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A couple of Ha narrowband questions for a DSLR


swag72
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I have decided that I am going to treat myself to a Ha filter for my DSLR. I know that it will never be as good as using one with a mono CCD, but that is a little way off at the moment.

My question is how do you add the Ha data? I assume that I would stack the subs (excluding Ha) as normal in DSS, then I would seperately stack the Ha and then blend them somehow? Or, do you add the Ha in with the DSS stack, but as a different action?

Also, do you take flats with a Ha filter? If so, how do you expose them?

Thabks for your help guys.

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Ha needs significantly longer exposures especially on DSLR's and even more so if they havent been modded.. the Shortes HA exposure i would use would be 15 mins and typically I would use 30 mins or longer... and they are very good LP filters...but only for emission nebulae :)

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Thanks for that - Will have to do some reading then about blending.

Just to confirm then - I'd be better stacking the Ha images on their own in DSS, the saving the amge without any adjustments - Then processing before blending? Or do I not process before blending?

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OK, another question then having looked at the link posted - I would be using an EOS clip Ha filter, so the image will not be aligned with the other image that I want to blend with - How do I get around that? This is not something I've had to even really think about too much before with just 1 image, or a stack of different images, which are aligned by DSS and I can just crop as required.

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I use DSS to register seperate images...I create a new folder and in it I place a copy of my already registerd and stacked TIFFs- in your case a RGB stack and an Ha stack.

Load both TIFFs into DSS -no darks flats or bias, and check all.

Then click Register Checked Pictures and the Register Settings box will come up.

Click Stacking Parameters, then click the Intermediate Files tab and tick Create a registerd/calibrated file for each light frame. Then OK and OK again.

Dss will do its thing..when its finished close it down - dont save the file..In the folder you made will be the 2 original files and 2 others eg RGB Stack.reg and Ha Stack.reg - the .reg files are the ones you load in to Photoshop

Edited by martin_h
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If the Ha is going into a blend rather than be a stand alone I process it for very high contrast, too much in fact. Then I align in Registar like Billy. I apply it to Ps in the red channel, blend mode lighten, starting with about 30 percent and increasing in subsequent iterations. I might then use it as luminance at no more than 15 percent.

Olly

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