Processing

I've previously used free tools like Siril and GraXpert, and to be fair, I achieved some good results with them. However, as I've matured in the hobby, I've expanded my toolkit to include more advanced software. For stacking my FITS files and applying calibration frames (bias, darks, and flats), I now use Astro Pixel Processor (APP), which offers excellent integration and control.

For post-processing, I've invested in PixInsight, which I use for tasks like nonlinear stretching, noise reduction, and star removal—unlocking a much higher level of detail and refinement in my images. After completing the core processing, I bring the final image into Lightroom, where I convert it into high-quality JPEGs optimised for social media sharing.

This workflow gives me both precision and flexibility, allowing me to produce images that reflect the full potential of my data.

Tracking Software

When it comes to tracking and controlling an imaging session, there are several excellent software options available, each with its own strengths and learning curve. Over time, I've experimented with different solutions including NINA, Stellarmate, and ASIAIR, before ultimately settling on ASIAIR for its convenience and integration.

NINA (Nighttime Imaging 'N' Astronomy) is a powerful, open-source PC-based platform favored by many advanced astrophotographers. It offers a high degree of customizability and supports virtually every imaging setup via ASCOM drivers. Its plugin system is fantastic for automating sequences, focusing, plate solving, and more. However, it requires a dedicated Windows laptop or mini-PC at the scope, and the initial setup can be intimidating for beginners.

Stellarmate, on the other hand, is a Linux-based ecosystem similar to ASIAIR, using the INDI framework. It provides cross-platform support, including for non-ZWO gear, and can run on devices like Raspberry Pi or dedicated hardware. Stellarmate is very flexible, but its interface and system management can be somewhat complex, and troubleshooting INDI driver issues can require technical know-how.

After evaluating , I chose ASIAIR because of its plug-and-play simplicity, mobile app interface, and tight integration with my ZWO hardware (2600MC Pro, 678MC, ASI guide cam, EAF, and filter drawers). It abstracts away the complexity and just works, letting me focus on imaging rather than configuring software and drivers. Features like polar alignment, auto-guiding, plate solving, and imaging sequences are all built-in and optimized for mobile use.

While ASIAIR is limited to ZWO devices, Cannonand Nikon camera for someone like me who is fully invested in the ZWO ecosystem, it's a perfectly streamlined solution. It’s portable, reliable, and makes astrophotography sessions efficient.

Calibration Frames

1. Bias Frames

• Purpose: Correct for the camera's electronic read noise.

• How to Capture:

  • Use the shortest possible exposure time (0.001 seconds or less).

  • Keep the camera covered (no light reaching the sensor).

• Number Needed: 50–100 for good statistical averaging.

2. Dark Frames

• Purpose: Correct for thermal noise (hot pixels and amp glow).

• How to Capture:

  • Match the exposure time, gain, temperature, and offset of your light frames.

  • Keep the camera covered.

• Number Needed: 15–30 for good results.

3. Flat Frames

• Purpose: Correct for vignetting and dust spots on the optical train.

• How to Capture:

  • Illuminate the telescope evenly (e.g., using a flat panel, white t-shirt with a bright sky, or a tablet screen).

  • Set exposure so the histogram peaks at about 1/3 of the maximum value (mid-histogram).

  • Do not change focus or optical setup after taking flats.

• Number Needed: 15–30.

4. Dark Flats (Optional)

• Purpose: Correct for noise in the flat frames.

• How to Capture:

  • Use the same exposure time, gain, and offset as your flat frames.

  • Keep the camera covered.

• Number Needed: 15–30.

Notes for Your Setup:

Since you're using an uncooled ASI678MC:

• Temperature control: If you can't regulate temperature, try to match the dark and bias frames' temperature to your light frames as closely as possible (capture them in the same session).

• Consistency: Avoid changing the focus, filters, or rotation between light and flat frames.

• Amp glow: The ASI678MC can exhibit amp glow, which will be corrected by dark frames.

1. Exposure Settings

Exposure Duration:

• 2–3 minutes per sub (120–180 seconds):

  • At f/5 and 51mm, you'll collect a lot of light quickly. Longer exposures can risk star trailing if polar alignment is rough.

  • Test for your sky brightness. If light pollution is high, reduce exposure to ~60–90 seconds to avoid overexposing.

  • Monitor the histogram: Ensure the peak is roughly 1/3 of the way from the left edge.

2. Gain

Recommended Gain:

• Unity Gain (100) for the ASI678MC:

  • This is the manufacturer-recommended setting for a balance of dynamic range and noise performance.

  • If your sky is very dark, you can try lowering to Gain 50 for higher dynamic range.

  • For light-polluted skies, increase to Gain 200 to boost faint details but watch for potential noise.

3. Total Integration Time

• 2–4 hours (or more):

  • The more total integration time, the better the signal-to-noise ratio (SNR).

  • Divide this into multiple subs based on your chosen exposure time.

4. Calibration Frames

• Bias Frames: Shortest exposure time (50–100 frames).

• Dark Frames: Match your light frames' exposure, gain, and temperature (15–30 frames).

• Flat Frames: Use a flat panel or twilight sky to correct vignetting (15–30 frames).

• Dark Flats: Match exposure of flat frames (optional but recommended).

5. Filters

• No Filter: If under dark skies.

• Light Pollution Filter (e.g., Optolong L-Pro): If you're in a Bortle 5 or brighter area.

• Dual-Narrowband Filter (e.g., L-eXtreme): Can enhance emission regions but may suppress broadband details of M31.

6. Additional Tips for Your Mount

• The Sky-Watcher AZ-GTi in EQ mode benefits from:

  • Rough Polar Alignment: Use tools like NINA's Polar Alignment Assistant or a polar scope for better tracking.

  • Auto-Guiding: If using a guide scope and camera, aim for 2–3 minute exposures.

  • Backlash Management: Keep payload well-balanced slightly east-heavy to improve tracking.

Expected Results

• With 2–4 hours of data, you'll resolve:

  • The galaxy's bright core.

  • Dust lanes.

  • Some star-forming regions in M31's spiral arms.