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Showing content with the highest reputation on 18/10/19 in Posts

  1. 5 points
    Ten hours of data LRGBHa - from summer 2018 but only just got round to processing it. Very hard to bring the faint outer shell out without blowing out the stars. Lots of very small galaxies in the background.
  2. 5 points
    As you can see, this ad has been tidied up. Can members please remember that this is the for sale section and NOT the equiptment discussion section. When someone posts an item for sale, they don't do it with the expectations of being badgered. The seller has made it clear the price she wants. If it's not what you want to pay, make an offer. If it's not accepted, walk away. Your reasons for thinking YOU know how much an article is worth means nothing. Whether the seller decides to revice the price is up to them.
  3. 3 points
    You heard it here first, folks: Gina deals in stolen firearms James
  4. 3 points
    So, there was this interesting telescope on auction on Ebay.co.uk last week and I just bid the lowest amount - 35 GBP - yes 35! I was the highest bidder - kind of surprised there but oh well, luck struck and I picked it up the other day. This is Vixen made 6" Newtonian on Vixen Polaris mount. Condition I would say is not ideal but still servicable. Would need some love but the mount is smooth and I just love Vixen's slow-mo controls. These are rusty though. It has a sled focuser and surprisingly it is in mint condition and very smooth. One of the better focusers I used. The mount looks like a great one. Smooth and it can be set up in Alt-Az as well. I am still debating myself if I should tackle a little cleaning and regreasing or just send it somewhere. The same for the mirror. I can see the coatings deteriorated but still usable imo.
  5. 3 points
    Nice!! Along time ago I had an 80F5 with a 32m plossl. This summer I picked up a 30mm wide field for an 100F7 and had so much fun that it reminded me why I always had fond memories of the 80F5. Wide field is can be such a joy and really can be a inexpensive way to enjoy the night sky. Everybody should just do this from time to time it's so relaxing and entertaining. Kevin.
  6. 2 points
    Focal Ratio has nothing to do with field of view (fov). Fov is entirely controlled by the focal length of the telescope for any given eyepiece. Your 115mm f/7.8 Vixen has a focal length of 897mm (115 x 7.8) while a 6" f/5 is 750mm. The ratio 897:750 gives you the difference in field of view and will remain at that ratio between the two telescopes for any given eyepiece. Using a simple ratio you will get between 16 and 19% ( depending on which way you work it ) extra linear field of view with the 6"f/5 using your existing eyepieces. Personally, I would go for wider field eyepieces rather than the Newt as they will give bigger and more pleasing images. More field stuffed into narrow field of view eyepieces makes everything smaller. Nigel
  7. 2 points
    Here's my take on the Elephant's trunk nebula in Ha, along with some of the output from Starnet++. I was just trying to understand it a bit better. The extraction of the stars seems very clean to my eyes 19 x 5mins, Skywatcher ED80 x0.85 / Baader 7nm Ha Starless (PixInsight w Starnet++, default settings) Starmap from Star Starless + Starmap layer (colour dodge, 80%)
  8. 2 points
    I would not do that either, but if you are starting AP on a limited budget - you can in fact use it to get decent results. It is also good to know that it can be done - and more importantly why it can be done and under what circumstances.
  9. 2 points
  10. 2 points
    With a 90% moon Ha is pretty much the only option available so this is 58 (out of 60) x 300s of Ha taken with a Samyang 135mm + ASI1600MM-Pro unguided. I've struggled to know what this should look like in terms of surrounding dust/nebulosity. Images of NGC7822 vary widely on the internet with anything from pristine blackness surrounding the NGC7822 to so much surrounding nebulosity it is almost difficult to distinguish the target. I've been guided by the apparent dark/near black patches towards the centre of the nebula. The image was calibrated and integrated in APP, then processed in PI (ABE and HistogramStretch) followed by a very small amount of noise reduction in PS. The image is cropped a little to remove some dodgy looking stars in the corners - an ongoing issue with my 135mm+1600 setup I am failing to solve Thanks for looking and as ever comments and criticisms are alway welcome. Adrian P.S. There is a funny little curved artefact near the very top of the image; any thoughts on what that might be? I removed two lights that contained satelite trails but this feature is only distinguisable on the stacked image.
