Extended Halo of the LMC, 170 megapixels.

[gregbradley]

This is an image I took on the weekend to attempt to pick up the extended halo of the LMC.

Its a start. I think a long exposure version will follow at some point soon.

Sony A7r3, Zeiss Batis 85mm F1.8 lens at F2.2 and ISO6400. Tracked on a Vixen Polarie portable tracker (tiny little thing that is surprisingly good).

This is 5 x 30 seconds pixel shift images (a pixel shift image is a feature of the camera where its sensor stabilisation system moves the sensor 1 pixel between each of 4 images so every coloured pixel gets exposed giving deeper colour and higher resolution). This also makes this a 170 megapixel image (4 times 42.4 mp of the sensor).

http://www.pbase.com/image/168479526/large

Greg.

[Andy01]

Very interesting project Greg, don’t think I’ve Really seen that done before - looking forward to seeing the finished results.
Where can we read more about that camera technology?

[RickS]

Would love to see a long exposure, Greg. There's a lot of halo already.

[multiweb]

Cool project. Maybe you can pick up the tidal streams too. :thumbsup:

[PeterSEllis]

Hi Greg,
That is very nice picture, generally people are so intent on getting the core, that they miss the extended Halo. NGC 5128, is another classic halo that is generally missed, because the core looks more interesting.

Cheers
Peter

[strongmanmike]

Pretty darn cool Greg :thumbsup:

Mike

[gregbradley]

Hi Andy,

Its here:

https://support.d-imaging.sony.co.jp/support/ilc/psms/en/index.html

Its useful for static subjects. If there is any movement then it causes problems. There is software though that can deal with some movement.

The advantages are lower noise, higher resolution and deeper colours.

Its not a replacement for long enough exposures but it does add a bit to images at times. I quite like it for nightscapes as 1 click takes 4 images at 30 seconds. I have software the scans the resulting files, identifies the pixel shift images from those that aren't and combines them into a single DNG file. Pretty handy.


Greg.

[gregbradley]

Thanks Marc. I am not sure how best to do the next long exposure. Either with my FLI camera and a lens or the Sony on top of the CDK17 (I have mounting gear already sitting on top of the CDK) and use an intervalometer. The CCD may be higher sensitivity I think although the Sony is backside illuminated CMOS full frame with a QE of about 60% so its no slouch. Pixel shift is the closest thing to filtered imaging with a digital camera. Pentax has it so does Olympus.



Thanks Peter. Yes its been on my to do list for a while since an image of it was posted on this forum a while ago.



Cheers Mike. The theme for the last 4 nights of imaging was LMC!
Got some more LMC nebs from the CDK.


Greg.

[Peter Ward]

Very Interesting :thumbsup:

...but I am not sure whether I am looking at an instrument artifact of a real part of the Magellanic Bridge that joins the LMC and SMC (the AAO survey has it looking more mottled)

How was the image flat-fielded?

[gregbradley]

No flats its just a lens image on a mirrorless. Lens corrections were turned off.

I do have another version that is more heavily pushed and the circular halo is more structured and mottled and so that made me feel it is correct and not an artefact.

Having said that I do intend to do a much longer image with my FLI camera and a lens and see what comes up. That'll be over the Christmas break.

Greg.

[alpal]

Hi Greg,
nice try but I'm not sure you picked it up.
Your image looks like a flat frame
which of course is darker at the edges.
Here is a similar image & it looks different:
http://spaceweathergallery.com/indiv_upload.php?upload_id=141917


cheers
Allan

[multiweb]

ahhhh.... no flats. It didn't happen then. :P

[Atmos]

I've photographed this area a few times looking for dust. The attached image is specifically for photographing dust with 53x120s with a QHY163M, Lum filter and a Sigma Art 85mm F/1.4 @ F/2.8. It's hit the edge of the LMC and I have another couple of panels that I have on another HD to show how some of the dust varies around the LMC.

[Peter Ward]

Well, while I don't want to rain on Greg's parade, very low surface brightness features *need* to be calibrated, as all optical systems vignette, including albeit very fine , Zeiss lenses.

I could take a similar image using the best L-Series glass available
and it would still have a centre of field hot-spot. Flats are essential.

