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billyharris72

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Everything posted by billyharris72

  1. Hmmm.. Well, I've tried imaging again, having done the following: 1) Replaced the push fit eyepiece holder with a screw fit so the whole imaging train is threaded. 2) Tried varying the spacing (currently up to 59mm and increasing - or will when the weather clears). Results so far are not great. CCD inspector shows the curvature lowest at 58mm and 61.5mm, and higher in the intermediate values (is this normal)? The elongated stars are still there with all setups - with some spacings it seems to be in all corners, in others only the right hand side of the sensor. The whole setup is threaded and I can't detect any movement in the focuser (if I hold the back of the camera and try to move it up and down the whole thing feels rigid - could move it slighly by applying force I'm sure but there is absolutely no play or wobble that I can detect). Pointing the setup at the zenith for test shots makes no difference at all - elongation remains and is about the same. Again, I've attached a couple of images for reference - I think there might be a slight improvement, but the edges (especially on the right) are still very poor. Struggling to know what to try next, so thoughts are much appreciated. Is it worth continuing to adjust the distance, or do the elongated stars mean I'm wasting my time? Billy.
  2. Absolutely. IMO this bit really isn't optional if you want to ensure good collimation. An unbarlowed laser can be useful for rough alignment of the secondary, but that's about it in my view. On its own, I'd rather use a basic collimation cap than a laser. Billy.
  3. Good news - unscrewed the nosepiece on the OVl flattener to reveal an M48 female thread. And with this on FLO ... https://www.firstlightoptics.com/adapters/lynx-astro-m48-adapter-for-sky-watcher-72ed.html Goodbye tilt (hopefully)!
  4. Thanks - pointing at the zenith seems a good idea. I think I've identified the set-screw eyepiece holder as a definite source of a little flex in the system, so that seems an easy one to fix. Focuser movement would be a lot worse, but I tend to agree with Ray - the tube is only racked out maybe 10mm or so and the camera and mini filter wheel is not that heavy (fingers crossed...) Something that concerns me - is it common to have this elongation predominantly in one corner of the image? I would have thought if the camera is tilted it would affact the whole image plane, at the angle of the tilt, but the elongation I'm seeing tend to be concentrated in one corner and looks radial, with the elongation pointing towards the centre of the image. I've attached a test image (see how the elongation is much worse top tight corner) and an output from CCD inspector in case anyone can make some sense of it. Thanks, Billy.
  5. Interesting thoughts there and plenty to work with. Sounds like I definitely have some tilt - wondering if the compression ring adapted that FLO sell would help here, as might be more rigid than the set screw adapter it comes with. As yet I don't hink there is a screw fit on the market (though let me know if I#m wrong!). As for the distance, I'm thinking perhaps a Baader adjustable tube is in order. Billy.
  6. Hi all: I've just had a first go with my new scope (Skywatcher ED72 with OVL flattener) and early signs are good - think it's going to be a keeper. However, I'm struggling with what I assume is field curvature (never imaged with a frac before so this is new for me). The stars in and around the centre are great but at the edges of the field they are both out of focus and elongated (pointing towards and away from the centre of the image). I just had a couple of questions that I was hoping someone more experienced could weigh in on: 1) Does that sound like field curvature? (90% sure it is but worth asking)? 2) The effect is not equal in all corners (some are actually not too bad). Now I think the setup is square - could this be a distance issue, or do I need to work more on getting the setup square (and if so, any ideas on how / what helps)? 3) On the off chance someone has already dealt with this, does anyone out there know the correct sensor distance for this scope and flattener combo? Initial messing about suggests I might need more than 55mm, but any pointers would be really useful. 4) If not, is it possible to infer anything about the spacing (whether I need more or less) from looking at the curvature? Sorry ... that's not a couple of questions after all. Cheers, Billy
  7. I feel for you Olly. Maybe this will help. There are a surprising amount of sites offering advice like this out There, so you are not alone! https://photographingspace.com/howto-diffraction-spikes/
  8. I actually liked the article quite a lot. The points it makes about the disadvantages of fracs are all valid at some level, and it's written more as a polemic (i.e. I think, or at least hope, that it's not intended to be taken entirely seriously). I seem to remember a similar couple of articles (one on why SCTs are basically rubbish for most people and one on why 80mm fracs are a bad choice for imaging). Wish i could find them to post links. I enjoyed both and thought they made some good points in a way that was amusing and combative. I'd still like one of each though! Billy.
