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The Admiral

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  1. I don't think that there is a right or wrong, it's equipment that allows one to achieve what one wants to achieve. If this thread achieves anything it is that it dispels the myth that to do any astrophotography one has to have expensive mounts accurately aligned, with guiding to boot (the so called right equipment). Ian
  2. Thanks very much happy-kat. Yes, it is bit gross really; I think in future 30s subs would be more reasonable! They don't half fill up the hard drive! In fact the M106 image has a longer integration time than the Horsehead, using 30s subs. Ian
  3. I am so at sea with PixInsight at the moment. But I managed to squeeze this one out of the pot! After using Advanced Background Extraction to remove a strong green cast, I find that the targets are also left a bit green. Previously I tried Colour Calibration to remove the tint, but this time I used the Curves Transformation to lower the green channel before upping the saturation. I wonder if Colour Calibration removes the colour information too much. Not saying it is anything like it should be, but if anything, it shows I've a lot more to learn Ian
  4. Here is my attempt at M106 and friends. I used ~100 x 30s subs together with 50 flats and bias frames. Other details: Fuji X-T1 through an Altair 102mm f/7 Super ED, all mounted on a Nexstar 6/8SE mount, 10th February 2016. 1600ASA. The original images are quite feint. This first image is stacked in DSS and processed in Star Tools. I'm also trying to get to grips with a trial of PixInsight, and this is what I achieved today after many sweated hours! It needed a lot of stretching; in fact I did it in two stages. The fainter details are more obvious, but there is no way that I could get any colour into the galaxy, like the Star Tools processed one. It is still quite noisy. Any ideas from you experts? Ian
  5. I thought I'd have another go at the Flame and Horsehead nebulae, but with greater exposure. Here I've used about 250 x 10s subs, compared to ~64 x 15s subs I'd used previously. Otherwise: Fuji X-T1 through an Altair 102mm f/7 Super ED, all mounted on a Nexstar 6/8SE mount, 10th February 2016. 1600ASA, stacked in DSS and processed in Star Tools. I used about 50 darks and 50 bias frames (no flats). I know that there is a lot of nebulosity in the region, so I find it hard to know how much is noise and what is genuine signal. I also had a go at the Beehive Cluster (M44). An easier target I guess as there is no faint nebulosity to contend with. For this I used about 50 x 10s subs; other settings as above. Stars are a bit turquoise rather than blue I feel. Ian
  6. Hi Herzy Well as long as the object is visible in the eyepiece after you slew to it, I'd say that was OK. You just inch the 'scope to centre it. So far as imaging is concerned, what is more important is how much the object drifts in the FoV over time, so that is something you'd need to check out, but it will be dependent on how well you set up. As for another OTA, well that's your decision, but I'd have a good crack at imaging with your current set-up first, acknowledging its limitations, as you might decide it's not for you in the end. Remember, this is imaging on the cheap, and if you get images you're satisfied with, all well and good. It's a learning experience anyway. But if you want something better, there's a whole world out there only too willing to take your money for an upgrade, and then you have to decide just where to draw the line! It can get very expensive and very time consuming. That's why I'm content to get the best I can out of the simple stuff Ian
  7. I don't know what may be available for Macs, but if all else fails I guess you could run it on a Windows boot within the Mac OS? When you say that the alignment was only perfect 1 in 5, what was the problem with the other 4? Again, of course, tracking errors will be exacerbated with a long FL 'scope, and although OK for visual observing they might be a challenge for imaging. You may have to image in blocks of, say, 10 minutes and re-centre between each block. Ian
  8. Hi Herzy, don't get too disheartened, it is an uphill challenge but I think has its rewards in the end! But there are a lot of things that can impact on your image. In addition to what Steve said, your 'scope has a focal length of 1250mm, and the longer the focal length the more demands it will place on your mount. This is because any movement in the mount, either intentional or unintentional, will show up more than with a 'scope with a short focal length of, say, 500mm. So, what can you do about it? My two-pence worth would be: Place the tripod on solid ground. Keep the legs as short as convenient. Mount the 'scope/camera so that it is balanced on the mount. Avoid imaging when it's windy. Use mirror lock-up on the camera. Operate the camera using a remote release. Keep the exposure time as short as possible consistent with getting results. Keeping the exposure short? At one end of the scale, if you image bright objects, like the planets or the moon, then your exposure time can be sub-second. As Steve pointed out, field rotation may be evident when you exceed 30 seconds, depending on where in the sky you are