[gregbradley]

Fair enough. The possibility is that there is a hot spot although I have not seen one in other images. As I said its a start and I intend to do a full long exposure image with full callibration.

Greg.

[silv]

Hi Greg,
love the blue tone in it. And I'm very into the cirrus thingy since I read Dana's article she posted sometime this year. Perfect for small lenses and heaps of short exposures.Looking forward to how you progress your project very much.

I first looked at your picture from an angle at my MacbookPro and noticed weird patterns in the star field. Then I changed my viewing position and it was gone. Dirt on the screen? Something in my eyes? Clicked on your big version and saw the same in the same areas of the picture again. And then it vanished.
Stripes. Or an areal of a city from very high up, streets and housing blocks. And stripes again like loosely woven fabric, slightly irregular but a pattern that stands out.
I'll attach screenshots of some. The patterned stars are mostly visible in the upper half of the image.
The very small screenshot is not straight line but a curved line of stars which appears to be doubled up.

Like I said: it's there... and then it isn't. Only to appear again after having scanned a different part of the image and coming back to a particular area.

Does someone else notice that pattern?

[gregbradley]

I just had a look at it again. I don't see that. What happens sometimes with high resolution large file images is it takes a while for it to display the full resolution image. It starts off with a lower resolution image and then if you wait a few seconds the higher resolution shows. Perhaps that is it?
I used Sequator to align and stack the images so unless its a little off in its aligning? As I say it looks OK on my monitor.

I could use PixInsight to align the images, that does quite a good job.

I have another longer exposure set and when boosted as well I see the same halo and also it picked up the tidal stream from the Small Magellanic Cloud.

I am going to take some flats tonight and reprocess this and finish the processing on the other stack.

Greg.

[Stefan Buda]

Greg,

I think my image from a few years back is reliable enough to be used as a reference for figuring out what is real and what is just due to wignetting: http://www.iceinspace.com.au/forum/showthread.php?t=146721&page=2

[strongmanmike]

No doubt you have captured some of the outer LMC halo features and even the vertical stream, very faintly, Greg but they have been adulterated by the lack of calibration and exposure.

Mike

[alocky]

Hi Greg, it’s a nice high resolution picture indeed, although as others have said flats will help bring out the asymmetrical shell around the lmc. You have definitely captured it, but because of the uncorrected vignetting I’m sure you’re seeing a combination of the halo and the illumination drop off. Here’s a similarly deep image that has been calibrated and is inverted to show off the cirrus. Taken in remote WA with no light pollution whatsoever, and you can see the halo isn’t circular.

https://www.astrobin.com/309256/

Cheers,
Andrew.

[gregbradley]

Yes I remember that image - its a stunner. I have another set of wider images taken with a Sigma 35mm F1.4 Art and its showing this when I push the ridiculous hell out of it. Its 30 minutes exposure at F1.4.
Yes I get the vignetting is causing an issue. Complicating it is the fact that the recent V2.0 firmware update seems to have caused a vignetting issue with one lens at least. Later in the weekend I turned off all lens corrections in camera as I didn't trust it.

It really wasn't a serious attempt, more a survey of what framing, how much exposure, what focal length would be best.

The 35mm for a full frame camera seems about perfect.



Yes I'll take some flats for sure next time but I probably will use the FLI camera rather than my Sony to go really deep. It'll be easier.



Thanks Andrew,

Yes I agree. I had processing version of this and it looks like yours but the processing was too harsh so I didn't publish it. This version was "soft" in comparison!!

I am planning to do a full on attempt now I have done the preliminary surveying.

Greg.

[silv]

Hi Greg,
I had a look during daylight at the "large" version. No pattern. Now it's dark and the "loosely woven fabric" is back, again, depending on the angle and some form of averted viewing.
But since no one else sees it it can't rally exist, can it. In any case, you wrote you'll be using a different camera for the real LMC halo project.

Galaxy halos play a role in a new article about dark energy and matter. Qyite astounding. Here's the article in 17 tweets by the author https://twitter.com/Astro_Jamie/status/1070302359325151233

the real thing: https://arxiv.org/pdf/1712.07962.pdf

And Oxford's proud press release: https://www.eurekalert.org/pub_releases/2018-12/uoo-bbt120318.php

Intriguing. Hope you'll get heaps of fine weather to work on your project. :)