alan4908

If you zoom in to a high degree on the unbinned (first) image you can see that all the stars suffer a severe elongation. You can also see that the noise is quite high and that the RGB colours and not quite correct. I suspect that the non-round stars are due to the fact that your guiding was not working and so the lack of roundness is simply a manifestation of your mounts tracking inaccuracy. If you look at the binned image, where you have decreased the overall resolution of the image, they appear more round. You can also fix this effect to a large degree in post processing - I'd suggest Photoshop - take the image, duplicate the layer. Set the top layer to Darken and then apply the offset filter to the top layer (this moves the top layer by fractions of a pixel with respect to the bottom layer), until you get rounder stars. To improve your RGB star colours I'd suggest you separate the result into an RGB and a luminescence image and process these separately. This relies on the fact that almost all the detail comes from the luminescence rather than the RGB image. So, take the RGB image and blur it until all the stars look quite blurry. You might also want to increase the colour saturation slightly. Then recombine if with the lum image. On the noise front - I'd make the background less dark - in Photoshop I'd suggest a background level of between 18 and 24, your image is currently around 3 to 5. I then suggest you look at the image and see where the main sources are, in general I'd always suggest applying any noise reduction scheme in conjunction with an object mask so that it is targeted where it is most needed. Hope this helps. Alan

Thanks for the comment - if you do attempt this, then I'd suggest quite long exposures for the outer arms since I found them very faint. Alan

Thanks Lee - yes, NGC 4399 is very strange looking - looks a little like a planet made of stars. Well, given poor UK weather and the fact that I don't have a clear horizon, it does take me rather a long time to get this amount of data. Due to these two factors, I do rely on my automated imaging set up a lot ! Thanks !

NGC 4395 is low surface brightness dwarf galaxy about 14 million light years distant in Canes Venatici. Although visually dim, the apparent size of the galaxy is quite large, about 13’ x 11’. Unusually, it does not have a central bulge of stars in its central core and is significantly variable in X-Ray emissions with luminosity emissions varying by a factor of two within 300s. Three star forming regions, have separate designations (NGC 4401, 4400, 4399). Most galaxies contain central black holes and radiation is produced as objects fall into them. For NGC 4395, the core is extremely dim, so the mass of the associated black hole mass is believed to be extremely small, probably somewhere between 10,000 and 400,000 solar masses, making it one of the smallest black holes found in galaxies. The LRGB image below has an Ha blend into the red channel and was taken by my Esprit 150 and represents about 18 hours integration time. Alan NGC 4395 NGC 4395 (annotated) LIGHTS: L:32, R:17, G:15, B: 18 x 600s; Ha:8 x 1800s. DARKS:30, FLATS:40, BIAS:100 all at -20C.

Good luck with your capture ! Thanks Paul. Yes, a long focal length helps and also small camera pixels. With my Esprit 150 and my Trius 814 camera set up, I'm at 0.7 arc seconds/pixel which gives me quite a high resolution imaging set up. Thanks for the comment Lee

Thanks - yes , it doesn't appear very often on SGL, perhaps because of its small apparent size Thanks - its definitely worthy of more attention that it currently seems to get. Thanks for the comment. Thanks - if you are going to attempt this just be aware of its small apparent size. Thanks Peter. The tidal tail is very, very faint - even with my quite dark skies and 600s subs its only just above the noise floor . Alan

