wimvb

After a few years with the small sensor ASI174MM-Cool, it was time for an upgrade. I got the new ZWO camera ASI294MM-PRO with Optolong 31 mm LRGB filters. As a test I pointed my scope at the Perseus galaxy cluster Abell 426, with its main attraction ngc 1275. This is just short of 4 hours of data. Humidity was too high to capture any luminance data. Besides, the moon, though late to rise, was still too bright for any decent luminance. I also couldn't collect any Ha, because the screws that hold the 31 mm filters in place, are in the way for my 1.25" Ha filter. I will need to get a 31 mm Ha filter to complete my set. Technical details: 30 x 150 s (each) RGB, flats and darks, taken with the ASI294MM-PRO on my SW MN190-DS. Mount: AZ-EQ6 Filters: Optolong LRGB 31 mm filter set. Captured using INDI/Ekos, guiding with the internal Ekos multi star guider. Processed in PixInsight. Atmospheric conditions were far from perfect. The relatively warm weather we've had, has caused the air to be saturated with water vapour. We've had mist forming every night and this has cut imaging sessions short. As a result, this image is a bit soft. Guiding RMS was just below 0,9", about the same as my imaging scale (0,95"/pixel). There are still plenty of things to work out with this new combination. For one, I need to move the prism of my OAG up a few millimeters, as it creates a shadow/reflection where it sits now. I also have to figure out how to activate the internal window heater in the camera, because I may have had ice build up, causing circular gradients that I couldn't remove completely. About the target: The Perseus galaxy cluster is quite fascinating. Its main member (ngc 1275, about 250 Mly distant) is a very active galaxy that is in the process of devouring another galaxy. This is just about visible in this image. The remains of the victim galaxy are just visible around the predator. Ngc 1275 has a massive black hole at its center that spews out radiation and hot gases. These gases form Ha filaments that surround the galaxy. These filaments are 200 ly in width and 20 000 ly long, and are kept in place by very strong magnetic fields. The Ha filaments are also just visible as red patches around the galaxy, in this image. So, despite various issues with this image, the full size version shows some very nice details. The whole field is filled with galaxies. PixInsight identified the larger and more prominent of these galaxies. 19 November: A reprocess, removing gradients, etc

Use Photoshop, GIMP or any other photo editing program to adjust colour balance and stretch the image. Btw, you also need flats in order to remove the vignetting.

Why do you drizzle? Judging from the provided image, I don’t think you gain anything. You’re just processing a larger image with more noise. Drizzle is only necessary if the subs are undersampled. In other instances it will give you a noisier image.

LRGB isn't that difficult if you adhere to the principle that you process the RGB image to get maximum colour impact (level of saturation) and the L image to get maximum contrast and detail. LRGB combination will then combine these two: detail and contrast with colour impact. In an OSC image, it's more difficult to separate colour from lightness, because they are both in the same image. in LRGB imaging, colour and lightness are separated and you optimise each before you combine them. Once you get used to this, LRGB processing can in fact be easier than OSC processing.

Yes, that's how I would do it. For vignetting gradients, one sample in each corner, one further in from each corner along the diagonals, and one along each edge. Make the samples larger than the default 5 pixel radius. I sometimes go up to 35. Stay away from large stars, but don't mind covering smaller ones. And as Olly already warned for, don't even get close to the main object. (You can always take an image from the internet as a reference.) Increase tolerance until sample weight (next to the sample image) is larger than 0.75 for all three colours. The sample image should look as neutral light gray to white as possible, without a distinct colour cast. In the correction section, if you leave "normalization"(?) unchecked, you will get a neutral(ish) background. Personally, I have this option checked, in which case any colour cast is left as it was. I like to keep background neutralisation separate from gradient removal. But that' s just me. For a linear gradient, you need fewer samples, about 3 along the gradient and 2 - 3 perpendicular to it.

Olly, the way I interprete the original post is that no flats were applied here. When flats were applied, they removed dust shadows. That's what is confusing me (too). I agree with your comment that ABE should not be used here.

