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M42 to Flame. Wide-wide field. (My first mosaic)

MikeWilson

By MikeWilson
in Imaging - Deep Sky

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MikeWilson

MikeWilson

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Evening all,

Here's my first mosaic. It's made of two panes (see if you can spot the join).

M42 section: 20 x 30 seconds + 8 x 10 minutes. Stacked using DSS' "Entropy Weighted Average" (AKA "lazy mans HDR").

Flame section: 2 shots on one side of the meridian, followed by a reflip and 6 more shots. All 10 minutes.

All done in one night, including setup and pack away under light polluted skies. (Sadly I didn't have time to drive the hour to my favourite dark site).

6422399365_4c5f5240a1_b.jpg

A panorama in Orion by MikeWPhotos, on Flickr

I'm not happy with how the M42 section came out, I've far overprocessed it. I may even have used exposures that were too long, ten minutes took me to a max ADU value of ~62000 (just ~3k shy of the maximum possible value).

Comments, critique, pies or tomatoes all welcome.

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rocketandroll

rocketandroll

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That's really nice... the middle of M42 is a little bright, but nothing a little overlay of some shorter subs in a seperate layer wouldn't fix. I love these Orion widefields/mosaics.

I was hoping to do something similar with the Meg72 + focal reducer, I am fairly confident I can get M42, almost to the horsehead in a single frame given it's 345mm focal length... definitely could get it in 2, but manually setting the two up could be a headache, I can just see me ending up needing to shoot 4 extra panes to fill in gaps because I missaligned it :-)

Which scope did you use? Just so I can get an idea of focal length?

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Aris Panagiotopoulos

Aris Panagiotopoulos

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The first thing about mosaics is not to be able to spot the the join points...and you done an excelent job, because as u said you can't see the join!!

Now, for the Orion Nebula you need to take sub exposures of the core from 30 sec to 1 min. and join them together,with the longer ones, so that you don't have a white spot area instead of the Trapezium.

Great Start!!!

Mosaics are awesome!

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MikeWilson

MikeWilson

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@Zakalwe: Thanks! How are you finding the QHY8L nowadays? I really like mine, with the exception of a rather loose USB port that I now support with blu-tack (thanks to Nadeem for this tip).

@Episkey, @Steve1962, @Astroblagger, @Telrad, @Penfold: Thanks :icon_confused:

@Casperovic: If I do this again it's 20 minute exposures on the flame and the nebulosity above and below it. I get nervous going above 10 in case something ruins the sub. Shorter subs are safer :rolleyes:

@Crunchard, @RocketandRoll: Yes, M42 looks a bit sucky. It's my fault for rushing the processing (3 hours [!!]) and also I used the Entropy Weighted Average and stacked the 30 seconds and 10 second subs together in DSS. It generally worked but everyone's noted, it's almost certainly best to take the shorter exposures and manually overlay them. In fact, I might just do this for the nebula itself - restack the 30 second subs and layer it over to preserve the details lost from stretching and noise reduction in other areas of the same image.

I found that while stretching the curtain at the left, I spoiled M42. And while stretching M42, I spoiled the curtain. I suspect that the best way to process these mosaics is first to render each image seperately and then attempt to blend them together, rather than level them both a bit, stick together and then process the whole lot in one go which is what I did.

@glowjet, @Aris: Thanks. I'm really chuffed with how the join came out. I was panicking trying to get the levels of the two layers (one image in each layer) balanced right. Levels set to blend most of the image in still would still be harsh towards the edges. My trick was to use the eraser brush as soft and large as Photoshop could go and click far away from the left image to erase it very mildly and eat it away. It worked, probably because there is no single vertical line, it's more of an arc.

Thanks everyone for your comments. Mosaic making is rather fun!

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ollypenrice

ollypenrice

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First off, Mike, Bravo! And in a single night?? I needed 30 hours on this blighter.

This is a fine first mosaic.

OK, I have some suggestions. If you have Pixinsight you can leave the images linear and combine them unstretched because PI will give you a preview of what they will look like stretched. Harry (Bless'im) Page has a video tutorial on how this works.

Without PI you will have to stretch each first, before combining. If you put one image on a big canvas and paste the other one onto that and shove it into the right position you can do the levels and curves routine on first one then the other iteratively, keeping them in close approximation at each stage. If they are close you can then just give them to Microsoft ICE (free) to merge or merge in Ps. Whatever. Now here's a trick for fading the join if doing it manually. Paste right over left and run a partial eraser over the edge. Then Paste left over right and run a partial eraser again. If you crop the images in a slightly different place each time this works even better.

My own weightings for M42 at F5.3 were 11 seconds, 50 seconds and 300 seconds. I used this layer masking technique which is the one I teach on imaging courses, duly credited to Mr Lodigruss; Compositing 2 Different Exposures via Layer Masks

Without short exposures I am certain you can get much, much deeper into the core with what you have. Do a partial stretch, looking only at the Trapezium area, and follow the tutorial using that as your short exposure. I do multi streches on many images.

