The Admiral

Olly Penrice reckons that darks for a dslr are a waste of time because without stabilising the temperature the darks won't be representative of the actual taking conditions. Now I realise that this is somewhat at odds with your findings, but he uses a master bias instead of darks, which would save a lot of time if it could be made to work for us. I'm sure that there is more to it than that and I'll have to get more info, but it may be one route to go. I think he's also said that he uses Astroart for stacking, which is supposed to be a lot quicker than PI. I downloaded a copy but I've yet to make it work, as you can't save on the trial, and it throws up some odd error messages. Ian

Fantastic images there Nige, a real credit to the Alt-Az community! I wish I had your endurance . I can't see me getting much imaging done until some interesting objects appear from my vantage point at a sensible time of night, later in the year. There's a bit more colour in some of the brighter the stars in the second one, and there's an interesting difference in general colour. What the 'correct' colour should be I wouldn't hazard a guess. Knowing that without going through the Startools.log and re-entering the same parameters, it is most unlikely that I can process to give the same finished appearance. To what extent do you think the difference between these two is difference in processing rather than source files? Ian

Interesting comparison, and I'm not at all clear why ignoring darks should make such a difference. I prefer the colours of the ring in the second image, and it is odd the way the stars are rendered compared to the first one. Not only do they have more colour but some are smaller. Ian

As you say Ken, very different renditions of the same image, it's hard to believe that they are the same! I think I still prefer your original version using ST, it shows the nebula very well. I suppose purists might argue that the second one is more realistic? I know what you mean about ST, but the more you use it, the more sensitively one can tune it. I had a trial of PI too, and although the workflow is supremely logical there are so many facets to it that I wasn't really prepared to commit. It isn't cheap either. I wish it was possible to directly set the black-point in ST, but on Steve's suggestion I tried the Life module and it does seem to give one a bit of control over that. Else I set it after ST in a final polish in my standard photography application. Do you think you'll migrate to PI? Ian

I just had a play with your processed jpeg image in Lightroom, using curves, sharpen and noise reduction, and I couldn't really get any more detail out, though it looks a bit brighter (below). I like seeing what extreme processing will do . Definitely you've got nebula there. When I did mine I used 130 x 10s subs, bias and darks, but no flats (don't ask me why so short, it was early days!). I think I'm fortunate that my camera seems to have an inherently good red sensitivity. Mind you, I don't think I could replicate the result that ST gave again. Ian

You surprise me Ken, 'cos you got a super image of the North America nebula with the same sort of exposure. I have no experience using PS, but can I suggest that you have a play with StarTools. May be it's a case of the devil you know, but ST does seem tobe able to reveal faint stuff. Ian

Nige, that's what I find to be the problem with this short exposure stuff, is deciding whether you've got nebulosity or just noise . You can definitely see structure in there though, amazing for just a single frame. And Mike's confirmed it. What happens if you up the contrast, does it bring out more detail, or is there just too much noise? Ian

I agree whole heartedly with happy-kat, you've got little to lose by giving it a go Paul. One thing this thread has shown is that you're by no means doomed to failure if you do . What about the 130P? I've no experience with reflectors, but Nige might be able to offer an opinion. Refractors are more amenable to slapping a camera on though. Ian

That's very flattering of you to say so, but we're all doing the same thing with the same sort of equipment, have the same challenges, and produce great output. All very much ongoing proving of concept. Ian

Not me gov', honest! Nexstar 6/8SE is the only mount I've got. Ian

Ooh, now where do you begin! There are so many factors at play here Nige, but I would think for me the foremost consideration was focal length. If you are going to use an Alt-Az then it needs to be fairly short in order to keep star trailing in check. Mine has a native 700m and it works, and it has a FoV of ~ 1.85° x 1.25° with an AP-S sensor, which will be a bit tight for say M31 and the Pleiades, but it was OK with M42. These sorts of focal lengths are easily had in refractors. To me, the next thought would be aperture, 'cos you want to get as many photons down that tube in the time available. Large aperture refractors cost the earth. Large aperture reflectors tend to be long focal length, unless you go for specialised astrographs, which cost half an earth. How I envy those large photon hoovers, but then I think, OK, what do I put it on, it's got to be an AZ-EQ6 (expensive) if I want to continue with Alt-Az imaging, but then, really shouldn't I be using it in EQ mode? And then I've got to carry it all from upstairs and set it up in the garden each time. With no sight of Polaris. And with a reflector, I'm going to have to collimate it aren't I? I'm afraid I'm of an age where I want to be using the gear and not waste time fettling before I use it. Now, if I had an observatory the whole argument might be different, but there's no way that's going to happen! As an aside, when I bought my refractor, convenience of use was uppermost, and that, together with cost, dictated the OG size. I wanted a reasonable focal length because my expectation was that I'd be mostly visual, with perhaps an occasional foray into astrophotgraphy. How wrong that was . Still, 700mm I found is not too long, and with a reducer could be made better for larger objects. Yes, I'd love a huge aperture, but with it comes a lot of other baggage which I'm not really prepared to accept, and at the end of the day I've no expectation of gallery class pictures, but I do enjoy the challenge getting the best out of the system and pictures of things I'd never get to see visually. My two-pence worth anyway. Have fun going through all the options, dreaming, and window shopping. ian

