This journey has been both challenging and rewarding, as I worked to perfect the optics and fine-tune the acquisition process, it started with the bane of RC telescopes:
the dreaded collimation!
The first major upgrade I made to my RC8 was adding the nateman_doo modification to the backplate (CN link). This mod allows independent adjustment of the primary mirror and the focuser alignment, making collimation much easier.
To further refine the notoriously tricky collimation process of an RC telescope, I started using SkyWave collimation tools, particularly for correcting astigmatism. This made collimation more precise and manageable.
Next came the challenge of finding a suitable focal reducer for my imaging setup. My camera, the QHY 268M, has an APS-c sensor, I wanted a reducer that could maximize its real estate without compromising image quality.
- 0.67x Reducer: A classic choice, but not ideal for an APS-C sensor. No matter how much I fine-tuned collimation, the stars in the corners remained distorted. Of course, modern AI tools like BlurXTerminator (BXT) can correct these issues in post-processing, but I wanted a cleaner optical solution.
- Starizona Apex ED 0.65x L: This reducer is supposed to work for RC telescopes, and while it did provide excellent focal reduction, I encountered persistent reflections in my images that I couldn’t eliminate. I suspect the small T2 aperture, or the concave final lens element was reflecting light onto the CMOS sensor.
- FF 0.8x Corrector: Typically designed for 10”+ RC telescopes, I decided to give it a try. Adapting my optical train to it was tricky, and I barely had enough back focus, but once I got it working — perfection! A beautifully flat field with pinpoint stars all the way to the edges of the sensor. Hurrah!
I captured this image over the course of a week, shooting from my balcony under a Bortle 7/8 sky — definitely less than ideal conditions.
My trusty CEM60, mounted on a homemade pier, handled guiding with ease, maintaining an error of 0.4”–0.6”.
Astrophotography doesn't end with capturing images — post-processing is an art in itself. My workflow was relatively straightforward:
- Gradient Removal: Corrected gradients in each channel individually using GradientCorrection.
- Channel Combination: Merged the channels in an SHO palette and created a synthetic luminance by integrating them.
- Decovolution and noise reduction: Applied BlurXTerminator (BXT) and NoiseXTerminator (NXT) for noise reduction and sharpening.
- Star Removal: Used StarXTerminator (SXT) for star extraction.
- Stretching & Color Processing:
- Stretched using Generalized Hyperbolic Stretch (GHS).
- Combined LRGB.
- Applied SelectiveColorCorrection for final color balancing.
- Used UnsharpMask & MultiscaleMedianTransform (MMT) to enhance details.
- Star Reintroduction: Added stars back using SXT-extracted stars and SetiAstro’s NB to RGB Star Combination tool
All in all, I’m happy with the result — though that’s just my personal take. I’d love to hear feedback from more experienced astrophotographers.
Thanks to everyone who takes the time to comment, and clear skies!
Massimo
