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Grogfish

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Everything posted by Grogfish

  1. Check out “The No EQ DSO Challenge!” thread - because it’s all Alt-Az the exposures are all sub 1min (or near enough). Worth a look through. I also suspect there’s something of a self-fulfilling prophecy regards image quality. If you’ve got great gear, then you have a high resolution, high bit depth sensor and can track for multiple minutes. Plus with some lovely LP filters. And given you own all that kit, that’s precisely what you do. Hence fantastic images from “long exposure”. And as it works so well, why try anything different. On the other hand most people that are doing “short exposure” are doing it because they can’t afford any better tracking. That also tends to mean you can only afford cheaper sensors with lower bit depth and lower resolution (like my GPCAM IMX224), and lesser (or no) anti-LP. So the “short exposure” pics are taken at say 1280x1024 12bit (that’s me!) compared to perhaps 5000x3500 14bit for “long exposure”, which is another reason why some images look better than others. Gosh, could really sound like I have chip on my shoulder, but I really don’t ?
  2. Firstly I should say that everything I do is very short exposure by most standards (typically 25s or so) because I’m Alt-Az. And given my vary modest setup I’m pretty pleased with the results - stacking 100 frames does considerably reduce noise. (Except that with Alt Az I have frame rotation, and that means the number of frames being stacked drops dramatically near the edge - thus cropping is needed (or shutting up and putting up ?)). Also I’m a firm user of SharpCap Pro, so I greatly appreciate Robin! However, whilst I felt Robin explained noise in some detail, he didn’t really seem to touch on the question of sensitivity... And a short exposure will be less sensitive than a long one, no matter how much you stack. So for some objects (or for the particular appearance you desire), you will simply need a certain amount of exposure. I’m a rank amateur, but my experience has already shown me that, for example, there’s a certain amount of nebulosity I can image in M45 using 26s no matter how big the stack. If I could image with say 45s, I’d expect to see much more nebulosity. The comparison images he used were of M42, but actually I don’t think that was a great object to choose because it’s so bright. If for example he’d picked M33, I’d have eaten my hat if 100x1s would show anything of the galaxy at all, whereas at 4x25s you certainly do see something. Increasing bit-depth of the camera would presumably also be a way to improve the effective sensitivity (via stretching). Ahh, to be able to take subs with triple digit exposures!
  3. Many thanks for pointing this out @Skywatcher130 ! I’ve found Hertfordshire provides Sky at Night through RBdigital, and I’m considering it as £5 off the Council Tax each month ? Definitely a top astro tip for all to check out.
  4. Hi Arran Many very well respected forum members have given you the down-low on your idea, and I believe you can safely rely on their judgement. However, if you want to give it a go, I say, give it a go! Do it because you’ll enjoy the project, and because it’ll be fun to play around with telescope bits, and because you’ll learn a heck of a lot doing it.... but just don’t hold too much prospect of it working. You might want to take a look through the DIY astronomy section to see what others have got up to. Perhaps take some pictures of your project as you go and maybe start your own thread?!
  5. Very nice image, and a fascinating galaxy - not one I recall seeing before. Thank you for sharing
  6. Welcome from another Herts resident! Glad to hear you’re already enjoying the new scope. We’re having some great weather at the moment for it ?
  7. Through thin clouds this evening I've had my second go at the Rosette Nebula, and my first go with bias frames. Using Altair IMX224 with 200mm lens at f4 piggybacked on my Nexstar 4se. I'm super proud of this picture - it only took me an hour or so this evening, and I'm pretty limited with Alt-Az, but slowly improving my technique and I think I'm starting to get some reasonable results - hope you like it too. 60x26s, 24 darks, 100 bias. DSS+GIMP I found the bias frames do seem to have helped out with a bit of a left-right gradient I was getting before. Interestingly when I shot them with the very shortest shutter speed (0.1ms) the noise pattern seemed very high... so I slightly slowed it to (0.3ms) and found the noise dropped right off. When I tried processing with the 0.1ms and 0.3ms bias frames, I found the 0.1 made the stacked image far worse, whereas 0.3 helped. In summary, when running the IMX224 at very high shutter speeds it looks like maybe it (or the Windows driver??) engages some kind special mode which unfortunately also makes it very noisy. Well, that's a lesson learnt! Also wished I tried using bias frames before!
