wimvb

Quite correct. Guiding corrections can be up to 2 500 ms or 2.5 s, the default maximum pulse length. Besides, why would one use sub seconds exposures with a guide cam anyway? You'd be chasing the seeing.

ngc 2768 is a lenticular Seyfert type galaxy in the constellation Ursa Major. It is the main member of the ngc 2768 group of galaxies, which also includes the smaller spiral galaxy at the top of the image, ngc 2816 or 2742. The latter seems to have two entries in the new general catalogue. The group is located about 60 - 70 million light years distant. Right in between these two sits RM J091015.4+601901.2, a cluster of galaxies. This cluster is approximately 3 BLy distant. This is an RGB image with added synthetic luminance. Total integration time: 8 hrs and 20 minutes (125 x 4 minutes subs). As usual, captured with the SkyWatcher 190MN and ASI294MM camera

I did a bit of homework on the faint fuzzies in the background. Managed to get quite a few. Quasars with redshift up to 2.8 (whatever that is in lightyears) and galaxies up to 6.3 billion Ly distant (z=0.48). Plus a few unidentified objects that are most likely dwarf satellite galaxies belonging to ngc 3359. The streaks at the top are reflections from a bright star (HD 93551) just outside the fov. I didn't remove them from this image. QSO: Quasy Stellar Object ClG: Cluster of Galaxies BCG: Brightest galaxy in a cluster WD: White Dwarf (there is even a brown dwarf in the fov, but those are a bit hard to capture 😄 )

I did a bit more digging. It looks like both the ZWO 5 x 1.25 and the 8 x 1.25 filter wheels can take both 1.25" mounted and 31 mm unmounted filters. But only in the larger wheel can both types be combined.

The ZWO mini filter wheel can't take both types at the same time. The screws and washers that hold unmounted filters in place, come in the way for the screw in filters. But it can take both types (1.25" and 31 mm) separately.

1.25" filters are ok, they have about 30 mm glass diameter, while the camera has a 16 mm diagonal sensor. 1.25" filters are mounted (have a threaded ring). 31 mm filters are unmounted (only glass), and are held in place by either small screws with washers or plastic filter rings (provided with the filter wheel). Imo, go for an electronic filter wheel. As you already have automation from the ASIAIR, buying a manual wheel makes little sense. If you have a manual wheel, you need to be at the scope for each filter change. This will mess with your framing, because touching the scope will most certain push it a little. So you would need to redo a plate solve after each filter change. Also, manual wheels have a greater risk for light leaks than electronic wheels. If you live in an even modestly light polluted area, starting with just nb filters makes sense. Besides, autumn and early winter are more nebulae seasons. Unless you insist on having RGB stars in your nb images, you really don't need rgb filters yet. They could wait until after Christmas (hint), when galaxy season starts. Edit: with nb and rgb filters, you don't need and shouldn't even use a uv/ir cut filter, as colour filters already block uv and ir light. The camera should have an AR cover window. Any glass that is not AR coated, such as filters, will only increase the risk for reflection artefacts.

Have you considered one of the newer ZWO cameras that don't have amp glow (which the ASI294 has) or micro lens diffractions (which the ASI1600 has)? If amp glow free cameras are beyond your budget, there are cheaper brands with the same sensors, such as Rising Cam or Omegon.

In March I tried to image the compact blue galaxy Little Cub in the constellation Ursa Major (Great Bear, hence the galaxy's name) together with its big companion ngc 3359. Since then I have added more luminance and even collected Ha data for this image. The integration time is 28 hrs and 46 minutes. I never really got around processing this data, but recently I bought a new computer (with i9 processor), calibrated its display, and upgraded my version of PixInsight. I decided to test the upgraded image processing gear by redoing this image from raw subs. The added data didn't do much to enhance the Little Cub, but I did manage to isolate two unidentified stellar regions near the larger galaxy. These are most likely either extensions of the spiral arms, or dwarf galaxies. Here's the final result More information on my Astrobin page. https://www.astrobin.com/x4zhbz/

The SynScan handcontroller has a built in all star polar alignment procedure which works fairly well and is simple to follow.

