Celestial hemisphere:  Northern  ·  Constellation: Perseus (Per)  ·  Contains:  13 Aur)  ·  39 Per  ·  47 Per  ·  48 Per  ·  51 Per  ·  53 Per  ·  7 Aur)  ·  Al Ma'az  ·  Alanz (ε Aur  ·  Alhajoth (α Aur  ·  The star 7 Cam  ·  The star 9 Aur  ·  The star Almaaz  ·  The star Capella  ·  The star b Per  ·  The star c Per  ·  The star d Per  ·  The star δ Per  ·  The star λ Per  ·  The star μ Per
Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck
Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck

Chasing faint nebula in the Sharpless catalog

Revision title: Improved noise reduction

Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck
Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck

Chasing faint nebula in the Sharpless catalog

Revision title: Improved noise reduction

Equipment

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Acquisition details

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Description

The legendary 50 mm f/1.8 lens has to be one of the most popular prime lenses for many photographers. Is often nicknamed ‘plastic fantastic’ or ‘nifty-fifty’; since it combines a very wide aperture with an inexpensive construction, which makes it an excellent alternative for the typical 55mm f/5.6 kit-lens. I bought my Canon EF 50mm f/1.8 II in 2010 and captured many daytime photos with it. That said, I never used it for astrophotography until recently. The field of view with my ASI1600MM is 20×15 degrees, absolutely massive for a “telescope”. My large 800mm FL f/4 Newtonian has a field of view of only 1 degree! So what do you shoot with such a setup? I picked an obscure field on the border of the constellations Perseus and Auriga; plenty of stars to check the lens performance. Plus, the DSS red plate showed several large and very rarely imaged nebula in the field.

Sharpless objects in Auriga/Perseus
There are a whopping 12 Sharpless objects in this single image! Revision B is a starless inverted version to show where they are located. Below is a short description of each object, if it was available:

Sh2-205 – Large, faint diffuse
Sh2-206 (NGC 1491) – also known as Fossil Footprint Nebula
Sh2-207 (PK 151+02.1)
Sh2-208
Sh2-209
Sh2-210
Sh2-211 – very small
Sh2-212 – open cluster NGC 1624 lies embedded in the emission nebula
Sh2-216 (PK 158+00.1) – one of the largest known planetary nebula, 2 degrees apparent diameter
Sh2-217 – molecular cloud
Sh2-219 – small HII region
Sh2-221 (SNR 160.4+02.8) – very large supernova remnant
BFS44 – does not have a Sharpless number but appears to be a separate object and and is almost never described

Technical
My Astromechanics EF adapter could control focus and I was able to get a nice V-curve in SGP’s autofocus routine after tweaking some settings. The lens has a lot of optical aberrations when used full open at f/1.8, however I found performance acceptable when stopped down to f/4. Humidity was 100% during the night. Luckily, the lens stayed clear with just a simple dew strap and I was able to collect a little over 7 hours of hydrogen-alpha data.

This was also the first time I tried the Normalize Scale Gradient script in PixInsight to stack the subs. The first sub was taken at an object altitude of 32 degrees and shows a strong light pollution gradient (left image below). I used the best sub-frame (object at 88 degrees) as reference for the script (right image below) and it worked very well to reduce the impact of the light pollution gradient in the final stack. The normalized stacked image was only treated with a 2-degree ABE before stretching.

low versus high altitude gradient.png

The Canon EF 50mm f/1.8 II is very sharp in the center at f/4, at least with the H-alpha filter. I have not yet tested the broadband performance. 2X Drizzled crops show nice round stars and a good amount of small details in the nebulae. Check for example this crop of open cluster NGC 1528, Sh2-209 and Sh2-206.

NGC1528_Sh2-209_Sh2-206_drz.png


With careful stretching and sharpening of the data, it was even possible to reveal several stars of the open cluster NGC 1624 and some dark dust lines inside Sh2-212. The smaller object in this crop is Sh2-211. Note that these details are blown out in the full field of view, which was stretched much harder to show all the faint nebulosity in other areas. 

Sh2-211_Sh2-212_drz.png

Comments

Revisions

  • Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck
    Original
  • Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck
    B
  • Final
    Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck
    C

B

Title: Annotated overlay (starless inverted)

Uploaded: ...

C

Title: Improved noise reduction

Uploaded: ...

Sky plot

Sky plot

Histogram

Chasing faint nebula in the Sharpless catalog, Victor Van Puyenbroeck