wimvb

As the title says, this is a rework of an old image. I collected the data for this one back in the spring of 2020, so it must be one of the first from my observatory. New tools and a little more experience allowed me to pull out more detail and better colours. Dwarf galaxies that are forming in the tidal tail of ngc 4216 are just visible, but to show the tidal tail itself, I would need more data.Technical details: gear: SW MN190 on SW AZ-EQ6 with ZWO ASI174MM-Cool camera and ZWO LRGB filters Total integration time: 13 hours Processed in PixInsight with BXT and NXT. I used GHS stretch just to test it on galaxy images, but imo, it doesn't make much of a difference compared to histogram transformation and curves transformation. In the inverted and super stretched luminance master, several more interested features are visible. I've annotated the image with reference to this article: https://iopscience.iop.org/article/10.1088/0004-637X/767/2/133 A, B, C, and D are dwarf galaxies. The galaxies are the darker areas just above the letters, except for galaxy D which is just below the D. The darker structure F4 is a tidal stream extending from galaxy VCC 165.

I haven't imaged the Orion nebula that often, because of various reasons. For me it's a bit low in the sky and obstructed by a few trees near my observatory. This means that I would have to toss a substantial number of subs, of a sequence. Another reason is that this target is so common, that it doesn't offer anything new. But, in 2021 I pointed my scope at this nebula for about half an hour and collected 72 30 s subs in R, G, and B. This is what I managed then Processing this target is a challenge, and I've now procesed the data a number of times, as new tools have become available. The newest kid on the block, for me, is GHS transformation in PixInsight. I followed Adam Block's YouTube tutorial and, in combination with Russel Croman's Blur- and NoiseXTerminator, this is the result. The objective was to keep detail and colour right into the core, while showing as much as possible of the fainter regions. After several passes of GHS, I almost got the nebula where I wanted it, but I found the core a bit flat. There's a lot going on near the Trapezium that I wanted to show. So, with a range mask exposing just the very core, I used MMT to add a little more local contrast in that area. As I wrote before, the data consists of 72 subs of 30 s, with camera gain at its lowest, in order to keep the highest possible dynamic range. Technical details: SkyWatcher MN190 with ASI294MM camera at 0 gain and -10 C temperature, Optolong RGB filters Exposure time: 30 s Integration time: 36 minutes. More subs might have given me more signal in the weakest areas, but I started to see horizontal banding in the image. Probably the exposure time is a bit too short (my normal exposure time at this gain is 300 s), and the read pattern starts to show. So I'm not sure if more subs or a higher gain would have made much of a difference. Using the high conversion gain of the camera would have reduced read noise, but it also would have reduced the full well depth.

As @Clarkey wrote, it's not so much the weight. It's the size. A larger telescope will catch more wind, which will affect a mount's tracking. Unless you can have the telescope in a dome, you're probably better off with the 200PDS. With cmos cameras that have "small" pixels, you'll be hard pushed to see the difference in image quality between a 200PDS and a large telescope with a 400 mm mirror. Unless you have that telescope on a dry and cold mountain top. But if you want a managable scope with long fl, you should probably check out RC scopes.

According to a recent article, Betelgeuse is expected to go supernova within decades. We might experience it during our lifetime. See drBecky's latest video for details.

Very nice. Is your camera astro modded (ir cut filter removed)? It seems to pick up Ha quite nicely. When you calibrate the images in stacking, try without darks, but activate "cosmetic correction" in DSS. Darks may only introduce more noise, without correcting anything. With an uncooled camera, you should always make sure they don't do more harm than good. In post processing, avoid making the background very dark, ie, avoid clipping pixels (difficult to see on my mobile device). The Milky Way is quite bright compared to the rest of the sky.

Because the worm gear isn't perfectly round, backlash and stiction will vary with where you point the scope. When you run GA, try to always do it in the same area, eg on the same side of and near the meridian, and near the celestial equator, but at least 40 degrees over the horizon to minimise atmospheric effects.

I don't think you can polar align more accurately than a few arc minutes. To move the mount by arcseconds requires very smal adjustments of the alt and az screws, and virtually no friction between the mount and tripod/pier plate. What looks like backlash in the GA, can in fact also be stiction. Slew the mount and listen for changes in the sound it makes. If you can measure the current that the mount draws, you can check for any changes while slewing. A binding mount will draw more power than a smooth going mount. Backlash lower than 1 s (1000 ms) isn't much of a problem. If it's much larger, you should adjust the worm gear. Your RA corrections are small, but random, which is an indication that you are chasing the seeing. Try guiding with a lower aggression next time (30%), and increase if needed. Seeing differs between nights, so what works one night, might be less than optimal another night. The EQ6-R can do 0.25" rms guiding with an 8" Newtonian, but only under ideal conditions and near zenith. Depending on where you point the scope, rms can be 1" with the same setup. So, don't chase small numbers. As long as you get tight round stars, enjoy your time in the dark.

