If you want to capture images of the moon, planets or sunspot groups, one favoured method – and certainly the cheapest – is to use a webcam.
The CCD variety, such as the Phillips Toucam Pro and Phillips SPC900N, are more commonly used as they’re generally more light sensitive than their CMOS counterparts but that may be an old-fashioned notion nowadays. Googling the webcam name will let you find online astronomy retailers that still have these discontinued webcams in stock – they should also provide a nosepiece, IR filter and the right software to get you up and running for well under £100/$150.
Okay so how do you set up your webcam? Well this couldn’t be easier – the provided IR filter simply screws into the end of the nosepiece, which prevents the resulting images being oversaturated in IR light. Then screw the nosepiece to the webcam and pop it in your telescope where the eyepiece would go. You may need a diagonal or extension tube to provide enough back focus to achieve a sharp image.
To get the images saved to your PC/laptop, all you need is some free software (like SharpCap or Astro-Snap) and a bit of patience with the gain, exposure and brightness settings. Do spend some time getting the best focus you can and tweak these settings until you have the best image and contrast visible on the screen before you start recording.Preparation is everything and each scope and target will require a different balance between gain, exposure, sharpness etc.
You’ll also have to make sure that you select the external webcam rather than the internal camera, which may be your laptop’s default setting. Then, choose the highest resolution setting possible for your webcam – this is typically 640x480.
How long do you need to record for? Well, a minute would be about the minimum time to be sure you have enough quality frames for stacking software to work with – if you take a few minutes’ worth, you stand a better chance of capturing more steady frames (you’re battling the rippling of the Earth’s atmosphere here) but you’re also creating more work for your laptop/PC which older machines may struggle to align and stack.
Aligning & Stacking
This process is crucial as the software chooses the clearest images – those that are least affected by the shimmering of the Earth’s atmosphere – and combines them into a single super-resolution image ready for some cosmetic final touches!
Click ‘Select’ or ‘Open’ depending on which software you choose, and find the .avi file you want to work on.
I’m demonstrating Registax here because this is probably the most common stacking software.
Unless you’re planning on reading the full instructions for your choice of stacking software, leave the settings as they are. The default settings are perfectly fine until you get more confident and want to push things a little. All icons to click next are in the top left portion of the interface.
You can either click on ‘Set Alignpoints’ to let Registax automatically chose the points on your image that it will use as reference points, or you can click on the image and choose your own.
- Next you click on ‘Align’ and let it do its stuff.
- Then click ‘Limit’ and wait a few seconds (or minutes if it’s a large .avi file)
- Finally, click ‘Stack’ and wait.
If you’ve used, say, Autostakkert instead of Registax, the process is much simpler and comprises of clicking on:
- ‘Open’ and choosing your .avi file
Once this has finished it will have automatically saved the finished image as a .tif file in the same folder on your computer as the original .avi.
Whichever software you’ve used to align and stack your .avi frame, you’ll want to run it though Registax’ ‘Wavelets’ function next – this is the first, and most radical, way to tweak your .tif file to bring out the detail in your final image. You’ll love this bit!
If you used another software, make sure it has saved the finished product as a .tif file and open it up in Registax by clicking on ‘select’. It will automatically take you to the wavelets screen. If you stacked your image with Registax, again it will automatically take you to the wavelets screen as the next step once it has finished stacking.
This screen will intimidate you – but don’t let it!
If you’re working on a whole planet or the entire moon, click on ‘RGB Align’ in the middle of the ‘Functions’ matrix on the right-hand side. Drag the corners of the yellow box to completely fit outside the subject sphere and click on ‘Estimate’. When finished, click the ‘x’ on the RGB Alignment Tool window. This will reduce any false colour fringing to your object, so you’re unlikely to need this if you are working on a close up lunar or solar image.
Now comes the really scary/exciting bit. You will be surprised by how much detail you can draw out of the image here…
The sliders on the left add contrast to specific colour regions in your image by increasing noise. Noise is the enemy of astrophotography so you have to be really careful not to overdo it here. The first slider is the overall noise layer so this one very important to balance right. Play around with all of them as only your own eyes will tell you how much or how little to move each of the sliders to the right.
Finally, use the ‘Contrast/Brightness’ sliders on the right to add the desired illumination to your target and the requisite darkness for the blackness of space.
When happy, click ‘Do All’ in the top left of your screen, followed by ‘Save Image’.
This stage is wholly unnecessary and only you can tell if it improves your image or just increases the noise, but delicate Brightness/Contrast tweaks and the gentlest hint of Sharpening in Photoshop can finish your image off.
In any event you’ll want to crop your image to achieve that perfect framing.
I hope this tutorial was helpful. If you have any images you want to show off, tweet them to me@ActiveAstro and I’ll retweet them.