The Admiral

A nice rendition and a difficult target. I used 122 lights of 30s each for mine (could always use more!), and the good red response of the X-T1 made all the difference. There are some very bright stars in the field, in particular Alnitak, so there is some advantage in reducing the exposure here rather than pushing it further I think, as some parts of the image appear to have blown. Also, if you can work with a lower ISO to improve the dynamic range then that is an advantage. I run my X-T1 generally at 1600 ISO (sometimes 400ISO), because a look here indicates that something odd happens at greater ISOs, possibly digital amplification. Ah, just realised you're not using the Fuji , so something odd happens, but at a higher ISO with the 5300! (see http://www.photonstophotos.net/Charts/RN_ADU.htm) Ian

I think that the Pentax has sensor shift image stabilisation which is able to be used to correct for star movement, within limits. May be that's how it was done, though I'm not familiar with that post. Ian

I'm thinking more of a general use computer costing £££, not one specifically for astro where the power can be quite small. Certainly for astro use, I'd probably opt for a pre-installed system. Ian

Isn't it because new computers could be locked into MS and would make installation difficult? And of course, you wouldn't want to seriously invest in something that isn't going to work. Well, rightly or wrongly, that's my concern. Ian

I hope you have the storage capacity and computing power :<) Ian

I posted M31 comprised of about 160 x 30s fames. Any use? On page 39/40. Ian

There is a video by Forrest Tanaka where he takes a pic of Andromeda without a tracker. He uses 1.6s lights and takes 400 of them. The video is a bit tedious. Probably not the post you are thinking about though. Ian

Welcome to SGL. You might think that but the celestial motion gets a bit more complicated when you try to image with an Alt-Az mount. With a perfectly aligned mount, you should not get what you might call conventional star trailing, because the telescope tracks the stars. In the real world though, mounts aren't perfect, and Alt-Az mounts by virtue of the way they move, you will get star trailing. This worsens the longer the focal length of the scope. Really, the only way to know what sort of exposures to use is to experiment, starting at 30s and less. There is also another type of trailing caused by the apparent rotation of objects over time. Again, this is inherent in the way the Alt-Az mount moves. This field rotation is least towards the East and West, worst towards the South and North, and worsens with altitude, being worst at the zenith. If you look back in this thread there are discussions about this. This alone can limit exposures to between a few seconds and a minute or more, mount willing. In fact I posted about this recently. What imagers normally do is take a number (more often, quite a number, in the hundreds!) of short exposure frames and overlay them on top of each other, or stack them, in software such as Deep Sky Stacker (free) in order to reduce the noise levels caused by the short exposures. Good luck. Ian

To be fair, alacant's statement was in response to my comment that the thread had gone way over my head, as all other Linux threads end up doing! Ian

To be fair, I did dabble with Linux Mint a few years ago. It ran, slowly, from cd on an old Vista laptop of my wife's. I also swapped the hard drive and loaded the OS onto the machine. I was surprised that wi-fi worked, and I never had all this trouble that Stub Mandrel is going through. Then again, I didn't try loading any astro software as my wife wanted access to old files so I had to swap the hard drives back again, and I haven't dabbled since. Is all this trouble because of the 'flavour' of Linux being installed? Ian

I admire your persistence Neil! Ian

I would have thought that was a skill, whereas it seems like Linux is purely brain cell activity (if my memory of using a lathe at school is anything to go by!). To be honest, this thread has now gone completely over my head. All threads regarding Linux seem to be taken over by the cognoscenti and leave me standing. Perhaps that's my failing, but there must be many like me and it becomes a bar to the general uptake of Linux in general. Didn't this thread start out bemoaning this very point? Ian

The simple answer to that is to try it. Startools trial version is fully functioning apart from saving. Ian

Pity if you can't get it to work, as it seems to give good results for our sort of imaging, and at a reasonable price. Mind you, Startools and PI have quite different approaches, as I'm sure you are aware. Ian

Folk do use Gimp though I don't. Best let them advise. But why won't Startools run as a matter of interest? Ian

Me too. Ian

Thanks happy-kat. This is a bit confusing, as the 'latest version' thread on the ST forum hasn't been updated since Oct 2017. Having looked on the download site though I see Ivo refers to a 1.4.332 alpha version! He really ought to keep his version lists up to date. Ian

The latest one? Is that v1.4, issued almost a year ago, or has there been a later edition I've not spotted? Ian

Not at all. Think of it as a sky chart, with N-S parallel to the horizontal axis and E-W parallel to the vertical axis, and vertically above you is the zenith, at the centre of the chart. And as happy-kat says, each of the coloured lines corresponds to an exposure time in seconds to give a 0.1° field rotation; the colour key is shown on the side. Ian

And why not! Sounds good to me. Mind you, having just checked on goggle I see that such a word is in use for much the same thing! Ian

As a result of a question on another thread, I've managed to plot (after a fashion) the field rotation rates across the sky. I thought that it was worth posting the map here as well, as it's pertinent to Alt-Az imaging. I've had to use demo software, hence the watermarking, but the overall picture can be seen. This map shows the number of seconds for a 0.1° field rotation relative to the position in the sky. The physical scale is the wrong way around, i.e. the horizon should be 0° not 90°, but I can't change that with the demo software. The elevation rings are at every 10°. The zenith is at the centre. The N-S axis is horizontal, and the E-W axis vertical. The advantage of imaging in the East or West direction can be clearly seen. There are some mapping artefacts on the RHS which will need to be ignored. Hope that is of some help. Ian

Well done calli, but I can't help thinking you could get rather more out of your data. Further stretching and a lower black point? Have you tried Startools? Free trial is not restricted other than saving, not expensive to buy either. It works well with the sparse data from Alt-Az imaging. Ian

Hi John, I bet you didn't expect your thread to run to over 3000 replies! But I for one am grateful for you posting as it sparked my interest in the possibility of Alt-Az imaging. And as you say, its simplicity is a major plus-point, even though there are some inherent limitations. It's a super entry into (relatively) low cost imaging too. I look forward to seeing your images grace these pages again soon! Ian

In fact I'd planned to download both flavours and compare. I stopped at that point because of some horror stories with early Yoga 2s. If I understand correctly, one needs to switch off secure boot and fast boot, but this also turned off wi-fi. Trouble is, wi-fi became switched off permanently, even after re-instating the initial conditions. Apparently this was a problem with UEFI, which had to be updated. Began to get cold feet at that point! Ian

Nope! Except I would copy to a memory stick, but I think it still means downloading an application for Windows. I also have a feeling that changing the boot order on a Lenovo and switching off something or other (UEFI boot) in order to do it, plus Windows locking out other OSs and general messing about, just to run from mem stick, is probably more than I care to embark on. This is why I say, for the uninitiated it ain't easy! Perhaps a Dell laptop is more accommodating. Whenever I delve deeper I find the quagmire just gets deeper! Simpler in the olden days when you just had BIOS to deal with. Everything was simpler with valves, too :<) Ian