NINA

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.