Found it! But I wouldn't have spotted it if you hadn't mentioned it. Ian

They look good Ken. I think you are right, the 1st one has more star colour and a cleaner background, but forgive me, where is this satellite trail in the 2nd one? These predominantly northern nebulae aren't well placed for me at the moment, at least not at a respectible hour. Give it a month or two and I shall be able to see them towards the east before midnight. Ian

I accept that, but there are limits to my tenacity and endurance Ian

You've done well there considering you've had limited exposure. I've noticed that some of my frames have significant streaking, whereas other have none. I guess it's the way the mount zig-zags in jerks, and it depends on whether you're exposing during one of its zigs or zags, not to mention where the mount is pointing at the time. In that respect, shorter subs may help I suppose. I'm guessing here, but as Alt-Az mounts are intended for visual there probably isn't much incentive for manufacturers to adopt some form of smooth drive, so that both axes are driven continuously at the correct, and variable rates. May be it just needs much finer steps, much the same way that EQ mounts are driven. It would be interesting to know if the Skywatcher AZ-EQ mounts have a smoother movement, given that they use the same drives irrespective of whether they are in EQ or AZ mode. For some reason I've regarded M63 as being a difficult object, not sure why. Having only 1/2 hour's exposure sure makes life difficult. I've always thought that the suggestion of using shorter sub lengths in the same stack really only applied when the standard sub length, reckoned in many minutes, causes the bright bits to overexpose, so the shorter exposures 'fill in the gaps'. With the short sub lengths that we use, I do wonder if that is a significant problem (with the exception of stars perhaps). Ian

Well believe me it's not much better than that here, even though I'm retired! Ian

I think I'd rather buy a focal reducer! I'm not good with late nights. But it's a possibility. Ian

That's very kind of you to say so Steve. I don't know about adding more frames, I need to balance up the suffering for my art (i.e. lack of bedtime) with the benefits of (possibly) improving the image. In other words, how much more would I have to do to make a significant improvement, and whether it's worth it. I'm finding that I use Lightroom more now since Nige suggested using Photoshop Express on my M64 image. I use the sharpen and noise reduction functions, and sometimes clarity, as I find it seems to smooth the bits that need smoothing yet leaves the detail there. I also use it for producing the files suitable for uploading to the site. Cheers - Ian

Thank you Nige and Herzy. Clear Outside shows it clouding up here around 23.00, and whether I'd want to go back to it I don't know. Not much else around that I can see though! Ian

As dusk approached last night I wondered if it would be worth imaging, as there was so much high cloud around. But by the time I and the twilight were ready it didn't look too bad so I thought I'd push on with Makarian's Chain. It meant placing my 'scope in a slightly different position in the garden so that I'd get long enough on it. All going smoothly, until near the end of my first batch of 60 x 30s subs when I realised that I had only roughly focused whilst aligning. Doh! A wasted 1/2 hour which meant a really late finish (for me). No stars in the FoV to focus on, so I slewed to Jupiter (clearly a Nige moment!) and focused on its moons, then back to Makarian. In the end I had 123 frames for DSS to munch on, of which it decided to stack 91, so in all about 45 minutes total exposure. Not long enough really, and it shows in the noise levels. All things considered, I'm quite please with the final result. NGC4477 looks a bit odd because it's in a stacking artefact and so doesn't benefit from all the subs during stacking, hence the noise. M84 is also a bit noisy, but the bottom RH corner generally shows rather more noise. I suspect the darks aren't doing much good there. 91 lights stacked in DSS, along with 51 darks, 51 bias, and 50 flats, processed in Star Tools, and polished in Lightroom. Fuji X-T1 at 1600ASA through an Altair 102mm f/7 Super ED, all mounted on a Nexstar 6/8SE mount, 4th May 2016. Ian

I do a 2-star alignment when setting up, and I generally focus on the second star. I admit though, that my 'scope seems fairly stable to focus drift with time, which I guess might not be the case with a Newt. Ian

You shouldn't be bashful, you've made a great start with those. Both have a lot of detail and M45 is showing some nebulosity, which you might be able to enhance further. My only criticism is that on my monitor they both look a bit green; the nebulosity in M45 should if anything be blue. That should be an easy fix in PS. With a 200P you should be able to hoover up the photons at a far greater rate than with my 102mm refractor. Ian

Why do you think the focus is out Nige, they look pretty sharp to me? I think you've done pretty well there, they are after all very small galaxies. Was there a thin veil of cirrus cloud whilst you were imaging? There was here, and I didn't bother to try. Ian

There is an 'unofficial' user guide and the one on the ST website, though they are pretty similar. Who wrote them I couldn't say, though the one on the website does look like an offical ST document. Ian