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ollypenrice

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Everything posted by ollypenrice

  1. If you have Photoshop or a program with similar functions there is something you could try. 1 Concentrate on a zone in the image where the elongations are all going the same way. Make a copy layer. 2 Rotate the image so that these elongations are now horizontal or vertical on your screen. 3) Set the blend mode in Layers to Darken. 4) Go into Filters - Other - Offset. You'll be able to nudge one layer (either vertically or horizontally, depending on how you rotated your image) relative to the other to mask the elongations. Use a large, well feathered eraser to remove those parts of the image damaged by this modification, keeping only those zones in which it's an advantage. 5) Flatten and repeat with a different rotation for other parts of the image. 6) Restore the original orientation of the image. Make no mistake, this is essentially a bodge, but done with care it might considerably enhance your image. Olly
  2. I'll just throw in one caveat here: if other reviewers are anything like me they won't accept for review a product which they think will be a waste of their time. The disruption to the observatory (my reason for not doing reviews any more) is considerable and not rewarding unless the product is decent - so doubtful products don't find reviewers while promising ones do. There's an invisible selection process going on in the background, I think. Olly
  3. A pretty cursory search on the internet will find a considerable number of disappointed customers. That's a plain fact. I have nothing to say about whether or not they are right to be disappointed - that's for their readers to decide - but I do know that one of my own customers was threatened with legal action by OOUK regarding anything he posted about them. Perhaps they'll threaten me over this post. They are welcome to try... Olly
  4. There are no star-removing filters, as others have said, though tight NB filters drastically reduce star size. Still, you want broadband star colour so that's not the solution. The thing about post processing, where you can reduce star sizes, is not to look for one magic wand. It's all about patience and small iterations, one small improvement at a time, often in layers. (Fight with masks in Pixinsight if you like but they are not for me.) Careful use of Curves in stretching also helps. There is no point in stretching anything brighter than your brightest nebulosity, so identify that point in Curves and don't stretch above it. It really is all about tiny steps, there is no One Big Fix. For all that, the image with which I'm the least satisfied in my collection is the Veil, despite every effort! Olly
  5. That's worked! There's a certain charm to persuading data from different sources to come nicely together. I love your thread title! It proves we're all mad... lly
  6. I think the outer halo would be helped by a more neutral background sky. It's pretty blue 'as is' and, since the outer halo has also emerged as blue in your mapping, the contrast is diminished. As you say, I think this will be a processing job to tinker with. Olly
  7. Sorry, I'm with Adam J. The sun 'joke' is an in-joke for astronomers. When you post on the net you have no idea who will be watching or how they will interpret what you say. They may well not 'get' your irony at all. (Irony is the term, by the way, rather than sarcasm.) And, I'm sorry again, I found the rest of the humour pretty turgid as well. Olly
  8. I've done five first year level courses under this consortium and found them excellent on all counts. Going further would have meant sorting out my maths, a potentially impossible challenge. I was a teacher at the time of my astronomical studies and, therefore, had an interest in the business of teaching and learning as a subject in its own right. What struck me was how well thought-out the courses were from a pedagogical point of view. I felt I was being very well taught. Olly
  9. No, I don't have it Vlaiv. I constructed a big mosaic recently using panels captured and pre-processed in APP by Yves Van den Broek and I also used his APP-generated mosaic as a template, but I post-processed exclusively in PI, Registar and Photoshop. The first thing I'd say is that many M31s (including my own) are probably too colourful with the arms too blue and the core too red. Personally I don't like to use any automated stretches, including DPP. The stretch is the defining operation in post processing and I like to do it slowly, in small increments, and by hand. Once I get the background up to a reasonable brightness I stretch only above that. Olly
  10. Stars are point sources. They don't follow the 'F ratio rule' even if you believe in 'the F ratio rule' - which I don't! (I believe in area of aperture per area of pixel.) Olly
  11. I agree with Alacant. Try to get a rough focus by day. The distant horizon is a good bet. Olly
  12. That's absolutely gorgeous: the texture of the surface is tangible, making you want to run your hand over it! Olly
  13. Very smooth, Carole, and a good field given how big this object is. To my eye the black point looks a little high and perhaps you might coax out a little more local contrast? Olly
  14. Late to this party but it's a great party!! Stunning image. I do love a wide M45 because it all makes so much more sense when you see the lot. And, as others have said, it's a treat to see you back, Peter. Olly
  15. 1) Do you have red lighting anywhere in the observatory or use a red torch when setting up, etc? Could that have been getting into the tilt plate gap? 2) I don't like the look of the original red flat at all and the arcs certainly shouldn't be there. Whatever is causing them (we hope the tilt plate gap, now fixed) may well have been at a very different intensity between the flats light source and the lights light source, so they wouldn't be expected to calibrate out. If the flats were under correcting the percentage interference by whatever caused the arcs in the flats was lower than the interference during the shooting of the lights. That would fit (I think) with red light in the observatory getting in through the gap during the imaging run. I would paint that tape with barbecue or stove paint as well. You need a pigment based paint rather than a dye-based one for blackening optics. Black dye paints can be reflective in IR. Olly
