The entire Milkyway, how do you...

Started 8 months ago | Discussions
ChrisBeere
ChrisBeere Regular Member • Posts: 231
Re: The entire Milkyway, how do you...
1

The problem is simply one of projecting a curved surface - the celestial sphere - onto a rectilinear one.

It requires translating/rotating/distorting the elements of the mosaic to enable them to be stitched together.

There are various types of projection. Examples include cylindrical, spherical, planar, mirror ball, fisheye, mercator, hammer.

The larger the area you attempt to mosaic the more translation/rotation/distortion the projection needs to apply to enable the panels to be aligned.

Any slight variations in background brightness and star size between panels cause noticeable aberrations at the seams. This is why you need to calibrate the panels before you stitch them to mitigate this.

To compund this you are dealing with all sorts of sky glow gradients that need to be neutralised as well.

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elgol20
OP elgol20 Contributing Member • Posts: 820
Re: The entire Milkyway, stopover

ChrisBeere wrote:

Yeah it's exploded over there and they have gone into lock down/curfew.

I'm hoping it will peak and settle down before Xmas but its impossible to predict.

To compound matters I fly via Joburg and although SA is on the downward curve and have relaxed the national threat level to 2 they don't look like allowing foreign nationals to transit any time soon.

If this is the case then i would fly to Frankfurt and then direct to Windhoek.

The downside is my BA flight voucher from the cancelled May trip would be of little use in this scenario.

So, yeah, complicated.

I am still waiting if to book a flight. Not sure if these comanies will survive, maybe in a coulple of weeks give it a try, since I am part of the team next year

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Best regards
_____
Stefan

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elgol20
OP elgol20 Contributing Member • Posts: 820
Re: The entire Milkyway, how do you...

AstroLauro wrote:

Hi

sorry to barge in and ask point blank but: where could I learn about the challenges involved in making Milky Way mosaic/panorama? I don’t understand quite at all what you’re talking about (calibrating panels??) despite having googled and read info about Milky Way panoramas, they all make it seem easier than what appears to be the actual problem in this thread ? Thanks for any pointers!

where to learn? The problem with what can be found in the net is that it omits the most crucial learning steps inbetween, all these failures and rise-agains - and... most important, there is no real ideal way. What you might do is get some good book on AP and read, maybe Charles Bracken's "deep sky imaging primer". Since many things are quite technical one might need the fitting language that is understandable. But if you only do landscapes with some milkyway all in all might be too much anyway.

What I do is stack each panel, that is a single frame, one unchanged skyview, with all calibration frames (at least flats and bias masters), reduce light pollution and calibrate the colors. With this you get rid of a huge part of sezzion differences. These panels you stitch to mosaics using a suitable projection, preferrably euqirectangular. Maybe look at some pano stitching tutorials for real life. softwares like PTGUI might need some help identifying the stars, socalled control points. Astrosoftwares of pros here. Then you end up with a "raw" mosiac and the real fun part starts ...

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