ollypenrice

I'd forgotten the blue snowball and agree. As for the others, I'm afraid I never saw colour as you've done, but I don't have good eyesight. From reading the forums over the years I get the feeling that visual sensitivity to colour varies greatly between individuals. Some see colour in M42, for instance, but, although I've had views which seem to be fairly deep, it has remained steadfastly greyscale for me. It's a shame because colour means a lot to me in astrophotography but also in my enjoyment of the art world. My parents and my wife were/are artists. Olly

8x is the most popular magnification in the birding community though some go for 10x. I'm one of those who prefers 8X. Although not as 'close,' the extra image stability makes up for it. If quality is a priority then buying second hand has a lot going for it. That's how I got hold of my Leica 8x42. They were about 60% of the new price (so still expensive!) and indistinguishable from new. Clifton Cameras and London Camera Exchange give honest descriptions of item quality. I'd say they even tend to be pessimistic. Olly

The only time I've seen any colour in a PN through a 20 inch at a dark site was the Cat's Eye, which seemed on the blue side. Obviously, an OIII filter can give them a green tinge but that's to be expected. Olly

Well done - and pretty low in the sky from Suffolk, I imagine. Olly

This is what I used to say about a series of concrete circles I left behind me in various parts of Derbyshire! The stars look super in you Tulip - which is a striking image in other ways, too. Let me know how you get on with the SiTech conversion. Olly

AstroArt has a superb stacking-calibrating system and is very fast. It's also very easy. Olly

I doubt this, though I haven't tried it. Levels gives a bog standard logarithmic stretch but any stretch done by any action can be replicated in Curves. In Curves you have total control - but you need to know how to use it. For a second dimension of control you can use Curves in Layers and use layer masked blending to combine the two (or more) layers. The great thing about doing it manually is that you're not using pre-ordained 'guesstimates,' you are looking at your own unique data and interacting with them as you see fit. Obviously I haven't tried all the pre-packaged stretches out there but, of those I have tried, none has tempted me away from individually constructed curves. I reckon it's worth thinking through what you're doing in Curves because no ready made stretch can, in the end, beat one tailor-made to your data and to your own taste and intentions. On top of that, you learn what is really happening when you post-process an image. Olly

The link to the photographer's video shows someone who knows what they're doing but he does make a serious error in saying that his focal reducer will give him a 'magical increase in light gathering power.' It will, in reality, give him no increase in light gathering power whatever. How can it? It lies at the back of the telescope and the light is gathered at the front. What it will do is reduce the size of the image of the Pillars of Creation projected onto his chip, so the original amount of light falls on fewer pixels, each getting more light as a consequence. The reducer gives a smaller, brighter image which is only brighter because it is smaller. The idea that focal reducers increase light gathering power has been done to death under the heading of 'The F Ratio Myth.' Sorry to bring it up again but this is a beginner part of the forum. Olly

Yes, you've jumped from blue to green! Give red a little shove... 😁lly

By 30 lights, did you meant 30 flats? If so, yes, the filter stays in. You need to replicate the light path of the lights. My processing advice would be, - don't stretch so far. The core of M27 is brighter than it needs to be and is losing contrast and detail as a result. The background sky is also very 'busy' and a softer stretch would help that. When you stretch, you might try this (in Photoshop.) Stretch in Levels till you get to a background brightness of 22 per colour. channel. Check this using the colour sampler tool. After that, continue to stretch - but in Curves. Put a fixing point on the curve at 22 (Alt click on background sky.) Put another fixing point below that. Now stretch by lifting the curve only above these fixing points so as not to stretch the background and so increase its noise. - Sooth the background sky by selecting it with the Colour Sample and reduce its colour saturation and try Reduce Noise set to colour noise. - Colour balance. This looks very blue-green on my calibrated monitor. I use colour sampler in the Eyedropper menu to check the background is equal per channel. On the capture side, are you dithering? A 12 pixel dither would help combat that diagonal walking noise. It's already a very respectable image. Olly

It seems to me that the diagram in James' original post is confusing. Why does the point of focus lie so far inside the tube? Olly

I do lots of mosaics and don't have a standard method because each one is different. The biggest division comes between stitching the linear data and stitching the stretched. On smaller mosaics, say up to 4 panel or maybe even 6, I will give the linear files a go and hope to be lucky. First, though, the images must be edge-cropped and have gradients removed. The background sky has to be as close to perfect as you can get it, so the same brightness per panel and the same colour balance. I always go for parity in R,G and B. In Photoshop I'm looking for 23/23/23 in R,G and B. I use Pixinsight's DBE to get rid of gradients. Next I go into Registar, a wonderful program. Sometimes it will give a perfect stitch of the linear. If so I can just treat it as I would a single image from there. When the linear stitch doesn't work I do a partial stretch of each panel (say about 2/3 of a full stretch.) I get the backgrounds equal in brightness and colour balance and feed those into Registar. Sometimes it's perfect, sometimes not. Maybe a couple of edge lines show? If so, I go back to the individual sub frame from Registar, the frame which covers the joint that's showing, and I paste that over the joint and adjust manually, like a patch, using a feathered eraser to blend it. In ICE I'd be inclined to use this 2/3 stretch method and give those to the program. Does GIMP have an 'Equalize' adjustment as Photoshop does? If so, it's a brilliant diagnostic tool. Run 'Equalize' on the mosaic and it will show all the defects of the stitch in gory detail!! If one panel is too green and another too magenta, you'll see it. Go back to the originals, adjust them, and try again in ICE. You don't keep or permanently apply Equalize, it's just there to exaggerate the problem areas so you can fix them. Olly

