(My) Astronomy Picture(s) of the Day

Messier 3 is a prototype of a Oosterhoff type I cluster, known as a "metal-rich" globular cluster. It also contains the largest number of variable stars out all the Milky Way globulars. It has a diameter of about 180 light years, and is about 33900 light years distant. In this image, you can also see a number of very small galaxies scattered throughout the background.

I took this March 9, 2021 with my 12 inch SCT on a Paramount MyT using my ASI2600mc. Interesting comparison between this image and my last attempt (only a 10 minute exposure) with my 10 inch (right above) rotated and cropped/scaled to the same field of view. Looking at the FOVs shows you what a difference the placement of a focal reducer makes... Meade series 4000 f/6.3 on a 12 inch (left) and OPTEC Lepus 0.62X on a 10 inch(right). You would think the field of view on the 12 inch would be at best the same or smaller, but clearly I'm actually getting a larger field of view on the 12 inch!

Aside from that, I learned a new trick in PI...to get rid of magenta stars, invert the image and use SCNR...works like a charm!

M97 is a planetary nebula about 2000 light years away in the constellation of Ursa Major. At the heart of it is a white dwarf, with an 8000 year old expanding double-shell structure forming the main part of the nebula and a much fainter, larger and significantly older (~40000 year-old) halo of ionized gas. The halo is thought to be the remnant of a red giant stellar wind and is just barely visible here in the photo.

I didn't realize the Owl Nebula could look so beautiful in narrow band (in this primarily Halpha and OIII). I'd been trying for years to get a decent picture of M97, but it always seemed so amorphous and lackluster in my limited attempts. Granted, my previous attempts were all limited in exposure time using my 10 inch and without a filter, but I had still held out more hope for it. Well, my effort finally paid off with this image, a 5 hour exposure with my 12 inch using my ASI2600mc and Optolong L-eNhance filter. It was done under a quarter moon in a Bortle 5+ sky but I'm thinking now it's definitely worth trying in a darker sky. I was even able to get a hint of M97's outer nebulosity - subtle - but definitely providing just enough signal to pull out its asymmetric shape. You'll have to turn up the brightness on your monitor to catch a glimpse of it though - it was extremely hard to do the enhancement to enable it to show up in the final image. What a beautiful planetary! I also like the colors the L-eNhance seems to pull out of my ASI2600mc. I don't get the blue I'd prefer from the OIII, but the green seems to come out more readily in place of it along with the occasional yellow, which is really great. My color calibration might be off a little, but I like it, so who's to tell me it's "wrong"? ***.

More experiments with my Optolong L-ENhance filter - I took a 3 hour exposure of NGC2371 known as the Double-Bubble/Peanut/Gemini Nebula, on Feb. 4, 2021 on a moonless night in a Bortle 5+ sky with my ASI2600mc camera using my 12 inch Classic Meade and Paramount MyT mount. Imaging details can be found here.

This is one of a handful of known planetary nebulae to have a central Wolf-Rayet star, an extremely hot, Sun-like star that has had its hydrogen atmosphere completely shed to reveal only a bare carbon-oxygen core. The central star's surface temperature is a blistering 240,000 degrees Fahrenheit and it lies at distance of about 4,300 light-years in the constellation Gemini. Apparently, this type of star in a planetary nebula is quite rare, which suggests that we don't really yet understand how such stars evolve.

I struggled with what to do about the color for this nebula. In broadband, the nebula comes out bluish, so I was tempted to shift the hue a little to get a blue tinge for the outer parts of the nebula. However the Ha and the OIII emphasis of the L-ENhance filter seems to want an reddish/orange and green tinge to it, so I left it at that, merely enhancing it somewhat. I was surprised at the nice detail I was able to pull out of it, especially comparing it to others' attempts out there with much larger scopes and longer exposures.

