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Leo A (also known as Leo III or UGC 5364) is an irregular dwarf galaxy, situated approximately 2.6 Mly from Earth. Its size is only about 6 500 light years. Although this galaxy has had fairly recent star formation, I found no evidence of Ha clouds (after 6 hrs of integration time). There are quite a number of distant fuzzies in this image. As always, data captured with my trusty SW 190MN and ZWO ASI294MM Total integration time 8 hours. I also have more than 6 hours of Ha data, but it barely shows the galaxy. There are probably no Ha clouds to speak of, so the data is not included in this image. Annotated version, showing galaxies (in pink) that have a redshift > 0.1

According to my Astrobin page, I managed to collect data for 23 images in 2022. All in all not a bad year. There are several images that I'm proud of, certainly those of difficult to catch objects. But the one image that I was never really satisfied with was ngc7331 and Stephan's Quintet. I find it very difficult to get the right balance between Ha regions and the blue outer arms of ngc 7331. Finally yesterday I got something that comes close to what I had intended. The only part that still nags me is the ifn that is in this image. But it's too close to the noise floor and I really need more data to do it justice, so I didn't push it in this version.

AfaIk, that's how colour calibration processes in PI work.

As I wrote before, spcc together with background neutralisation will in essence undo any G2V exposure matching. The disadvantage of G2V matching exposures is that each channel needs its own dark master. Since any colour calibration/background neutralisation step will equalise the channels to get a neutral background, you are implementing a more complex workflow in data acquisition that will be undone in post processing. Also, there is no need to match RGB channels with Linear Fit in PI, because even this will be undone in colour calibration. The only possible benefit of doing Linear Fit would be if you have a dominating colour that affects DBE/ABE. The excessive dominance of one channel may make it necessary to set such a high tolerance during background extraction, that it can affect the background extraction of the other two channels. (Just as a side note, ZWO once designed a set of RGB filters to match the QE curve of the then popular ASI1600MM, in order to achieve equal flux for all three channels with one single exposure time. They haven't done that for any newer model, afaIk.)

It seems to be a different size in the images in these posts.

Probably a planetary nebula. Couldn't find anything on Aladin or Astrobin, so it could very well be a reflection artefact.

The first time you save a project, it takes a long time, because everything is saved. But when you save the same project again, PI knows what was altered and only updates those images. It saves faster. And btw, disabling saving previews also saves time and hard disk space. As an alternative, you can just save process histories as process containers. Just pull an image's history to the workspace and save the icon. Next time you can load the icon to use on another version of the image. And by double clicking on a process step in a process container, you load that process with your own presets.

Suppose you want to do one copy of an image (A) with noise reduction just before stretching, and another (B) without. You process A all the way. Then you open its history and pull the triangle in History Explorer (tab) onto the workspace. It will show as a process container icon. Open this icon and double click on the check mark to the left of the noise reduction step you wish to omit. Then drag the open container (triangle) on to image B. All steps except the deactivated noise reduction, will be applied to image B, including any masks. Obviously, if you omit or change a step that has a profound effect on the image, such as stretching or color saturation, the final image will be different. But you can use this method to use a sequence of identical processing steps to several images. So you could process one copy with BXT, and another without deconvolution (or with classic deconvolution), and have all the process steps identical, except for deconvolution. You can also open any process with the settings you used for an image by double clicking that process in the history explorer. Suppose you have an RGB master and a luminance master. You have applied DBE to the RGB image, and you want to use the same samples for your luminance. You have the luminance image window active. Then you open the history for the RGB image, and you double click its DBE process step. DBE will open and fill the luminance master with the same samples placement you had for the RGB image. This is very handy if the images contain a lot of nebulosity and/or stars, and sample placement is tricky. Btw, make it a habit to save your images as part of a project. This will save the complete process history for all image versions and masks. It makes it a lot easier if you want to reprocess images later on.

