NGC 7094 is a planetary nebula in the constellation Pegasus, also catalogued as PNG 066.7−28.2, PK 066−28.1 and K 1−19. It lies approximately 1.8° from the globular cluster M15 and was discovered by Lewis Swift in October 1884.
With an apparent visual magnitude of approximately 13.6 and an angular diameter of around 1.6 arcminutes, NGC 7094 is a relatively small and faint target. Its nearly circular morphology reveals a subtle filamentary structure, making it a challenging object to capture in detail. An often-cited distance estimate places the nebula at approximately 5,400 light-years, corresponding to a physical diameter of roughly 2.5 light-years.
One of the most distinctive features of NGC 7094 is its central star, classified as a hybrid PG 1159 star (*). These extremely hot, hydrogen-deficient pre-white dwarfs represent a transitional evolutionary stage between post-AGB stars and white dwarfs. Unlike classical PG 1159 stars, hybrid objects retain a significant amount of hydrogen in their atmospheres. The central star of NGC 7094 also exhibits low-amplitude pulsations, with periods ranging from approximately 2,000 to 5,000 seconds. Ultraviolet spectroscopic studies have revealed a strong iron deficiency in its atmosphere, while no nickel lines could be identified in the analysed spectra.
(*) PG 1159 stars are extremely hot, hydrogen-deficient pre-white dwarfs in a transitional phase of stellar evolution. Hybrid PG 1159 stars, such as the central star of NGC 7094, differ from classical members of this class by retaining a measurable amount of hydrogen in their atmospheres.
Image Acquisition
Given the nebula’s small angular size, drizzle integration was required to improve the effective sampling of the data. All images, including both RGB and narrowband data, were acquired exclusively with the Takahashi TOA-150 telescope. Astrodon filters were used for the RGB and Hα channels, while O III data were collected using a Baader filter. The total integration time was 54 hours.
Note: This image is part of a wider-field project that includes several other interesting objects in the surrounding region. Completing the full-field image will require considerably more exposure time.
Image Processing
The processing workflow for this project differed somewhat from that of my recent images, primarily because of the need for a ×3 drizzle integration. This was the first time I had applied this level of drizzle scaling, resulting in a final image scale of 0.56″/pixel with my setup.
I began by generating three master images: Hα, O III and RGB. The RGB master was processed using my usual workflow, including gradient correction with MGC, followed by colour calibration with SPCC and MAS.
Next, I extracted the luminance from the RGB master and combined it with the Hα and O III data to create an enhanced luminance layer. The three datasets were processed separately before being integrated into an LRGB composition.
Finally, I used PixelMath to incorporate additional Hα and O III signal into the red, green and blue channels, enhancing the visibility of the nebular emission while preserving the contribution of the RGB data.
In this image, north is up.
Click on the image for the full resolution version, or visit the Gallery section for complete exposure details.
Image processing: Pixinsight.
Observatory automation and remote operation: Talon6.
No comments:
Post a Comment