  8. Hiya Jonny I have a few suggestions that may be of help. Firstly NGC7000 is a large object and if you’re using your DSLR with the Nextstar 8 then you’ll only see a tiny chunk of it - even with an amazing mount you’re so “zoomed in” that you’d probably struggle to expose it. Eg in screenshot from SkySafari I’ve got the blue circle what you’d see in a 32mm plossl, and the blue rectangle showing a Canon 450d, both with Nexstar 8. Only the “Gulf of Mexico” would be framed. If I understand your profile right you’re in the UK too, so NGC7000 is really really low in the sky at the moment. So perhaps suggest a target higher in the sky and smaller targets - perhaps M81 or M82 or M1. However, I’d also agree with the suggestion to try piggybacking the DSLR instead. I’ve been doing this almost exclusively with my Nextar 4 for some time. There’s a Celestron adapter for around thirty quid, and just using a camera lens you already own (somewhere 50mm to 150mm to start with maybe) the Alt-Az tracking will be far more able to keep up (the focal length being that much shorter). At least consider it as a way to get practiced even if you want to go back to shooting through the Nextstar later. Either way, yes, using DSS is pretty much a requirement. Good luck!
  9. A bit bodged together in my case, but the garden storage box makes a handy place to rest the laptop.... And if you don’t have to skip around kids toys in the dark then you don’t know what you’re missing out on! (Scope only so low because I’m having a late crack at M33... and for once I seem to be winning?)
  10. Thanks Rotatux. Sounds like I need to be braver at stopping down the 135mm. The Samyang looks fantastic, but out of my price range sadly. Regards star bloat I’ve not satisfied myself how much it’s due to poor focus, aberration, stacking technique, or bloom from a pixel well overflowing on the cmos (is that the right terminology?!). Not really thought about it like this before, but I suppose I need to work out how much each of those is contributing to star bloat to push my imaging on a level... that’s given me some homework for the next month!
  11. What aperture do you tend to use with the 200mm? Do you run full open, or shut it down a bit? I’ve also got a f/2.8 135mm cosinon lens, but I’ve not had a chance to try it out much- and when I have I wasn’t particularly impressed- it appeared very soft at f2.8
  12. Sooo... I have an M42 to C mount adapter - cost around £18 on eBay. I also have the Altair GPCAM bracket that holds the camera and provides various screw mount points. That I attach to the Nexstar 4 using the Nexstar 5/6/7 piggyback camera adapter. And because it’s designed for a SCT, it doesn’t quite fit.. however mounting the piggyback holder reverse does seem to fit ok (and not block the eyepiece holder), but it means the holder (and thus the camera) stick out to the side of the Nexstar, rather than being on top. All a little Heath Robinson... but.. kinda starting to get some results!
  13. Ooops, my mistake! In my own mind I’d always thought of this method as the “raspberry of doom”, but I love the IBC!
  14. Madly and unjustifiably, I always harboured a secret hope that somehow Opportunity would get to Beagle2, flip out the stuck solar panel, and spring it to life! Oh well, another dream crushed ? I suppose I feel slighty sad, and perhaps bad, for these shutdown probes and robots on distant worlds. Still, it’s pretty incredible any of them made it there in one piece in the first place. Am I right that Opportunity was lifted down on the amazing “sky crane”?
  15. Good question! For M31 it was around f/4.5, but I tried stopping it down a little more on NGC2244, around f/5.6. Not sure it made a lot of difference to sharpness. While I nothing about camera lenses it seems pretty sharp, even wide open at f/4. And my thanks to @Bobby1970 who sold it to me a while back! Viewing this page now on my iPhone the colours are all a bit mangled (or absent) compared to on my laptop last night... so... if you’re looking at my pictures and wondering what’s going on then close your eyes and imagine Hubble took it ?
  16. Last year I started experimenting with using a 200mm M42 lens piggybacked (well actually side-backed) on to my Nexstar 4SE to give a larger field of view through the GPCAM IMX224. I'm still early on the curve, but finally feel confident enough to share, especially as last night was suddenly a clear sky, and very welcome it was too. So please see M31 (59x16s subs, 14x8s darks) and NGC2244 Rosette Nebula (166x15s subs, 14x8s darks) taken last night. Oh yes, and just to confirm the Nexstar was running Alt-Az! All processed using DSS followed by GIMP for some stretching. Frankly I think my GIMP work could use some more practice! It's only when you give it a go that you realise just how much hard work goes in to even getting a half-decent image... The pictures you all take are amazing! Well, clear skies to all.
