wimvb

You also have to consider software support. When I was scanning the market for an astro camera, I removed qhy from the list because there were too many reports from people who had problems with them under Linux. At the time, qhy's linux drivers were just not stable, and they didn't seem to have anybody working on it. This despite the fact that qhy cameras were better engineered than zwo. Qhy cameras had a window heater, amp glow elimination, and a memory buffer as standard, whereas zwo introduced heater and buffer only much later in their pro models.

I wouldn't worry too much about those numbers, it's pure theory. What you should consider imo, are: Sensor size Pixel scale ("/pixel) Read noise Dynamic range I believe the 174mm was discontinued because ZWO had many models with small chips. They just cleaned their catalogue.

Gremlins

Depends on whom you ask of course: https://astrodon.com/products/astrodon-narrowband-filters/ AfaIk, there's only one manufactuter of 3.5 nm filters. But I could be wrong. Are there any independent (bench) tests of nb filters?

Maybe you should apply for a grant to build a research station with a roll off roof. If Musk gets what he wants, that problem got be solved next time you visit the island.

that is correct.. The transmission peak of a nb filter shifts towards the longer wavelengths for oblique rays (ie low f-numbers).

That would certainly help.

Why not do the stacking in pixinsight? Use the script (BatchPreprocessing).

If you haven't found these already: https://www.easypixinsight.com/ https://www.lightvortexastronomy.com/tutorials.html https://www.harrysastroshed.com/Pixinsighthome.html And a bit more advanced, but a real treasure trove: http://pixinsight.com.ar/

A proper mask and blending the offending region with a less stretched version works reasonably well to remove this microlensing artefact. The top star in this image has the same problem, but I was able to reduce it enough for it not to be a nuisance anymore. https://www.astrobin.com/397054/B/?nc=user

I wonder if you shouldn't go down further still in iso. The stars are very bright and need short exposures at low iso/gain to avoid bloating. Also, at low iso there will be more dynamic range. If you take many more exposures (maybe 2 - 3 hrs worth), the lower noise will allow you a harder stretch to bring out the nebulosity.

It really is. And considering that this was captured with a photographic lens and a Star adventurer. Astrophotography is as real estate, about three things: location, location, and location.

For good filters, it's not what they let pass, but what they block. Eg, if you have a 3 nm narrowband filter with 99% peak transmission and 1% transmission off band, then you still get a lot of unwanted light in. This is simply because 1% of all those photons that should be blocked make it through. But if the filter has 93 % peak transmission and only lets 0.01% through off band, that filter is much more light pollution proof. Then there is hardness. A quality filter will have hard, durable coatings, that can "take a beating". Less expensive filters may look good on paper, but the coatings can be less dense and have poorer adhesion. This is impossible to see when you buy, and may only show after a few years of use. Finally, there's the back side of the filter. This needs a high quality anti reflective coating in order to avoid reflections. Filter makers spend a lot of time doing product development and quality control. They want to be paid for their efforts. In short, quality costs, and you get what you pay for. As for multiband filters, I'm not convinced yet that they are time savers. In general, Sii, and Oiii are much weaker than Ha in a nebula. So you may want to use longer exposures for these wavelengths. Also Ha is more moon-proof than Oiii, and you can gather Ha when the moon is too bright for Oiii. If you only have an osc camera, a multiband filter may be ok, but I wouldn't expect the same results as for separate filters and a mono camera. Decide what you want, and what you are willing to spend, and shop accordingly.

It's very interesting reading with some unexpected possible effects of global warming. Göran was so kind to point me towards a few links.

Beautiful witch looking at Rigel, Göran. You nailed that one. The one above Rigel looks like a PN. There's also a very small galaxy a bit further up, and maybe a few more barely visible.

With a result like this, your transgression is certainly forgiven. Did she by any chance read the book(s) (not yours)?

Great image already. Regarding lrgb combination, you have to remember that white doesn't contain any colour information. If you combine white L with colour, the output will be almost white without any colour. Anywhere where you want colour, the L will need to be less than 1 (intensity scale from 0... 1). Adam Block has a good tutorial about lrgb combination in pixinsight. https://adamblockstudios.com/articles/Fundamentals_LRGB

The old, usb2, zwo asi120 is not supported due to issues with usb traffic. The newer with usb3 is supported. So is the narrow bodied 120mm guide camera, afaIk. The ZWO web site has a list of supported dslr cameras. https://astronomy-imaging-camera.com/product/zwo-asiair

Merry Christmas to you and yours. Your stay is turning out very productive. It seems to me that December sees a doubling of your year's output.

What does the new LHaRGB look like? If the blend is an improvement over the original, isn't then the new image even more of an improvement?

That's a very productive stay at the research station. I hope your field work is just as productive. God Jul till dig och Sjannie

Well, the flat is over exposed, the light frame is quite uniform with a median and mean value of about 0.35, and the dark looks normal in so far that it shows the ordinary ray-burst amp glow and a few hot pixels. Here's the deBayered light, using superpixel mode, so that no data was interpolated. I have no further ideas to offer.

In this case, that's correct. But generally, flats are taken under "day time" light conditions. But here there is so much light pollution that even lights have a high intensity level. I used DBE in Pixinsight with only eight samples along the diagonals in order to reduce the vignetting. This never affects weak structure such as the blotches. I start to suspect the quality of the bayer layer or the antialiasing layer on the sensor. Ordinary interference as in Newton rings could create blotches. That would not show in darks, and be masked in flats. This would be a very serious quality issue for Sony.

That wouldn't surprise me too much. The sensors that zwo uses come from various "families". Larger sensors are generally used in consumer cameras. Smaller sensors may be developed for machine vision an surveillance applications. Some basic on sensor image processing isn't unheard of. Otoh, that should affect darks and lights alike.

I don't think the drivers have a gain conversion table. I wouldn't trust the e/ADU, only the set value of 120. No idea, really. As you say, the values should be divisible by 4. I'm not sure it's data corruption, because that would more likely corrupt the whole file.