The Process I Go Through

1. Position the mount in a good spot in the garden so you have a good view of the sky

2. Ensure the mount has the correct inclination (51deg for my location in the UK)

3. Align the mount so it's facing north as accurately as possible (accurate alignment significantly helps with guiding accuracy)

4. Ensure the mount is perfectly level

5. Attach your OAT (with all the cameras/filters/dew sheilds, etc already attached)

6. Balance the mount using the counter weights (accurate mount balance significantly helps with guiding accuracy)

7. Turn on and set up the mount - ensure it's positioned in the 'home' position

8. Turn on and configure the ASI Air (cameras, focuser, dew heaters, camera cooling)

9. Focus the scope

10. Polar align using the ASI Air Polar Align routine

11. Plate solve, select object and move to that position (use ASI Air auto-goto and centre tool)

12. Activate auto-guiding

13. Set up and run auto-run imaging sequence

There are several factors to consider when choosing what you're going to image. There's plenty of good apps available to tell you what's up there at whatever time of year you're imaging and to help you decide.

1. How high in the sky is the object? The higher the better. The higher the object is, the less atmosphere you're looking through. Less atmosphere means more stable images.

2. Are you going to have a clear line of sight to the object for as long as you plan to image it? Make sure that as the object moves across the night sky, it doesn't disappear behind the neighbour's roof or a near-by tree before you've finished your imaging time.

3. What's the Moon doing? Are you going to need a Moon light filter? 

4. Is the object better imaged using a Hydrogen and/or Oxygen filter?

5. How big is the object? Something like the Andromeda galaxy is huge. It'll completely fill the frame of my current imaging system, giving an image that's not that great. By contrast, other deep-sky objects are perfectly framed (sized) for my current rig. 

The imaging process for most objects is similar, apart from planets. Once you've decided on your target and have it framed, you need to gather as much light as possible, known as 'light frames' and you're likely to need some 'calibration frames' as well.

Light Frames - gather light from the object

1. Make sure your mount is tracking the object very well. This is done using the star tracking camera and scope that provides real-time adjustments to the mount. This enables long exposure times to be used without 'star trails' and/or elongated/egg shaped stars.

2. Take as many 'light frames' as you can, with the longest exposure times you can manage whilst still maintaining round stars. I'm currently using 180 second exposures for each light frame. This is giving lots of light gathering time and keeping the stars nice and round.

3. Once you have lots of light frames, you can take the 'calibration frames.

Calibration Frames

There are typically 3 types of calibration frames: Flat, Dark and Bias. Each one helps to get to a better image once the imaging stacking and processing has been done.

Flat frames - These are taken using a stable, diffuse and 'flat' light source. I use a photography LED light panel and a white t-shirt stretched over the telescope. The imaging software takes care of the rest. I typically take 30 flat frames. The purpose of them is to 'flatten' the light field of the final image to make it more consistent across the entire image, to remove light gradients across the image and to help remove the circles that come from 'dust motes'. These are the circles that appear on the image and come from dust particles on the camera sensor or other parts of the imaging train. Flat frames can be taken any time but they should be done with the focus being precisely the same as it was during the main imaging session.

Drak frames - These are taken by putting the lens cap on the telescope and taking images using exactly the same settings and exposure times as you were using for the main images. Just think of them as taking a frame of the object, but with the lens cap on. The purpose of these frames is to help reduce noise in the final image. Electronic noise in the image comes from many sources. It helps to be able to cool the imaging sensor. I typically take 30 to 50 Dark frames. Even with a very cold imaging sensor, Dark frames still make quite a big difference to the final image once it is stacked and processed.

Bias frames - These are taken with the lens cap on and with the fastest shutter speed you can get. Their purpose is to help remove the 'sensor read noise' from the image. I typically take 30 Bias frames.

Stacking the data

I use 'PixInsight' as the image processing software. It took a while to learn, but it's an 'all-in-one' astro-photo data processing software package that does everything you need to do to get a final image.

'Stacking' the data is done by adding the light, dark, bias and flat frames all together in the software and running the stacking process. It can take quite a while for the software to complete the stacking process. Once complete, you'll have a basic image file you can start processing.

Once all the data is stacked, you're left with an image file that you can process into a final image. There are many different techniques for image processing and there's a lot of artistic license in what you want to get for your final image. 

Stretching - Most of the data in the image once stacked will be squashed towards the black/dark end of the spectrum. You probably won't see much at all in the initial image. To see the detail, you need to 'stretch' it. This can be done automatically using some software, such as Pix Insight, or you can do it manually. Either way, the process 'stretches' the light distribution histogram to pull the data from the dark end of the spectrum so it's more evenly distributed across to the light end of the spectrum.

Additional processing - The numerous other processes and techniques to get to a final image typically help to reduce noise, enhance details on the image, enhance colours and sharpen stars and other details. This processing can take a lot of learning, experimentation and trial and error. There are lots of YouTube and other resources on the internet to help. The end result is what you want to make it.