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HotCarlWithaK t1_ja7ef2k wrote

Can you tell me about your setup?

I have a Dobsonian and would love to start capturing images like these…


I_Heart_Astronomy t1_ja7icnn wrote

Not OP, but I image through my dob as well. The key is in the camera. A dedicated planetary camera from ZWO, QHY, or PlayerOne makes all the difference over a DSLR or a cell phone. The downside is that you need a laptop with a solid state drive and at least USB 3.0 to be able to handle the firehose of data coming from the camera.

The way the technique works is the camera records high speed video, uncompressed. Generally you should be able to get ~150-180FPS from such a camera (even higher if your scope can track and you can set a small region of interest around the planet to get your frame rate up). You record for about 120-180 seconds and then process the video in a stabilizing program like PIPP (PIPP works best for stabilizing untracked video). From there you can stack the video in a stacking program like AutoStakkert. AutoStakkert automatically ranks all the frames from sharpest to blurriest, and you can choose which percentage of frames to keep (e.g. the best 25%). The best frames are stacked together to smooth out noise.

Once you have a smooth image, you then need to sharpen it. Astrosurface or Registax are popular programs for sharpening, and give good results. Astrosurface can also do stacking, but I haven't used it enough for stacking to recommend it over AutoStakkert yet.

All of the programs I mentioned are free, but do require Windows. They all have some pretty confusing interfaces and take some getting used to, but once you know how to use them, processing a video into a final image takes about 5-10 minutes or so. Mostly just trying settings to see what works best.

For the camera brands I mentioned, they all basically use the same Sony sensors, but have different capabilities built around them. I use a ZWO ASI224MC. Excellent sensor, just very small. If your scope doesn't track, you don't have a very large field of view to work with, so it can limit capture potential as you're constantly having to re-position the planet on the sensor and you have to let it drift across the sensor.

Image scale is important to consider. The general rule of thumb is to image at a focal ratio that is 5x the pixel size in microns. For the 3.75 micron pixels of the 224MC, optimal focal ratio is F/18.75. If you have an 8" F/6 dob, then you'd want a 3x barlow to bring the focal ratio to F/18. BUT, the catch is that if the focal ratio is too long to manually track the planet, you're going to have a bad time. So I would recommend starting out imaging at the telescope's native focal length even if it's under-sampled (hopefully the camera can reach focus without a barlow!) Practice imaging at the native focal length until you get a feel for it, then add a barlow to increase the image scale. Things become exponentially harder as you go up in focal length, which is why I recommend starting out conservatively.

Just note that we are at the end of planetary season now so results are going to be generally poor. Jupiter is too low in the sky, Saturn is too close to the Sun, and Mars is too far away. The Moon is always a nice target though. You can produce some beautiful mosaics with a planetary camera and untracked dob.


ender2851 t1_ja85t4u wrote

new to the hobbby, we have planetary seasons?


I_Heart_Astronomy t1_ja86l1d wrote

Not technically, no, it just how it’s referred to when planets are visible in the sky. For the last few years, Jupiter and Saturn have been in the sky together. Even Mars oppositions have been around when both Jupiter and Saturn were around. So because of that, they were all visible around the same time of year, so it’s been referred to as a “planetary season”.

Eventually though, Jupiter and Saturn will be opposite one another for a while and thus there will be at least one major planet visible in the sky all year long, with Mars popping in every couple of years. So there won’t be a “planetary season” per se, just individual planet “seasons” like “Jupiter season” etc.