The images on the right show a comparison of raw images for the nebula using various combinations of data from two different nights, one completely moonless, the other with a gibbous (93% full) moon in Leo about 10deg away. The bottom row compares the same length of exposure (37 @3min per sub ~ just under two hours) with the Moon (bottom right) and without the Moon (bottom left). Comparing stars, the focus is practically identical. I would have to say I must reserve judgement on whether the difference in detail is due to atmospheric conditions or Moonlight, or a bit of both. Comparing the bottom left with the top left, both taken without the Moon, is much more straightforward. There is a clear reduction in noise going from 111min (bottom left) to 171min (top left) and the detail improves noticeably. Comparing the top left (171min) with the top right (288min) which combines data from the two nights, the result is less clear. Is it the worse data from the moonlit night that limits the quality improvement? Or is it the diminishing returns going from 3h to 5h? It's likely a little of both, but I'm tending towards the latter. Although you get detail and noise improvement going from 2 to 3 hours, I've seen much longer exposures from people with results that are the same or worse. All this says though, is that there is likely a sweet spot in terms of exposure time for all objects, but going beyond that doesn't necessarily pay.

Well, I finally did it. I purchased my very first narrow-band filter, the Optolong L-eNhance and took a stab at the supernova remnant M1, known as the Crab Nebula. I was curious to see how well the filter performed in moonlight, so I took the image on the right about 1 deg away from a gibbous moon. I came to a sudden (maybe obvious) revelation. I was trying to think what I should compare this to... If I compare it to the same filtered image with no moon or without light pollution, clearly the latter will be better - so the moral here is (without even having to take a picture), better to image without the moon or without light pollution (a tad obvious). What about comparing it to a non-filtered image in either condition? Well, it's still not an apples-to-apples comparison because you are seeing completely different things!

All this rambling about how narrowband filters allow you to image in moonlight is a little bit of a red herring. The bottom line is that a narrowband filter will simply rebalance the wavelengths of light that land on your sensor. You basically *see* different things because Ha, Hbeta and OIII areas of the spectrum are enhanced at the cost of other parts of the spectrum, which happen to lie in the parts where moonlight and light pollution are most prevalent. Clearly, contrast in the image is enhanced when that light is omitted, but *THAT IS TRUE WHETHER YOU HAVE A FILTER OR NOT*. And, no matter what filter you use, you are omitting wavelengths of light that might or might not be "important" to visualize your object of interest. So ultimately, it's your object that matters and what you want to emphasize with respect to wavelength, not sky conditions!

However, that said, if your sky is worthless because of light pollution or excessive moonlight (or both), you might as well get rid of as much of it as possible, and concentrate on the wavelengths that are interesting to see in your object - but make no mistake - the object will naturally look different, but it will NOT be a cleaner version of the unfiltered one. If you're (extremely) lucky, a broadband light pollution filter will eliminate light pollution and moonlight but leave in, say, galaxy light that still makes the galaxy look similar to its unfiltered appearance - if so, great, but it needn't always be the case. In all likelihood, the broadband filter will remove the same light that makes your galaxy look like the galaxy you expect to see! So remember: Filtered image = different image, NOT Filtered image = same-but-better-unfiltered image.

Anyway, this may seem obvious to most of you out there, but my desire to do an apples to apples comparison (with filter/without) really opened my eyes to what this is all about. Imaging details are here for the unfiltered moonless-sky version of M1 and here for the L-eNhance version of M1 in a moonlit sky, both imaged in my Bortle 5+ sky.

This is my very first dark nebula! With over 12 hours of exposure time using my new cooled ASI2600 camera, it's no wonder I hadn't tackled this object before. This is also my first time processing one in Pixinsight - it was especially important to get the DBE to work right. For that I also incorporated flats for the first time into my workflow to try to limit the vignetting and its effect on the DBE process. I'm still struggling with star halos, but hey, making progress. This is a product of several nights of images taken the first week of January, 2021. Full imaging details are here .

