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HiloDon

NB Ha LSX2c and LL v0.12

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Hi All,

Finally got some clear skies last night to test out Paul's latest version of LL. Thank you very much, Paul. I decided to try the narrow band Ha filter with the color Lodestar. Because of the Bayer mask and the NB Ha being in the red part of the spectrum, resolution suffers, but as Dom has shown results are still pretty impressive. The other advantage with the filter is that it blocks also all other unwanted light, including the moon. Those in LP areas should give it a try. It only works on emission nebulae, but there are plenty of them out there.

I thought I would share a few with you. There are more in this link. Last night's are the last nine images.

http://stargazerslounge.com/gallery/album/3621-nb-ha-and-lodestar-x2c/

post-36930-0-67645300-1435278770.jpg

post-36930-0-88232400-1435278796.jpg

post-36930-0-81535400-1435279029.jpg

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Hi Don,

Nice images! Do you think the color with Ha adds noise over the mono version? Seems background is blacker using mono and Ha?

Richard

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Thanks, Richard. The noise definitely seems higher in color. It may be that color accentuates it more. I find the mono Ha first exposure acceptable, but the color needs stacking to start looking good. Not sure I understand your comment on the background. Both color and mono seem the same to me. It may be that white against black makes it look darker.

Don

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Very nice images Don!

I was particularly impressed with the large collection that you posted on the CN gallery track http://www.cloudynights.com/topic/144516-astro-video-image-gallery/?p=6650144.

Regarding Richard's question, I can say only the following. I have only the color Lodestar x2c and have had no chance to directly compare mono and color. But to tell the truth, I have never been fully satisfied with my single frame captures or sum stacks from my color LS. The texture is just not smooth enough for my taste. They look like close up views of the facial skin of a pretty actress without the makeup. Very pretty but not quite up to what you were expecting...

Stacking three frames solves everything but is necessary for my taste.

I believe that the reason is that four base pixels are needed to make one color superpixel, that is the smallest unit of resolution in color. So, to start out, the resolution in color is 1/4th of the mono resolution. Narrowband filters further accentuate this handicap. E.g. H-alpha light excites only two (Y and M) of the four constituent elements of the 2x2 superpixel. True, the debayering algorithm tries its best to interpolate and smooth out things. But still, one cannot create something out of nothing. If there is no signal coming out of half of the pixels, that will have an effect.

To illustrate, I attach two captures from earlier this spring of the same complex made on the same night with the same equipment. The first (left) one is sum-stack, i.e. the pretty face without the makeup. The second (right) one is mean-stack, smooth, ready for show time. (I believe that if you click on the image, then you get it in full resolution and can see the differences better.)

post-26379-0-95436500-1435295411_thumb.j

Clear Skies!

--Dom

Edited by Dom543
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Sorry, I accidentally double posted and now I cannot fully erase it. I have to post something, or the double post comes back. --Dom

Edited by Dom543

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Thanks, Dom.

I agree with your assessment. Mono isn't as bad as the color, and I think you have explained why. The first color capture gives this mottled look. Three stacks clears it up. I also noticed more color noise in the nonlinear scaling modes. Moving the black level in to clip the histogram helps, but, you do lose some object data. I did that with both M17 and M20 above.

Don

Edited by HiloDon

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Hi Don - Splendid images! As someone moved to try "narrow band" I was wondering:

What make of H-Alpha filter are you using? I note e.g. Baader (my default choice) 

exist in 7nm or 35nm bandwiths. Maybe the latter is better / sufficient for VA? :)

At the moment, I have yet to even fully explore my existing Baader UHC-S.

I suspect (hope), for VA, standard "visual" filters would be an OK start... ;)

Most of my local LP chagrins are (old-style orange) streetlights... :o

Edited by Macavity

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Thanks, Chris.

I have the Orion 7nm. NB Ha filters are pretty expensive and Orion's is somewhat reasonable. I haven't tried anything wider than that, but from what I read, if you want to get the best contrast on emission nebulae, narrower is better. Some even use 5 and 3nm, but then you start losing stars. One of the things I forgot to mention is the elimination of star bloat that plagues VA. I have the Baader UV/IR filter and haven't found it to be that effective in that department, even on my refractors. With the NB Ha filter, I get pinpoint stars even with my little 50mm guide scope I use for wide field shots of large emission nebula. It is one filter I found that is worth the investment.

Hope this helps.

Don

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Splendid stuff Don!

Some of the comments regarding noise and resolution - one factor could be the conversion from the bayer matrix to RGB pixels involves interpolating with the neighbours, so if only the pixels that receive red light (in the CYMG) in the sensor array receive signal, I suspect the others will contribute to noise and no signal - its a theory anyway...

Still, doesn't detract from an amazing set of lovely emission nebula!

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