You need to go back to basics in order not to flounder around in a sea of confusion. Basics, in deep sky imaging, begins with image scale in arcseconds per pixel. In other words, what area of sky lands on each pixel? Too much sky per pixel means low resolution of detail. Too little sky per pixel means not enough light per pixel. The atmospheric seeing (stability of incoming beams) imposes its own limit and the accuracy of your guiding may worsen that limit but cannot improve it. Let's start with your shortest focal length, the ED80 DS Pro. With the ASI178 this focal length is already far too long. It images at 0.83 arcseconds per pixel. You have no hope whatever, in long exposure imaging, of resolving detail at that scale. The atmospheric seeing will not allow it. That's with a non-negotiable full stop., alas. It would be realistic to double it, meaning that your focal length should be half that of the ED80, something around 300mm. Beyond that, you are in the realm of imaginary resolution, sometimes called 'empty resolution.' Your target gets bigger on the chip but has no more detail than a smaller version of the same, but your field of view is pointlessly reduced. Your camera's tiny 2.4 micron pixels would be brilliant with a camera lens. (Samyang 135?) Why does it work as a planetary camera at long focal length? Because you take hundreds of ultra short exposures, a small number of which 'beat the seeing' by good luck - and you select and combine these. Once your exposure times go up to even a few seconds, let alone minutes, you can no longer beat the seeing. In deep sky imaging you must match pixel size with focal length. (Some very advanced deep sky imagers are experimenting with fast frame deep sky techniques but this is not beginner territory.) Olly

You're not a million miles from me and the sky is excellent in the dark spots. For the best seeing, rather than transparency, we usually do better in the last part of astronomical darkness when the land has cooled. Wind is also bad news because it creates layers of air at different temperatures. Enjoy the region! Olly

I'm not a DSLR imager but Tony Hallas suggests a minimum of 12 pixels for dither. If your dither really is happening it must affect the second scope. If you see no loss of resolution on the scope imaging during the dither then I suspect the dither can't be happening. Software can lie! Olly

Yes. It gives a decent star test and, from memory, enjoyable views. I used it in the early days as a second string instruments for guests of our astro-gite but the business evolved more into imaging and we now have a 14 inch Meade for visual so the 150/1200 went into the loft. It's worth peanuts and really wasn't bad. Olly

I have the 150 version branded Bresser. Although it isn't bad, it is, like yours, in retirement. Maybe when our grandchildren are old enough... Olly

Not all of Europe! Here in South East France, just outside a tiny village, I sometimes get zenith SQM readings of 22. The Zodiacal light is easy and, when my eyes were younger, I could see the Gegenshein. Guests who also go to Namibia say there is no difference between the skies at the zenith, though the desert skies are darker towards the horizon. Olly

The de-starring has worked well. Very well, in fact. Personally I wouldn't publish a 'final' starless image, I don't think, but I use them all the time in my present processing because, as Tomato says, you can put the stars back at a fraction of the stretch given to the nebulae. Remember that, in amateur telescopes, stars would not exceed a single pixel without atmospheric blurring and other artifacts. I love the way that such de-starred/re-starred images can give that 'big telescope' look. (The bigger the telescope, the smaller the stars it will produce in images, all things being equal.) Regarding your excellent Eagle, my suspicion is that it may be slightly black clipped. I may be wrong, but I'd want to hunt around in the bottom end of the signal for any faint stuff that might still be lurking there. Olly

This thread tells you how to make a camera tilt adjusting jig so that testing on the stars isn't required. Olly

With dual or tri-band filters available I think we're getting very close. Maybe fast optics are also important (I don't know) and the aim needs to be enhanced broadband rather than pure colour mapping. Olly

OSC. Filters and the RASA carry too much baggage. Olly

I thought it crazy this year, quite honestly, Rodd. And I thought the processing would all be about gradient removal. In fact, this hasn't had any because I couldn't find any way to do it. This wasn't a complicated image to process, really. Olly

Yes, I felt there was a whiff of green across the middle, going horizontally. However, trying to fix it threw the other regions out of colour balance so I decided to let it be. I didn't run SCNR green on the linear data. Perhaps I should have done. Olly

Unmounted filters are simple to fit but you must have a filterweel designed to take them. The carousels are different so you need either the mounted or unmounted version. I really wouldn't over-estimate the added complexity of mono. With OSC you have to stack and calibrate. You just do the same per filter with mono. I combine RGB in AstroArt, which takes about a minute. After that you'll have gradients to remove but that applies to OSC as well. Olly