I also used StarNet for the first time to try processing a starless version of this nebula, then adding the stars back in. The result wasn't bad for a my first time...you can see my final image above on the bottom left, along with the starless foreground on the right, which I enhanced to showcase the nebulosity.

This is actually a set of three dark nebula: B26, B27 and B28, from Edward E. Barnard's 1919 catalog of dark nebulae. The dark nebulae are all due to the extensive interstellar dust clouds in this region of the sky, which stand out nicely against the background star field. The beautiful blue and yellow reflection nebula is vdB 31, the 31st object in Sidney van den Bergh's 1966 catalog, surrounding the stars AB and SU Aurigae. The hot blue star AB Aurigae is around 470 light years away, which Hubble has shown to be surrounded by a disk of material in the middle of planet formation!

I really didn't think the weather would cooperate, so I didn't really prepare for this. But this is the beauty of having a semi-permananent mount with a beautifully aligned scope...everything was ready to go within minutes. The clouds cleared and I ran out to uncover my scope. I hadn't even tried out my ASI2600mc for planetary imaging yet, but the standard ZWO capture program let me get it up and running just in time to catch some spectacular photos of this 1-in-800 year event. This image is what you would have seen had you looked through my 12 inch scope at 4:24PM EST on the day of the solstice. The images here (a stacked version) and here (a magnified, more focused version) are better, but I liked the spontaneity of this one - not completely in focus, but wondrous in the realness of the event - even the great Red Spot made an appearance. Now how spectacular is that? So big deal you might say...a part of me thought the same initially...the event has no significance physically - just a meaningless superposition of two planets we see all the time. But then I thought...think of how beautiful these two planets are...the largest planet in our solar system, with colored bands and a 400 year old raging red storm - the other, a gas giant planet with almost fake looking (but real!) rings of ice and rock - both in the same field of view for human eyes to witness in a moment in time that won't come again for almost a thousand years. You're alive now in just the right time in history with technology sufficiently advanced for you to get to see it. That's something isn't it?

NGC672 is a spiral galaxy interacting with a dwarf galaxy called IC1727. The pair is located about 23 million light years away and is thought to be part of a cluster of dwarf galaxies formed along a filament of intergalactic gas accreted on a dark matter "backbone". Methods to detect that intergalactic gas are currently underway.

The sensitivity of the ASI2600mc camera is notable in this 5 hour exposure, revealing nice structure in the larger pair of galaxies but also bringing out multiple edge on galaxies in the field as well, in addition to several "fuzzies" around NGC672 itself. There's no way I could have gotten this much detail using my DSLR! I took this image Dec. 10, 2020 with my 12inch classic Meade SCT on an MyT Paramount. I acquired images using a cooled ASI2600mc stacking just over 100 3 min exposures. You can see I'm slowly improving my processing with Pixinsight! You can see another processing attempt here.

Also known as NGC598, this rather large distended galaxy is about 3 million light years away. I've struggled with imaging this galaxy over the years, but all it really took was a longer exposure and here I am! Of course, to get to that longer exposure, I had to go to an MyT Paramount and a cooled camera. And, along the way, I picked up a 12 inch scope and some dedicated software for image processing (Pixinsight)...and that's all there was to it! :) But seriously, this galaxy has some beautiful color to it, and you don't need an Halpha filter to get to it. This was taken using RGB only, with some restrained color saturation to boost the "natural" colors. Here is a version with even more saturated colors - I think I like the subdued version a little better! Inevitably, you hear astroimagers combining Halpha images with RGB, but the bottom line is that *all* that information is there already - you just need a long enough exposure and a reweighting of the color to show it. You can see my full imaging details here. Two of my previous attempts are here: at 7 minutes and 53 minutes exposure time with my T3i on my 10 inch.

For those of you interested in Pixinsight workflows...screen transfer function stretch, dynamic crop, DBE with carefully selected points, histogram transformation, color calibration, deconvolution, multiscale linear transform for noise reduction, local histogram equalization (250 pixel window size), curves transformation, and finally, a masked curves transformation to eliminate vignetted corners.

