ollypenrice

You wouldn't care to swap OIII filters with me, would you Steve? No, didn't think so! 🤣 This is a great image and capturing the bow shock is a real buzz when you think of the bizarre physics going on to create it. You have it really cleanly. In our case we were plagued by halos so some belligerent processing of the OIII data was necessary. However, Tom is shooting some more from his robotic rig here. Also the Tulip is lovely in its own right. Olly

Since H beta (blue in colour) traces the same gasses as Ha, but with far less signal, Ha can justifiably be added to the blue channel as well at low opacity. Olly

Glass products, on the other hand... 🤣lly

I put both into the pot, brought to the boil and lived happily ever after - or, until the pandemic appeared, at least! More seriously I think the only way to do both in normal life is to robotize your imaging rig. Olly

William Optics is a fashion house with new scopes for the catwalk every season. Olly

Done! Olly

I don't know about diffraction artifacts and how they behave. We need Newt experts on the case! Olly

Steve, let me send you some of my TEC140/Atik 460 data as a 16 bit linear TIFF stack for you to compare with your own. I have a lum stack on M101 which would give you a helpful comparison. PM me an email address and I'll send them via Dropbox if you'd like to try it. If I give this data a set of pure log stretches, bringing in the black point as usual but doing absolutely nothing else to it, it looks like this when saved as a JPEG. How does this compare with yours? The only filter here was a Baader luminance. I'm using the TEC flattener. I regard my TEC140 as giving the best stars of any refractor I've used including the FSQ106N (the old Fluorite) and the Baby Q. Before I had the flattener it did bloat on blue stars to some extent. Yuri Petrunin insists that the flattener has no effect on colour correction but, like a lot of his customers, I don't agree with him. (It may be an interaction between glass elements in the camera or filterwheel and the scope, so maybe not really to do with colour correction, but the flattener did improve my stars.) The shots below show how the TEC140 has controlled Alnitak. A stack of 10 minute luminance subs with the linear image on the left and a pure log stretched version on the right. Absolutely no artificial control of Alnitak whatsoever. I think this is an astonishing performance by the TEC. Maintaining Alnitak as a double was a complex processing job using multiple stretches and layers with the Tak data. With the TEC the optics did the lot. For all that, I do frequently individually process big stars from the TEC stacks. Masked stretching is vaguely helpful but I reverse-process them in Photoshop. That's another story but it beats masking! Olly

Personally I like handsets and dislike computers, so I run handset mounts - albeit good ones. (Mesus with Argonavis handsets.) But this is not your problem, the optics are the problem. The intruding focuser should not be dismissed. Don't give up! It's so sweet when you get it all working. Olly

Well, what the five crops from one sub tell us is that the tracking is not the primary problem. If you had a guiding error in one axis, all the trailing would be along that axis. We don't see that. The two left hand crops show distortion more or less in this axis: \ . The bottom right shows distortions comparable to these but more vertical. However, the top right distortions are angled just into this direction: / . It would be absolutely impossible for a tracking error to produce this pattern. All elongations would run along the same axis. Very severe polar misalignment will produce rotation (around the guide star) resulting in a pattern like this: top left and bottom right / . Top right and bottom left the opposite: \ . Connect all these elongations up and you'd get circles, just like those of a star trail image and the pole star. Also, the distortions, though elongations, are not neat lines as they would be with a tracking error in a well-collimated scope. In the middle of the image they are clearly 'shuttlecocks' of a kind often seen in mis-collimated optics. I once had a TeleVue Genesis which had been bumped and gave these shuttlecock stars at the eyepiece. It was remarkably easy to re-collimate the front lens cell and turn them into nice concentric rings in and out of focus and a good pinpoint at focus. So we can be pretty sure your problem is optical. I'm not an expert on collimating or troubleshooting Newts but there are plenty of people on here who are. It might be worth reposting with 'Optical problems with 130PDS' in the title. The distortions are bad enough to mask very small tracking errors which is why I say tracking isn't your 'primary problem' but your tracking might indeed be excellent. It absolutely is not the main problem. If, you've used the instruments you have, and followed the collimation routines you know, you are left with a choice. Do you believe the tools and the routines which tell you it's right or do you believe the image which tells you it's not? I would believe the image... Olly

The thing about real luminance is that it is very strong, the L filter passing nearly three times the flux of the colour filters per unit time. This means that the bright signal (other than the stars) can be heavily sharpened and noise-reduced and the faint can be be dragged out above the background. When I compare synthetic L with real, it's always very disappointing. My feeling about star colour is that it's soon lost to saturation, at which point it simply becomes white. Olly

Sorry, I false-clicked during my post and hadn't finished my explanation of my own take on this. I think I've answered your question in the full version but, if not, let me know. Olly

