ollypenrice

You can have mine! lly

I do have the linear stacks but have never applied L over RGB at the linear stage because I have always wanted to process them differently, the L for deep stretch and high detail, the RGB for low noise with detail unimportant. I'll see what happens... Olly

This is a very good question and, while I was typing, a little worm in my ear said, 'Have you ever tried it?' I haven't - and that is a very bad reason for not tyring it now! I don't think I'll try it in Pixinsight because I'd end up in a psychiatric ward but I'll try it for sure. Your image is great. I have this object myself but have never been happy with it. Olly

I was distinctly unimpressed by another member accusing you of talking nonsense, just recently. You do not talk nonsense and, even if you did, SGL is not a place where that kind of remark is acceptable. Which brings me directly to why I like it here. It's so civilized. And helpful. There are lots of areas in which I have no competence at all, notably IT and electronics, and I can post a question and get an answer here within an hour. It's also a chance for me to chat in my native language, which is relaxing. Olly

The active ingredient in 'F ratio' is aperture. That's why, in regular photography, aperture is usually referred to as 'F stop.' This OK when neither the focal length nor the pixel size is being changed while the aperture is being changed by opening or closing the diaphragm. There is no 'F ratio myth' here but there is no diaphragm on a telescope! The F ratio myth creeps in when an astrophotographer becomes fixated on F ratio when 1) comparing scopes of different focal length 2) ignoring pixel size. When comparing two setups of the same focal length and with the same camera you can rely on F ratio to indicate the speed of capture because aperture is the only variable. It's probably worth adding that resolution (of fine detail) and signal strength are, in theory, different entities. In real world imaging, though, they have an interconnected relationship. Few of us expose for long enough to get the absolute best out of our systems. Many fine details in galaxies are quite faint. The more signal we have, the more we can sharpen - and that's where signal strength impacts upon the final resolution of detail and, if we are honest, perhaps, the final impression of detail. This is where a faster system will be a benefit. (Here I'm using Vlaiv's definition of a faster system, not just a faster F ratio.) Olly

The problem is that the RASA will be OSC and the present image LRGB. The ideal time to combine them is at the linear stage but the L and RGB can't be combined before stretching. Perhaps the OSC could be copied into one luminance and one RGB version and the present L attached to the L version and the RGB to the OSC. These concoctions often sound possible on paper but might give nothing but nonsense in reality! Olly

I take this point but have little experience of binning with CMOS cameras. What's your view on how this should be done and how effective it is? Olly

False click. Sorry.

Agreed. I don't find any difference in green noise or balance between OSC and mono captures. If the image really is strongly green then an incorrect debayer is very likely. Olly

That's the problem. Not enough dynamic range left once the extensions have used up so much of it. Olly

It's on the list. A marriage made in Heaven or a processing task from Hell??? lly

A recent thread on the tidal extensions of M63 made me go back to 25 hours of old linear data (TEC140/Atik 460). The problem, of course, is to try to wring the neck of the faint extensions while preserving a decent core. Well, I'm not sure. Opinions welcome! Olly

I don't see why the version below wouldn't work. This was given a soft stretch in Ps Levels and de-starred in StarXt. The artifacts from the two big stars were lassoed and given Content Aware Fill before the stretch was taken further using custom shaped curves. Terrible shame to throw it away! (If it would be any good to you I could dropbox you the 16 bit Tiff. Just PM me an email address.) Olly

Are you absolutely sure the OIII can't be used? I'm a bit of a hard-core 'fix it and use it' merchant! Could you not stretch it, de-star it and use Content Aware Fill on the haloes? I don't think there would be any need to put the stars back since you could use the OIII as a colour layer while leaving the stars as they are. It is a lovely image and, as you say, dramatic because the colour change brings the Jellyfish forward, visually. It's just a shame to lose the outer OIII shell. Olly