Well, after about a year playing around with my MyT Paramount, I finally have things humming with my 12 inch scope. You might think a year is a long time, but if you want to do high quality imaging, you really need to put the work into understanding your system, because there's a lot that can go wrong. The Paramount MyT is really a wonder of engineering, and I'm finally starting to take advantage of that. Here's a 5h exposure of NGC891 in Andromeda I took Sept. 19th, 2020, with my Canon T3i DSLR using my 12inch Meade Classic. It is well beyond my previous 52 minute exposure with my 10 inch before my MyT. Longer exposures is really where it's at. All those wonderful photos you see people taking are really a function of exposure time - it's really quite simple: the longer, the better - simple as that. Sure you need the skills to process the image as well, but the bottom line is dark skies and long exposures. Oh wait...did I mention perfect focus, excellent collimation, flawless tracking, no moon and good visibilty - oh yeah, forgot about those :)

NGC891 is a beautiful example of an edge-on galaxy, about 30 million light years away. Its many filaments and tendrils extending out of its plane are thought to be the result of the ejection of material due to supernovae and intense stellar formation activity. In the upper left part of the image, right under NGC891, you can also see a tiny image of a distant spiral galaxy in the background. For more imaging details, look here :

This is my first serious attempt at using Pixinsight for astroimage processing. Pros will no doubt find much to criticize, but for me, it was a resounding success. I always thought processing in GIMP or some other general processing program could attain very similar results and I generally discounted what I thought were exaggerated and illegitimate embellishments. However, I am forced to take some of that back. In my limited time during Pixinsight's 45 day trial period, I found several features to be truly indispensable. First, Pixinsight does a fantastic job of removing vignetting and/or other uneven illumination using a relatively easy semi-automatic algorithm. Second, it allows you to create fuzzy masks and star masks that are very useful in enabling smooth transitions between enhanced and unenhanced regions of the image. And finally (but no where close to lastly) multi-scale (wavelet) transforms enable selective enhancement of different scales of detail in the image, allowing all sorts of precise, scale-targeted enhancements. So here it is: M106, a Seyfert galaxy in Canes Venatici...taken with my "new" 12 inch Meade scope on a Paramount MyT mount and my trusty Canon T3i. This is a four hour exposure,stacking 120 2 minute exposures at ISO1600, with dark frames. I also used dithering for the first time to minimize "walking noise". Nice, right?. I love this hobby! Compare this with my previous version of M106 an eon ago: here .

This isn't my first image with my 10" inch Meade on my MyT mount, but it is the most beautiful example I have so far of the potential capabilities of this mount. Also, with the 2019 Christmas season right around the corner, the beautiful colors in this star field seemed appropriate for the occasion. This image had two other important characteristics that made me post it. First, this 11.3 magnitude planetary nebula - known as IC5217 in the constellation Lacerta - is the smallest one I have yet imaged: a mere 6" x 8" in size. Second, the tracking for the 66 one minute exposures I stacked to create this was practically perfect, as evidenced by the almost perfectly circular star images visible throughout the field, and no lost frames. The inset (below, center) shows a magnified view of the nebula but contrast stretched differently to expose its subtle elliptical/rectangular shape. Normally, I wouldn't even consider looking for detail in such a small planetary as I doubt my seeing is better than about 3", but given the beautiful circular stars of my one minute exposures, I'm pretty sure the elongated shape in the north/south direction is real and not an artefact of any tracking, collimation or processing issues. Its shape is also consistent with other observers with much larger telescopes. The inset below left, shows OIII, NII and Halpha images of the nebula using a 1.5m scope, while the inset below right shows a visible light image using an 80cm scope, both clearly showing the elongated shape of the planetary. There's a slight hint of blue and red on east and west sides (respectively) of the nebula in my image, which may also be real, based on observations I have read. More detailed imaging information is given here .