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Narrowband

Multi-colour Narrowband in LodestarLive


Dom543

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As clear skies returned, I continued my experimentation with color narrowband near-real-live observing. I bought an 8.5nm Oiii filter to complement my 7nm Ha and set my eyes on synthesizing multi-colour images using LodestarLive's excellent sum-stacking feature.

The procedure is simple: We start with a monochrome narrowband image, then change filters and stack on top more frames with the different color filter. Some experimenting is needed to find the right balance.

Here are my initial results with Thor's Helmet NGC2359.

We start with a stack of three 60sec Oiii images.

post-26379-0-47268200-1426625777.jpg

Then we add one 60sec Ha frame.

post-26379-0-14233300-1426625859.jpg

Emboldened, we add another 60sec Ha frame.

post-26379-0-93451700-1426625944.jpg

This is about enough. With more than two frames Ha would overwhelm the more subtle Oiii.

But to see the whole picture of what components were involved, here is a two frame stack of pure Ha.

This is essentially what was added to the initial pure Oiii image to produce the third image.

post-26379-0-93221400-1426626251.jpg

This is about it for the first nights of experiments. Votes are welcome on which mix you prefer and also suggestions for improvements.

Please note that the composite colour changes as we add the pure red of Ha to the blue-green of Oiii. Those astrophotos, which show part of the helmet in pure teal and others in bright red are fakes engineered in photoshop. As the first and last pure single-band images show, the areas radiating in the different bands heavily overlap.

I would like to thank to Paul for making LodestarLive and for also helping me with sorting out some issues with stacking. I can elaborate about the more subtle tricks involved later, after I develop more experience. I would also like to thank to Don Rudny (a.k.a. HiloDon) for suggesting Thor's Helmet as an interesting target and for explaining me the sum-stacking technique that he developed. (Mean-stacking doesn't seem to work well in this multi-colour synthesis context.)

Feedback and suggestions for improvements or for other promising multi-colour targets are welcome.

Clear Skies!

--Dom

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Excellent pioneering work Dom! I like both: the 1xHa just shaves it perhaps. I guess its the ratio that matters, so collecting more O-III might allow for more Ha to be added. The O-III is really bringing out the striations which the Ha lacks. What does this look like with no filters?

Presumably you're also getting the benefits of stacking (noise reduction) at the same time? Looking forward to hearing more details at some point.

Martin

BTW In this colour scheme it no longer looks like Thor's Helmet and more like a snail….

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Excellent, Dom. I agree with Martin. I like both. I also think that going more on the OIII might allow more Ha and might smooth the image more. As you found, five stacks appear to be the ideal noise reduction number and you need at least three. Perhaps you could do six in OIII and three in Ha.

I was wondering how you changed the filter without moving your position. Do you have a filter wheel?

Don

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Thank you Martin and Don!

I like the "helmet morphing into snail" interpretation. A new, nature centric version of the "forging swords into plowshares".

I do have a TS filter drawer that is now integrated into all my setups. I planned to post some pictures but the photos turned out ill focused. I'll have to make new ones.

I tried to include more Oiii but my problem is that there is no more space left to adjust the brightness downward. If I sum more than a total of 5 minutes of NB exposures then the resulting image has large regions blown out even at the most leftward possible position of the brightness slider. I am only a beginner at sum-stacking, having always used mean-stacking before. I should take a second lesson on your sum-stacking-and-adjusting method Don...

Cheers!

--Dom

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Great stuff Dom - very clever idea and the result is a great observation of Thor's Helmet.

One of things I want to do it the future is to build in support for mapping filters into the R, G and B channels such that you can observe in different bands (this is something pro's do so why not for EAA), be it colour filters (to bring colour to mono cameras) or narrowband. Although I have not yet given it much thought, I'd like to keep the user interface easy. Any ideas always welcome!

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Thank you Paul for your help and all the good work you put into LodestarLive.

Playing with colors is fun. Mapping filters to channels is a great idea. It would also allow mono camera owners enjoy the fun of comors. And we could also have Hubble-like palettes. I have not invested in H-beta or Sii filters because in natural colors thay wouldn't add much to Oiii and H-alpha. H-beta is very close to Oii and Sii is just another red. But if one could map Oii to green and H-beta to blue, that would change the game.

I will provide more feedback as I gain more experience with the method. One thing is certain changing filters in a filter drawer is easy and feasible to do real time. The TS filter drawer that I use is under $100 and comes with a spare drawer.

Right now I am working towards a March 31 deadline for my job. Will post more images as soon as I get to it.

Cheers!

--Dom

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Here is a subtly colored sequence of images of the Rosette nebula with increasingly more and more Ha allowed to blend in.

We start with a 3x30sec pure Oiii image.

post-26379-0-05214400-1427519379.jpg

Then we add one 30sec H-alpha filtered frame.

post-26379-0-45365400-1427519479.jpg

We add another 30sec H-alpha frame.

post-26379-0-70203900-1427519553.jpg

To speed up things a bit, we now add two H-alpha frames.