pointing. But for deep sky objects you will need to experiment to see what is the longest exposure you can use with your mount so as not to give star trails. In your image of M42 it looks as though the exposure has led to saturation in the core of the nebula, so perhaps even 30 seconds is too long at that ISO. You won't get the best results, or indeed any result, by using just the one exposure. What you need to do is take dozens, or hundreds (yes, hundreds!), of exposures each less than 30s. You then combine the best of these into one image in specialist software, a process called stacking. For planetary imaging such free software are Registax and Autostakkert, and for DSO imaging, DeepSkyStacker. The images of your target object are termed "lights" in stacking parlance. You can improve the output of stacking by taking account of noise by taking a lot of images with the 'scope capped, so as not to admit any light, using the same exposure length. These are termed "darks". By repeating the darks, but using the shortest exposure your camera can take, you can account for the camera's read noise. These are termed "bias" frames. And finally, you can correct for unevenness of sensitivity by using exposures called "flats". As final thoughts, when you set up your mount: Make sure it is as level as you can. Use a proper spirit level, not one of these buttons with a bubble in the centre which I've found to be hopelessly inaccurate. Enter you precise location. Enter you time as precisely as you can, say within 5s. Centre the star as closely as possible (you indicate that you are doing that). Make sure that the 'scope doesn't slip on the friction clutch when you swap from the eyepiece to the camera. This is a problem I've had, and I've now found that with my red-spot finder well aligned I can use the camera's live-view to centre the star, so avoiding the need to swap. I hope this helps, but as you see, there are quite a few things that need to come together to get a satisfactory image. Ian
  9. Nice capture of the cluster and nebula there Steve, and it's good to see what creeps out of the shadows when the wick is turned up! Ian
  10. Here's my attempt at the Flame Nebula and the Horsehead. It's not a great success because the cloud rolled in before I'd barely managed to capture 70 frames, and on some of them a finger of thin cloud passed over the target area. Still, it's succeeded in showing both NGC2024 and IC434, and a suggestion of NGC2023 and IC435. I just need a lot more imaging time. Oh this weather! Details: Fuji X-T1 through an Altair 102mm f/7 Super ED, all mounted on a Nexstar 6/8SE mount, 3rd February 2016. 64 x 15s subs, 1600ASA, stacked in DSS and processed in Star Tools. I took about 50 darks and 50 bias frames (no flats). Ian
  11. Forgive me asking a stupid question, but how is binning done on 4-pixel arrays? Ian
  12. Thanks NigelM, I wondered about whether that might be an important factor, which is the reason for my last paragraph in the OP. But I've no idea of the scale of these factors however, and whether the signal from sky background (incl light pollution) dwarfs the read noise, or vice versa. If the former, then I presume a reducer would be of marginal help? Ian
  13. Thank you Olly, it's comforting to know that I'm not going on a wild goose chase! Ian
  14. Thanks for that AB. Yes it does make sense, but let me take an example. For the sake of argument, suppose I am imaging, with a sensor of 2000 x 2000 pixels, an object whose dimensions are half that of the sensor (i.e. 1000 x 1000 px). Now, I introduce a 0.5x focal reducer. The image of the object becomes 500 x 500px in a 2000 x 2000px frame. In other words, all the photons from the object are now spread over 250,000 pixels rather than 106 px, and so each pixel will receive 4x more photons. At the same time, the image will have 'shrunk', the resolution will have dropped, and so the image will need cropping if it is to appear the same relative size in the final image. The cropped image size would need to be 1000 x 1000px. If instead, I bin 2x2 in the processing, the SNR will improve. My image proportions will remain the same (i.e. I won't need to crop), but the overall image size will halve to 1000 x 1000px. So it looks as the two approaches achieve the same thing. I end up with a smaller, lower resolution, 1000 x 1000px image (assuming I want the object image to be the same relative size), in which the SNR is improved. I can see that if you actually want to image a wider field, then a reducer is the only way to do it, but if I don't, then from my very naive perspective it seems that using a reducer or binning pixels are equivalent. So I'm really looking for confirmation from you experienced guys whether or not my naive logic is correct, and if not, what have I got wrong. As to whether binning the camera output or in post-processing is the same thing is a moot point really, as I'm not in a position to bin the output from the DSLR, though I can see that there would be a difference. Ian