Thanks ! Alan

Yes - a very interesting target - thanks for the comment. Alan

Thanks for the comment Alan

NGC 4449 is a dwarf galaxy located in Canes Venatici, 20,000 light years across and c12.5 million light years from Earth. Its structure is similar to the Large Magellanic Cloud (LMC), the satellite galaxy to our Milky Way. Evidence for a very high rate of star formation is indicated by the presence of many young blue stars and pinkish star forming regions. It was the first dwarf galaxy to have an associated tidal stream identified which is the product of violent interactions with another satellite dwarf galaxy, NGC 4449B. The faint remnants of NGC4449B appear as a dim trail of stars and dust which will eventually merge with NGC 4449. The observable mass of NGC 4449 is insufficient to explain the interactions with other objects and so the missing mass is called dark matter. Dark matter is believed to surround all galaxies, including our own. Dwarf galaxies have higher proportions of dark to normal matter and so what appears as a minor amount of observable stellar matter interacting with NGC 4449 may actually represent a large amount of dark matter, which may explain the very high rate of star formation. The LRGB image below was taken by my Esprit 150 and represents just over 15 hours integration time. Alan NGC 4449 NGC 4449 (annotated) L:40,R:21, G:10, B:20 x 600s; DARKS:30, BIAS:100, FLATS:40 all at -20C.

Thanks - yes, the galaxies, particularly the (annotated) background ones seem to be be particularly distant (c700m light years). If you look closely at the image, you can also see that Pixinsight did not pick up all these in the annotated image, maybe these are even further away Alan

Thanks for the comment Michael. Alan

M108 is a spiral galaxy 46 million light years distant in Ursa Major. It is inclined at 75 degrees from the viewers perspective, so the spiral structure is hidden from view. Visually it appears as a relatively small object (11.1’ x 4.6’) with an apparent magnitude of 10.7. Its core is estimated to contain a supermassive black hole with an estimated mass of 24 million solar masses. I was pleased to capture quite a bit of detail on the galaxy including the Ha emission areas. The background also contains many small, more distant, galaxies. The LRGB image below was taken with my Esprit 150 and represents 14.5 hours integration time. Alan M108 M108 (annotated) LIGHTS: L:34, R:20, G:15, B:18 x 600s; DARKS:30; FLATS:40;BIAS:100 all at -20C.

Thanks Martin. Yes, this is not often imaged, probably because of its small apparent size - I was at 0.7 arc seconds/pixel but still cropped the image in order for the detail to stand out a little more. On the Ha blend with the RGB I'm now use Adam Block's technique, which I find more effect than my previous method. Basically, you create a starless Ha and blend only the brightest parts via a Screen script into the Red channel. A video tutorial on this can be found at https://www.adamblockstudios.com/ - I would definitely recommend the videos. Thanks for the comment ! Alan

Thanks for the comment ! Alan

Discovered by William Herschel in 1790, NGC 1491 is a bright emission nebula in Perseus about 12,000 light years distant and about 21 light years wide. Despite its large size, its distance from Earth means that it appears visually small. The HII region displays a great deal of structure. The 11th magnitude white/blue type O5 star BD+50 866, located near to the centre of the image below, illuminates the nearby hydrogen gas with high intensity ultra violet radiation, ionising the gas. Material ejected by the star has also created curtain fold and half bubble effects in the surrounding HII region. The bubble, which is closer to the star, is probably the result of high speed, gas outflows that push nearby gas and dust outward, creating a shock front and forming a layer around the star with variable density. A similar effect also seen in the bubble nebula, NGC 7635. Further from the star, the ionised ejected gas gradually slows down as it expands into non-ionised hydrogen. The boundary between the ionised non-ionised hydrogen is called an ionisation front which may have created the curtain fold. I decided to try to extract as much detail as possible by acquiring a significant amount of Ha data which was then blended into the Lum and Red channels. The structure within the brightest regions was better revealed after application of PI’s HDRMT. The image below represents 21 hours integration time and was taken with my Esprit 150. Alan LIGHTS: L:19, R:20;G:20:B:23 x 600s; Ha:21 x 1800s; BIAS:100; DARKS:30; FLATS:40 all at -20C.

Thanks for the comment Adam. Alan

Thanks for the comment Peter. I did spend quite a lot of time on the star field colours, mainly because I acquired quite a few sub frames in non ideal conditions. However, I agree, I think the end result looks OK - it is amazing what you can do in post processing ! Alan Thanks Paul - yes, not often see here - which probably due to its small apparent size. As I mentioned above, even at 0.7 arc seconds/pixel, I decided to crop the image to create more visual impact. Thanks Michael - good luck with your forthcoming capture. Alan