I don't think there can be a singe rule for the weighting of luminance against RGB. It's very target specific. Firstly, are you going after anything very faint, too faint to have any real hope of finding colour in this faint stuff? If so, you can't have too much luminance when it comes to finding this faint stuff. However, if you don't have matching amounts of RGB you'll need to be careful not to burn out all the colour with the L. This will need subtle application of L over RGB and careful stretching of the L. It's easier to add x hours of L to x hours of RGB but, if you're chasing tidal tails, IFN etc, it's perfectly possible to add 10x L to xRGB if you suss out how to do it. Steve is saying the same thing when he refers to APOD images. Binning RGB? I can see why people do it but here's why I don't: I want star colour to go deep into the stellar cores. If you want it all the way in you won't get enough faint colour, but colour going well into the cores can be dragged further in by processing. If you bin your colour (assuming reasonable sampling rates since huge over sampling will negate this point) you will probably burn the cores to white which is precisely what you don't want to do. So... not only do I not bin colour: I also shoot it in 10 minute subs rather than the 15 to 30 I use for luminance. This is effectively the absolute opposite of binning colour. And it brings another bonus. In my RGB layer I have, in effect, a set of 'short' subs for regions over-exposed in the L layer. There is no reason not to use my far less exposed RGB layer as less exposed luminance. In Ps you don't even need to convert it to greyscale. You can apply RGB in blend mode lulminance. When it comes to filters and channels and layers in astrophotography I have a golden rule. What am I going to do with this channel? So suppose I'm going after ultra faint Ha to sit the Double Cluster in an Ha background. Obviously I'm going to need shedloads of Ha. Will it burn out the stellar cores? Sure it will. Does that matter? Not a bit, because I'm going to throw the stars from the Ha into the bin! Olly

Oh yes! I'll have to ask Madame if there's a French equivalent. I first heard the English version, I remember, from my primary school teacher, the formidable Mrs Cook, whom I adored. Olly

My data was quite like this but already it was below the limited LRGB threshold I achieved, so I had to process it rather brutally. I was also fighting OIII haloes from my dismal OIII filter! Your data gives a nice clean arc from the loop. Mine was not so clean, largely because the filter wasn't holding down the stars. There is an old English saying: A poor workman blames his tools. That might be me!!! Thanks for your input. Olly

Hey Vlad, very best wishes from the south east of France. You are a giant in this community. Take care, you and your wife. Olly

Dave, I didn't pay enough attention to this comment and have just responded to your own post on this target without making the connection. I do apologize but I'm dog tired at the moment after a run of long nights and lots of IT faffing about by day with our robotic sheds. I really think another look at your data would be worth the effort. Sorry not to have been more attentive. Olly

OK, honestly I think you're black clipping your data. The Tulip is popping out of nowhere as a nice discrete object but I've been working on this region recently as well and I found it didn't do that in either Ha or OIII. There's a strong low level signal around it and then there's the bow shock from Cyg X-1 which I think must be in your data, most notably in OIII but also in Ha. You're using great filters. I genuinely think there must be more low level signal in your data than is appearing in your images here. Olly

I did use that trick, yes. Plus a jackboot or two! Olly

For a good few years I've had the pleasurable company of Paul Kummer and Elaine Seddon around this time but that nasty little thing in the air has put paid to that for 2020. However, Paul is full of good ideas for targets and suggested going after the visual bubble created, it is thought, by the first observationally recognized black hole, Cygnus X1. The bubble is thought to have been generated by one of the polar jets perpendicular the the black hole's accretion disk. It's most prominent in OIII - but that doesn't make it prominent! Also I have a lousy OIII filter in this rig which makes life difficult. So... when it comes to processing, the Spanish Inquisitors themselves would have turned pale had they seen me at work with this data in Photoshop. Iron bars, hammers and angle grinders a go-go. Thuggery. Shameful! But you can see the loop part of the bubble. The Tulip Nebula is thrown in for good measure.😁 Twin TEC140 rig co-owned by Tom O'Donoghue and Mr and Mrs Gnomus. Idea by Paul Kummer. L 12x15mins, OIII 25x15 mins, Ha 20x15 mins, R and G 6x10 mins, B 7x10 mins. Sky: transparency fantastic, seeing awful. Cyg X1: Olly

I ran a pair of Atik 4000s, one OSC and one mono, for a couple of years. It seemed like a logical solution at the time but I ended up feeling it wasn't. At around the same time two other SGL imagers came to the same conclusion. I found that the OSC data proved to be very thin under the mono luminance and I gave up on OSC as a replacement for RGB. Instead I used the OSC for the base image and the mono for Ha. That was OK - ish. What soon became screamingly obvious was that two mono cameras would be a lot better, so I went that way and they certainly were. I've been running dual mono rigs for quite a few years, now, and find them far more productive than OSC/mono. Olly

If you've got four times this sensor size you have one almighty chip! 😀 But, more seriously, your pint is perfectly sound. Olly

It's not just the blue stars, there's blue nebulosity missing as well. It may be to do with your colour balancing routine. What do you use? It's possible to manipulate the blue channel independently but I never find managing colour channels manually at all easy and try to avoid it. (Or could it be your white balance causing the offset away from blue?) I used to find your reds rather yellow and your blues rather cyan but, if anything, I think your Veil is a tad the other way. It's still very good but we all want that last drop! Olly

Multi star guiding is a pretty obscure topic for the beginners' forum. I think it might be time to move on, no? I've never heard of this system and I'm naturally interested. Very obviously the image is extremely well captured and guided with tight stars right across the field. Great stuff. Regarding the Veil itself, I think the stars show that you are capturing all three colours but that blue is under-represented, though certainly not absent. There is strong blue signal from the outer parts of the 'Network Nebula' so it might be worth working out how to capture them. Are they falling foul of an LP filter? I've no idea. Olly

It's nice. The H palette is intended to emphasize the distribution of the different gasses and that's very obvious here. Olly