  16. Sure. Resolution of detail is generally dominated by the sampling rate of the imaging setup, measured in arcseconds per pixel. There is a calculator here: http://www.12dstring.me.uk/fovcalc.php The resolution goes up as the pixel size goes down or the FL increases, or both. You may also be limited by the optical resolution of the telescope, particularly when using small refractors with small pixel cameras. There is little point in trying to image below about an arcsecond per pixel because other factors, notably the seeing and the guiding, will blur out the theoretically possible detail available below that. When you try to over-sample in this way you simply reduce the amount of light striking each pixel and slow down the imaging process. Your final image will give you a bigger object but a bigger one containing no detail not found in a properly sampled one. As pixels get smaller it becomes increasingly possible to over-sample. For example, you could put a Canon 5D Mk4 in a C11 and this would be sampling at 0.39"PP. This would be an utter waste of time because that level of detail cannot be resolved and, at a more realistic focal length, you could capture the same real detail while putting more than twice as much light on each pixel. My own high res imaging is done at a metre focal length (TEC140 refractor) and at 0.9"PP (Atik 460.) This gives a decent 'real world' result in my view. A 10 inch F5 Newt would give a similar result with slightly larger pixels and would be faster because of its greater aperture. Just keep your sampling rate realistic. Olly
  17. I think that's a beautiful rendition, revealing less of the gas but more of the dust than we usually see. It absolutely must be seen at the higher res (click on the image and click again) because it holds up superbly and the details within the Trunk are gorgeous. Crazy-deep Ha has its place but it isn't the only way to go and this is one of the most subtle versions I've seen of this target. If you do want to emphasize the Ha a little more and have Ps (I don't know about Lightroom) the simple trick is to go into Selective Colour, Reds, and move the top slider left to lower the cyans in red. This always brings out Ha signal. Olly
  18. No, it still hooks on using the standard two bolts which sit on the dewshield. I suppose it would be better to mount it on a new card so that it was centred on the lens but since it gives a perfect result as it is I've never bothered. Olly
  19. I use a mask designed for an 85mm refractor on a 106mm refractor and find it works perfectly (checked by also measuring FWHM values at the same time.) Olly
  20. The cure for aperture fever is focal length. In this telescope, at the nearby Observatoire des Baronnies, a 31mm Nagler is an excellent planetary eyepiece. In the end an enormous aperture inevitably ends in a small field of view. Personally I wouldn't want that. Olly
  21. I'd begin by finding out what sampling rate you'll get at various focal lengths with the camera you intend to use. Because pixels are getting smaller you can reach high resolution with shorter focal lengths these days. Other factors: - You'll be lucky if your seeing allows you to get down to 1 arcsec per pixel and very lucky if it allows better. - Your guide RMS in arcseconds needs to be half or less of your imaging sampling rate. (So to image at 1"PP your guide RMS needs to be no higher than 0.5".) - If going for a 250 or 350 Newt, are you well protected from the wind? Olly
  22. I've been mightily impressed by a QHY OSC camera recently but if you're mainly going to do narrowband then mono still makes more sense. Very good Heart nebula! Olly
  23. The term 'magnification' isn't used in astrophotography and with good reason. It is literally meaningless. What is being magnified? Certainly not the Ring Nebula because that is quite a bit bigger than any picture of it ever created! We say something is magnified 100x when an eyepiece magnifies an image on our retina by 100x. That makes sense. A scope/camera doesn't produce an image on our retina so what are we magnifying? Nothing. We're not. So what are we doing? We are using a telescope to project an image onto a camera chip. The longer the focal length of the telescope, the larger that projected image will be. But -and this is very important- how many pixels do we put under that projected image? The more the pixels (i.e. the smaller the pixels) the larger the final image will be. The useful and meaningful unit here is arcseconds per pixel. How much sky lands on each pixel? The smaller the amount of sky per pixel, the larger the final image will be. This is the closest we can get to talking about 'magnification' in astrophotography. It is worth getting your head around this because, until you do, you'll be confused. Olly
  24. There's little point in considering the optics without considering the camera and the mount since they make a single entity in use. So the first question is, 'What is your guide RMS in arcseconds?' (If you give PHD your guider's pixel size and focal length your RMS will be given in arcseconds.) Whatever is your guide RMS, mulitply it by two to get an idea of the resolution your mount will support. If your guide RMS is 0.5 arcsecs, don't try to image below 1 arcsec per pixel. The resolution of an imaging rig is not determined by focal length or by pixel size but by both. There are lots of online calculators but I use this one: http://www.12dstring.me.uk/fovcalc.php You then have to consider the chip size and whether or not 'scope x' can cover it. Not many scopes will cover a full frame (35mm) chip, for instance. Olly
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