August 4, 2013: First H-alpha mosaic

[michael.h.f.wilkinson]

I just made my first mosaic using the DMK21 and LS35THa. A total of 35 panes went into this. I stitched them with autostitch, which I think scaled things down a bit (haven't touched any settings, just tried it out of the box). Quite pleased with this first effort.

[Montana]

Fantastic work! wow 35 panes, well done, I would be lost by 10

Alexandra

[David Smith]

Nice work Michael

[michael.h.f.wilkinson]

Thanks all. 35 panes is a case of slight, but harmless paranoia . I might use fewer later.

I have had another go with other settings in autostitch, and got slightly better results

[michael.h.f.wilkinson]

I forgot to mention I used a 2.5x Powermate, hence the need for more than for more than four panes.

[DrRobin]

Very nice Michael, looking very good to me and congrats on your first mosaic.

Autostitch default settings are not all that good, the scale is set to 10%, up this to 100%, try upping the blending bands from 2 to 4 and the blending sigma from 10 to 15. Tick the brightness adjust and use defaults.

Then on the RANSAC values, try upping the first value from 10 to 15 and the second value from 0.2 to 0.17. Change the iterations from 500 to 750 and finally the output quality from default (0.75) to 0.95.

Sorry doing it from memory but I think all of those changes will give more detail and a smoother image, at least those are the settings I use as default.

Robin

[allcart]

Very comprehensive instructions there Robin. Lets see if michael can do another version for comparison.

Very good first try Michael.

[smerral]

That's worked very well.

[michael.h.f.wilkinson]

Cheers everyone! I tried Robins settings (assuming gain correction was the same as brightness correction and these are the results. My previous settings had upped the jpeg quality to 100% already, which helps a lot. I think the new settings are indeed better. They allowed me to push wavelets a bit more.

[michael.h.f.wilkinson]

I just noted a little bit of a stitch line visible in the latest version. I will play with the settings some more.

[JamesF]

Very impressive. Thirty-five panes is a monster mosaic.

James

[michael.h.f.wilkinson]

Just altered the settings again. 2 bands seems to be better than 3 or 4 (no stitch line visible), gain correction on or off does not make much difference. Here are the results.

No gain correction

With gain correction

[Luke]

Excellent first disc, Michael, well done for taming those tiles

[DrRobin]

Hi Michael,

I was looking on an iPad last night and didn't spot the bands on there, but they are clearly visible on my desktop PC. I agree 2 blending bands does give a better image. Autostitch was written as a demo tool to show the imager stitcher, I don't think it was ever intended to be used in anger. I did try one of the commercial products which uses the Autostitch engine, but I couldn't get any useful results at all.

As Autostitch is not a commercial product the notes on the settings are somewhat lacking and I had to go by trial and error. I started with the defaults, changed output size up to 100% and JPEG Quality to 95%, but left everything else as is. If it didn't stitch then I tried changing the settings.

Eventually, I made a note of the settings I use and just enter these every time, they are as follows:

Defaults apart from

Scale 100%

Rendering - Multi-band

Blending bands 4

Blending sigma 10

Gain compensation - On

RANSAC Parameters

Alpha 15

Beta 0.17

Max iterations 750

Jepg Quality 95

I must admit I haven't seen any horizontal dark bands like in your image, but I have seen a quadrant (around an 1/8th) that lacks detail or is darkish. Perhaps those settings I use suit my scope/camera set up and number of panes and maybe each of us is going to have to work out our own set of settings?

Robin