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M81 82 and Integrated flux, work in progress

MartinB

By MartinB
in Imaging - Deep Sky

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MartinB

MartinB

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This is an Olly Penrice MartinB collaboration from Olly's dark sky site in south eastern France.

One thing I wanted to do when going out to Les Granges was to go deep in the area around M81 and 82 to see if I could capture the integrated flux. Olly had also had this in mind.

The integrated flux is interstellar dust within the Milky Way. It has nothing to do with M81 and 82. We normally see dust either as dark nebulosity when it is silouetted against a bright background e.g. the horse head, or as reflection nebulosity when it is illuminated by a very bright star e.g. the Iris nebula. The integrated flux is illuminated solely by the star light of the Milky Way itself and is therefore incredibly faint. If someone from M81 has their telescope pointed this way they will see it as a dust lane and will probably be using a high pass filter to tweak out a bit of extra detail as I write!

My data was captured over 2 nights. M81 and 82 were directly over the nearby hamlet and quite low down compared with the UK. Despite this there didn't appear to be significant LP being thrown up so I used a plain IR filter. The second night I used a CLS filter and used this to control the tiny amount of gradient in the non LP filtered data.

So luminence info - Scope Tak FSQ 106 with 0.73 reducer giving around F3.7 Camera QSI 532

Subs - around 9 hours mostly of 5 mins

Olly ran his Atik 4000 OSC with his FSQ 85 for 2 nights getting a similar amount of time using 10min exposures. This was used for the colour.

Olly also used his TEC140 to get higher resolution data on M81 and M82 to blend in. I've not yet used this data.

So far this has been a challenging processing job. The flux needs a very fierce stretch which destroys the brighter data including the stars. The vertical star spikes are due to microlensing artefacts on the chip, a feature of the KAF 3200. More work to do on tidying up the background and controlling noise but it stands up ok at this forum resolution.

I hope to get Olly's high res data processed and blend that into a completely new process. I also have some decent Ha but I haven't been able to successfully integrate this so far. This is all going to take a long time!

I have to admit, when I did the first stretch of the combined data and saw the amount of flux there I was jumping up and down. I tried to explain to Jackie but I just got a pitiful look.

post-12794-133877435546_thumb.jpg

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barkis

barkis

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As good as this Image is,

I hope you guys can devise a process to combine the stars/ galaxies and flux. It would produce an incredible result, and surprise a great number of people, who I'm sure are still unaware that this stuff is there.

Ron.:)

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Whippy

Whippy

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Good work! I've seen a few images of the IFN around that area from guys with serious setups in the states and this is well up there with them so congrats to you both, I'll be looking forward to the 'final' edit when everything's been thrown in the mix.

Tony..

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MikeD

MikeD

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Stunning result Martin/Olly, the amount of flux you have is fantastic.

I have been working on an M81-2 background shot with my 80Ed to bring together my hi-res M82 and M82 images, so far I have 4 hours L (with no lp filter) and have not got even hint of the flux so I can appreciate what you have there.:)

Congrats

Mike.

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ollypenrice

ollypenrice

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Staggering amount of Integrated Flux, Martin. I remember being thouroughly Eureka-ed out when you showed me the rough stretch. However, I fear I have let the side down on the colour because I am pretty sure the One Shot camera was and is acting the goat. Its last two images have been bizarre. I am away at the moment but will get testing when I get back. Of course it might be software but I really think it is something else. In any event I WILL get you some decent colour for this, by hook or by crook!

Olly

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FraserClarke

FraserClarke

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Very cool indeed :)

I've taken the liberty of generating an IRAS 100-micron map (attached) and trying to match it to the same field as your image. These long wavelengths (visible light is ~0.5 microns wavelength) are sensitive to the cool (~-250C) dust. You can see some similar structures in the IRAS data (much much lower resolution) as in your data. Compare, for example, the 'loop' just above M81. Definitely seeing the cool (literally) interstellar dust :mad:

The three bright objects in the IRAS image are the three galaxies in the image -- you don't see stars at these wavelengths. I suspect the diagonal streaking in the IRAS image is an artifact of the way the image was taken (strip scans of the sky).

BTW -- the IRAS data show a huge dust cloud just off the top of this image. Might be interesting to try this again and point a degree or so further north...

post-18754-133877435917_thumb.jpg

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MartinB

MartinB

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Thanks a lot guys. Thanks a lot for the IRAS info TeaDwarf. Wider field shots show that the area Olly and I have captured doesn't have the highest density of flux but that there are greater concentrations over to the right of the image as orientated here.

I'm working on how to control the stars better and have just acquired Neat Image which will hopefully help to control noise. Just working on the high definition subs that Olly captured with the TEC

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Tim

Tim

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Excellent Martin. The IF is without question the hardest thing I have tried to capture on camera (spent over 20 hours trying :mad: ) so what you have caught there is amazing. It'll be the devils own job to get the best from the data, lots of layers coming up methinks :) Very worthwhile though.

Out of curiosity, what stacking method have you used? I wonder whether something like the flux would be the ideal use of the MAX type of stacking so that every pixel of data is found and used, and then could be redone with sigma stacking as normal for the galaxies and stars.

Again, great result, really looking forwards to seeing the final composition of this one.

Tim

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MartinB

MartinB

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I used a sigma clip Tim. I guess the terms may not be the same on different platforms but I understood Max/min to be where the highest and lowest pixel values were discarded. I've not seen Max on it's own, what is is supposed to do?

I've done lots of layering but am looking at doing the star reduction in stages in an attempt to iron out background artefacts. Other images I've seen have been wider field and capture the brighter flux further away from the galaxies, The flux in the areas we've captured has then not been given as much of a stretch. The stars are always going to be bloated and, given the big stretch for the background the galaxies are always going to be short of dynamic range real estate so lack the usual contrast. Anything else just looks like an odd decoupage. I may try being a bit less aggressive and leaving the flux a bit less "in your face". I've downloaded Neat Image which I think will help things as well.

Give me a couple of days!

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Tim

Tim

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I'm not sure if Maxim does it, but DSS has a stacking method called MAX, which as I understand it, take the maximum recorded pixel values and adds them to the final image. Of course you get all the noise and hot pixels, but for really faint things it is useful for checking what is there that has been rejected by sigma clip etc. It was useful for finding the extent of the very faint outer ha regions of m57 for instance.

I know what you mean about making the composition look odd, even that fabulous well known widefield of the area has M82 and M81 not looking "normal" :)

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