ollypenrice

I was about to make the same post having read this article. https://www.sciencemag.org/news/2020/11/famed-arecibo-telescope-brink-collapse-will-be-dismantled?fbclid=IwAR1F6P5P7jqRzXf_K1UWys0vQBsF08WOYbRWmnpR1orVtaZbCFtE72Vc8i4 A shame when we lose a great instrument, especially such an exotic one. Perhaps it could be turned into a jungle skateboard park! Olly

'Little Dumbbell' my foot: it's worse than a little pest, this one. I've never imaged it before and have always been struck by the fact that it rarely looks the same in any two renditions. Now I know why! It's very tricky. This is a WIP since I was also battling the data. There was differential flex in the dual TEC meaning that the Ha side was affected by slight trailing. For some reason the darks on that side clipped the Ha but not the RGB so I used a bias only on the Ha, which was also noisy as a result. These things are sent to try us. Plus the wind kept nudging the Mesu's elbow etc etc. However, I was anxious to play with what we had so this is the result. (About Four hours each Ha and OIII and 80 minutes per colour.) The object has an extremely high dynamic range so I needed two distinct stretches both in Ha and OIII. I used Ps layer masks to blend them. Trying to retain detail in both the outer wisps and the core took a ridiculous amount of effort. It's also unreasonably small! Anyway, here it is for now but I really want to nail this little devil when I've sorted out the technical issues. Olly

Indeed. Truth to tell, I'm cribbing a thought of Mark Twain's here. He was an atheist and said of death, 'I was dead for billions of years before being born and it didn't inconvenience me in the slightest.' As I move nearer to the fatal bellman I do find this thought reassuring! 😁lly

Interesting. Thanks Wim. New to me.

I'm curious to see the shower cap! I never wear one myself, while imaging, but nor do I wear one in the shower since my three hairs (one at each side and one at the back) dry quickly even in poor weather. Pictures, please!! Since NB emission is very limited from galaxies I don't think they offer much scope for the colour mapping enthusiasts, especially if the galaxies are old ellipticals without star forming regions. What you have here, mostly distant ellipticals without hot young stars, look very like the galaxies of the Virgo cluster and have the same orange colour. Even when you see the odd spiral in there its blue light will have been attenuated by the distance. I always think of places like this as the 'old sky' with that reddened look. Very interesting to find such a view in Perseus since we normally associate them with the springtime galaxy season. Nice one, and no reason to doubt your colour. Olly

Hi Jordan, welcome back and say Hi to your folks! That's a really fine result. Portable setups have made the most progress of all, I reckon, with good mounts, and cameras which sample well with lenses. Those are cracking little stars. Olly

I'm right with Wim and Goran on their comments. The bulk of the galaxy is thick and rich and satisfying. Like them, I think the dark ends have been created by a gradient tool reading the ends of the galaxy as background sky and pulling them down. And then there's the colour, which is almost entirely lacking. This will be something to do with your workflow and can almost certainly be addressed but what software do you use? I know some tricks in Photoshop if they'd be any help. Olly

It can, in fact, be shown that the surface brightness of an extended object cannot be increased by a telescope. This is a rather surprising bit of science but also a misleading one since, subjectively, we don't see it that way. While it's technically correct that the surface brightness can't be increased, I've always found this to be a rather 'dry' point since, in order to see fainter objects, we need a bigger telescope. What's really happening is that a smaller telescope, in increasing the object's image size, is spreading the light out too far and dimming it. More aperture allows for the object to be spread out over a larger area without being so badly dimmed. So telescopes do make faint objects bright enough to see but they do it by making them bigger rather than brighter. Olly Edit: Think of a a rear bike light made of one LED. It won't be very visible at a distance. Add another twenty LEDs of the same brightness, and it will be.