  15. This question relates to using short sub-lengths of less than ~40s taken with an APS DSLR. I'm not referring to long exposures using an accurately aligned EQ here. If I use a focal reducer, the FoV is increased and photons from an object which fall on the sensor are spread over fewer pixels compared to without a reducer. Consequently, those pixels are filled at a greater rate and the exposure can either be reduced, or one can benefit from increased SNR. Now, when I come to processing I have the option of binning pixels (Star Tools), which again has the effect of increasing the SNR, if I understand correctly. So my question is, is there any advantage to using a focal reducer when I can get the same effect using pixel binning in processing (except of course when the object extends beyond the normal FoV)? I can appreciate that with perfectly black skies using a reducer will help overcome the inherent system noise and allow one to see deeper, but in normal skies with the ever present light pollution, is that of particular relevance? Ian
  16. Thank you Steve and Olly for your kind words. As you say Olly, it is not an EQ mount , but what a beast. Are there any images from it that can be viewed? Well tich, you should go for it, you might be surprised at what can be achieved with modest equipment. This thread has shown that dedicating large monetary sums and huge amounts of time aren't at all necessary to get into astrophotography, and for those thinking of dabbling in the black art, it's a good way to start without being sucked into the all-consuming black hole to which many have fallen! I'm currently reading a book called "Astrophotography on the Go - Using Short Exposures with Light Mounts" by Joseph Ashley, and it seems a good primer. Ian
  17. Well, after posting about my rather feeble attempt at M31 using a spotting 'scope, I've now acquired a proper astronomical 'scope and I've been keenly awaiting the arrival of Orion so that I could have a try at imaging the glorious M42. Being so bright, it represented a rather easier challenge than many. This is with a Fuji X-T1 through an Altair 102mm f/7 Super ED, all mounted on a humble Nexstar 6/8SE mount, 19 January 2016. About 100 x 15s subs, 1600ASA, stacked in DSS and processed in Star Tools. I took about 100 darks and 60 bias frames (no flats), but I forgot to do these at the time so they were done early the following morning, after leaving the camera out to cool in the still frosty morning. Given that this is my first proper DSO image and that I'm still trying to figure out how both DSS and ST work, I'm pretty pleased with the outcome. Even with a 15 second exposure the core is blown out, so it'd be nice to get some more data with shorter exposure. Also some banding is visible, which I guess might be to do with not taking the darks at the time of the original exposure? I then moved a little to the east and had a go at the Rosette nebula. As above, but 130 x 10s subs. I think it needs a lot more data though. Ian
  18. Having just acquired a 102 triplet myself, I'd agree it performs well. Only used it for visual, and with the deplorable weather we've had of late, even that has been in a few short snatches. Nice to hear a positive comment about Altair too. Mind you, it seems to have taken 3 years! Ian
  19. Welcome Astronator. That's a lot more than a white blob. I'm looking forward to seeing what you achieve with a telescope! Ian
  20. I'm sure the cognizanti will recognize this (and I don't include myself!), but I'd appreciate knowing what it is of please. Nice to see some colour coming through. Ian
  21. I use Kays Fasteners on eBay, a good range of stainless steel nuts and bolts which you can buy in small quantities, postage free and a good service. Prices are sensible too. My daughter wanted to attach some casters to a couple of boxes, and she needed 32 nuts and bolts in all. It would have cost 15 quid for zinc plated items in B&Q; cost from Kays, under a fiver for stainless! Ian
  22. When I posted my thread "Messing about with M31" I had no idea of the existence of this excellent thread and the superb work already achieved with 'lowly' gear. Having read the thread "To stack or not to stack: 30 x 1s = 1 x 30s?" by Martin Meredith on 28 May I can see that there is great potential to be had with stacking of short duration subs. OK, I guess at the end of the day, there is no substitute for photons, and that means aperture and time, so we might not be able to see the faintest of detail, but hey, we can still get a good way along the quality scale . Keep 'em coming. Ian
  23. Welcome to the fold Badger! The subject does have a tendency to draw one in . I use a horizontal Yagi in the loft, and I've found, particularly recently, that my background noise levels are well up, up as high as -84dB. I know that other folk's noise levels are below -100dB, so I'm deliberating whether to purchase a low noise antenna, or move it outside, which I'd prefer not to although it would be technically better, or both. I'm not using the S@N design, but I put it together from another design. Using a dummy load at the end of the cable I'm getting -105dB-ish, so it has the potential to be low. Still, it's challenges like this that make the subject interesting. Happy hunting. Ian
  24. I must admit that Spectrum Lab is a bit daunting at first sight. Have a look at another Sky at Night article, which you can download from the Brit. Astro. site: "Configuring Spectrum Lab for Meteor Scatter" here: http://www.britastro.org/radio/downloads.html Ian
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