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Two different views of the North America Nebula


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These images were taken about ten days ago from the Lake District in England. Bortle 3 site. Interesting comparison to see what a OSC camera can do in about half an hour from a decent site at full spectrum and narrow band.  The images were taken with the same exposure time and same scope and camera but with different filters. The first image is taken through an IR/UV cut filter so basically the full visual spectrum. I live in a Bortle 9 site so couldn't contemplate 1 minute long exposures never mind 5 minutes. The second image was taken through an Optolong L-eXtreme filter which passes just 7nm of Hydrogen Alpha and 7nm of O III. 

Equipment: TS71 quad apo, ZWO ASI 071 MC-Pro camera, AZEQ6-GT mount guided with Astro Essentials 32mm F4 guide scope with a ZWO ASI120mm mini all controlled via ASI Air. 

 

Image 1: 7x 5 minutes at gain 150, temperature set at 0 degrees C. ZWO IR/UV cut filter. Seven darks. Stacked in DSS and processed in Startools. 

Image 2: 5x5minutes with all other settings the same. 

 

NGC700 - 7x300s IRUV with darks st1.jpg

NGC7000 - 14.08.20 - 5x300s - LXtreme with darks st1.jpg

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It was just an experiment really to see the difference that a narrowband filter makes as against no filter in a dark sky. In terms of nebula captured, I agree that this L-eXtreme filter is going to be a winner. Next clear night (whenever that is!) I will try and get a few hours hours time in and also do proper calibration frames too. I like both images for the different things that each show. I love the star colours in the  first one. The nebula is a bit shocking pink though!

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5 minutes ago, Graham Darke said:

It was just an experiment really to see the difference that a narrowband filter makes as against no filter in a dark sky. In terms of nebula captured, I agree that this L-eXtreme filter is going to be a winner. Next clear night (whenever that is!) I will try and get a few hours hours time in and also do proper calibration frames too. I like both images for the different things that each show. I love the star colours in the  first one. The nebula is a bit shocking pink though!

Depends if you want true colour or something else.

For true colour the first image , emission nebulae are not as bland as the second image.
Emission nebulae should be very bright vivid colours like neon as the emission lines are very narrow.

Colours can vary a bit depending on the exact elements, pink, magenta, blue and teal with brown to orange
as more dust is involved.

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"Por qué no los dos?" :)

Have you thought of using the Optolong L-eXtreme as luminance and using the full spectrum dataset for the colours?

Assuming the datasets are aligned against each other, it should be as simple as loading them up in the Compose module (L=Optolong, R, G and B = full spectrum) and setting "Luminance, Color" to "L, RGB" and processing as normal. 

It should yield the detail of the second image (and reduced stellar profiles), while retaining visual spectrum colouring.

Lovely images as-is!

Edited by jager945
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1 hour ago, jager945 said:

"Por qué no los dos?" :)

Have you thought of using the Optolong L-eXtreme as luminance and using the full spectrum dataset for the colours?

Assuming the datasets are aligned against each other, it should be as simple as loading them up in the Compose module (L=Optolong, R, G and B = full spectrum) and setting "Luminance, Color" to "L, RGB" and processing as normal. 

It should yield the detail of the second image (and reduced stellar profiles), while retaining visual spectrum colouring.

Lovely images as-is!

I had thought about doing that but had no idea how to do it. My processing skills are pretty basic but I will have a look at the Compose module now. Thanks Ivo! 

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Gave that a try. The result came out a bit strange. It looked great after the first Auto Dev, Bin, Crop and Wipe, but after the second Dev and particularly after the Colour module it all went a bit weird. Green blotches all over the image and no colour to the stars. It will be something I’m doing wrong...

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5 minutes ago, Graham Darke said:

Gave that a try. The result came out a bit strange. It looked great after the first Auto Dev, Bin, Crop and Wipe, but after the second Dev and particularly after the Colour module it all went a bit weird. Green blotches all over the image and no colour to the stars. It will be something I’m doing wrong...

feel free to share the data you got on both versions with the forum.  i am not experienced neither. but i am sure some others here can.

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4 hours ago, wxsatuser said:

Depends if you want true colour or something else.

For true colour the first image , emission nebulae are not as bland as the second image.
Emission nebulae should be very bright vivid colours like neon as the emission lines are very narrow.

Colours can vary a bit depending on the exact elements, pink, magenta, blue and teal with brown to orange
as more dust is involved.

How can it be true colour if narrowband is false colour?

Some people make the images very vivid, it's down to taste although it's not my idea of a image,  as my mate says "less is more"

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3 minutes ago, newbie alert said:

How can it be true colour if narrowband is false colour?

Some people make the images very vivid, it's down to taste although it's not my idea of a image,  as my mate says "less is more"

I'm under the impression the first image is straight from a colour camera, no filters apart from a cut filter.
So it's not false colour or should'nt be.

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Narrowband from a mono camera can be false colour if the channels are mapped differently to the wavelength that each filter captures in, Hubble palette for instance. Both images above are true colour, full spectrum for the first and narrowband for the second. Taken with a colour camera the narrow bands are mapped straight to the colour channels that the camera’s matrix captured them albeit “narrowly”. I take the “less is more” point though, these are a bit loud. 😉

Edited by Graham Darke
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