Really good, Martin. You'd never know this was a camera lens image, so tight are the stars. Olly

Here are some experiments using Starnet++ as a star reduction tool. I started with this image, on which star control had always been difficult. This is as far as I could get with existing methods like star masking during the stretch and Noel's Actions. It's still pretty 'busy' with stars so I ran it through Starnet and got this. Clearly not satisfactory on its own but a start. The larger (damaged) stars I would replace at the end but the golden pair near the middle had leaked out their colour quite badly so, using the clone stamp set to colour, I just reddened the golden spread. I then made a three layer stack with the original on the top and the bottom with the starless version between them. I set the top layer's blend mode to lighten and pulled down the curve as below, experimenting with different curve shapes to find the best looking stars. You could take the reduction considerably further but I like to work in small increments so I settled for this. After flattening the top onto the starless I was left with those larger damaged stars. I simply erased them from the modified layer to restore the originals. Below we have before and after, before being on the right. Remember that I was starting on an already star-reduced image so the difference isn't extreme. Olly

If it ain't broke... Olly

I've wondered about this and had the same thoughts as you. On the other hand, when we hold an Ha filter up to the daylight we have no difficulty in seeing colour through it so its passband must lie in the visible. I remember a thread elsewhere started by imager Bob Anderson on what colour Ha really was. I found myself wondering why it wouldn't the colour we saw when we looked through the filter! (A simple experiment...) To remind myself I've just this minute looked through a Baader 7nm OIII and an Astrodon 3nm Ha filter, naked eye, at the sky. Exactly as you'd expect the OIII hovered between green and blue depending on where you looked, and the Ha was an exquisitely beautiful deep red. RGB filters, likewise behave as we'd expect. The notion that the Ha line is outside our range maybe comes from the conservative view of visible light passed by DSLR filters. They may be deliberately over-restrictive in order to avoid atifacts generated by the chip and the optics. Olly

I've never been a fan of DSS though its price is unbeatable! 😄 Starting from scratch I'd probably go for APP but I've been using AstroArt for too long to change. Olly

Like you, I think this is normal. It arises from slight eccentricity and explains why some mounts use a spring mechanism to maintain constant pressure in the mesh. Is the backlash in the RA drive or the Dec? If it's RA just run the east side slightly heavy to keep the worm pushing against the wheel. Olly

Galilleo was the first (or possibly the second) to observe the sky telescopically and that's his medal. We must give him another one for his grasp, theoretically, of what he had seen. (Phases of Venus, an alternative centre of rotation in Jupiter, the stellar nature of the Milky Way, terrestrial-type features on the moon...) But for the sheer volume of his discoveries, his knowledge of the sky and his incomparable visual acuity, I think we should recognize Barnard. When two colleagues were unsure of whether or not they were seeing a new double they called him to the eyepiece for his opinion. He excitedly confirmed the new double and added that one of the components was itself a double, something which would only be confirmed later via spectroscopy. Olly

My understanding is that they only did so after Lowell got them started and that Lowell's brain probably primed itself to see them from Schiaparelli's observations of 'canali.' This merely means channels in Italian but possibly planted the canals notion in Lowell's mind. It would seem that Lowell had a mind which went a long way with a little evidence, hence his assertion that Martians were right wing Republicans like himself because only such a political system could organize civil engineering on a global scale. While the patrician Lowell was sending astronomers off on this wild goose chase the greatest telescopic observer of all time, the humbly born E.E. Barnard, quietly said, 'I can't see 'em...' Take more water with it, Perce!!! 😄lly

We are very exacting in our requirements (reasonably so, given what we pay) but with so many optical elements in the train it is difficult to know what causes what. It might be that the tight bandpass produced by the filters is eliminating a blurring of the same phenomenon when the bandpass is wider. Very hard to know. I would begin by asking Chroma. Olly