  9. Thanks for posting Stu. I like the Lunar 100 (only done less then half of it) but would warn anyone just starting on it about some of the odder descriptions, which caused me no end of confusion at first. Don't get put off it you sometimes just can't see what the accompanying text suggests - some of this is heavily summarised "points of interest" that you won't see. The description of Flamsteed P (an ancient crater caused by an impact) is the most confusing I've come across (I had to ask for help on here in fact!). The young volcanic crater it speaks of is not Flamsteed P but a tiny 100m craterlet embedded in it's wall, and well beyond the resolving limit of any amateur scope. It's a great object list though; I find it gives my lunar observing a bit more structure and direction that it would probably have otherwise. Billy.
  10. This would be a good plan. Before I sold it I used to use the OTA on an AZ4 and it was a great combination.
  11. Was my first scope. I eventually sold it, which I regret. Really nice optics (I have a couple of scopes in the £300-£500 range that are not better) and incredibly good value. The focuser, while primitive, does the job well. Can't go wrong with this one. Billy.
  12. Is that Epsilon really £130, or am I misreading the ad? If so I'll take two! Always wanted one of those.
  13. billyharris72

    M31 Andromeda

    Lovely image. Great job of showing the dust lanes and spiral arms without blowing out the core.
  14. No, I'm really not. Some of these images are superb, and with exposures I wouldn't have thought possible. I thought the EQ3 didn't support guiding, so wondering if these are manually guided or the mount has been modified in some way? Actually, just seen reference to Eqmod so that answers that one.
  15. Thinking about it, the new cooled CMOS cameras could make a great pairing with an EQ3. Rarely need subs over about 30 seconds; even narrowband won't need more than about a minute.
  16. No! You can't do deep sky imaging with an EQ3. You just cant. So stop it ... right now!
  17. A bit of Googling on this suggests bins from about 20 x 80 should do the trick. Seem to remember doing it in my Heritage 130P with a 25mm e.p. (which would be x26) though much easier around x40. As others have said it's not the distance (which is pretty wide) but the relative faintness of te companion that can make Polaris a bit tricky. Billy.
  18. There is an interesting article by Simon White in Decembers BAA Journal that covers just this issue. He argues that, where the errors in polar alignment are relatively small, the declination of the target is of little practical importance (note that he's assuming PAE of the order of 1 arcminute or so). His little thought experiment is roughly as follows (it's based on the small angle of error meaning we can treat the sky as a flat rotating disk): Imagine a perfectly polar aligned mount, with the scope focused dead centre on a star (any star will do). Now move the scope out of alignment by a small amount (say 1 arcmin). The star will move exactly this much in the field of view, so it is now offset from the centre by 1 arcminute. If we leave the mount to track for 1 sidereal day (and imagine we could watch the star the whole time) we would see the star describe a circle in the eyepiece, around the centre of the field of view, and return exactly to the point where it started. A distance of 2 x Pi x PAE, or 0.262 arcsecs per minute for a 1 minute error. We know that pixel scale in arcseconds is given by 206 x pixel size / focal length. That means the time to drift 1 pixel (in minutes) is given by: 206 x pixel size x 24 x 60 / (2Pi x focal length x PAE(arcmin)) He uses this to work out a little table of time (in the article for a Nikon D90) for a one second drift with various lenses and focal length scopes (with an 805mm scope there is 1 pixel of drift every 322 seconds; while a 200mm lens will take 21 minutes for the same drift). The figure from that table can then be divided by the actual alignment error (assuming this is known) to calculate the approximate achievable exposure time. The figure is easy to adjust of you are happy to accommodate more than 1 pixel of drift. Not mathematically exact, but a straightforward rule of thumb that (according to White) gives results that are very close to the original Hook formulae.
