The Admiral

That first link is a long thread, but well worth checking out. AZ mounts are perfectly capable for astro photography, though for good results there are limits. If you don't already own such a mount, then it's probably worth going for an EQ mount in the first instance. Ian

I guess the problem with superpixel debayer is that it is best for over-sampled imaging, I believe, which is likely not what the thread starter will be achieving with his short focal length set-up. I'm not sure how important that would be though. Ian

Do you mean that it won't include the readout noise for the redundant blue and green pixels? Ian

Without wishing to derail the topic, if you are just imaging Ha with a OSC camera, with the blue and green pixels essentially redundant, does just selecting the red channel to process improve the noise levels? I'm thinking that if you only use the red pixels you only have their read noise, or am I being too simplistic in respect of de-Bayering OSC data? Ian

I've not used the APP mosaic tool, but I thought it was highly regarded. There are video tutorials: https://www.astropixelprocessor.com/video-tutorials/ Might be worth a visit. Ian

OK. Though the fov on the long side is 3.4 degrees, and the corrector plate aperture extends almost to the tube, so it would depend on the dew shield's extension of course. Ian

Is the dew shield a little oval? Could that conceivably have an effect? Ian

May be the odd star can be ignored, but I do find that when all the stars seem to have oval halos with their major axes in the same direction, it does detract from the image. Just my take of course, YVMV. Ian

Well now, there's a thought! Anyone tried a thatched dome on their obsy? Ian

I may be wrong but I also vaguely remember something about not using very short subs for flats. Ian

I presume that you looked at CN, I know that there was much discussion on flats uniformity there. Ian

Well I for one was looking forward to reading something with fuller details, but as the link wasn't working for me I can have no opinion. Pity. Why it works for others I don't know, but I can assure you I was in no way trolling. Rather, just providing a heads-up. Ian

The link seems a bit flakey to me. The first time I tried it the page wasn't available. I've just tried it again and it opened the site quite quickly but clicking on the links within didn't seem to do anything. Ian

I agree with happy-kat, JPEG is perfectly adequate for web use. If you are ever wanting to produce a large format print of your results, then 16-bit TIFF would be my choice. If you ever want to present an image for others to process, then use FITS or 16-bit uncompressed TIFF as a file for others to download. Given the sizes, you might need to use a link to a cloud service (I use Microsoft's OneDrive as I have an Outlook account). Mind you, having said that, I see that this sites upload file size is 1GB! Ian

JPEG is only 8-bit and of course is highly compressed. TIFF can be in 8-bit or 16-bit. To be honest, don't know much about PNG. You should always work with the highest bit-depth uncompressed, linear data you can. It is customary to use the 32-bit FITS format with astro files (they are large files ). So, import RAW files into DSS, export the output of DSS as a FITS, and import the FITS into StarTools. It is only when you come to export the output from StarTools that you can decide what file format to use, it will depend on what you want to do with it. Personally, I export as a 16-bit TIFF, because I can always create a JPEG from that later if I want. Don't forget, data is lost during compression to form a JPEG, and that is lost data that can never be recovered. For StarTools, there is specific guidance on what settings of DSS you should use to provide the optimum input. https://www.startools.org/links--tutorials/starting-with-a-good-dataset/deep-sky-stacker-settings Hope that helps. Ian

That is a long thread but Mark Shelley has come up trumps. Skip to the end to find the solution! I don't use Nikons but it will be a saviour for those that do. Ian

Welcome Stefan. To be honest I think that your results are pretty good despite your trials and tribulations. You will always have to reject subs if you are after decent results. The mount of course has a big influence on the proportion of rejects, and entry-level AZ mounts will be worse than high end. I recall that Filroden's EVO mount seemed to perform better than my SE mount. But I think the biggest challenge you will face is that you are using a long focal length 'scope, 1500mm. This means that any mount deficiencies will be magnified. When we started, the focal lengths we used were about a third or less of that and we were taking wider field views. Now that doesn't help you I'm afraid, though there are many examples on here which 'disprove' that, but I think imaging small objects will always be more challenging. If it were me, I'd use an f/6.3 reducer which will reduce the focal length to ~950mm, though I say this without any practical experience of this as I imaged with a refractor, not an SCT. But, as I said earlier, don't be discouraged, because what you have achieved so far shows that you are well on the way. But just be prepared for the collateral in sub rejects. Other views may vary . Ian

Hmm, interesting. Forgive my asking, but isn't the Ha filter a 'broad band' Ha filter rather than the really ultra-NB, Angstrom-wide, etalon type which are used for viewing the proms etc? Is it's function then more of a blocking filter/ERF, requiring the addition of something like the Quark to view the Ca-K or Ha? Ian

I've never tried it, and I don't know if this is of any interest, but there is a short chapter in a book called 'Constructing and Astronomical Telescope'. It was first published in 1947, but this is from a second edition from 1955. 'Elf & Safety' of course is nowhere in line with what we have today! It is an immersion process. Silvering.pdf Ian

Well, if I follow this correctly, it looks as though the satellite coverage rotates anticlockwise, but the vortex itself rotates clockwise. A link to an interesting video animation can be found here: http://lasp.colorado.edu/aim/download-data-L3B.php Ian

I was looking at the 'daisy wheel' for NLCs on the spaceweather.com site, and this is what I got today (but dated 22nd) I would guess that the patches seen over the Northern parts of the UK were what were observed on 23rd, yet the dates are wrong, but there is nothing else seeming to be upcoming. I gather that the wheel rotates clockwise anticlockwise with time, but I think I need to get to grips with what this display actually means. I've found http://lasp.colorado.edu/aim/index.php so that might be a start. Ian

Thanks Paul, I just wish I had your scenery! Given their supposed height, of around 80km I believe, would we have been looking at the same clouds do you think? Ian

Thanks. Me too, particularly as I've never been aware of them before. I wasn't quite expecting them to extend as high as they did, more like a display near the horizon. Ian

Checked the sky after the late night news, and could they be NLCs? If so, the first I've ever recognized as such. Well chuffed. Taken around 10.45pm; they'd more or less faded by 11.00pm. I have a lousy Northern horizon, and so these were taken from upstairs windows. Ian

A beautiful backdrop to the display. Ian