You're most kind! The question you ask is a good one. Assuming you're in sharp focus you're in the lap of your optics, mostly, when it comes to capture and, while the scopes I used on this are excellent, they cannot give tiny stars on a hard stretch of long subs so it's mostly down to processing. If you're shooting LRGB you already have a set of effectively 'short' subs in your RGB. The point of luminance is to get more signal so, if you want a stack with less, you probably already have it in your RGB. Sometimes that's useful to bear in mind. On this image, made a few years ago, I used familiar star reduction techniques. An initial, gentle stretch was done with the stars masked, but this can only be done gently or it will soon show, especially where stars lie on faint nebulosity. It's a help but not the answer. After that I used the Astronomy Tools 'Make Stars Smaller' routine. This is great and was formerly known as Noel's Actions. Well worth having. However, the arrival of Starnet++ transformed star control in DS imaging. It's free and either Standalone or incorporated into Pixinsight. Basically it removes the stars in a single click - but don't expect miracles. The output image often looks quite artificial and 'blotchy' where large stars have been removed. I took it into Ps and made a three layer stack with copies of the original top and bottom and the starless image in the middle. I wanted to replace the stars with smaller versions of the original so I set my top layer to blend mode lighten and, in curves, pulled down its brightness till the stars were tiny. In Blend mode Lighten they were now the only part of the original showing in the blend. By playing with the curve I could get them to look crisp, natural and small. Trial end error. Flatten top onto middle when happy. In one or two places (the satellite galaxies) Starnet had done some damage but I had an original as my bottom layer so I could just erase the remaining top layer where necessary. One or two stars needed a cosmetic fix post starnet but nothing drastic. Olly

No hijack, Dave. My M31 has appeared before and it's here again specifically to invite opinions on colour. Olly

Indeed the Hii regions really are widespread. I very much like your rendition, Dave. It has a softly softly look. But then that's part of the charm of this game: we don't just put out buckets, we seek to emphasize different features of an object and create a particular atmosphere. Olly

Second one for me, Goran. No doubt about it. Our 'outer glow' regions agree, I notice, but don't you want to do an extra panel on the left? It's a shame to crop out something so rarely seen in images of M31 as that upward twist. Go on!!! 😁 (The outer glow on mine is somewhat over-stretched but that was a processing decision taken because the project had that in mind. Yours is more subtle. Maybe I'll ease mine down a tad at some stage.) Olly

I think the framing has a lot to do with it. I'd like to add more background around this two panel, in fact, because I do like a galaxy to 'hang there in space.' It's tempting to fit it on the diagonal but even full frame at 530mm won't get anywhere near to catching it all. I was originally motivated, on this project, to try to find what the star charts all show in terms of its outer reaches. The 30 minute L subs provided the breakthrough. I'm quite sure of that because I had a good set of 15 minute subs which weren't finding what I was hoping for. Olly

I've been convinced by vlaiv's arguments that galaxies are usually presented with too much colour and, in particular, with exaggerated blues in the spiral arms. I've already revisited my M101 and M33 so this time the Andromeda galaxy got the treatment. In one of his posts (which I can't find) vlaiv linked to the Hubble Team's rendition of part of M31. https://hubblesite.org/image/3476/gallery/73-phat Using this for reference I found it wasn't difficult to get fairly close to it. Although the change from my original colour was striking, the adjustments were remarkably slight, raising the cyans and yellows in red to cool them down and tweaking the cyans and magentas themselves before lowering, considerably, their colour saturation. Initially I wasn't too pleased with the result and found it lacking in punch. Waking up with fresh eyes I find I prefer it. I never liked the original colour anyway and have floundered around with it in the past. This version's growing on me. Edit: I also gave it the Starnet++ treatment since that wasn't available for the original. (The original idea behind the image was to try to find the galaxy's outer limits. Main image FSQ106N/Atik 11000 mono with 30 minute luminance subs. Core, TEC140/Atik 11000. Mesu 200 mount.) Olly

A bold and striking image. Olly

Very striking with a good background sky (always an issue with mosaics.) The colour saturation is too high for me but that's personal preference. The colour itself I do like, along with the star control. Olly