First Succesfull (ish) Ha Mosaics

[Notty]

I reckoned if you put an infinite number of monkeys in front of the Autostitch settings screen, they'd come up with a combination that joined everything up, and I was right! Tried three different types, a straight montage at prime focus through the PST (mono QHY5L-II), a mono mosaic through a 2x Barlow (with a v.small chunk missing, which I think is because to be fair on AutostitchI actually I might have missed that bit of the radius off), and a straight prime focus with the Colour QHY%L-II.

The Newton bands are much worse through the Barlow and I don't think the increase in detail made the effort worth it really, although it really is a cheap SW Barlow I'm not sure how much better I'd get with a decent one. Seeing them side by side I now totally see how much less is captured through the Colour CCD. THe last 2 were from footage on the 1st Aug, and the first image was shot on 19th Jul when I think the seeing may have been better.

Any tips would be appreciated.

[DrRobin]

Hi,

The first one looks the best, I think that is the one at prime focus? You throw away a third of the resolution with a colour camera as it is only the red pixels that record any useful data, so it doesn't surprise me that it is lacking in detail.

Newton rings are always worse with a Barlow and the other thing with a Barlow is that it reduces the brightness, increases the exposure time and makes focus that much harder, everything working against you. I don't know what exposure you used, I always try for at least 1/100th of a second, faster if I can.

Autostitch is only a demo programme and as such there are very few notes on the settings. Like you I had to sit and go through by trial and error until I found settings that worked for me.

To produce a mosaic, I get the best individual frames I can, stack them and then do a very small amount of sharpening (Sharpen+ in Paint.net, I use radius 1 or 2 and level about 400-450). I crop the image to get rid of the any bright/dark edges and also any stacking artifacts.

After Autostitch has run, I then load the image back into Paint.net and use Sharpen+, High pass and Local contrast tools to sharpen the image, trying not to over do it.

I hope that helps.

Robin

[Notty]

Thanks as ever Robin. Yes the first one was at prime with the mono CCD and is clearly the best. I'm still trying out different things with Paint.net, (along the lines you told me recently) but for the mosaic I've been using the "sharpened" images which pop out of Autostakkert if you tick the "sharpened image" box, as they look quite good.

Regarding the pre-cropping, that's a great idea and I hadn't thought about it, but did wonder when cropping in paint.net, does it resize the image in any way or literally throw away the unwanted pixels so that as far as a mosaic program would be concerned you are still looking at things the same size? I'm guessing that is the case.

when I took the main disk shots for the first image I also upped the exposure and took some lovely proms simultaneously as I moved round the disk. auto stitch is having real problems knitting them together and is coming out with some real weird shapes! Any ideas as to which setting might be the best to control this? I know there's nothing inside the disk but solid light in this case so it's only looking at the edges. Would the ransac sample size be the key to this? I've tried upping it massively but still gives me some weird egg-shaped objects, even when I decides there are any images that match at all.

Thanks again for your feedback Robin, it's very much appreciated.

Andy

[DrRobin]

Hi,

I think you might find that the Sharpened function in Autostakkert over does it a little. Try Sharpen+, radius set to 1 or 2 and amount to around 450. The idea of this sharpening before stitching is to give the stitching program more to go on, but not so much that it makes mistakes.

I find Autostitch is similar to stacking, the output is lightly soft and that is why I do the most mount of sharpening after Autostitch.

I haven't tried stitching proms into th main picture, so don't really know how you would do this. I think you would have to add these manually afterwards as there won't be enough features in each picture to stitch.

Keep trying, it's all practise finding out what works. I never managed to do more than about a third of a disc with my PST and then Alexandra stitched it for me as I didn't know how to do it.

Robin

[Montana]

An excellent first attempt

Alexandra