So this image is 3x30sec Oiii + 4x30sec Ha.

post-26379-0-38174500-1427519656.jpg

In this sequence we always include all Oiii data but allow only the most intense part of the Ha data.

This is to keep Ha on short leash and to prevent it from taking over the entire image.

As more and more frames are added, the image would get brighter and brighter. To keep the members of the sequence comparable, we reduce the overall brightness of each new image to the level of the brightness of the first (3x30sec) image. As I am still inexperienced with this method, in this particular sequence I run out of downward adjustment "elbow room" at this point.

For those of you, who prefer more boldly and brightly colored images, I posted a different sequence on the CloudyNights "Astro Video Image Gallery" thread. My post is #2238 on p.110 of the thread. Hopefully, this link takes you there http://www.cloudynights.com/topic/144516-astro-video-image-gallery/?p=6513617

Rosette is a very large and rather bright nebula. Accordingly, these images were taken with Nikkor 180mm f2.8 photo lens, TS filter drawer, 8.5nm Oiii and 7nm Ha Baader filters and my Lodestar x2c with lodestarLive v.011.

Clear Skies!

--Dom

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More great multi-spectral stuff Dom! I have a Ha filter now but not had a chance to try it (my astro stuff is stored away whilst we are re-decorating our house).

Been thinking about the multi-channel mapping and I have a route forward. I want to get a couple of bits sorted in LL first (the separate repeat video window for outreach and NSN) then I am going to turn my attention to allowing mapping of exposures to colour channels  :grin:

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Thank you Martin and Don!

I like the "helmet morphing into snail" interpretation. A new, nature centric version of the "forging swords into plowshares".

I do have a TS filter drawer that is now integrated into all my setups. I planned to post some pictures but the photos turned out ill focused. I'll have to make new ones.

I tried to include more Oiii but my problem is that there is no more space left to adjust the brightness downward. If I sum more than a total of 5 minutes of NB exposures then the resulting image has large regions blown out even at the most leftward possible position of the brightness slider. I am only a beginner at sum-stacking, having always used mean-stacking before. I should take a second lesson on your sum-stacking-and-adjusting method Don...

Cheers!

--Dom

For those of us (me) still working on setup, could you show the components between the SCT and the Lodestar........thank you so much

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Amistybeu,

Currently I am travelling and away from my astro gear. I posted in a separate thread the setup that I use with photo lenses. For that I had the photos already taken. I use the same setup also with my SCT. The only change is that I replace the very first adapter (the one with the chrome flange on the photos) by a T-threaded 2" nosepiece.

Of course, this setup is more complicated than minimally necessary, due to my desire to be able to change filters quickly.

By the way, I posted my setup with an SCT and a flip mirror last fall here http://www.cloudynights.com/topic/144287-post-a-picture-of-your-assisted-visual-setup/?p=6210387

The flip mirror cannot be combined with the photo lenses as it way exceeds the allowed lens to sensor distance. But the short focal length lenses provide such a wide field that it is not a problem to get the objects on the sensor. So a flip mirror is not needed. If you want to know more about the flip mirror setup, then please go to my profile here on SGL, go to my content and you will find an entre thread there about the flip mirror, including photos.

Please feel free to ask, if I can help with more info.

--Dom

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Amistybeu,

Currently I am travelling and away from my astro gear. I posted in a separate thread the setup that I use with photo lenses. For that I had the photos already taken. I use the same setup also with my SCT. The only change is that I replace the very first adapter (the one with the chrome flange on the photos) by a T-threaded 2" nosepiece.

Of course, this setup is more complicated than minimally necessary, due to my desire to be able to change filters quickly.

By the way, I posted my setup with an SCT and a flip mirror last fall here http://www.cloudynights.com/topic/144287-post-a-picture-of-your-assisted-visual-setup/?p=6210387

The flip mirror cannot be combined with the photo lenses as it way exceeds the allowed lens to sensor distance. But the short focal length lenses provide such a wide field that it is not a problem to get the objects on the sensor. So a flip mirror is not needed. If you want to know more about the flip mirror setup, then please go to my profile here on SGL, go to my content and you will find an entre thread there about the flip mirror, including photos.

Please feel free to ask, if I can help with more info.

--Dom

Thank you Dom,

I am currently looking at using the Lodestar X2 Color on a C8 SCT with 3.3 and 6.3 focal reducers. I currently have a combination of T-Thread spacers that originate from a Meade Variable T-Adapter that = to 80mm, and a Baader 1.25 / T-2 Focusing eyepiece holder to accept the LSX2. Am I on the right track? I know with the f/3.3 that I need 57mm between the CCD chip and the focal reducer, and more distance with the f/6.3.

I also want to add a filter drawer but I am a bit confused on where that would be positioned in the setup, and if it should be for 1.25" or 2" filters.

