Working on a Narrowband Mosaic Project: ~20 panels per channel

[AndyUK]

I'm afraid binning is something way above my head - I used it once, but am now going to leave it alone until I've got the basics sorted.

Like you though, I'll look forward to someone elses response on this, although the idea of taking 45 min subs is something that would fill me with intrepidation - One thick cloud passing over every 35 mins would be REALLY annoying!

[roundycat]

Whatever you do don't bin the chip. You do not gain much sensitivity, longish exposures (if possible because of a dark sky background), will not leave you read noise limited and the detail will suffer from binning. I have done parts of this area and never binned, the exposures were deep enough to make an acceptable picture and that was with short subs.

Dennis

[roundycat]

have a look at this as an example of what binning can do for you. I should add that only the S2 was binned.

Dennis

[antimorris]

Andy - yeah I have never really done much research on binning yet as every time I ask a question or someone else does I get very strong opinions on both sides. I have pretty much only ever left my chip at 1x1, but do see a lot of people - esp on narrowband, bin SII & OIII which is why I asked. . . .

[antimorris]

Dennis - Thanks for the comparison. Which is which, though?

[roundycat]

Which is which? Are you serious?!! The unbinned pic is the one on the left. Sharper detail and much finer red channel stars as there is no need to re-size.

Dennis

[antimorris]

Well that is what I assumed but processing differences can make a world of difference as well.

What about everyone else?

Here is my thinking: Each filter is looking like it will be 20-21 panels. With the Ha each panel so far is not binned and is 10x1200s. The full-size image, SO FAR, is around 92 inches square. With this said, I am never going to be printing this as an 8 foot wall-sized poster. Yes, I realize that by the #s I should not bin for the fl and chip-size I have, however, a bit lower resolution on the SII & OIII would not be the end of the world seeing as I am not designing a wall from this when I print it. I will be getting it printed at a normal size of at most a couple feet Since the Ha is not binned and I hear that the SII & OIII are much fainter, will the apparent sensitivity increase be worth the decreased resolution? In a project this size, would you bin the SII & OIII or just continue on unbinned like the Ha is?

[MikeD]

Fantastic progress Anna.

I will follow this thread with great interest as I am on a very similar project myself (Ha only though), looking forward to seeing yours grow and develop colour.

Mike.

[OzDave]

It is projects like this that I find particularly inspirational. If I can get results like this some day I will be very pleased!

David

Sent from my iPhone using Tapatalk

[antimorris]

I have created a zoomable image and will update the image as this progresses. Once you zoom in to 100% you will see that noise definitely varied throughout the different nights based on transparency as each panel is the same # of subs (10) at the same exposure (1200s) and processed exactly the same. . . . Let me know what you think of the zoomable version.

Warning: this file is HUGE and the zoom sometimes takes a minute or two to catch up and in the meantime shows horrible resolution. Be patient and the resolution catches up.

North American & Pelican Nebula Mosaic Project

[AndyUK]

Anna... Thank you very much for posting this - Although not quite the same as being able to use the scrollbars to quickly zoom around a canvas, it's certainly the next best thing! I have to say, I couldn't notice anything amiss and considering the 1:1 size, I doubt that anyone is going to notice any seeing issues on any pane. The result you have so far is absolutely stunning (or did I say that before?!)

[antimorris]

Thanks so much Andy. I might be being a bit too critical. There are a few places as well that I noticed my alignment wasn't quite perfect on panels that spanned two nights and I stacked those stacks. I will be going back in the next few days and just doing stacks from the original subs rather than the night stacks (I was being lazy and trying to save time) ....

[MikeD]

Great stuff Anna, really good to see the full scale image.

Mike.

[roundycat]

Regarding the binning issue...

I am surprised that no-one that bins their camera has chipped in with chapter and verse on the finished results. Lots of people here bin one channel or another but we never hear about any comparisons that have been done to justify binning.

Surely there must be some binned examples that forum users are prepared to put up for discussion.

I would also be very interested to hear about the sensitivity gains that have been seen.

Dennis

[antimorris]

I am not even 1/3 of the way through the project yet and I already have 47hrs of imaging time .... for some reason as I was processing this tonight "this is the song that never ends" popped into my head in a "this is the mosaic that never ends" version

I am nearly (only about 5 panels to go) complete with the Ha portion of the mosaic. I had a few nights from last week I hadn't fully processed and integrated into the mosaic and then the last two nights were clear so I got a few more panels done then too ... today was rainy and I was tired from being up for the past two nights so I hung out on the couch and got caught up on this.

In case you were wondering, I don't regret doing this (yet) although I just wish I hadn't decided to do this in England where the clouds and rain will guarantee that I will be at this for quite some time. Once I finish, though, I am quite certain that I will be incredibly happy with the result and it will have been well worth the months and months of imaging the same target

Here are a few options to see it in higher res:

For up to 15% size (that is quite large) you can go HERE (on Flickr)

For a zoomable version where you can zoom all the way to 1:1 and pick out all the imperfections, noise differences based on different nights' seeing and transparency then you can go HERE (zoomable on my website)

[AndyUK]

Good grief...! You just have to stick with it now... You've gone way too far to turn back, and this is stunning. One question though - How big would a 1;1 print be?

