On the stellar content and structure of the spiral galaxy M33 - observed from my balcony

About the Image

My son was born on the 10th of October and this the beginning of a new era also for my astrophotography projects: I do not prefer longer sessions anymore during the whole night far away from home. Instead of this I tried to build up a new concept and do astrophotography directly from our balcony. Because we live in the middle of the village light pollution is an important limiting factor and a lot of building obstruct the free view to the most parts of the sky which makes deep-sky photography very challenging. The key to solve these problems was a light pollution camera filter and the critical choose of target objects. The use of such a filter requires special post-processing steps and consequently has a learning-curve...

As a "first-light target" I chose a local H II region, the IC 1805 or so called "Hearth Nebula" which is an emission nebula showing glowing ionized hydrogen gas and dark dust lanes. This object lies 7500 light years away from our Earth in the Perseus arm our Galaxy in the constellation Cassiopeia. It is realtively wide Nebula and may be not very optimal for the 800mm focal length of my only imaging telescope, but its actual location on the sky and its narrow-band red emission made it an ideal object to try with the CLS filter and the newly modified DSLR camera.

This was the result:

Not a perfect one, but the post-processing was easy and light pollution is not an issue anymore...

I was really amazed and wanted to do a further project but the "beautiful" spring weather closed me into the house for several days. The moon was growing but on the 6th of November it was finally clear...

With the next target I wanted to test two aspects: the capability of the filter on the moonlit sky and the effect of the filter on the wide-band spectrum of a galaxy. November is the month of the M33 or so called Triangulum Galaxy which was on that time in a perfect position to shoot it from my balcony.

The image-aquisition itself was unfortunately interrupted to early by clouds and rain therefore the planned 3 hours exposure was limited to about 1,5 hours... This resulted of course more issues during the post-processing but after all I am satisfied with the "final" images.

Image data

17x5min, ISO 800


Altair Astro 200/800 imaging newtonian telescope

Skywatcher NEQ-6 GOTO mount

Canon 700D mod

Baader MPCC MkIII image flattener

Astronomik CLS-CCD light pollution clip-filter

60/240 guiderscope

Orion StarShoot Autoguider camera


PHD2 Guiding for autoguiding

ASCOM - Stellarium for telescope control

DeepSkyStacker and Photoshop CS6 for image processing


Overview of M33

Starless M33

Annotated M33 (color)

Finding Chart - Structures and Stellar Objects (b&w)

The spiral galaxy M33

The M33 is a spiral galaxy located 3 million light years from earth in the constellation Triangulum. The is the third-largest member (diameter about 60,00 light-years) of the Local Group of galaxies, which includes the Milky Way, the Andromeda Galaxy and about 44 other smaller galaxies. The M33 may be home to 40 billion stars, compared to 400 billion for Milky Way, and 1 trillion stars for Andromeda.

Structure and identified stellar objects

(the images are available in bigger size in the Slideshow at the bottom of the page)

It is clearly visible on my photo that the M33 is a disk-shaped galaxy with prominent arms of gas and dust that spiral out from the nucleus. The Triangulum galaxy has 10 arms, 5 on each side of the center (I-V).

Prominent H II regions of star formation (like the previously shown Heart nebula in our home Galaxy) are visible too on this photo. The brightest are designated NGC 588, NGC 592, NGC 595 and NGC 604. Some much fainter H II regions and star clouds described as IC### and A### objects are also annotated on this amateur capture.


1) Wikipedia

2) Humphreys and Sandage, The Astrophysical Journal Supplement Series, 44:319-381, 1980 November

Made and designed by ATELIER KURUCZ in 2018