The narrowband images were processed in a starless mode, so first StarXTerminator (SXT) was applied. On individual images there was barely any signal visible, and only after stacking the signal came through. Lots of structure, and in some areas even more detail than in H-alpha. But what was unknown to me was how much signal there was in the SII line. NGC1499 is a very bright target in H-alpha. The early higher gain value narrow band images were combined with the gain 100 images without any problems. But now WBPP allows in an easy way very precise targeting of calibration frames to light frames. In earlier iterations, such a complex set of calibration combinations would have required multiple runs of the script, each focusing on different images. This is a testament for how flexible WBPP is these days. Nevertheless, WBPP allowed to manage everything in one go. When putting all of this in WBPP, the complexity of what needed to be calibrated with what was enormous. Taken together, this resulted in a large variety in exposure times and gain settings, for which all (Flat-)Darks were taken. Also, some early images were taken at the wrong gain values. So for that panel exposure time was used to get to the target ADU values. As a consequence, Flats were taken with two different Flat panels, one of which did not allow brightness control. At the time of taking these images, some experiments were conducted around making Flat frames. So a manual adjustment was made to the positioning, and a reference image was saved to position in exactly the same way in subsequent sessions.Īll frames were calibrated with Dark (50), Flat (25) and Flat-Dark (50) frames, registered and integrated using the WeightedBatchPreprocessing script. When doing a regular GoTo command with the software, the target did not really fit very well in the frame. The target is very large and only barely fits within the 3.5º Field of View. In total this led to a pretty long overall exposure for my setup of almost 22h. To make sure the stars would have their natural colors, a small set of broadband RGB data was acquired. The exposure of other channels was almost matched. So I decided to capture a lot of OIII and ended up with ultimately almost 8h of OIII data. It is only with stacking that the nebulosity comes out. At my not so dark bottle 5 skies, there is hardly anything visible in a single 5min OIII sub. To bring out the OIII signal was not easy. So I decided to image in all three channels and process according to the Hubble palette. However, there is also a very strong SII signal and there is also a fairly significant area that shows a faint OIII signal. In those cases, the nebula comes out as an intense red nebula. It is a great Ha-target, and many astrophotographers show the image in either broadband or Ha mapped to the red channel. There are different ways to image NGC1499. Together with the calibration complications of the Flat frames (see above), the overall calibration got a bit complex, but nothing that WBPP could not handle. This complicated the calibration efforts quite a bit, requiring extra darks. In some instances that wrong gain setting had somehow unintentionally carried over to the imaging sequence. However, to speed up the focusing routine, many of the focus frames were taken using gains of 300 or 400. Narrowband imaging with these 3nm filters and the FSQ-106 is usually done using 300s (5 min) exposures at Gain 100. This meant a lot more calibration frames when using the Aurora. For the Aurora I had to modify exposure times to get to a target ADU, whereas for the Flatmaster, which brightness can be adjusted in software, all frames could be taken at 5s. The result is that the RGB images were calibrated using the Aurora flatpanel, while the SHO images were calibrated using the Flatmaster panel. During this period I was testing out different flat panels. And while I did refocus fairly regularly, still some frames had to be thrown out due to poor focus. The shift in focus during that first 1-2h of imaging is quite significant. A drawback of these last minute decisions however, is that the telescope is still acclimating to the cold outside temperatures during imaging. The new setup with rolling pier proved itself extremely efficient and allowed very short setup times. For some sessions even, the decision to setup and image was made well into the evening. Due to the fluctuating weather conditions the equipment was not left outside between all five imaging sessions. The Takahashi FSQ-106 was used for this image in its standard configuration and paired to the ASI6200MM full frame camera.
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