Sorry for the short previous answer; I was in a hurry. LRGB combination isn’t an RGB pixel operation, but rather performed in the L*a*b colour space. You can verify this by using channel combination in PI. Choose the Lab colour space, uncheck a and b, and enter the name for the L image in the L box. Then apply to the RGB image. The result is identical to LRGB combination.* RGB combination is an RGB pixel action; it applies the R image to the R channel, G to the G channel, and B to the B channel. Neither process is simple addition, hence L+R+G+B is not equal to L+RGB. Edit: * Actually not quite identical. I checked with PixelMath 1. created a colour image with only a red gradient (X() in PixelMath) 2. created a luminance image with another gradient (Y() in PixelMath) 3. Combined L with the red RGB image (LRGB combination) = image_3 4. Combined L with the RGB image (L*a*b channel combination) = image_4 5. subtracted image_4 from image_3 ( abs(image_3 - image_4) in PixelMath) The resulting image wasn't completely black, so image_3 and image_4 where somewhat different, but not much.

Assuming that the channels are added as in math (ie, assuming that LRGB combination is additive). But, the range for pixel values is 0 to 1. What if the sum is large than 1? Clip? Rescale?

Alignment as per @VectorQuantitys reply. LRGB combination does’t do any alignment. In fact, you can combine any mono image with any RGB image as long as they have the same number of pixels (width and height). Before LRGB combination: create an RGB image from the three masters. Process this for optimised colour. Never mind the details, but do keep the stars in check. Make sure that these don’t lose their colour. Process the L master for details and local contrast. Deconvolution, sharpening, local contrast enhancement, etc. Finally combine the L with the RGB. Uncheck R, G, and B channels in LRGB combination. Choose the L master for L and apply the process to the RGB image. An Easter Egg here: the LRGB combination process can assign weights to the various channels. Set the weight for L to 0.2-0.5 if you want to apply the process in small steps.

At this stage in the process, I would apply green reduction, to make the colours pop. Scnr green in pixinsight or hastalavista green in ps.

You set them as RAW8. That would explain things. deBayer after calibration but before star alignment. Whatever program you use for stacking, will have a setting for this. Also, RAW16 for dso imaging will help during post processing

That ’s a heavy weight to lift for that mount. But the result looks great. (Pictures show alright.)

Did you deBayer during stacking?

Next year ZWO will offer a new generation. Not that I have inside information; it just seems how they operate.

It depends on how you create the mosaic. If you first create two masters that are to be combined, it seems better to remove gradients from each. But if you stack all subs at once, this becomes harder. Pixinsight could do it, because it allows processes to be applied to groups of images. But I’ve never seen it done that way.

This is what the histogram looks like for my image, after processing. Green and blue are narrower, because there is no signal to speak of, just background. Your cls filter clips most of the yellow and green. Imo, you should try imaging without the filter. Bortle 4/5 should be dark enough. I've seen great images processed in PI and in PS, but am not familiar with Affinity, APP or Startools. Processing is an important part of AP, and if you are willing to spend money on gear, you should, imo, also be willing to spend money on processing software. Most software allows an evaluation period. Use that to find out which software feels best.

I let Starnet do its thing during dinner, and processed the starless version a little harder. Then added the stars back in. In retrospect, I could have used a less stretched version for the star layer. Here is the starless version

Some of the unusual gradients may be due to the fact that this is a mosaic. If gradients aren't removed from each panel before mosaic composition, they can in effect repeat in the final image. And given the fact that this is a very difficult target for gradient removal to begin with, that may very likely be what we are all seeing.

Imo, this isn't a gradient. In this case your gradient removal tool removed valid data as well. Careful marker positioning, as you already noted, should resolve this issue. That explains the lack of colours and the strong red signal, which I also found.

Quick & dirty in PixInsight: cropping the stacking edges gradient removal background neutralization stretching slight enhancement of local contrast With an image like this, I would try to do star removal and process the nebula seperately from the stars, then recombine. But the image is a bit too large for my old laptop, so I left the stars untouched. There's nothing basically wrong with this image, other than that it's still a bit noisy. More data is of course the best solution to that problem.

Do such adapters exist? The disadvantage with st4 is that phd isn't aware where the mount is pointing, and needs a new calibration for each new target. Far better to connect the mount to the computer that runs ascom and phd using an eqdir cable. Windows: computer with ASCOM based software, cameras to usb, mount to eqdir/usb. No st4 Linux: computer with INDI based software, cameras to usb, mount to eqdir/usb. No st4

Hmm, according to the premises, situation A has a camera with 5 um pixels, whereas situation B has a camera with 9 um pixels. I would start with swapping cameras: A. 9 um @ 5000 mm fl: 0.35 "/p B. 5 um @ 500 mm fl: 2 "/p 😉