wimvb

Fantastic image, Rodd. A lot of detail and depth in there. I also found gain of these CMOS cameras a bit of a challenge. In principle, it should be as easy as ISO in DSLR; the higher you set it, the shorter your subs need to be exposed. But with all this decreasing read noise and dynamic range, it suddenly becomes very complicated. I would love to get into the action again to test, but astrodarkness is still almost a month away up here. And right about that time we will move to a new house. (But fortunately with dark skies.) My point journey is still on hold.

But the light that makes up the Bahtinov pattern all comes from the star, not from clouds.

A simple message "We do not ship overseas" would have been easier. I wonder how many domestic sales this nifty solution costs them.

I had to reread the post as well, just to make sure. From the full frame it seems that spacing is slightly off, but should that give the bent spikes on a star in the centre of a frame?

Nice. If the moon.plays nice, why not collect Ha first for a monochrome mosaic. You can always add colour later. Or do a bicolour (Ha and Oiii).

AfaIk, this was with a zwo camera, which doesn't have a mechanical shutter. But the suggestion to also look for other causes is a valid one. Spacing offset should be visible as elongated stars towards the corners. My first guess was actually seeing or turbulence. But then the curving would be different between frames.

I think @spillage makes a valid point in favour of the smaller scope. The 150pds has slightly more light gathering power, but the longer focal length, distributes that light differently over your pixels. In the end the difference is small. I would check fov of both scopes, and go with the one that suits your intended targets best.

Very interesting reading. Thanks for posting this, @John. I'd seen this blog before, but forgotten about it. According to the blog, there were two similar OO incidents, one is reported in German. The other interesting factoid is the generally excellent quality of Skywatcher ED and triplet optics. And it seems that since the blog was written, SW have taken the advice to heart and improved their products (quality of their lens cells).

If you want to tone down the stars a little, try this recipe: Make two star masks that target small to medium size stars: first a mask with default settings, but increase noise threshold to about 0.4 - 0.5. Make the second mask with large scale set to 0 and decrease blurring (4). Then subtract the two masks to create a contour star mask. Increase brightness by bringing in the white point of this mask. The reason you use this method to create a contour mask, rather than the option "contour mask" in the star mask process, is that it will put a contour around all the stars, and not just the larger. Apply the mask to the image and reduce stars with MT, morph selection. Selection = 0.2, amount = 0.5, iterations = 5, wuth a 3x3 element. (You may need to experiment a little with the settings to create the mask.) This will reduce some of the stars, bringing the nebula to the forground, but still keep it an image of the Milky Way.

Great image, and excellent rework of the jpeg by @Stub Mandrel. An apo of TAK standard shouldn't have CA, but f/3 may be pushing it. Do you refocus between filters? Chromatic aberration is just light of different wavelengths coming to focus at different positions. Refocusing between filters should solve the issue. (But not for the current image, of course). In PixInsight, create a star mask and desaturate only blue, with the colour saturation process. This may be easier than color mask, which also captures any blue in the galaxy.

You can always use it with a mask, to avoid the trifid.

Lovely image. "When all else fails, you can always try color," a famous photographer once said, supposedly.

Looks very nice! Star reduction can be a challenge if the stars are small to begin with. It's all about getting the mask correct. The trick is also not to try to overdo it. Afterall, this is a portion of the Milky way. If you post the (final) xisf, I can have a go at it.

Beautiful. Glad to see that the Milky way is still there, in all its glory. We've been deprived if it for too long now. Btw, it's probably the screen on my phone, but there seem to be some green patches in the image. Scnr would clean that up. Thanks for sharing. Edit: The green is probably something caused by my phone screen. It doesn't show on my computer

Thanks. The data certainly is good, but the histogram was very much to the left, and it needed a very hard stretch. There is also some banding which is probably from the camera's read pattern. So, I wonder if, despite the 3 - 5 minutes sub exposures, exposure time could have been longer. Luminance collects the data from three colours at the same time. So, if luminance exposure can be 3 minutes, colour exposure could be 3x3 minutes, with the possible exception of green. Most mono cameras have their highest QE at green. Blue and red are less sensitive. If luminance exposure time is 3 minutes, then green could be at least 6 minutes, and blue and red at least 9 minutes each. For the ASI1600, with the matching rgb filters, this doesn't apply. For this combination, all three colours should have an exposure time of 9 minutes, if luminance is captured at 3 minutes. I must test this "theory" coming imaging season. (It's still too bright up here, with only the summer triangle visible at the darkest of night.)