  11. 1 point
    http://www.deepskywatch.com/Articles/what-can-i-see-through-telescope.html Have a read of this.
  12. 1 point
    I've not powered mine up yet. I'll wait until the morning when I can see better. Still, pretty much ready to go, I think. I've no doubt it will need a few mechanical tweaks. If not, I'll be very happy! Time to cook some grub! Louise
  13. 1 point
    The Pup star follows the primary star as it drifts across the field of view with the mount undriven. The separation is around 10 arc seconds so thats not the challenge - it's spotting the much fainter star amidst the glare from the primary that is the trick. I did it 1st with my 12 inch dob a few years back and I've since got the split with my 130mm refractor and my Tak 100 but not as yet with the ED120 ! The seeing conditions are a key part of spotting the Pup - they can make or break the attempt.
  14. 1 point
    Yes the fringing problem is a big problem in high resolution spectrographs (eg the LHIRES with 2400l/mm grating). It is due to internal reflections in the cover glass. It also produces newtons rings in solar h alpha imaging and can arise from subtle changes in sensor design. eg people who upgraded from an ATIK314 which is free of fringing, to an ATIK 414 immediately ran into problems due to the lack of AR coating. Not sure if it is connected with microlensing artifacts though which is a different phenomenon. The AR coating has a downside though if you want to work far into the UV. Here are a couple of curves for different camera windows for example (note in this case this is the protective window on the camera, not the sensor cover glass http://www.spectro-aras.com/forum/viewtopic.php?f=45&t=2085&start=30#p11740 For optimum UV performance for spectroscopy (but not high resolution) some users are taking ATK414 cameras with no AR coating on the sensor cover glass and replacing the AR coated camera window with uncoated clear glass with good UV transmission Robin
  15. 1 point
    Rings Bought some 230mm tube rings from Telescope Express. Nice solid pair of rings. I wanted to make some chages to make it better for Alt-Az mounting with the handle on the top when fitting the scope to the mount. Makes it easier to be able to hold the scope in position with one hand while tightening the saddle clamp. Removed the dovetails and radius blocks from the OTA. Fitting the Losmandy radius blocks to the rings required drilling a couple of new angled holes in each block and tapping the holes to M6. Countersunk bolts were used to fasten on the blocks from the inside of the rings. The Vixen radius blocks on the top were easier as existing holes in the blocks could be used to bolt them in place. It’s so much easier fitting the scope to the mount now. Oh and the new knobs on the saddle worked a treat. So easy to get a good grip and get them good and tight. Had the scope out the other night. Left it to cool for an hour. Dew was dripping off the scope and had to wipe off the finder and eyepiece but zero dew on the scope primary or secondary. Had read that this scope just doesn’t dew up. Took a tour of the moons terminator and was impressed by the sharpness, contrast and detail showing. Then tried the Morpheus 4.5 which would give 541 mag. All I can say is wow. Unbeliveabe detail !!! The sensation of just floating above the moons surface was remarakable. I had thought the Skymax 180 was a good lunar scope but this is in a different league. I could see more detail than I ever did in the 180. And this was with mist and not great seeing. Can’t wait for a clear night with great seeing And also the collimation needs some fine tuning.
  16. 1 point
    Carrying on with my ebay £5 camera I managed to grab this 15 minute live stack using the AZGTi and 72mm Altair scope. Processed in Startools. I feel that my Altair GP Cam is nowhere near as sensitive as this tbh. So, if I were to buy a modern camera, to use for EEVA with my 72mm scope, what should I buy? Are there any options around £300 to £500 ? Thanks for looking
  17. 1 point
    If you are having to deal with light polluted skies, I suggest getting a UHC or OIII filter to make seeing nebula easier. Galaxies are going to be all but impossible to see except possibly for their cores (M31 comes to mind). Higher powers will make globular clusters stand out better from the background as @Mr Spock suggests.
