Multi-colour Narrowband in LodestarLive

[Dom543]

Thank you for the positive comments and likes.

I checked the Trifid yesterday night again. The blue under the red part has quite a bit of Oxygen III and H-beta in it. But also has additional blue unexplained by the narrowband components. I assume that it is reflection on dust. The part that is blue on the final image has no emission components at all.

My OTA will need some collimation adjustments. It was shipped by USPS twice and I am hauling it in my car twice a week to a dark site.

By the way, here is a trick of the trade for the multi filter stacking method that I have been playing with. When using mean stacking for objects, where the different colors don't overlap, one has to shoot for the double of the final brightness for each individual component. On the example of the Trifid, the result of the initial two blue frames was twice as bright as the blue area on the final image. This is logical, as mean stacking does averaging. And the red frames contributed just black background to the blue area. Mean of blue and nothing is half as intense blue. I could see in real time the blue get suddenly dimmer and dimmer, when the two red frames came in.

This also applies to the Network nebula, where H-alpha and Oiii do not overlap. On the other hand, it doesn't apply to the Rosette, Carina or Lagoon, where the three narrowband emissions spatially overlap. The red part of the Trifid ends up brighter than the blue part as it is the average of a bright blue and a bright red.

Clear Skies!

--Dom

[Dom543]

I am reviving this thread with some multi-spectral Lodestar captures of the North America Nebula from last night.

North America turns out to be quite a colorful land! This is how it pops up without any adjustments.

The image is the result of 4x60sec O-III + 3x60sec H-alpha + 3x60sec S-II frames mean stacked together in LodestarLive v.0.12.

The exposures are way overdone. But I am in Seattle now, where the air always contains a lot of moisture that reduces transparency. The night before I struggled with this and got rather muted results. This time I wanted to start out better. The final image also includes three S-II frames. But they contribute very little as there doesn't seem to be much sulphur signal in this particular nebula.

The nebula is in the Milky Way, so there are many small stars everywhere. It's the O-III filter that lets them through. H-alpha and S-II filters block most starlight. I, actually, am in peace with those small stars. They make the image more real and don't obscure the nebula too much. The second image with the shorter exposures has a better balance of the stars.

I also include a later capture, that looks more like coming from a geography atlas.

This is 3x30sec O-III + 3x30sec H-alpha frames mean stacked together.

As you can see, I learned from the previous image, reduced the exposures and dropped S-II altogether.

I shifted the hue slider to about the -15 position to achieve this different tone.

Unfortunately, I forgot to turn off the red light on our deck after I was done with the setup. It was on all night and, through reflections on the fascia board, it also shone in the lens. The contamination is even worse on the upper left side of the later image as the mount turned more in that direction. I have already spent two nights on NGC7000 and there are other interesting objects waiting out there. So I am not likely to return to this nebula to correct the error.

I was debating whether to post these images on this thread or on the one about the photo lenses. The reason is that this was the first use of the new Samyang 135mm f2.0 ED lens that I got for my birthday from Denise. Based on the first impressions, I am very pleased with this lens. For this kind of multi-spectral work one needs optics that focuses all colors to the same point. Achromats and old photo lenses can't usually do that and require focus adjustments after filter changes. This is not feasible while a live stack is waiting.

Clear Skies!

--Dom

[Paul81]

Hi Dom,

Great stuff, and I hope will only get better / easier when the multispectral stuff is in place for the next release.

Reading your post - one tip is that you can pause the live stack by pressing the pause button on the exposure tab, or if you switch modes (to Focus / Alignment / Framing) it automatically pauses the live stack. That way you can switch modes to FAF to re-focus with the different filter, switch back to image acquisition mode and carry on stacking having slightly shifted the focus for the different filter. Any misalignments due to refocus should hopefully be eaten up by the stacking algorithm....

Paul

[Dom543]

Thank you Paul!

The trick saves a fair amount of money, as AD and APO optics are expensive. Also extends the life of old lenses.

--Dom