The gradient can come from light pollution. You may need to do background extraction in two steps: first using division to get rid of vignetting, then subtraction to get rid of the colour gradient. Use DBE, not ABE, because it’s easier to control.

AP and the responsibility/work that comes with small children doesn’t mix well. If you like visual, consider selling the 150pds and eq5, and invest in a Dobsonian. This may even get your kids interested once they get somewhat older.

The guide camera doesn’t need perfect focus. In fact, some argue that a tiny amount of defocus is beneficial. Unless there is a large difference between focus positions for the filters, you may be ok. You can set the guide camera focus between the extreme focus positions for your filters

Tricky. The LP filter may block light that the RGB filters pick up, so there may not be much improvement. Or the LP filter may block so much light that it affects the colour image too much once you combine the L with the RGB. Otoh, RGB filters have a gap between red and green, because that’s where the most common light polluters are (Sodium and Mercury lights). This makes RGB filters somewhat LP tolerant. I would at least experiment by just collecting RGB and creating a synthetic luminance, before investing in a LP filter.

Ha enhances the red from RGB. You can also blend it into luminance. But because most of the information is in the narrow band Ha data, luminance (broad band) doesn’t necessarily add much quality wise.HaRGB may be all you need. The Ha provides structure and detail, while the RGB provides colour in the stars. Reflection nebulae are broad band targets which don’t gain from using NB filters. Eg, the Pleiades (m45) are imaged with traditional LRGB techniques.

The general guideline is to use much more luminance than rgb, so you can get enough data to enhance detail and weak signal. You use RGB to provide colour to the L image. But the crescent is different, because it’s mainly an emission nebula. Especially if you have light pollution, you should consider to go for Ha rather than L.

That’s correct. I totally forgot about that.

Does the power LED on the mount blink when you slew to a target? If so, the voltage is too low. Next item to check is slew speed (press 2 on the hand controller, plus 7, 8 or 9).

It should be in the Mount or Telescope section. I don't have the asiair, so I'm not sure. But it would be the obvious place to start looking.

Make sure you set the flip to occur some time after the object transits (passes the meridian). Otherwise the mount can get confused, because of polar misalignment, cone error, etc. With your setup, you can safely track up to half an hour after transit.

Just check my astrobin page. I use zwo filters (lrgb) exclusively, atm. https://www.astrobin.com/users/wimvb/

In a distant future, this scene will become reality. We're on a collision course.

According to an article by Jerry Lodriguss, you need to multiply integration time by 2.5 for every magnitude you lose due to light pollution, in order to get the same snr. And from Bortle 1 to Bortle 8 is at least 4 magnitudes difference, or 40 x longer integration time. So, 40 hours integration time to get results similar to yours. In theory. And not taking into account any gradients that may be difficult to remove. Imo, life is just too short for this. That's what I would do too.

You need a dark library for each combination of exposure time, gain and temperature. Otoh, darka last a long time. And you don't need flats for every filter. Dust bunnies on filters are so far from the sensor that they rarely matter, in my experience. Dust that interferes is located on the sensor or the camera cover glass.

Hiep hiep hoera! Congratulations

You can leave the filter wheel (and possibly an oag) attached to the camera, and put it in a padded plastic container when not in use. It's just as easy as an osc camera. Even if you want to shoot broadband (rgb) a mono camera has advantages. Most RGB filters have a gap between G and R, so as not to pick up light from the most common lp sources, sodium and mercury. They also have an overlap between G and B, so as to pick up Oiii. And if you replace the L filter with a light pollution filter, you can shoot RGB or LRGB. Processing mono isn't more complicated than osc. And finally, mono imaging is more tolerant to chromatic aberration, because you can refocus between filters.

I've been informed by Andreo a while back, that he's looking into finding a suitable retailer, but this may not happen. Mastering PixInsight is published privately, not by a publishing company. This may complicate matters? There's always the pdf version if the physical version is too expensive.

If only there were cameras with round sensors, and desktop software with round windows/workspaces. 🧐

With a square sensor you don’t need to rotate your camera, you just crop to the aspect ratio you want. Much easier, in my opinion.