Sagittarius Mosaic from SPSP 2013

[multiweb]

Completed stitching all the panels I shot at the star party.
The thumbnail posted is only a crop of the area. I just can't fit it all in 200KB.
The 80% res of the full uncropped field is here (http://www.astropic.net/astro/sag_600mm_fff.jpg)[21.2MB - 5622x4931px]
I also made a smaller for download here (http://www.astropic.net/astro/sag_600mm_ff.jpg)[10MB - 3514x3082px]
and an even smaller version here (http://www.astropic.net/astro/sag_600mm_f.jpg)[3.16MB - 1757x1541px]

Sorry the files are huge but it's a massive area with a pretty good image scale. Thanks for looking. :thumbsup:

[Larryp]

Marc, all I can say is WOW :thumbsup:

[Rod771]

That is really nice!

Very well done Marc , great result :thumbsup:

[multiweb]

Thanks guys. :thumbsup: I hope you've managed to look at the big one. The stars and colours are a lot better in the big one. Smaller versions suffered clipping and contrast issues by reducing the file size. I think PS doesn't keep the original histogram when reducing. Maybe I should bin the FIT files to present smaller areas or save to TIFF 16bit and bin in CCD Stack preserving the flux. Will play around with it. Not happy with the luminosity and colours the reduced files came up with. Stars look clipped without colors and the black point shot up. :shrug:

[RobF]

Very impressive Marc. Subtle processing too - you haven't gone overboard. The skill in knitting this together and presenting so well is not easily appreciated.

[multiweb]

Thanks Rob. :thumbsup: Stitching is one thing I'm used to now. It's second nature. But it's the first time I've had this issue with presenting a very large area at a smaller scale. I've just done a bin 3x3 test in 16bit environment and it's chalk and cheese with the smaller files I posted, so due for a repro.

[multiweb]

Well the proof is in the pudding. I think this will be of interest to people resampling their work at lower res for fast web display.

First thumbnail is reduced 50% from the orginal by doing a resize in Photoshop. TIFF 16bit. You clearly see that the stars become white clipped and the plack point is raised as a result of the increased contrast. Not what you want.

Second thumbnail is the same shot but this time I did a bin2x2 in CCD Stack then did some pixel math and divided the file by 4. The histogram is not clipped and the stars retained their color. (maybe not obvious in the compressed JPEG but obvious in the original)

So repeating the resizing only compounds the issue which I usually do so every smaller picture gets clipped again and again and gets worse.

I'll go through the various versions and update the previous pics in the post. :thumbsup:

[naskies]

Great mosaic, Marc!

As for your clipping, normal bicubic resizing shouldn't clip your whites if they weren't already clipped to begin with. Unsharp masking, however, will clip them - especially if your images were already high contrast to begin with. If you use the "Bicubic - best for reduction" mode, it behaves as if it applies USM to the result - which might explain your clipped whites? Are you applying any levels/curves/USM to your resized version?

[multiweb]

Thanks Dave. :thumbsup: The clipping occurs in PS when resizing down. Even if the pic you're resizing doesn't have any clipping to start with. Once it's clipped you cannot recover the clipped data via curves or level.

[bradley]

awesome

[naskies]

Yep, what I'm getting at is that this clipping shouldn't normally be happening to such a noticeable extent - since it's clearly modifying the content of the images, not just resizing it.

I've attached histograms before vs after resizing using the various modes in Photoshop CS5. You can see that only "Bicubic sharper" results in the clipping spike that you're talking about. You'll get similar results with "Bicubic best for smooth gradients" mode followed by unsharp masking.

[multiweb]

Actually now you've mentioned it I did this in CS6. I'll try doing the same in CS5 and check the results.
PS: You're right. CS5 doesn't do it. CS6 does. I'll have to google that up see what's causing it.

[multiweb]

Thanks Bradley. :thumbsup:

[astronobob]

Maizing Stuff Marc, I cant get over how you do such a veriety of stuff, and putting panels together as this ! Very inspiring for some but over this ducks head mate,
champion stuff & :cool:

[multiweb]

Thanks Bob. :thumbsup: It's actually very easy to stitch stuff. Not much skills involved. You can use registar to align the panels then use PS to blend them in. It's pretty much all automated. Just little touch ups there and there. The trick is to get the right color balance in the different panels as close as possible before joining them. But you do that by the numbers too so no guess work. Just practice.

[multiweb]

Figured out what it is after posting on the adobe forum.
In CS6 the bottom drop down defaults to bicubic (automatic) in the image resize window. I never noticed it before TBH. Changing it to Bicubic (best for smooth gradients) sorted out the issue although it defaults back to its original automatic settings. No clipping now. In CS5 it defaults to Bicubic (best for smooth gradients) which is why it worked in one but not the other.

[naskies]

I'm glad you sorted it out :thumbsup:

[Octane]

That is truly beautiful, Marc.

