DSLR Ha Images

[ashworthacca]

The last couple of nights have been clear (Hooray:p) so I thought I would give my 12mn Ha filter a workout in my modified Canon 1000d.

A couple of issues.

1. On the Elephant and Bubble nebulas I haven't got enough data......both crossed the meridian and I lost an hour or so subs on both as I was in the house watching TV:iamwithstupid:
   
2. I don't really know how to process Ha images from a DSLR as this is my first foray into Ha.
   
3. Not enough data captured (by far) so the images are very noisy.
   

I stacked as normal with Nebulosity 2, opened in Pixinsight and extracted the Red Channel. Processed in Pixinsight and Photoshop.

Here is what I have so far but do intend to add much more data, weather permitting:)

Gamma Cygni (Sadr) Region by ashworthacca, on Flickr

Elephant Nebula by ashworthacca, on Flickr

Bubble Nebula by ashworthacca, on Flickr

Thanks for looking

[Shibby]

Nice! They have worked very well, looks like with a few more subs on each they will be some cracking dslr images.

[Smeg]

How much Ha will get through an unmodified DSLR and how much Ha is lost?

[ashworthacca]

Thanks Shibby, appreciated.

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I am here: http://maps.google.com/maps?ll=53.544931,-1.487031

[ashworthacca]

How much Ha will get through an unmodified DSLR and how much Ha is lost?

I think only 10% of the ha gets through the filter but up to 80-90% if modded.....not sure of the exact figures though.

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I am here: http://maps.google.com/maps?ll=53.544883,-1.487281

[swag72]

These look good for DSLR Ha images. I have always found noise to be a problem though with Ha, even with my Heart and Soul, with excess of 8 hours, it still seemed a little noisy for me.

Someone did explain something to me about Ha and a DSLR which did make sense and explained a lot. As you only capture on the red pixels, you only get 1/4 of the signal. It was then said that perceived noise can be a problem as you in effect have 3 out of 4 pixels with NO data in them at all. So, you can't really work with nothing - If that makes sense.

Maybe that is wrong. but it seemed to make sense in my mind.

[ashworthacca]

Sara, what you say does make sense and I did wonder what effect discarding the Blue and Green channels had on the image.

I'm going to see these through to see what I end up with before I jump ship to a dedicated CCD camera.

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I am here: http://maps.google.com/maps?ll=53.544931,-1.487031

[swag72]

If what I said is true, the I guess you would need at least 4 x more data, then you stand a chance of getting signal in the other 3 pixels!!! I'm sure it's really not that straight forward, but like you, it made sense!

[dmahon]

Although a 400x400 sensor colour camera will have only 100x100 red pixels, the others are interpolated so not missing completely. Destroying the G and B channels will not make a difference to this.

[Smeg]

So this is a problem with all colour sensors or just specific ones?

[swag72]

Although a 400x400 sensor colour camera will have only 100x100 red pixels, the others are interpolated so not missing completely. Destroying the G and B channels will not make a difference to this.

OK, cheers for that - I thought it was way to simple for me to understand before!!

[morimarty]

Hi martin,

I was thinking of trying the Ha/O111 clip filter in my modded 450d camera.

So i will watch your progress with interest.

Just a thought, did you have to alter the camera settings ie. white balance. picture style. iso. to get the best possible image?

ATB

martyn

[ashworthacca]

Martyn, I didn't change any settings at all. Kept it at iso800 with default White balance settings. The hardest part for me is getting the focus spot on. With the ha filter it's difficult to get a star to appear using liveview...to me anyway.

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I am here: http://maps.google.com/maps?ll=53.544970,-1.487085

[morimarty]

martin,

thanks for your reply i could see this being a problem.

Did you take a test exposure with b/mask?, and would this do the trick.

ATB

martyn

[ashworthacca]

I've never seem to get on with my BM so I use Astrophotography Tool software to take a few test exposures and use the focus tool to get the best focus score.

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I am here: http://maps.google.com/maps?ll=53.544837,-1.486994

[morimarty]

Martin,

I use backyard eos software. i have heard good reviews about apt, i must give it go sometime soon. if just to try the focus tool.

ATB

martyn