Experiment: M101 in Ha / Near IR 742nm

[Menno555]

Here an experiment of showing the Ha and Near IR (NIR) data of M101 in 1 image.
I was wondering what was in M101 in NIR 742nm and there is nothing really "spectacular". Nevertheless always cool to see that there are stars that only really show in NIR and that that are some (very) weak spots in M101 also. But we all know the colorful captures of M101 where broad- and smallband are blended.
So decided to go off the beaten path and see if I could get an image with only Ha en NIR in it and show it in a way that makes sense.

After some experimenting on how to show it best, the best result was to use the NIR data in the Red channel and use the Ha data in the Green and Blue channel.
So the green/cyan parts are Ha rich and the Red parts are NIR. Really bright red means that it's only showing in NIR and not in Ha. The stars that are white are around equal in both Ha and NIR. The soft red/orange in the center is weak NIR.
It's far from perfect yet it shows M101 in a rather an interesting (and semi scientifically) way
For those interested, a bit bigger version can be seen here: https://i.ibb.co/f183g7y/M101-Ha-NIR.jpg





Bortle 6/7
Meade LX200 8" f/10 ACF OTA
Ioptron CEM25EC mount (no guiding)
Optolong L-eXtreme filter
Astronomik ProPlanet IR-Pass 742nm filter
Zwo ASI071MC Pro camera

Captured with SharpCap Pro @ -10 Celsius / White balance R50 B50
Optolong L-eXtreme: 30 x 600sec / Gain 200 / Offset 10
Astronomik ProPlanet IR-Pass 742nm: 22 x 300sec / Gain 200 / Offset 10
Per set: 20 x darks, 50 x flats and 50 x darkflats

Separately stacked with DeepSkyStacker

Processed with Siril and Photoshop
Siril: each set Background Extraction and Histogram
Photoshop: placed NIR data in Red channel, Ha in Green and Blue channel, Levels, Camera Raw Filter (brightness, blacks, white balance, shadows, color saturation, clarity, noise reduction)

[oopfan]

Hi Menno,

Imaging in IR is a very effective technique for piercing through interstellar dusty dirt and grime. This technique is used to measure the scale and structure of the Milky Way's dusty core by measuring the period and magnitude of Cepheid variable stars. In green light (a Johnson "V" filter) the stars look fainter than they really are. However if you also use an IR filter, you can make corrections to the distance formula to increase its accuracy.

Last year I employed a photometric database of stars in the Milky Way. I chose only those that are in the galactic plane. I generated a 2D plot of longitude vs distance. I could definitely see the nearby arms of our galaxy, but the distant arms were unrecognizable due to the incorrect distance measurement.

I purchased a photometric IR filter from Baader to see if I could do my own plot using the corrected distance formula but my meager 71mm aperture and CCD were not up to the task. The sensor's QE precipitously drops off beyond 700nm. The integration times turned out to be crazy long

When the Hubble Space Telescope was first brought into service, one of its missions was to perform a multi-band survey of stars in the galactic plane. From that data, astronomers were able to derive corrections to the distance formula. Henrietta Swan Leavitt is credited with the discovery of the original formula. Interestingly, Leavitt worked closely with Edwin Hubble.

https://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt

Brian

[Menno555]

Hi Brian

I only wish we could capture in Deep IR No piercing dirt and grime for us.
For now this is just a cool way to see what is possible.

Wasn't Leavitt the woman who at first couldn't get her work to be taken seriously because she was a female, so she gave it to a male colleague and then it was accepted?

Menno

[oopfan]

Menno,

It's possible. I'll have to research it. However, snobbish behavior among elites is usually directed towards people who have no formal training or credentials. Leavitt graduated from a top college (for women) and had already built up creds as a "human computer". Still, I'll look into it. Perhaps Hubble saw her potential and brought her into his group despite the objections of his peers. We'll have to see.

Brian

[oopfan]

Hi Menno,

A cursory Internet search uncovered the name of astronomer Margaret Burbidge. She was born around the time that Leavitt made her discovery of the period-luminosity relationship in the 1920s together with Edwin Hubble. A Sky & Telescope article says that Burbidge was denied access in 1945 to the Mt. Wilson Observatory due to her gender. Edwin Hubble joined the staff at Mt. Wilson in 1919. Knowing how pivotal Leavitt was to his success, I find it hard to believe that he was responsible for denying Burbidge due to her gender. More likely what happened was her affiliation with Fred Hoyle, the father of the Steady State Theory. In a story that I'll link to in Sky & Telescope, someone at the Observatory was heard to have said:

"You can’t give telescope time for this junk science! Who does she think she is?” blustered a young upstart upon hearing that an elderly astronomer wanted half a night with one of the brand-new Keck telescopes to observe objects that might disprove the Big Bang theory."

To me it looks like professional bias against Burbidge's line of inquiry. Now whether or not that made it to the ears of Edwin Hubble, we will never know. (At least I could not find such a claim in the article.)

Here is the link to that article:
https://skyandtelescope.org/astronomy-n ... -burbidge/

Depending on where we get our news, the gender-denial angle is pushed for political points:
https://www.sandiegouniontribune.com/ne ... ies-at-100

EDIT: Thanks to Tim's sharp eye, I misspelled Margaret Burbidge's name. Now corrected.

Brian

[timh]

I like the picture that you have made from the data Menno - a logical colour scheme. It is good to be thinking of what deepsky stuff is possible with near IR - it seems like there should be something interesting for amateurs to do with that waveband.

Thanks for researching the background to the Burbidge story Brian and straightening it out somewhat (as you will notice as I have also just done with the spelling ) -- your reasoning rings true and I'd bet that you are right but I guess that we will never know

Tim

[oopfan]

Tim,

Thanks for pointing out the misspelling. I can't tell you how many times I proofread my post before submitting, but that slipped through.

Brian

[RMSQueenMary]

Nice image of M101.

I have done some near infrared myself with the ASI294mc Pro. I use #29 red filter, Lumicon Night Sky H-Alpha filter, and 850 nm filter.

I have gone deep with them as faint as over magnitude 20.

[Menno555]

Thanks, Tim, Brian and Queen Mary

Brian, so sorry I misspell your name so often. Somehow my Dutch brian ... ehr ... brain has difficulties with the ai and ia combination

And yes, capturing in NIR can have surprising results. Like in M82 where in the central bar, there is a point NIR source (I presume a star) that doesn't show up in neither Ha smallband nor broadband.

Menno

[oopfan]

Menno,

No worries, it happens a lot. I have had credit cards issued to me as "Brain" . I just refuse to pay the bill (not)

Brian