I love, love, love the subtle processing on this. You could have gone overboard and pushed the saturation to +9000, but, you didn't.

One of your best images to date!

H

[White Rabbit]

Yeah, I had a rummage around your sky drive images and it seems to be a characteristic of your work. Your processing is very subtle, and it works.

I couldn't even begin to think about how to achieve what you've done here.
Truly beautiful.

Really bummed I never got the star party this year. Did you ever put together the time lapse images that you took last year? I'd love to see them. And did you ever get a pair of those bino's from bintel?

Cheers
Sandy

[bloodhound31]

Lovely, subtle and fascinating image Marc. This is one you can fall into if you're not careful.

Wonderful work.

Baz.

[multiweb]

Here's another response from the Adobe forum that explains the issue.

[multiweb]

Thanks H. :thumbsup: When the data is good enough and you have star colors very little processing is involved. Dark skies help a lot.


Thanks a lot Sandy for checking the gallery too and the nice feedback. :thumbsup: I've been at it again and again for a while now. Each time you get a little better and learn new tricks. It's a slow process and you've got to enjoy the journey. That's all there is to it really. :)


Sure did. They're all here (http://vimeo.com/astropic/videos/page:2/sort:date) at the bottom. I even got a time lapse of Fred doing a time lapse with his trolley system. :lol:
Haven't got a pair of Bino yet no but it's on my list of things. I don't have access to dark skies very often and when I do I image but I remember using yours. Thanks for letting me using the dobs too. I ended up looking around that night and after a couple of hours ended up not imaging at all. See what you've started. ;)


Thanks a lot Baz. Glad you liked it. :thumbsup: This area is so rich in stars of all sizes and variation in colours and density in the various parts of the field it is pretty immersive when you browse around.

[Ross G]

A great looking mosaic Marc.

Sharp and detailed.

The colours are beautiful...great processing.

Ross.

[multiweb]

Thanks mate. :thumbsup:

[David Fitz-Henr]

Super mosaic Marc! Great to see it in large scale too; these images need to be viewed like this otherwise all the detail that has been painstakingly stitched together can't be seen. :thumbsup::thumbsup:

[strongmanmike]

This is great Marc, such a cool area of the winter sky, looks good in subtle colours too but a tad more saturation might be worth a look :confuse3: :)

Mike

[multiweb]

Thanks David. :thumbsup: The stitching turned out alright but for a small area 8 o'clock of M8. I think I had a slight field rotation and the stars are going in a different direction from the other panel. :lol:


Thanks Mike. :thumbsup: Like this one (https://skydrive.live.com/?cid=6930D3AD12D5044C&id=6930D3AD12D5044C%21863#cid=6930D 3AD12D5044C&id=6930D3AD12D5044C%21924)? I'm in a no saturation phase right now. :lol:

Oz skies are so cool in May hey? My fav time of the year. I remember one night about 3 or 4 years ago at the house when we were all looking up. The field was illuminated. The milkyway up ahead was blazing bright. Was bloody cold too.

[jase]

Awesome work Marc! Do you know what your average panel overlap percentage was? You've covered the key targets but was it as efficient as you had hoped? Your attention to detail with the seamless panel stitching needs to be commended. Now, to just expand it further to M16 and M17 ;)

[multiweb]

Thanks Jase. :thumbsup: About 10% but some are a little 'tight'. As you've probably already figured out it wasn't really planned. But for the 4 panels including M8/20 and viscinity. M16/17 are way too far mate. Check this one (https://public.bay.livefilestore.com/y2p6R6f8d-uWxdq9rrtLs-oLJkyjgsgpraefdk1gQSbQHrKoAQHKTF92M P8IVQzn9ufk0xn-EgwpRCiiisDun7VJEJzDxxflFOeo2LjZ2Vt pbo/M16_to_M8_ha_150mm_sf.jpg?psid=1)at 150mm. I'd be still mosaicing into next year. :lol:

[jase]

M16/17 are not too far away. The image you presented reminds me of my rendition of the region I did back in 2009 - here (http://cosmicphotos.com/gallery/image.php?fld_image_id=186&fld_album_id=11). Still, you're operating at a different focal length and FoV. Hope to see more of your mosaics in the future.

[multiweb]

Great rendition. I remember that one. I'm at 600mm FL F/6.6. I'll tell you what. If I get another good run at Ilford next new moon week-end I'll plot along towards the eagle and the swann. Planning to keep doing color while the milkyway is still up. :thumbsup:

[DJT]

That's a great image, beautifully done

:thumbsup:

[multiweb]

Thanks a lot David. :thumbsup:

[strongmanmike]

Yeh that's really nice :thumbsup:

Mike

[Shiraz]

beautiful work Marc - subtle and detailed. Regards Ray

[multiweb]

Thanks Ray. Glad you like dit. :thumbsup: