wimvb

I also collected 3 hours luminance, but because of poor guiding I decided not to include it in the image. Still, by inverting and superstretching, it does show the 48 identified stars in this galaxy.

@symmetal, as promised: my version of faint 😁: UMa I dSph

This galaxy is as faint as it gets. UMa I dSph is a dwarf spheroidal galaxy to the Milky Way. It was discovered as late as 2005, mainly because it is the third dimmest galaxy known (after UMa II Dwarf and Boötes Dwarf galaxies, discovered in 2006). The galaxy is only a few thousand light years in diameter, yet it spans about 20 arc minutes of the night sky, which makes it quite large compared to other galaxies (comparable in angular size to M 81). Capture details: Telescope/Camera: SkyWatcher 190MN with ZWO ASI294MM Exposures: 3 x 60 x 240 s; total exposure time: 12 hours Processed in PixInsight Can't see it? That's probably because at a distance of 330 000 light-years, we can image the individual stars of this galaxy. Here's an annotated version with the brightest stars marked. Each cross is a star.

That should be ok. I've only heard about people having trouble with weird things going on if they put a flat panel / led panel on top of the scope. Light can get reflected off surfaces where it otherwise wouldn't.

Are the shadows visible on uncalibrated lights? You can stack all lights without flat correction (but do use darks) to get better signal to noise ratio. If the shadows are absent, it’s the flats that are to blame. (what does a stretched flat look like?) How do you take flats? A light box on top of the scope can cause priblems.

Problems with spider vanes, or rather, diffraction spikes, is why I invested in a SkyWatcher 190MN. But I've never seen them cause shadows like this.

Collimating this scope is tricky. Maybe this old thread is of interest to you. https://www.iceinspace.com.au/forum/showthread.php?t=140193

Couldn't agree more. Unfortunately, astro darkness is drawing to an end here, and the moon is getting brighter every day. Astro season is all but over until mid-August. Otherwise, I would image the Draco dwarf. I did image UMa 1 earlier this month, and I'm still processing it. Compared to this galaxy, the Draco dwarf seems like a light house.

To get the galaxy cluster you may need to take new flats. It looks like you have dust bunnies that gåhave shifted between lights and flats capture. Anyway, good luck!

The UMa I dwarf was discovered in 2005, and is one of the faintest dwarf galaxies ever (UMa II is fainter). https://www.astrobin.com/0gvm5z/ Draco dwarf is much brighter in comparison. https://www.astrobin.com/397657/?q="PGC 60095"

Nice! Now that you've got the UMi dwarf under your belt, you should try the Draco dwarf (ugc 10822) and the two UMa dwarfs. 😁

With a group of small galaxies such as these, I research the surroundings in Aladin. Usually there is more interesting stuff in the fov, and I adjust the framing to include this extra. You have ngc 5390 just outside the fov to the left (you'd need to rotate the camera 90 degrees), and a distant (3 billion light years) cluster of galaxies just to the south. http://simbad.cds.unistra.fr/simbad/sim-id?Ident=%402210954&Name=NSC J135404%2b394427&submit=submit http://aladin.unistra.fr/AladinLite/?target=13 54 25.134%2B40 05 24.38&fov=1.09&survey=P%2FDSS2%2Fcolor

Excellent! Once again, a 190MN delivers. I've imaged this galaxy three times now, and haven't been able to extract more detail. If you stretch the data very aggressively, you find out that the galaxy extends a little further, but not much, and no additional details. So, well done. https://www.astrobin.com/jd2hjn/

Congratulation, winners. Awesome entries!

Are you about to make him an offer he can't refuse? 😉

9.55 x 4.07 arc minutes according to Aladin with a magnitude of 11 (quite dim). @tomato where did you find the 4 x 2 arc minutes?

Excellent. I've seen this galaxy come up in Aladin searches a few times, but never thought more of it. With your fl/chip size you've really done it justice. Will you collect more data? I think this galaxy could have some very nice Ha regions. Edit: just searched the interweb, and found Block's image which confirmed my guess.

The guider works in pixels, but the mount moves in arc seconds. Otoh, if you have calibrated with the same setup as you use for guiding, it will still work. But the numbers in arc seconds are nowhere to be trusted. Which also means that you have to recalibrate now that you've changed fl in the settings.

Reported rms @650 mm was 0,32", which corresponds to 3.25 x 0.32" = 1.04" if your guidescope fl = 200 mm

You need to select the guidescope. If that scope is 200 mm fl, then your guide rms is abt 3 x larger than what is reported when you have selected the imaging scope (650 mm).

Differential flexure? The main mirror in a Newtonian can move relative to the guide camera. That's why oag is usually recommended for reflectors. Have you tried imaging and guiding near Zenith? At this position, the mirror rests evenly on its support.

Applying common astrophotography processing steps, I came up with the following result. As usual, all processing done in PixInsight Tone mapping: Red to Green, Green to Red and Blue to Blue To get rid of the strong green cast I applied SCNR green, and because there is no magenta in nature, I inverted the image and applied SCNR green a second time. Then inverted back Stretch: arcsinh stretch to keep colour ratios, followed by curves transformation with a strong S-curve and colour saturation. Multiscale Median Transform to enhance local contrast. Frame added with PixelMath And, dare I say it: 😉

Lovely. You've been quite busy reprocessing recently. I hope the clouds lift soon.

They may very well use germanium based senors. Germanium has a smaller bandgap than silicon and can detect longer wavelengths. IR sensors require special cooling. Otherwise any heat signature can manifest itself as glow. The longer the wavelength, the lower the temperature. 20 um definitely requires cooling, with most likely liquid nitrogen.

Remember that NASA’s IR imaging telescope pre JWST was airborne, to exclude most of atmospheric influences. Silicon devices could, in principle, detect wavelengths longer than 1 um, but internal losses increase with increasing wavelength.