I think that sky survey data is systematically scanned for "abnormal" stars. First by citizen scientists, and students, but now also by AI. Any interesting areas are then studied further and findings published. Before deep sky surveys were common, such investigations were impossible, because no one knew where to start looking. It's not just finding the needle in the hay stack, but rather finding the wooden splinter in the hay stack. You can always contact one of them. The first author of scientific publications is usually the young one on the team, who has to gain academic recognition. Most likely this author has earned his degree by now, and may have moved on, either as a post doc or as a senior researcher/assistant professor. One of the last names on the author list, and recurring on many publications in the field, is usually the established professor who supervises the team of researchers. Two pieces of software are used in the book, both freeware APT - aperture photometry tool TOPCAT - data management and diagramming software

In all fairness, I'm not so sure that the authors of those papers can get more information out of your data than what they already have collected. As you haven't used photometric filters, it will be difficult to extract data for a calibrated colour magnitude diagram from your masters. What you could do, is try to extract a C-M diagram from your image with a wider field than what was included in the 2018 article you refered to in your original post. That would be a challenge, and you'd learn a lot about what professional astronomers do. I found this book a great help (the one or so time I've tried it on my own data, and never on such faint signal) https://link.springer.com/book/10.1007/978-3-319-23377-2 Chapter 10 is about creating C-M diagrams

Great! It's nice to see a fellow astrophotographer also go for the fainter than faint. It seems you've accepted the challenge. 😄 The first reference that I've found on your target is from 2015 https://iopscience.iop.org/article/10.1088/0004-637X/813/1/44 This is truly an intriguing deep sky object, and at first I thought that 3 hours of imaging time wouldn't be nearly enough. But you are using a photon hoover (aka RASA). Well done.

I think it's the scope in this thread. A real beast with probably 1.8m focal length.

Is this with the same camera? If so, the raw images and the stacked images should be of the same size irrespective of focal length. The jpeg image otoh, is an entirely different beast. Jpegs are always compressed to some degree. I see a size difference in jpeg if I use different stretches. Also, since the C11 has a smaller pixel scale than the TOA, each pixel would collect fewer photons if the aperture were the same.

Thanks. That gives me something to process while nights are too bright up here. Here's my first version, very different from yours. I don't process nebulae that often, so it's a bit trial and error. You can download the process list and examine it in PI. The mask that I used is just a luminance mask from the image after star removal. Brought in the black point in histogram transformation (auto zero shadows) PI_VdB152_Alan.xpsm Added HDR transformation at the very end, in order to restore some of the detail in the reflection nebula

👍 That's on my todo list

I took the liberty of downloading and playing with your image. In histogram transformation I used the "auto zero shadows" button to get a different colour balance (not star colour, but background). This cleared up the colours, separating reds and blues more. I then increased colour saturation for red an blue to get this. And this version when using DBE to change the background.

Doesn't look overcooked to me. With so much nebulosity, it's very difficult to do proper gradient removal. The result will very much depend on where you put the samples. But this looks good to me.

Nice find. There's a lot going on in this area. This is from Simbad in France: https://simbad.cds.unistra.fr/simbad/sim-coo?Coord=01+33+40.08%2B30+21+37.2&CooFrame=ICRS&CooEqui=2000.0&CooEpoch=J2000&Radius.unit=arcmin&submit=Query+around&Radius=5

Another one lured over to the dark side. "You have done well."

Photographing those is more Göran's area, although I do like the images. https://www.astrobin.com/w9m6cv/G/?nc=&nce=

That link refers to what Alan thought was a small galaxy with a "black hole", but which in fact is a small planetary nebula which is ring shaped. The cropped small nebula that Alan had found (the Pelican's tic) contains several sources, including an Hii region, but it seems to lack an overall identifier.

Hence the hole. It's a ring nebula. Fame is a fickle thing.

Shouldn't it? 😁

Very nice image. I found this in Simbad. Nothing for the whole nebula, it seems. https://simbad.cds.unistra.fr/simbad/sim-coo?Coord=20+45+37.80%2B44+15+02.8&CooFrame=ICRS&CooEqui=2000.0&CooEpoch=J2000&Radius.unit=arcmin&submit=Query+around&Radius=2 Maybe we should just call it the Pelican's chick.

Thanks, DP. Glad you like it. I prefer to photograph unusual and sometimes obscure targets.

Unfortunately, Sweden gets most of its clear nights during spring. In my neck of the woods, we've had mostly clear nights since astro darkness ended, with maybe just a handfull exceptions. In the last few years, weather patterns have shifted. The clear nights we usually enjoy during winter and early spring, this year didn't materialise until March/April, making for a very short galaxy season. During winter, nights can be very cold and "crisp", with low humidity and excellent transparency and seeing. But last winter most clear nights were mild with higher than usual humidity, giving below average transparency, but good seeing.