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Old 10-08-2008, 09:45 PM
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Ha filters with color ccd's / DSLRs?

Anybody know if a Ha filter will work for imaging using a DSLR or a Bayer Matrix CCD?

I love the HaRGB images that have been displayed recently, and would like to give it a go when all my new bits and pieces arrive... So, Should I add a 2" Ha filter to my 2ft long order? and if so, whats the difference between all of them, 7nm, 5nm etc Obviously, the wavelength of light it allows through is the difference, but what is the effect on the image?

Cheers.
Alex.
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Old 10-08-2008, 10:04 PM
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yes you can use a H alpha filter with a one shot colour CCD.

you will lose 3 out of four pixels but still manage a decent image

There was a fine article on this subject in the Astrophoto insight magazine-I think by Alan Chen ... but I cant seem to lay my hands on this.

There is also a relationship between your system and the optimum bandwidth for your H alpha filter but I cant remember where I saw the original reference..maybe someone else can help

but I have used the 13nm from astronomik with my modded DSLR on an ED 80-it has to be modded of course-and the baader 7nm with my QHY 8, also on an ED80

Dont get the lumicon night sky H alpha filter for a refractor
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Old 10-08-2008, 10:06 PM
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I was looking at the Astronomik 2" Ha CCD filter from bintel... it doesnt mention is wavelength... It will be used with the Orion EON ED80 + QHY8.
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Old 10-08-2008, 11:50 PM
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http://www.iceinspace.com.au/forum/s...ad.php?t=33430
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Old 11-08-2008, 04:32 AM
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Baader 7Nm for me (with a QHY8).
I have also used this filter with a Canon 20D.
Shoot longer subs, but everything else as normal.
Gary
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Old 11-08-2008, 05:12 AM
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Won't this only work properly with a modded DSLR?
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Old 11-08-2008, 05:16 AM
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Can't say for sure. It worked with my non-modded 20D, this was with the QHY8.
Try it.
Gary
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Old 11-08-2008, 08:33 AM
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Won't this only work properly with a modded DSLR?
Mike,

I think it would work with unmodded 20D - but with only 2-30% of the Ha signal hitting the bayer matrix and the 3/4 being rejected there the exposure times required will be very long for decent s/n ratios so I don't think the re****s will be very acceptable.
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Old 11-08-2008, 07:36 PM
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not really worth it with an unmodded camera
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Old 11-08-2008, 07:41 PM
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sweet... thanks everyone... You just saved me $499... for now
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Old 12-08-2008, 12:49 AM
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I see in maxim DSLR that using using RAW image, fast mode off, 2 x 2 binning you get a monochrome 12 bit image out of a canon dslr.

I'm guessing that using this mode with a HA filter still means only the red cells will register the image as the HA filter will block blue and green?
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Old 12-08-2008, 11:48 AM
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I was just about to ask this question as I am tossing up the choice of a one shot colour CCD or a monochrome CCD. Thanks for asking it. I take it from the replies that if one has the choice a monochrome CCD would be the better choice as 4:4 pixels would register rather an 1:4 for a bayer matrix colour CCD. Have I got this right?

Roger
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Old 12-08-2008, 12:00 PM
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Quote:
Originally Posted by Tandum View Post
I see in maxim DSLR that using using RAW image, fast mode off, 2 x 2 binning you get a monochrome 12 bit image out of a canon dslr.

I'm guessing that using this mode with a HA filter still means only the red cells will register the image as the HA filter will block blue and green?
Robin RAW is RAW - that is you get the pixel values, colour is synthesised from those raw values via a debayer algorithm.

All maxim is doing when you choose monochorme is taking a 2x2 grid and summing the pixel values to give one value for the larger "pixel". This is not the same as binning at the hardware level on a CCD. You will have (with the Ha filter in line) a sum of RGGB with only signal in the R cell To cut a long story short there will be no improvement in S/N ratio using Maxim 2x2 mono.
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Old 12-08-2008, 12:07 PM
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Quote:
Originally Posted by rogerco View Post
I was just about to ask this question as I am tossing up the choice of a one shot colour CCD or a monochrome CCD. Thanks for asking it. I take it from the replies that if one has the choice a monochrome CCD would be the better choice as 4:4 pixels would register rather an 1:4 for a bayer matrix colour CCD. Have I got this right?

Roger
Yes you do Roger, mono is 4x sensitivity compared to one shot colour for a given size and number of pixels. However your choice of camera should consider other factors - not the least of which is ease of use. Mono is more labour intensive to acquire and process - you need at lease 3 exposures to get colour which offsets the sensitivity argument quite a bit.
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Old 13-08-2008, 02:56 PM
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Oh that I understand, I have been playing with the really nice equipment on the Global Rent a Scope systems. I figured the best way to learn was to start with something that I could assume was set up correctly.

As I am interested in nebula photography the narrow band filters are important consideration and four time sensitivity means four times shorter guiding times which is consideration as guiding and mounts need to be costed into the considerations as well.

Does anyone know if there are any moderately priced anti blooming CCD cameras or do they only come in the expensive SBIG etc variety

Roger
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Old 13-08-2008, 05:48 PM
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Originally Posted by rogerco View Post
Does anyone know if there are any moderately priced anti blooming CCD cameras or do they only come in the expensive SBIG etc variety

Roger
Roger,

Depends on your budget I suppose, there are some "reasonably" priced options out there eg based on the Sony ICX285AL Exview HAD design (low dark current and ABG):

Artemis285
Starlight Express SXV-H9
OpticStar 145m Ice
QHY2 Pro
Meade DSI III mono

I am sure others will chime in with other options and recommendations. We really are spoilt for choice and it only getts better as time goes by...

I have a 145m at the moment - and am very happy with the sensitivity. It should be fine for Ha as well as the Qe is at 60% or so at the relevant wavelength - but I have not got to narrowband imaging yet.

Have fun choosing!
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