If I hijacked this post please let me know and I will re post.

post-43574-0-36932800-1427918197_thumb.j

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Amistybleu,

Your setup looks good. You could also use this same setup with the 0.63 reducer. But since the spacing is less than required for the 0.63 reduction, you will get less reduction. Something around 0.8.

In the long run it makes sense to add another longer t-thread spacer. You can always push the camera further in if less distance is needed.

You know that the sensor of the Lodestar is 12.5mm inward from the front flange. If you look at the side of the body of the camera, you will see that is pieced together from a 12.5mm front ring and the rest of the body. Where the two pieces join, that's where the sensor is located.

The easiest and least expensive way to attach filters to the Lodestar to have a 1.25" to C-mount nosepiece screwed on the camera's C-threads and 1.25" filters on the nosepiece. 1.25" filters are substantially cheaper and are plenty large for the Lodestar. I use 2"filters only because I have them. The filter drawer takes both 1.25" and 2" filters. There is a drawer insert for that. But, as said, until you will want to change filters quickly, the best solution is to simply screw them on the nosepiece.

Best,

--Dom

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I do currently have a 47mm T-Thread extension on the way which should give me a lot of flexibility while using the different focal reducers.

thanks for the info regarding the recessed sensor, that will help during setup. 

I am going to mill over the filter information you have given and do a little research..........I am certain I will have more questions when I am done.

Thank you Dom

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Dom,

Does the 1.25 to C mount nose piece screw in to the camera and then accept the filters which would then all slide in to the eyepiece holder? if so, wouldn't removing and replacing the Lodestar for different filters during a stacked exposure potentially cause slightly different f/ ratios over the full exposure? kick me if I am talking nonsense..............lol

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Amistybleu,

You are right. If you want to play this multi-filter game that this thread has in its title, then taking the camera in and out to screw filters on and off is way too much distraction and may kill the fun. In that case a filter drawer, filter slider or filter wheel is the way to go. The filters can go between the reducer and the camera and 1.25" filters are sufficient. If you are interested in that, then we can maybe discuss that on the other thread, where I posted the photos about the equipment. That way everyone interested in the equipment involved can find all the relevant info in one thread.

--Dom

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Thank you Richard. But credit should go to Paul's excellent stacking algorithm. That's what allows to suspend the process to change filters. And then continue and have the new frames' stars placed exactly on the stars of the earlier frames. Without that one would end up with ugly elongated stars and smeared nebulas.

--Dom

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  • 4 weeks later...

To add some jazz to the otherwise color deprived galaxy season I revive this thread and include a sequence of multi-spectral captures of the Carina nebula ranging from the green of pure Oxygen-III to the red of pure Hydrogen-alpha. Made using the uniquely excellent sum-stack capability of LodestarLive.

post-26379-0-31475000-1429938400.jpg

post-26379-0-59420000-1429938437.jpg

post-26379-0-58847600-1429938469.jpg

post-26379-0-61941900-1429938491.jpg

post-26379-0-41493300-1429938538.jpg

post-26379-0-52421900-1429938577.jpg

post-26379-0-34891000-1429938623.jpg

The first image is a 20sec exposure of pure Oiii. The second image is a sum-stack of three 5sec Oiii and one 2.5sec Ha frames. From there on Ha frames are added to the stack in 2.5sec increments. The last image is a 10 sec exposure of pure Ha and is from an earlier night. (When I completed image #6, my equatorial mount hit the tripod and needed to be meridian flipped. By the time I did that, an Asian tour group arrived and turned on the flood lights.)

The careful observer may notice that as red is added, the teal of the oxygen is getting progressively desaturated turning into gray. I believe that the reason is that teal is composed of about equal amounts of blue and green. When the same amount of red is added, we have the full spectrum, i.e. a shade of white. That's what grey is, a not fully saturated shade of white.

Clear Skies (with no flood lights)!

--Dom

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  • 4 weeks later...

Network Nebula in Swedish palette.

post-26379-0-03595800-1432332438.jpg

They use false color palettes all the time in narrowband imaging. This is my attempt to compete with Hubble...

Three 90 sec frames of Oiii and three frames of H-alpha mean stacked together in LodestarLive v.0.11

Here is the same in natural colors.

post-26379-0-31589700-1432332704.jpg

Does anyone know how to erase attachments from older posts? I am running out of file space.

Clear Skies!

--Dom

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Trifid with blue and H-alpha filters mean stacked together in LodestarLive.

post-26379-0-03031700-1432472193.jpg

This is not a purely multi-narrowband image as the blue filter used is a wideband blue.

It is interesting to note that there is also a lot of blue under the red part of the nebula. It just gets overwhelmed by the red emissions. The frames taken with the blue filter showed that the area that ultimately turned red was, actually, brighter in blue than the area that remained blue on the final image. That means there is dust mixed in with the hydrogen and it reflects the light of the brighter star.

Clear Skies!

--Dom

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