  17. Grogfish

    New to the forum

    Welcome to SGL Sean! Yes, it’s worth giving some thought to the best scope for you. You’re also lucky to live near one the bigger astronomy shops (Rother Valley Optics), so you may want to go and have a nose-around. Buying online is great, but seeing the real thing is super helpful.
  18. I kept a log for several years in OneNote, but like Paul, I found the pursuit of AP meant I stopped updating it. Not that my AP is any good... I’ve never been gifted with artistic skill, so it’s largely my impressions of an object using different eyepieces, and how easy/hard it was to find. My most common log entry probably goes along the lines of: “spent ages looking for M33, must have been looking straight at it at times, but just didn’t see anything”? And actually, yes, as several have reflected in different ways: I find observing and logging is somehow more satisfying than just observing. Should just get the bins out sometime for 20min cloud gaps , just to get some logging done if nothing else! From a practical perspective it is also handy at times, particularly being electronic as it makes it quick to search back through, e.g. to find my last observation of Uranus to confirm I do see it green (on a recent thread a few people reported seeing it blue, and I was questioning my memory!!)
  19. +1 to both of you! Thank you for spending the time thrashing this one out - I too have often wondered about the theory and practice of using an EP for focal reduction. Eyepiece projection has often appeared to me to be a dark art that is only discussed in hushed corners, and you get funny looks for talking about it out loud... I think you’ve handsomely demonstrated why this is the case; it’s fiddly and the results don’t merit the effort compared to the alternatives. Ah well, good job I spent the twenty quid years ago on a simple x0.5 reducer......
  20. Wowsers! The Nirvana is a bargain at that price - what a shame they don’t do one around the 10-12mm length as well.
  21. Hi Hapii. Of the options you've looked at, I'd go for option 2, except with a 10mm Hyperion - as I think using the x2 barlow on a 13mm will be too much, but you will be able to use it with your existing 25mm plossl for an effective 12.5mm.... Giving you 25mm, 12.5mm, and 10mm options each evening. I've never used a Hyperion, but many people hold them in high regard, and in my experience 1 "great" eyepiece gets much more use than 3 "ok" eyepieces! For planetary I find 10mm a pretty good balance on my 4SE, as others have said. Occasionally the seeing is good enough to go to 8mm, but rarely shorter than that - I have a lovely 7mm X-Cel LX that I've hardly used! In France the planets will be that bit higher in the sky than for me (I think?!), so you may get away with more power than I do in the Uk. Again, I'd agree with what many are saying - a 32mm plossl eyepiece is the go-to for most deep sky objects on the 4SE. (I say most, because globulars etc you might want more mag). I liked the 32mm Meade 4000 which is good, but sadly not been made for a long time. I've also got a 32mm Baader Classic Ortho (actually a plossl) which is also pretty good - and may be a good choice for you too (~£50). However.... I now have a 16mm 82deg Skywatcher Nirvana that I use almost all the time for DSO - the optics fantastic and the visible field is basically the same as the 32mm plossl. If you can afford it (~£130), it's definitely worth considering at some point. Good luck whatever you choose, and clear skies!
  22. Yup, a few people have used the Startravel 80 on the 4SE mount (such as Sxinias’s post on AF), as it’s quite short, and you can often pick it up for £100 new, and a lot less second hand. Given the expense and difficulty with attaching an SCT FR, it’s worth a thought. I’ve only played with wedge and frankly didn’t find it worth the effort.
  23. There are some good objects in this list published in Sky and Telescope. It includes a mix of object types, including double stars, and unusual objects like the garnet star. (Personally I found I’d ignored doubles from my own observing for the first few years, but am glad I developed a taste for them.) If you have the SkySafari app then the list is already available as an observing list so it’ll highlight them for you ? In Search, if you click on Import from Online Repository, it’s listed as “111 Objects for light polluted skies”.
  24. I can’t quite work out where in my head the Pleiades would have been from HK, but yeah, if they were near zenith the scope may have started spewing to one position before deciding they’d moved enough overhead that it needed to slew round the other way. Also it may have the Cordwrap feature kicking in (dunno much about it to be honest), or simply that it had reached it’s maximum slew in one direction and found that it suddenly had to about-turn 359deg, to get back to nearly where it has started (because the Nexstar mechanics can only turn around so far). if it happens again I’d give it 5 minutes, with my guess being itd be one the above and it’ll sort it self out within 60s
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