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Monthly archives: április, 2017

Popularity of Deep Sky Objects according to Astrophotographers

2017.04.20.
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Distribution of 2900 photos of 250 objects

I was curious which objects are the most popular targets according to astrophotographers. I used their activity to answer this question.

To find out, I deployed a crawler on two popular Hungarian forums, on asztrofoto.hu and tavcso.hu and harvested all the photos posted from the sites’ beginning till november 2014. Most of the posts had a catalog number in their title, some only a variant of the popular name, but they were heterogenous, as none of the two forums apply strict title/naming conventions. I worked with those that had a recognizable catalog number like M7, Messier 24, NGC 7000, C 38 or something similar – so perhaps many Orion nebula and Lagoon nebula pictures are left out, especially because the most popular objects are easily identifiable without a catalog number. Then I created this table containing around 2900 posts of around 250 objects.

Let’s say popularity is the count an object has been photographed. No wonder the most popular objects are the most prominent Messier and Caldwell objects (like NGC 7000), although the Caldwell catalog”s usage is sparse, the NGC or IC numbers are used instead. I used my DSO to collapse most aliases. Another conclusion is that few objects get a lot of attention and many very little, which is not a surprise either.

(tovább…)

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Mélyég-adatbázis a csillagtúrán

2017.04.15.
belső hírek
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A DSO felület éjszakai üzemmódot használ

Észrevettem, miközben közreadáshoz készítettem elő a fotóimat, hogy azok máris mélyebbek, mint amilyen mélyre a legtöbb program megy.

A Stellariumnak megvannak az erős és a gyenge oldalai is. Az astrometry.net keresője (angolul plate solving) szintén korlátok között mozog. A Simbad adatbázis és az  Aladin böngésző asztali és web változata egyaránt gazdag kincsesbányája az asztrofotósnak, az asztali változatban a mozgó egér alatti objektumot kikeresi és mutatja például. Ezt a web változat is igazán tudhatná, de nem tudja sajnos (lennebb a javítása). A gyengéje, hogy mintha valós időben készítené elő az égboltot lefedő képeket, így elég lassú. De különben is, valami kézhezállóbbat szerettem volna.

Ezért készült a csillagtura.ro/dso. Azt hiszem, hadilábon állok a programjaim elnevezésével :P. Találtam githubon ezt az adatbázist, bő kétszázezer objektummal. A fotóimhoz jó ideig kellően mély lesz ez az adatbázis. A CSV fájlt SQL adatbázisba emeltem, az objektumok elnevezését pedig jelentősen bővítettem angol és magyar nyelven, illetve behelyeztem néhány román nevet is. Aztán megírtam egy erős keresőfelületet, amely szinte minden szempont szerint ki tudja ásni az adatbázisból a keresett objektumokat. És ami fontos: kúpkeresést is tud, egy objektum vagy egy adott koordináta környezetében. Hozzáadtam még egy virtuális égbolt funkciót: a látogató GPS-e alapján a program az objektumok látszó magasságát és óraszögét is kiszámolja.

(tovább…)

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DSO database on my Csillagtúra

2017.04.15.
belső hírekenglish
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A printscreen of the UI. It uses night mode.

While posting my pictures, and describing the photographed objects, I noticed they are already deeper than most of the shallow catalogs and softwares go. Stellarium has its strengths but also its weaknesses. Astrometry.net’s plate solver also has its limits. The database behind Simbad and the Aladin viewer their website has embedded is great in many ways – on the desktop edition I can point with the mouse, and the pointer’s coordinates get resolved into an object, but no such feature in the web version (I added it, see below). A weakness is that both the web version and the desktop edition are slow to render the sky, I wonder whether they have any caching or the tiles are morphed real time. Anyway,  I wanted something more personal, integrated into my website.

So I made csillagtura.ro/dso. I think I am bad at naming my programs :P. I found this database on github, with more than 200k objects. This database should cover my deeper photographs for a long time. I converted the CSV into an SQL, and extended it with popular names for objects mainly in English, many in Hungarian and some in Romanian. I also added functionalities like search by virtually any aspect of an object, and, very important: cone search around each result, or just a cone search around some coordinates. I also added some virtual sky features: based on UTC time and the visitor’s gps coordinates retrieved from the browser, my program also calculates the objects’ alt-az coordinates.

(tovább…)

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M104 Sombrero Galaxy

2017.04.12.
englishsaját asztrofotóim
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On 2017-04-01 I acquired some light from M104 Sombrero Galaxy (Virgo, 7.9m [wiki]), but the raws turned out to be of worse than expected quality so I didn’t invest the usual amount of time into developing the final picture. Equipment: modded HEQ5, N 150/750, Baader MPCC Mark III, Canon 1100D mod. 14 x ISO 3200, 1 min. As smudges, there are also some faint galaxies in the frame:

M 104 – Sombrero Galaxy

(tovább…)

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Extending Stellarium’s Nebulae Images

2017.04.10.
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Stellarium, showing my C38 image

For some reason there are relatively well known objects without a picture in Stellarium‘s database. It is a free project, a fruition of many people’s voluntary work, so no offence. It is well documented how to add new pictures on this page but I found no easy way to be productive at this task. Plus, there are some problems one needs to overcome in order to succeed.