Great image, Rodd. If you do all your process steps in PI, you can simply apply the process history of one image to another image. You can deactivate any processes that you don't want to apply to the second image. That should give identical images apart from the steps that were unique to each image.

SPCC will do its own recalculation of channel balance, so doing different exposures for different filters is not necessary.

Thank you. Ngc 185, ngc 147 and ngc 205 (M110) are the same type of galaxies, and all three are bound to and interact with M31. So they do resemble each other. Thank you. I looked for the GCs in Simbad/Vizier. To keep them safe from BlurXterminator, I masked them with a custom mask. The stars have been tightened a bit, but the galaxy and clusters not. The annotated image uses a custom catalogue, based on Vizier data and the Typecat PI script. https://skypixels.at/pixinsight_scripts.html

ngc 185 is a dwarf galaxy in Cassiopeia. It has many classifications: dwarf Spheroidal, elliptical, and type 2 Seyfert. It is located at a distance of approximately 2 Mly and has a diameter of 10 000 ly. The galaxy has an active nucleus and until recently even star formation. Unlike its twin (ngc 147) which is devoid of any structure near its nucleus, ngc 185 has some dust bands. The annotated image shows the galaxy's globular clusters. I imaged this galaxy 6 years ago, in fact it was the target of my first attempt at guiding. Technical details: SW 190MN with ZWO ASI294MM camera and Optolong LRGB filters 3 hrs RGB and 3 hrs L captured 27/12 2022 Processed in PixInsight

I searched Simbad and Vizier for objects in or near Leo A. I didn't find any globular clusters, which is a bit odd, because other dwarf galaxies (ngc 185, ngc 147 for example) do have them. Maybe Leo A is so much younger than other dwarfs? This is likely, because galaxies such as ngc 147 / 185 are yellow/red in appearance, which is an indication of older stellar populations. The colour images I have seen of Leo A show more blue stars. I think that the abundance of QSOs near the line of sight of Leo A is a result of cataloguing objects in the many observations and studies of Leo A. It's similar to what Messier did; if you want to exclude objects from a study, you need to identify them. Many of the QSOs have large red shifts, so they are not in or near the galaxy itself. I only found a handful of H-alpha (HII) regions in or near Leo A, but I will definitely image it with an H-alpha filter when I get the chance. If there are young stars, there is also very likely some new star formation going on, so there could very well be Ha regions which no one has images yet.

Thank you, Lee. Glad you like it.

Thank you, Paul. Why should the southerners be the only ones with irregular dwarfs to photograph? 😉 I didn't even consider ordinary globular clusters in or near this galaxy. Will have a look later.

Thank you, Alan. I think so too.

Thanks, Göran. Those lines are reflections from a star outside the field of view. Unfortunately they are quite common on my images this season. There's probably a shiny surface somewhere in my camera/filterwheel that causes them. Normally I can tone them down during processing, but since this a "quick & dirty", I haven't bothered this time. There aren't many images of Leo A (Leo III) other than Hubble and Subaru Telescope images, that I know of. So, this is something of a first, at least on SGL.

We've had a few clear nights recently, and after I'd finished my main target, I pointed my scope at the dwarf irregular galaxy Leo A (Leo III). This rather isolated dwarf galaxy was discovered by Fritz Zwicky in 1942. It is located approximately 2.6 Mly distant (the same as M31, the Andromeda galaxy) and has a size of only about 6 000 ly. The galaxy consists mostly of dark matter, approximately 80%. Its stellar mass is 3.3x10⁶ solar masses, while its H1 content is double as much. Before I collected data on this galaxy, I checked Aladin to see what was in the neighbourhood and came up with quite a lot. I decided to shift the fov so that a few interesting distant galaxy groups would fit in the same frame. These are indicated in the annotated luminance image. The most distant galaxy (group) has a red shift of 0.47, which puts it at a mind blowing 6.5 Billion light years distant. The brightest galaxy in this group, labeled "3651_0.4686", is roughly the same size as the Milky Way. There are several quasars in the image which have a red shift larger than 2. Technical details: telescope 190MN with ASI294MM camera 79 x 3 minutes exposures; total integration time 4 hours, luminance only so far. Processed in PixInsight with just a touch of sharpening with BXT. Still a bit noisy, and I didn't do anything about the reflection from a bright star outside the view (just above Leo A). I will fix that once I've collected colour data. Note that most of the fainter "gnats" aren't stars, they're galaxies or quasars. Annotated version Blue: PGC galaxies Purple: distant galaxies (G) and quasi stellar objects (Q), with their red shift Dark yellow: galaxies, with their red shift Light yellow: galaxies in groups My search in Vizier didn't pick up on all galaxies in this image. There are several more with red shifts of about 0.18 - 0.2, putting them roughly at distances around 2.5 Billion light years