[antimorris]

Oh I plan on sticking with it .... at the moment a 1:1 would be around 7.5 feet a side. Like I said earlier, I don't exactly plan on turning my wall into the North American and Pelican Nebulas but even a 2.5 foot print will be quite large and that size should give it really nice resolution (that is my hope at least)

[AndyUK]

Yes, 30"x30" narrowband image at 1:3 scale would be a site to behold...!

[michael.h.f.wilkinson]

Brilliant stuff! I am tempted to print it on one of the A0 printers here.

[msinclairinork]

This is looking so good Anna!!

I do like the zoomable image!

I am also impressed you have managed so much so quickly!..I'm sure 'Weather' wise it would take two or three times longer where I live!

Keep up the good work!

Michael

[antimorris]

Michael -

I am just as surprised. We have had a couple strings of 2-3 days at a time with clear nights and me being a bit obsessed with this mosaic at this point, stayed up for all of them to image. I surely never expected to already be almost done with the Ha only 3 weeks since I started the first panel. I mean, seriously, 14 panels in 21 days in ENGLAND when I am mostly doing 1.3 panel/night cause of lack of darkness?! I know the local farmers are cursing the lack of rain, but it has been nice for me. I fully expect a few week stall at some point here cause the weather will catch up with me. I just need one more week of clear skies to finish up Ha and then can chug through the summer on the OIII and then the SII.

[msinclairinork]

Well i wish you many more!!

Michael

[blackparticle]

Wow Anna.. That's really starting to take shape.

When it comes to printing, I reckon you're going to want to aim for at least 300 dpi compared to a screen resolution of 72 dpi to get the best from the printing process. This applies to either a photo print using RGB or ink print using CMYK.

Am I correct in thinking the full size image is approx 5300 pixels square? This would give an optimal print image size of about 17.5" square.

I'd also recommend not cropping the image before printing to give you some bleed area around the edge of the image which you can cover with the frame / mount.

Another option for printing, which apparently looks fantastic, is printing onto a thin steel plate. A photographer friend of mine was talking about this and he was saying the colour reproduction for this process is amazing. There is a company in London (I'll track down the details when I next contact him) that does this. The price he mentioned for a 12" print, which is then laser cut was only about £40.

Looking forwards to seeing this in colour.

Alan.

[ollypenrice]

Hey, you are winning, Anna! Just to move away from congratulating you on the sheer size of the venture, I'd like to add that the sheer darned quality of the thing is quite exceptional. Tremendous contrasts and balance, seamless construction.

When I did a 9 panel (pah, trivial!!) I found strange curvature effects which gave me 9 frames which did not make one big square. The corner panels curved outwards so that I was only just able to cut a square out of the whole without losing my objects (Heart, Soul and Double Cluster). Are you finding this?

Next time I do it I will take or borrow a widefield of the whole thing and register my panels to that, not to each other. This is how Karel Teuwen did his giant Veil nebula.

Anyway, a truly splendid picture, this. It deserves to be printed LARGE.

BTW, I see you went for a Geoptik. Pleased?

Olly

[antimorris]

Alan - def let me know the company once you find it. I would be interested. Yeah I figured around 250-300dpi for printing and was thinking that the overall would be around 18"-22". It is currently right near 5500 pix square. I have a large format printer (for my regular photography ventures) that I now have my monitors calibrated to so I can do do decently large prints myself, but might want to do something special for this project.

Olly - thanks for the compliment! As far as curvature, due to the scale I would have found the same, but I am registering them all to a DSS shot of the region that I resized up to be the size I need. I used DSA - Digital Sky Assist v1.0 to put in the region I wanted and then played with the mm settings until it covered the whole area I needed, downloaded the fit and transferred to tiff, checked its current size, calculated roughly what my overall mosaic would be, resized the DSS to that and I use it for the starfield to register my mosaic panels.

Doing this, I do occasionally notice some stretching in the image itself as it warps it to register it so I have been trying to view it at 1:1 and drag around to find these areas, re-register those panels and so far Registar hasn't stretched the 2nd one in the same place so I am able to use layers to fix the stretching errors. It is taking a bit of work but it seems to be working well enough.

I did go for a Geoptik - so far I have only gotten to just test it under some mostly-cloudy skies to see if I could reach focus easily enough and see how it all worked together. I have a little bit of coma on the lens I used for the test but I think that was a spacing issue. I was able to focus easily enough although it is a VERY small spot that achieves focus and I had to be careful not to move it too far for corrections. All in all, I am quite happy I got it. Having to switch filters manually might suck, but it should allow me to get some nice widefields once the skies are darker and I finish this current project.