Ursa Major Triplet reprocess

[wimvb]

Data gathered in April this year, processed a little more lighthanded. The many faint galaxies don't stand out as much as in the original image, but they're still there, and colour is better.

Luminance and RGB where processed separately, making sure to end up with the same median pixel intensity in both images, before combining with L*a*b channel combination.

There are a number of interesting things to image in this part of the sky:

NGC 3619 has a weak shell structure that I commented on in an earlier thread.

https://www.astrobin.com/342011/B/?nc=all

NGC 3625 has several low surface brightness (LSB) dwarf galaxies, that have been studied  with "small" amateur telescopes. One of these is just barely visible in the inverted, superstretched luminance image (with some imagination). You don't need ALMA or a Subaru telescope to contribute in astronomy.

[Adreneline]

Very nice Wim.

May I ask what does the L*a*b channel contribute to the image?

Adrian

[wimvb]

6 hours ago, Adreneline said:

May I ask what does the L*a*b channel contribute to the image?

L*a*b is just a colour space, where L is lightness, comparable to luminance. In rgb colour space, all three channels contain lightness. In L*a*b, the a and b channels contain only colour information, while L contains only intensity, detail and contrast information. I processed the RGB image to optimise colour, and L to optimise detail and contrast. Usual LRGB processing can result in washed out colours if L is too bright. Thinking in terms of colour (a and b) and lightness is just a way to force yourself to concentrate on what's important in the two images.

[lux eterna]

I agree, the galaxies look even better now. But I think the star colors look more natural (and less chromatic aberration) in the original picture. Overall a very nice image.

Ragnar

[wimvb]

28 minutes ago, lux eterna said:

less chromatic aberration

I agree. The star colour is better, but there seems to be chromatic aberration. This is strange, as I used a reflector to gather the data, and only one subframe was used as reference during star alignment. I collect rgb by alternating the three filters, so differences in guiding accuracy are unlikely to be the cause.