-2010, 06:25 PM
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telecasterguru (Frank)
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It is very difficult due to the small amount of light passing through the filter but focusing on a very bright star may be the way to go before moving on to your object if you don't do this already.

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Old 03-03-2010, 04:34 PM
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Hi Dean, I agree with Frank. I usually use a 2nd or 3rd mag star with my Bhartinov mask and Ha filter.

I never have a problem with focussing and can make out the spikes very easily.

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Old 06-03-2010, 07:14 AM
aworley (Alex)
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I too saw the dots with my dsipro ii, ha ccd filter and bahtinov mask on sirius. I took off the mask and tried nebulosity fine focus. Fifty fifty either way as nebulosity focus figures are really sensitive to seeing.

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