If you decide to spend your life lashed to a storm-blasted rock in the North Atlantic, what do you expect? 👹 The magic word is South. A more honest person than I would add that most of next week is given cloudy. Oops. lly

I think that, at Dec 44, we're probably going to pick up IFN, which complicates matters, maybe? Anyway, interesting stuff. Olly

My interpretation would be a little different. I'm inclined to think that the arms outlined in blue might be normal spiral arms lying in the galactic plane. The loop outlined in red seems a little odd since it leaves the galaxy and returns to it. The solid red line suggests this strongly. The closely dotted red line might be part of the same loop and the sparsely dotted line is pure speculation. My hunch (no more than that) is that the red loop lies a little out of the galactic plane. From the point of view we have here, I'd put the solid red loop as rising above the galactic plane and the closely dotted loop as dropping below it. In this interpretation the red loop would be the result of interaction. In cross section it would look like this, the galactic plane in blue and the loop in red, as above. There is pretty good agreement between three independently captured and processed images here and I found that neither StarX nor BlurX had any effect on the faint structures. I used DBE in PI and then stretch in Ps. I begin with a pure log stretch pushed too far and used for reference. My final stretch often involves kinking the curve to emphasize contrasts but I check it against the reference stretch to avoid invention. My rule is, 'Emphasis, yes, invention, no.' Olly

I'm not quite sure what you're asking. Are you suggesting that you consider your first stack as one light which you then put into a set of new lights as if it were one new sub? If so, you can't do that. To save time, you can make a new stack and then combine that with the existing stack, weighted according to exposure time. If your first stack had 2 hours and your second had 1 hour, you'd weight them 2 to 1. Olly

OK here is my lum data processed only to reveal any outer extensions. It has 14x30 mins, average combined with 36x15 mins (16 hours). I gave it an initial stretch, de-starred it, noise reduced it and then made a copy which I equalized in Ps. This produces absolutely extreme contrasts and brings out the faintest data. I then used the equalized version as a layer mask and stretched again through that. I would say we have three clear spiral arms on the right, the uppermost one having an angular bend rather like the arms of M101. What is, perhaps, more relevant to the consequences of an interaction, is the broad band of luminosity which seems to be drawn from the lower edge of the galaxy and out of the field of view in the lower right hand corner. This is the area I struggled with first time around. This time I think it might be a long, broad tidal extension, though the two bright clumps on the edge of the frame here will be starglow from two bright stars. The wider FOV and greater speed of the RASA rig ought to make or break this hypothesis. To be continued. Olly Edit: Trying to turn this is level of stretch into a presentable image isn't easy. I think the RASA will do better.

My M63 is here. I'm not totally certain about which outlying features you mean, so maybe you could annotate them on your image? Mine is quite an old image, processed before the X-suite was available, and I've long been meaning to revisit the linear data. This thread is a good prompt to do so. From memory I was far from confident while distinguishing extensions from gradients, particularly in the lower part of the image, I think the lower right in this orientation. I'll see what happens with a new look today, assuming I can find the original linear stacks. I've also been thinking about shooting this in the RASA, which would have two advantages. 1) The photographic speed of the setup would find more faint signal and 2) the wider FOV would give the gradient removal software far more information about the structure of the gradient to be removed. Naturally it would be nice to rely on flats for separating signal from uneven illumination but, for whatever reason, we rarely can. Olly

Bravo, that's a great object and good write-up. Even when you don't have the ideal focal length you can have a darned good look at an object. Olly

I'm not a Newt user but I think the usual answer is to move the primary mirror up the tube. A small movement like this can be done using the collimation screws but for more movement you need to drill the main tube. You might also be able to find a shorter way of going from 1.25 to 2. This is probably not the best part of the forum for your question. Olly

A strong image with something to say. Olly

Impressive resolution and colour differentiation, all the more so for the modest exposure time. An outstanding result, I think. Olly

Maybe we could ditch the dismissive term 'pretty pictures?' If so I'd be more than interested in joining the conversation. Olly