  18. 1 point
    Thanks Alan, I will try this- what a difference the Paracorr makes.
  19. 1 point
    Maybe one way to look at this is via extreme. If the focal ratio is effectively 0 then all light goes to one pixel. Max SNR min resolution. Extremely large focal ratio minimum SNR max resolution. Same diameter scope. Regards Andrew
  20. 1 point
    Sounds great, Gerry! Any chance to test the Docter and Zeiss Zoom too? I've not read a comment on how those two eyepieces perform with the paracorr2.
  21. 1 point
  22. 1 point
    BTW You can use phd2 along with Kstars it will integrate with it for guiding and or PA I personally use the Stellarmate OS as again it’s all done for you and it just works...but it is $49,
  23. 1 point
    DBE. Simple as that. Unfortunately it has to be applied to the linear image so it involves going back to square one. After an edge crop it's the first thing I do in post processing. I follow Rogelio Bernal Andreo and Harry Page in applying a small number of carefully placed background markers, scrupulously avoiding anything but pure background sky. Give the linear data a very aggressive screen stretch (called STF in PI) so as not to put any markers on fuzzies, the glow around stars, or outlying nebulosity - particularly when processing galaxies which get bigger as you stretch. The advantage of fewer markers is that they let the software estimate broad changes in gradient rather than more local ones. Don't use DBE to correct star flare, for instance. When the gradient map appears look at it before applying it to ensure that it really is a broad gradient map has no local details in it whatever. In your image I'd try one marker in each corner and one half way along each side at the edges. Maybe two more, one each side of the ring but half way to the edge in each case. You don't want it to mess with that faint outer glow or to read that little spiral. I can't promise that this will be right but it would be my own first guess processing this data. Screen stretch the result image after the DBE map has been applied using subtraction. If it still doesn't have a neutral background increase the 'Tolerance' value and try again. Once you get to a stage where there's maybe just a bit of green gradient left, stop. Switch to SCNR green at a low value on the slider and increase it till you get rid of the green gradient. You want to apply it as lightly as you can. Remember that you don't need to get a perfectly neutral background if your screen stretch is far more extreme than your real stretch will be. Final head-banging stretches for the faintest detail I do in Ps using layers. I make a copy layer and work on the bottom, top invisible. In Curves, pin the background sky where it is (Cursor on the sky, Ctrl click) and fix it just below that with a point, then lift the curve just above the background marker. This will stretch everything above the background including stars but you then go to the top layer and erase it over the stretched items you want to see in the final image. (Galaxies, nebulosity etc.) But the top layer will not have the stretched stars in it. This is a method unsuitable for images with widespread nebulosity but it's good for galaxies, PNs and images with lots of starfield. Olly
  24. 1 point
    Nice one, welcome to the frustrating but rewarding slippery slope that is Astro Imaging.
  25. 1 point
    Well done!!!!! a great achievement Alexandra
  26. 1 point
    Excellent Gav.. I look forward to great things from you on 11 November Mercury transit Dave
  27. 1 point
    Works both ways - for the same camera and same scope (aperture) - adding a barlow "makes pixels smaller" - they end up collecting less light and SNR will be less for same imaging time compared to same scope without barlow. It does not matter if you use longer focal length scope with same aperture or barlow (provided barlow is perfect and has no light loss - but even if it has, with modern coatings difference will be minimal). F/ratio myth is not is not a myth if you keep pixel size the same. It only becomes the myth if you assume it to be true always, regardless of the pixel size. Statement like F/5 scope will always be faster than F/10 scope is incorrect - because it does not consider pixel size. It will be true if you use the same camera, but if you put camera with pixels twice the large on F/10 scope (and otherwise equal camera) - they will have the same speed. If you put camera with x3 large pixels on F/10 scope - it will in fact be faster than F/5 scope with x3 smaller pixels.