  19. I recently picked up the Versascope (intending to use it for autoguiding) and was quite impressed. It has a bit more aperture, is flexible in terms of accepting a range of eps and has a standard Synta finder shoe. At a push I reckon it could double as an ultra portable refractor (albeit with significant CA and sub-optimal focuser) and should make an excellent, versatile finder. One thing I will say with regard to RACI finders is that, optically, you will lose relative to classical straight through finders. For me, comparing the Skywatcher 9x50 RACI and 9x50 straight through is night and day, with much more detail visible in the latter. That said I still prefer RACI - what you lose oprtically you get back in ergonomics and intuitve navigation.
  20. Got a (brief, between the clouds) chance to point this at the Moon about 20 mins ago. Thoughts as follows: CA noticeable, but not enough to cause an obvious problem, even at x60 on the Moon. Clear views of mountains and the Mare. Slight loss of sharpness at x60 vs x40, but the higher magnification still usable. Decent view of Theophilis, Cyrillus and Catharina. Central peaks of first 2 and flat floor of the last clearly resolved as is the apparent defile (or is it just shadow) between Cyrillus and Catharina. Heading across the Mare Nectaris, Madler, Isodorus and Capella all clear. Hopping over to Mare Crisium same is true of Proclus. Last night managed to catch the rings of Saturn (equally briefly), with views that were acceptable, though using it in darker conditions showed control of stray light is poor (the tube is well baffled, but made of plastic, so slighlty shiny). Also noticed what appears to be a tiny speck that may be inside the zoom eyepiece (though it's right at the edge and not at all intrusive). Compared with budget binos (I see this scope as occupying a similar niche) I'd say that optically is compares okay to the Strathspey 15x60 and Visionary HD 12 x 60 when it's operating in the x20-x30 range, and the additional range of magnification gives that bit more flexibility. Of course, I imagine quality control on these is non-existent - I may have lucked out and got a decent unit.
  21. My dad picked one of these up for £20 a couple of weeks ago when it was on offer - I'd toyed with getting one myself but thought better of it. I've had a play with it today (daylight only) and have to say I was pleasantly surprised. To be clear this is not a great piece of optical equipment, but it is also far from the unusable junk I was fully expecting it to be. Basic specifications and thoughts below. 50mm objective, with 20-60 zoom eyepiece 2.2-1 degree FOV from the instructions, looks bang on from my test. Narrow, but not unusable. Weighs about 1kg. Cheap and plastic feeling; not water resistant. Focuser knob on top of scope body. No difficulty getting a sharp image at any zoom setting Targets (roosting birds, church clock, household aerials) all very clean and well corrected at 20x, and good at 30x. Starts to struggle a bit at higher magnifications. Chromatic aberration negligible on targets I was viewing at x20. By x30 it becomes more noticeable, with a distinct yellowish cast to the image background above about x40. Even at x40 it was still possible to get detail on target. Above this CA becomes pretty bad and compromises fine detail. But even so, I was still able to see detail in the eyes of blackbirds roosting perhaps 200m away. Comes with a tripod that's so bad it's actually funny. Overall then, not an objectively great piece of kit, but usable, and for £20 actually very good value. If I paid £50 for bins and got an image as sharp as the image in this spotter at x20 I would not feel ripped off. It's the kind of thing it might make sense to leave in the car as a grab and go option, and at that price it's not something you'd need to worry about breaking. Could all change under the stars of course - if I get the chance I'll give it a try an post what I find. Billy.
  22. Another piece of software I've started messing about with is GCX (it's in the Ubuntu repos and I'm sure Debian also). Manages (among other things), image processing, reduction and stacking, fitting field stars to catalogue files / WCS, aperture photometry, telescope control and camera control. Just started with it but seems very smooth and the documentation is excellent.
  23. Good little scopes these. I went for the 80mm as I wanted something really portable and have been pleased with it. It's poor on planets, but with the Baader semi apo filter the lunar views are actually quite good.
  24. I think the other turn off is lack of documentation. A lot of the best Linux astronomy software is aimed at academic astronomers and observatories; it's not always the most user friendly.
  25. The following list is useful and highlights some of the main software available. https://help.ubuntu.com/community/UbuntuScience/Astronomy Also: Iris Siril (a simplified Linux native version of IRIS) Virtual Moon Atlas Distro Astro seems to have a tonne of bundled software.
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