wimvb

Thanks, Michael

Ngc 891 is an edge-on galaxy in the constellation of Andromeda, at a distance of 30 Mly. It has a tidal structure, but this is so weak that (to my knowledge) no amateur has yet been able to image, although R. Jay GaBany has come close. Because ngc 891 is located behind galactic cirrus from our own galaxy, it has a red appearance. I toned this down slightly in my image. Opposite the bright star HD14771 is galaxy cluster Abell 347. The members of this cluster are similar in size to ngc 891, but 8 times further away. The brightest galaxy in this cluster is ngc 910, to the left and near the bottom of my image. The edge on galaxy below ngc 891 is ngc 898, a member of Abell 347. https://www.cosmotography.com/images/ngc891_galactic_cirrus_comparison.html https://iopscience.iop.org/article/10.1088/2041-8205/714/1/L12/pdf I collected the data for this image during a few clearish nights this month, just before the moon put a stop to rgb imaging. This was also first light for the ASI290 mini guide camera. The kit is coming together nicely now. Gear used: MN190 DS on a SW AZ-EQ6 mount with OAG and ASI290 mini ZWO ASI294MM-PRO with Optolong LRGB filters Total integration time: 15.5 hours L: 344 x 90 s R: 55 x 150 s G: 48 x 150 s B: 62 x 150 s Processed in PixInsight.

Lovely. Just how small is it?

If stellar wind pushes matter, there nust be matter to push. On the side of the nebula there obviously is, but not so much on the opposite side. So you wouldn’t expect a structure there either.

Have a look at this

I think we should pin 📌 this thread. Just in case.

Do the photons bounce of the star’s ”surface” or are they absorbed in the collision? 😉

It’s very weak, and probably gas being pushed out by a stellar wind. It has a closer resemblance to the soap bubble near the crescent neb, than it has to the bubble nebula.

Yes 16 bit/ pixel = 2 byte/ pixel, so 94 Mbyte. 11 images will fill 1 GB of a hard drive. I captured 378 luminance subs for my most recent project. What can I say, modern cmos thrive on many, short exposures. But it costs...

I’m not sure about that, but there is a bubble in the full view. It’s in the upper right corner, and Rodd captured only a quarter of it. This image shows more of the structure. https://www.astrobin.com/nvnfw5/?nc=all

Thanks for the update. As it is, I won’t be using that feature in the nearest future. I come from 2.3 Mpixel and have now 12 Mpixel. My computer just can’t handle the increased data load of 47 Mpixel. It took me a whole evening yesterday to calibrate, align and integrate 344 luminance subs (8.6 hours worth of data). I wasn’t pleased with the result, so while I’m at work, my computer is integrating a new stack. A more powerful computer and more storage are on my wish list. 2.3 Mpixel was so easy...

Time for a Mosaic? I've seen quite a few images of the California Nebula over the years, but this version is definitely one of the best out there. I love the detail and the contrast. Those dark nebulae within the CN are rarely this clear. 👍

Helix nebula? Sauron's eye you mean. 😉 Another great image, Rodd. But I'm a bit surprised that despite the 22 hours of data, you still have noise. Light pollution , or a really weak outer rim around this target?

Try to get them as even as possible with DBE . Then background neutralization and colour calibration. Make sure that the panels have similar background intensity levels in L. Desaturate the background with a mask to remove any tonal differences.

Gremlins at work. Netflix or HBO 😄

What you're seeing is the Bayer or CFA pattern (RGGB). All is as it should be.

If it's on the filter, it will vary from one filter to the next, and may be absent on a certain filter. Otoh, the specks are much too small to be on a filter. In what order did you take the exposures for the different filters? Can you repeat the results, ie, can you take flats for the various filters? One exposure per filter should do it. Is it on all the green and blue exposures? For instance, could it be tiny water droplets that were sitting on the sensor, but have dried up since? In that case, you wouldn't see it any more. And it would vary in size/intensity for subsequent exposures. So by the time you got to the red filter, it could have been gone. I'm just grasping at straws here. Does that happen? My wildest guess is that that wouldn't create specks, but a swiping vignetting pattern or gradient. In any case, I would take flats and see if the problem persists, or if it was a one time event.

Time to open the filter wheel, I’d say.

You may need to experiment, it seems. Similar to this

In a galaxy far, far away ... Have you checked how far away?

This definitely isn't walking noise, in my opinion. Walking noise is on a single pixel scale. To me this seems more a case of walking dust specks, but they are a bit small to be on the filters. Check your calibrated, unregistered subs. Do they have dark dust bunny-like features, all in the same place? Then register those subs, and compare again.

For cmos astro cameras, you not only set gain, but also offset. Offset is to make sure that you won't get any negative/clipped pixel values. You should probably check if offset has changed. You can add offset before image calibration, at least in Pixinsight. A change in offset can also be the reason why your flats aren't working.

A slow transition to PI then. I like this newer version of your image.

Btw, they're still there, just last in a long, long list. But you've probably figured that out now.