  28. 1 point
    I can easily refute that . It involves understanding how telescopes work, a bit of nature of the light and some mathematics. If you wish, we can go into details of it, but here is very simplified version of it. When using same camera (same pixel size, same QE, ....) and same telescope with reduced and native focal length - you will get different pixel scale. Let's say that at native focal length, your pixel scale is 1"/px, and reduced you have 2"/px. In first instance, pixel will gather all the light from 1"x1" area of the target. In second instance, reduced, pixel will gather photons from 2"x2". Because of the way telescope works - all the photons originating from said areas that fall on aperture will be focused on given pixel. In 2"x2" case, we simply have more signal collected in the same amount of time in comparison to 1"x1" case. Because of the nature of the noise sources present - more signal in given amount of time means better SNR (some sources stay the same per pixel - like read noise, dark current noise, while some have square root dependence on the level of signal - like shot noise and LP noise). Just to make it clear why is this observe following: 1, sqrt(1) = 1, ratio of those is 1/1 = 1 4, sqrt(4) = 2, ratio of those is 4/2 = 2 9, sqrt(9) = 3, ratio of those is 9/3 = 3 .... In another words - you increase signal and ratio of that signal and associated noise is increased (SNR), while other noise sources remain the same per pixel. I'm just showing here that more signal per pixel will always produce better SNR even if we account for all the noise sources (I can do precise math formula for SNR if you want - it will still show the same). Btw shot noise is equal to square root of signal because light comes in photons - Poisson distribution. For the same aperture - pixel covering more sky will have better SNR than pixel covering less sky. You have mixed in resolution in all of that, and yes you are right, in some cases system with reducer will loose some of high frequency components over unreduced system - there will be some detail loss, but let's look at what happens with SNR if you upsample the image - do you loose it? Here is a little test, we start with empty image and add gaussian noise of magnitude 1. Here it is - we measure it, and it is indeed 1. Now I will upsample image by x2, and again measure noise of it to see what we get: Ok, so noise did not increase, in fact it decreased somewhat (I'll explain why), and we know that signal remains the same if we upsample the image (resizing does not make image brighter or fainter). SNR of upsampled image remained the same, or to be precise - it improved a bit. There is no other conclusion but to say that in your mentioned workflow, for same total time - system with reducer will provide better SNR, even if you end up upsampling result image (which I would not personally do - nothing gained by it except larger scale but somewhat blurry image - I like better smaller scale sharp image instead). Just a final note - upsampling of pure noise image has less noise because noise is random, and is distributed over frequencies. When you upsample something you are in face missing those highest level frequencies - their value is 0 - that means that noise part in those highest frequencies is also 0, but pure noise should be distributed over frequencies, so it should also have component at highest frequencies. By upsampling we effectively removed noise from the highest frequencies and total noise has to go down because of this (it is equal to sum of noise over all frequencies).
  29. 1 point
    Just saw this announcement dated yesterday on the Takahashi website. There are pictures in there but I won't link them here. To save everyone doing a google translate, it states: "We will release an extension hood for FS-60CB that has the same white color as the lens barrel. The extension hood weighs about 420g, so it not only prevents stray light but also functions as a counterweight. FS-60CB is a short aperture telescope with a small aperture, which makes the camera side heavy and difficult to balance." I've always planned on getting a mini tak in the future, and this news came somewhat at a surprise to me. The weight balance I can understand, but stray light is a new one for me. For those with the scope, do you think it may help with visual / photo, or just a fancy add on ? I can imagine the 60Q is just about to get slightly longer though
  30. 1 point
    I have certainly had no issues with stray light using the scope visually. I would say, as with most scopes, the dew shield is too short relative to the aperture, so does not keep dew at bay as long as it could, so from that perspective it would be a welcome addition, and the extra weight up front could prove useful. Try balancing a FS-60 with a 2" diagonal and 21mm Ethos....
  31. 1 point
    By the way--I gave it a bit of a stretch. I think I was being too conservative. It still needs several hours of data--but I see some promise now. In the end--its not teh camera--its the photagrapher. As far as quality goes--FOV and pixel size are camera. Hosey is a bit dark--just a quicky to see how teh data is. Also--i will definitely take a cloer look at teh subs--I havent even looked at them yet! I am sure there are some nastis in there.
