15th Feb 2024: Astro Pixel Processor 2.0.0-beta29 released - macOS native File Chooser, macOS CMD-Q fixed, read-only Fits on network fixed and other bug fixes
7th December 2023: added payment option Alipay to purchase Astro Pixel Processor from China, Hong Kong, Macau, Taiwan, Korea, Japan and other countries where Alipay is used.
Hey, all. I am 20 years old and have just begun dipping my toes into the world of astrophotography stacking. At the moment, I have an old hand-me-down Olympus E-500 DSLR that my grandpa gave me. It has served me well over the past several years, but the technology is old and I am ready for something better. Soon I will be getting the Nikon D5300. However, for the moment, I am working with the equipment that I currently have.
That said, these three images are my first attempts at stacking. I am currently enjoying the 30-day free trial license, which is such an awesome opportunity that APP provides. When I first started, I had no idea what I was doing, but now I have learned the basics of this software and how to use it rather effectively. The first image is 29 60 second exposures through a 14mm lens at f/3.5, ISO 500. The second is 41 50 second exposures at 40mm, f/3.5, ISO 500. The third image is 48 50 second exposures with the same 40mm lens, f/3.5, ISO 640.
While I am quite pleased with the results at this stage, I would love to learn more about this realm of photography so that I can get better. I have been watching tutorials and reading all about how to stack images and take calibration frames, but my knowledge is still extremely limited. One of the biggest problems I am having right now is calibration frames. I understand the procedure and technical explanations for darks, biases, and flats, but in practice they aren't working out well for me. My current camera was released in 2005, and it struggles at ISOs anywhere above 400, with a maximum expanded ISO of only 1600. This said, the in-camera noise reduction is a must. I have read that the noise reduction essentially takes a dark frame and subtracts it from the original, thus eliminating the need to take dark frames. However, is it better to turn this function off and take dark frames of my own? I tried this the other day, but the overall result was very noisy and disappointing. I think this is a result of the awful noise tolerance of my camera, so I have been leaving the noise reduction on since then. My second question is about bias frames. Is it true that a dark frame also contains bias, which means that in taking both dark and bias frames, the effect is cancelled out? If so, how do you get around this? And are bias frames vital? My flats have been turning out fairly well, and after a little bit of experimenting, they are relatively easy to take. Going along with this, how many calibration frames should I be taking? Some people recommend taking an equal number of calibration and light frames, yet others say 20, 30, etc. Is there a sweet spot for calibration frames, or is it dynamic?
Next, I've been wondering how to enrich the colors in post-processing. APP seems to mute the colors slightly, and from what I have tried, the only way to combat this is to increase the saturation, which in turn increases noise. Take the picture of the Teapot of Sagittarius for example. The Lagoon Nebula is very evident and shows a fair amount of detail for the equipment and setup I used. However, the color is a very pale purple-gray, not the vibrant pink I want. Is this the result of my camera not being modified for astrophotography, my lack of filters to draw out color in nebulas, my setup, or is this a downside of APP? And whatever the answer is, how do I combat that and draw out the colors I want? In the same way, how do I get my backgrounds to be a richer, darker black, but without decreasing the overall exposure of the picture? The backgrounds I have are decent, but not great.
I apologize for this lengthy post, but I recognize that I am a beginner, and I want to get better. Please understand that I am currently a broke college student, so I don't have fancy equipment. I recently bought the Omegon Mount Mini Track LX2, and it is my first star tracker. It is a lightweight tracker and completely mechanical, so it is built for wide-field photography, not deep-sky. At this stage in my life, I will be focusing mainly on Milky Way shots and relatively wide-field starry compositions. My next goal is to figure out how to stack foreground images with my sky images, which will open up endless possibilities for beautiful pictures. Eventually, when I am old and rich (haha), I hope to have much better equipment so that I can dive into telescopic astrophotography and deep-sky imaging. For now, however, I will be content with where I am and what I have, and I will do my best to learn more about this amazing form of photography. If anyone has any helpful tips or pointers to help guide me in the right direction, I would love your advice. I'm here to learn and get better. Sorry again for this lengthy post, and thank you.
Hi Jonathan and welcome, I wish I started at 20!
So I almost read the entire post, but I quickly concluded you're basically asking about calibration data and workflows. Let's start with that, always try to do it step-by-step. Your results look very good already btw!
- Bias frames; these are to calibrate your data for the shot-noise, produced by your camera. You take (in complete darkness) around 50-100 frames and make a master-bias.
- Dark frames; these are to calibrate for hot-pixels and amp-glow (which can be a signal produced by a component of the camera and bleeds light into your data), 50 are a good start and you need one for each ISO and length of a light frame you intend to use. With these you can also create a BPM (Bad Pixel Map) which can be selected in the calibration menu. A BPM will also calibrate hot pixels, but can be used for any ISO and length of lights. If you don't have any amp-glow, you can even go without darks and use a good BPM.
- Flats; I would first get the above working well as these are the most tricky to get right. 😉
I would always switch off any processing that the camera is doing, these algorithms are very basic and never good for astrophotography. If you use the RAW data from the camera, no processing should be done on those in the first place (if the manufacturer indeed doesn't). APP is way more advanced and capable of doing the calibration right.
Regarding color; you can calibrate star colors with the tool in the tools menu, and on the right hand side there is a checkmark for saturation which you can switch on. Down on the right hand side, there are sliders for Sat. and Sat. Th. Sat. is the amount of saturation (you can crank it up to 0.25 for instance to see) and the Sat. Th. protects the background from getting extra saturated (which would cause noise to get more color), you can lower that a bit and see if it creates more saturation where you want it and play around with that so you avoid the background still. The standard value is a pretty good boundary already.
@vincent-mod Thank you for the helpful information. I will continue to experiment !