There are extension packs, but I didn’t find C38 (NGC4565) in them. I wanted to include this particular galaxy. I wrote this for version 0.15.

File structure

In the Stellarium folder (in windows, it is c:\program files\stellarium\nebulae\default) there are two kinds of files. The images themselves, and data files, among them the textures.json file. As the name shows, it is a json file easily editable with a text editor. The images should be 2^k (ie 64, 128, 256, 512, 1024…) pixel size, squared, png files. Do note that the square does not mean one has to limit the field of view: it is not the picture file that holds the aspect ratio information, but the coordinates. (tovább…)

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Messier 48

2017.04.04.
englishsaját asztrofotóim
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Messier 48

There is nothing interesting about the M48 open cluster, I imaged it as a test of the optics at minimum f – which it kinda failed projecting some ugly halos around almost all the stars. It is a 5.8m DSO in Hydra [wiki]. As a curiosity, this is one of the somewhat debated Messier objects, as there is no notable object at the position marked by Messier. This cluster, in present day also known as NGC 2545, is 5 degrees away from M48’s „original” position. In my picture, the bright star opposite to the cluster is C Hya, accompanied by 1 and 2 Hya and the orange HIP 41316.

(tovább…)

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Markarian’s Chain, through the telescope

2017.04.04.
englishsaját asztrofotóim
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Markarian’s Chain

After imaging the galaxy chain with the 200 telelens, at f/2.8, I turned the f/5 telescope to it. Not surprisingly, I registered way less light – also given the lack of guiding at the longer focal limiting the length of the exposures. I remember a discussion on the field with fellow amateur astronomers, about how objects are named, seemingly arbitrarily – however, many of the members of this chain are physically linked, not just a chance alignment, mostly, and it was an astronomer named Markarian who measured their motion. Member galaxies include the two bright ellipticals, M84, M86  and some other NGC members: NGC 4477, NGC 4473, NGC 4461, NGC 4458, NGC 4438 and NGC 4435.

(tovább…)

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M81 and M82

2017.04.03.
englishsaját asztrofotóim
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M81 and M82

It’s been a while since I imaged M81 and M82, the famous pair almost made to be photographed.

Messier 81 is the largest galaxy in the M81 Group, M82 the second largest in the group of 34 galaxies located in the constellation Ursa Major, at about  12 Mly. M81 is a spiral, M82 is a starburst galaxy, distorted by the interactions with M81. The intense star formation makes M82, though less massive, more luminous than the Milky Way. The very faint satellite of spiral, in this picture the patch at one o’clock from M81’s core, is the Holmberg IX dwarf, one of the youngest of its kind. (tovább…)

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M101 Pinwheel Galaxy

2017.04.02.
englishsaját asztrofotóim
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M 101 with NGC 5474

The Pinwheel Galaxy (Szélkerék in Hungarian) is one of the last entries in the Messier catalog, discovered by Pierre Méchain in 1781. It has a grand-design pattern, meaning nothing more than that the spiral arms are prominent and well-defined. Also known as NGC 5457, the galaxy lies at 21 Mly. According to this paper,  it has a mass of 9.8×1010 solar masses, way less than the Milky Way’s ~1012  solar masses, see this paper.

As a sidenote, our home is actually one of the most massive galaxies in the wider neighborhood, the exact value depending on the study, placing us somewhere a bit below down to at about half of M31 Andromeda’s mass, which is just heavy compared to the other spirals on the sky. As another sidenote, it is hard to find the masses of galaxies on the internet. As one more sidenote, it is tricky to find out distances of galaxies in scientific catalogs not meant for the general public, thus not containing a trivia section.

(tovább…)

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A wide perspective towards Markarian’s Chain

2017.04.02.
englishsaját asztrofotóim
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Galaxies in Vir/Com

I imaged a wide region on the border of Virgo and Coma Berenices, full of galaxies, members of the Virgo Cluster.

This area of our sky is very far from the Milky Way’s galactic plane making it fairly blank, thus acts like a window to see beyond it.  This region features objects well known to amateurs, like many Messier galaxies and Markarian’s Chain (formed by, among others, M84 and M86).

(tovább…)

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Jól kalibrált monitoron mindegyik számnál elkülönülő árnyalat látszik. Ha mégsem látszanak, akkor a megjelenített képek színhiányosan rajzolódnak ki. A monitort valószínűleg kalibrálni kell.

You should see distinct shades for each number. If those shades are not clearly visible, the displayed pictures will lack accuracy. Your display most likely needs to be calibrated (brightness, gamma, contrast etc.).