  32. 1 point
    Rolling shutters are a feature of interline type sensors, and shutters are used for full frame transfer sensors. Its all about the speed of which the image is read from the sensor (interline = fast, full frame = slow) http://www.optique-ingenieur.org/en/courses/OPI_ang_M05_C06/co/Contenu_07.html http://www.optique-ingenieur.org/en/courses/OPI_ang_M05_C06/co/Contenu_09.html
  33. 1 point
    I do. I owned ST102 - that is 102mm F/5 scope and chromatic aberration was horrible on bright targets, but that is not what the scope was intended for - it is wide field scope. I sold that one and got Evostar 102 F/10. Yes, it does have blue fringing, but I found that Baader Contrast Booster helps a lot with that. Moon is almost clear of CA with it and still has rather neutral tone. I briefly observed Jupiter with it on one occasion and again there was no bright purple halo with this filter. You can use wratten #8 yellow as cheaper alternative but it will give you slight yellow cast on the image. What you can further do to reduce chromatic aberration is to use aperture mask. It reduces aperture and increases F/ratio at the same time. It will limit max usable magnification, but will provide much clearer image. For example using 80mm aperture mask, you will get F/12.5 scope. If you look at above posted table - you are in the green zone and still have a scope capable of delivering around x160 magnification. I'm sorry but that simply won't work. You can image with such scope though and get some decent results. You don't even need mono camera for that. There are couple of tricks that you need to employ in order to minimize chromatic aberration issues (one of problems is that you will no longer have F/5 scope, but that does not matter - it is aperture at resolution that determines the speed of the system). Here is an example: First ST102 F/5 scope without any "tweaking": Image is rather poor as it was one of my first attempts with OSC camera (small sensor) and this scope. Camera had no cooling and it was QHY5IILc I believe - so not a very good camera. But that is not the point - resolution is terrible because of CA issues and there is large blue bloat around the stars (and red around smaller stars). Now here is the image done with the same scope and different OSC camera - but not too different. Still 3.75um pixel size, still uncooled - it is ASI185. And later same target, a bit smaller field but better color correction: As you see - no fringing and images are quite "decent". Trick is to use aperture mask (66mm) and wratten #8 filter - or that is what I used. No special processing was done to remove bloat from the stars.
  34. 1 point
    Have you heard of startools? Its very easy to use and initially appears a bit basic but has lots of hidden aspects and it actually very good. Within a few clicks you can have a good result. I have pixinsight but find unless I am using it allot I forget the workflows so have to go back to the books and vids for help. Knackered valve seals?
  35. 1 point
    Hi everyone, despite there being a bright moon last night i had to have a play. This is a one minute sub of ASASSN taken through my ODK 12 as it is passing the star Mirach in Andromeda. No faint tail showing on this one,i think the Moon put paid to that. Thanks for looking, Bob.
  36. 1 point
    And a couple of stainless steel knobs arrived from WDS. Will make tightening down the dovetail saddle a lot easier as you can get a proper grip unlike the stock knobs.