Sorry, I'm rambling, but you have a beauty there.

Olly

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Nosivad

Nosivad

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Absolutely astonishing, that an amateur with amateur equipment can take photos of that standard, which not too long ago could only be done by professionals with much larger and vastly more expensive equipment. Well done!

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AndyUK

AndyUK

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Hi Mike - Superb job sir! That 80EDT obviously suits you very well. Although I totally agree with Peter (our weather's not very conducive to larger mosaics) with the quality of these that you captured in one night, have you thought about extending the mosaic even further?

Obviously I'm not familiar with OSC's, but I wouldn't be too worried about going for longer exposures if you need to on the fainter nebulae - I thought 10 mins was long enough until a few weeks back, but now I'm having to use 20 mins (O3) and have a feeling that, if I can get good guiding, 30 mins maybe on the cards soon :icon_confused:. Admittedly, it would be devastating to lose a load of 20 or 30 mins subs, but if you have time and want to be able to get that extra detail, then you have to give it a whirl sometime just to see what the difference is... In the same way that I have to make a start on getting EQMOD working...

I'll do a deal with you - You have a crack at taking 20 min subs to see if there's any benefit, and I'll have a crack at getting EQMOD working... What have we got to lose?!

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MikeWilson

MikeWilson

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@Black Knight Andy: Go for it! I think you'll be pleasently surprised (follow Olly's directions :p)

@Austen4: Ta :-)

@Olly: Again you're too kind. Yup, all done in a single night, including pack up and strip down. Certainly, more time would be better. I only consider this image a draft, not a final version. I have PixInsight LE and if this 'stretched preview' layering works in that, I'll be a happy bunny. I can't justify the outlay (mostly in time but also in funds) for the latest and greatest version of PE, though and I already have Photoshop CS5 so ideally any work that I can do in PS I'd rather do there. I couldn't get Microsoft ICE to stitch even the stretched images and I only use a partial eraser over one edge. Doing it over two edges would be a much better idea. I'll do that next time.

I've seen your layer masking technique (you sent me a document about a year ago) which works brilliantly. I used it in my last M42 but I wanted to try out the HDR feature of DSS - it works ok but stacking seperate layers and then compisting them in Photoshop gives better results. I'm sure this mosaic would look a lot better if I took this approach.

Thanks for your encouragement and the tutorial on compositing. It shall be done when I next have a free evening!

@Novsivad: You're completely right there. Just tonight my wife put on Cosmos (for the first time since 2009!) and I sat down with her to watch an episode. Even in the remastered DVD's, the images I often see on SGL look orders of magnitude better than a lot of the demonstration graphics of various galaxies, presumably photographed by professionals with said vastly expensive equipment, twenty years ago. I'm feel really quite priviledged, not just to not be in the 80% of us who have to live on less than $10 a day but by a similar gap - to be able to use fairly basic gear that can all be transported in the back of a car to explore the galaxy via photographs. Quite incredible when one contemplates this.

@Billy: Thanks ;) And yep, the weather is dire at the moment. I see clear skies but it's blowing a literal gale outside.

@Andy: Thanks, the Orion ED80T really likes me. A good job too, since I really like it! It lives with the filter wheel, guidescope and camera and dewstrips all permanently attached to itself and my next investment for it will be a padded suitcase that I can pack the whole lot in. Setting it up is a breeze and there aren't any mirrors to tinker with in a dark, damp field! I will be extending the mosaic and certainly revisiting the area with Ha exposures (since sods law says a clear night will be a moonlit one). I've never done a Narrowband+RGB image before but if I can improve the contrast of the nebulae this way (I've seen some good results from others), I'll be happy.

Anyway, you have a deal. I'll take some 20 minute(!) subs (you do know that I'll be completely panicked the whole time!) on something (probably my next target) as long as you have a crack at EQMOD ;) What could possibly go wrong? :)

@TJ: I'm surprised! You've got some long focal length scopes there and a mosaic with those almost seems necessary on some of the wider objects to get the view in context. G'wan, give it a go ;)

@Kevin: Thanks! And as I'm a Photoshop noob it was a fairly strong learning curve. I've never blended layers together or worked on an image so large before. It's good practice though!

@Nightfly: Thanks :) There would be more detail if I processed this more carefully. I'll take the tips above on board and have another go next time I'm free. I'll definitely be keeping the data though, it's good enough to 'add to' later. (Note: I've never done a multi-session image before, partly why I rushed getting two panes in one night).

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AndyUK

AndyUK

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Mike - Even having the scope already set up like that (and it being a refractor of course) must save 10 odd mins on setup from having a mobile reflector... I do envy you!

I think you might need 20+ mins with the Ha filter (to get best use out of it), but one thing I haven't found yet is a telepathy plug-in for PHD so that you can will the graph flat all the time during the exposure - I've tried staring at the graph and telling it where I want the line(s) to go, but it doesn't listen very well ;). As you say what could go wrong for either of us?! My wife's away this weekend, so I should be able to drag the mount into the living room for a few hours and start doing battle with EQMOD ;)

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