This crop confirms what I saw in the original images; the 0.47"/p image looks a bit oversharpened. The dark lanes in front of ngc 1595 look unnatural. Whenever deconvolution (classic or bxt) creates squigly ridges like these, I dial down deconvolution a notch. Just my € 0.02

Great image. The gravitationally lensed galaxies are elusive, and probably beyond the specs (or at least beyond the grasp) of your gear. Although, with BXT not entirely unthinkable. Whenever I try my luck on this faint stuff, I don't use noise reduction nor star reduction. After all, these are never going to be "pretty" pictures in the ordinary sense. Btw, NED gives a Hubble distance of 1655 Mpc, which is closer to 5.3 GLy, not 4.1.

So far, I only have one of the three. I rarely use noise reduction in my images anymore. A dark(-ish) site has certain advantages. What I do find ironic is that a software package that boasts (boasted?) its processes being based on rigorous math embraces the AI route.

I think a 14" BXT processed image should beat a 6" APO BXT image, because what BXT does is take care of blurring by atmosphere, guiding, and focus issues. All that is left after that are telescope optics (read: diffraction limit or spot size), imaging scale, and SNR in the unprocessed masters (BXT is done before any magical noise reduction). I don't think that a direct shoot out is fully valid. Differences in images of the same target are at least as much due to differences in processing style and processing decisions as they are to differences in equipment and data acquisition. Case in point: Adam Block recently published an image of M51, processed with "xXT". https://www.astrobin.com/3ehcpo/?nc=all The addition of Ha, and different processing, makes this a completely different image from the one Olly linked to earlier in this discussion.

As in real estate, AP is really only about three things: location, location, and (you guessed it) location. So far, not even Russell Croman can beat the advantage that a dark site offers. 😉

The comparison before was that a 6" refractor could produce results comparable to much larger reflectors. But that was with atmospheric conditions and central obstruction effects included. In real life telescopes rarely perform at their theoretical limit. With BXT, we are able to remove many of the factors that degrade performance from the equation, and get closer to that theoretical limit. In my image comparison of Stephan's Quintet, the BXT image showed a lot of extra detail. Comparing the improved image with professional data from terrestrial telescopes, there was no false detail. BXT didn't invent anything. And of course, it didn't go online to check with the HST archive. I can only conclude that BXT brings the level of detail close to my scope/camera's theoretical limit (Rayleigh limit of 0.7" and pixel scale of 0.95"/p). If that is true, it should be able to do so for large reflectors as well. The playing field is constantly changing.

White light contains all wavelengths, including 656.28 nm (which is the Ha emission spectral line). Ha emission is defined by its source. Light from other sources can still have a wavelength (among others) of 656.28 nm. Ha filters pick up this colour/wavelength regardless of its source. That's why we don't need a Hydrogen discharge lamp to make Ha flats, but we can use ordinary white light sources (led panel). In fact, the bandwidth of any Ha filter determines the contrast and image quality you get. A 7 nm filter will pick up Ha plus red at wavelengths between 652.78 and 659.78 nm. A 3 nm filter will pick up Ha and red light with wavelengths between 654.78 and 657.78 nm. Less red light, therefore better contrast. But they all pick up some light that is not created by Ha emission.