  37. 1 point
    Over the last couple of weeks I’ve been imaging the Crescent using different focal lengths and filters Widefield 135mm I was working out that this is the fourth time I’ve been imaging in or around the Sadr nebula. On this occasion it was because I’d already started on the data for 900mm shots of the Crescent and I thought it’d be nice to have a wider shot of the general area, putting it into context. I was inspired by @Stub Mandrel's recent results with his Triband filter to see if the same (or similar) technology in a clip filter would help with wide frame nebula images and acquired a Skytech Quadband (that transmits 2 35nm bands around Ha, Hb, Oiii and Siii – hence the name) . I must say I’m quite impressed- I got this from a sequence of 20x 150 second captures on Sunday night under a 99% moon using a Russian made 135mm vintage lens on a modded Canon 600d and a Star Adventurer. Normally I’d only attempt proper Narrowband under these sorts of conditions, but I thought it coped pretty well under the strong moonlight. The only slight concern is the halo around Sadr itself. The photo picks out how prominent the Crescent is (below centre and to the right of this picture), but also shows how “busy” this bit of sky is- the Butterfly nebula pops out, with its prominent dark lane, but the fainter cloud that it’s a part of extends beyond the frame. There are also clusters aplenty- my favourite is M29 – the Space Invader cluster just below and to the left of the centre. Probably my eighties upbringing… Hydrogen Alpha These are taken using a Baader 7nm Ha Filter on a modded Canon 550d in a Skywatcher 200p- altogether I got 12 10 minute subs before clouds stopped me. I think this is the best of the shots for showing the structure of the object and the shockwaves that form its shape; the monochrome also highlights the cloud of the larger surrounding nebula. Oiii This came from the same setup and 10 more subs, this time with an 8.5nm Oiii filter, and a 99% moon on 13th October. The only Oiii visible in this shot is around the nebula itself. The signal was quite a bit weaker than the Ha; this picture was created by discarding the Red Channel and then combining equally the Blue and Green using Pixelmath in Pixinsight. Bi-colour Finally, it’s all brought together using the same process- this time feeding the Hydrogen into the Red channel and the Oxygen into the Blue and Green. I spent quite a bit of time playing with this one. Just feeding the data in, the red was total dominant and I progressively multiplied the Blue and Green until it was more prominent (the eventual multiplier used was 2). I also experimented with trying to change the balance to bring a little more colour into it, but that also artificially unbalanced the star colour so I decided to leave it even, which makes the Oxygen mostly white. I’ve really enjoyed taking these different views of the same object and learning about it. The nebula itself, 5,000 light years away, is 25 light years across and is caused by fast stellar winds erupting from the Wolf-Rayet star visible at the centre of the nebula. It’s thought the star will imminently (in astronomical terms) become a supernova.
  38. 1 point
    Don't know if you've found anything yet, and this is some shameless self-plugging but I made a editing tutorial that I tried to keep as user friendly as possible. Maybe it can help you?
  39. 1 point
    We can't leave Europe how the heck are we going to leave the planet.
  40. 1 point
    There is a sufficient spread of opinions on the internet that you can find good and bad reports of practically anything. Some are even based on reality and experience. Although it is often impossible to tell which ones those are. And since old opinions regularly get recycled by people who don't have any first-hand knowledge, even looking at the date of a post doesn't tell you much. All I can suggest is to heed the views of people who say they have actually owned an item - paid for with their own money - for a considerable length of time in the near past (the last 6 months for example) and to ignore all the rest. Ultimately it is up to you to decide which ones to believe.
  41. 1 point
    Well once you've got the moon centred in the eyepiece it should only take a few seconds to adjust the finder. The moon is really not going to move to any significant degree while you get aligned.
  42. 1 point
    You could also fit a Lacerta Micro Focuser 1:10 upgrade. This will not be free but it's not that expensive and works really well.
  43. 1 point
    Hello. Think Friday will be my day to go. Might try for a lecture as well Regards John
  44. 1 point
    I reckon I owe @FLO some donuts or something for all the countless questions you have answered and letting me return certain items.
  45. 1 point
    Does a genuine "Starter with Imaging" look at your excellent image and think "I may as well give up if that's the sort of result a beginner should get !" ? DSO section I think. Michael
  46. 1 point
    Took me a long time to get anything near that also with lots of advice from Carole and tooth doctor along the way. Very impressed
  47. 1 point
    Thanks, first time processing dust, took best part of a day to figure out how to make it show up well
  48. 1 point
    I have to agree John, whilst it may be present it is not too bothersome and probably not so noticeable to my inexperienced eye. At F/4 it was glaringly obvious, hence the initial enquiry.
  49. 1 point
    Thank you very much guys. Today I tried out Roger Clarke's RNC Colour Stretch to see how it worked. I've read his website a lot, the same articles more than once, so I decided to see if his stretching program worked for me, and also calibrating first which I hadn't done first time around. Please could you tell me which do you prefer, the original or this image...
  50. 1 point
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