As amateur astronomers, we use many tools to help us in our cosmic quest for knowledge. These tools range from the telescopes we use, down to what type of pencil you grab to note your nights observations. There is a lot to be said about planning BEFORE you observe. Some tools can help you with your night’s plans and sometimes, those tools can almost seem to work against you. A poorly collimated scope can kill any observing session as can dirty eyepieces or dead batteries. Planning is key!
With that being said, one tool amateur astronomers use is the Clear Sky Clock/Chart. It is an applet that takes data on weather conditions from the Canadian Meteorological Center and lays it out in a very nice format that makes planning easy. It offers predictions on how the sky should behave for the next 40 plus hours and gives astronomers a heads up on how great or how poor the sky might become. It’s an extremely valuable tool and one that I use almost every day. It will give you the most basic info you will need to judge whether or not you should try to observe on any given night. Data like seeing, transparency, cloud cover, humidity, wind, moon illumination, the darkness level of the site you’re planning to observe from and so much more. I’m not going to go into depth about how to read the chart, I only want to bring an awareness to the fact that sometimes, not every time, it can deceive you.
Let me start by saying the chart isn’t a fool proof crystal ball. It isn’t always 100% accurate but then again, no one is trying to make that claim. It is, however, far better than local weather predictions and is more reliable than a simple prediction of percentage of rain. If the local weatherman has you convinced the skies will be clear, odds are you should still check with the CSC and see exactly how clear. It also will help you decide how long you might want to be out. I’ve seen many cases where the chart calls for clear skies up to about midnight and then shows a complete cloud out. That can make a huge difference in what gear you take out to the field. If you’ll only be out for a couple hours, maybe that night isn’t the best for lugging your entire astrophotography set up to a field several hours from your home. Let’s face it, the weather is unpredictable. No matter how stable you think conditions will be, they will often surprise you, sometimes in a good way. It’s always a gamble. I try to look at this tool for what it can do for my frustration level verses what it can do for my observing quality. If I know the sky conditions are iffy, I’ll make plans accordingly and will somewhat lower my expectations of what I can get done that evening. That can make or break a night, so this tool is one I’ll use forever.
Recently, we had our monthly dark sky star party at our favorite place about two hours from my home. It’s quite the drive and it’s shame we have to travel so far just to have some good views. It’s worth the drive when skies are good. No argument there but when things don’t go as planned, it can be a long and frustrating drive home. Our last blog entry was a post about this particular star party in which I included a screen shot of the CSC for that night. Conditions looked very favorable but apparently, I hyped the event too much for the skies and they decided to revolt. We arrived at Martin Dies Jr. State Park hoping that the “high thin” clouds would burn off and that the skies would open up for us at some point. The thicker clouds began moving in before dusk and continued to get worse. So we set up, sprayed the bug spray, polar aligned and collimated our scopes… and waited. And waited. And unfortunately, the sky got worse. After 11pm, all realistic hope had been lost as even Saturn began to become more and more washed out. Spirits were still pretty high despite the milky layer of clouds ruining our views. We saw through the clouds, and that worked for a while but even the most diehard observers began to call it quits. Instead of being upset and shouting at the sky, we just had a great time fellowshipping and discussing the finer points of our hobby and occasionally wondering if the skies would get better. They didn’t until the last of us began packing in our scopes. Isn’t that how it usually goes?
The moral of the story here is don’t put too much reliance into predictions of the weather. Use the tools at hand and trust them, but keep in mind that nothing is set in stone when we’re talking about the ever changing sky conditions. The Clear Sky Clock is by far the best and most detailed tool we can use to assess the possible conditions. It can be extremely accurate and can save you a lot of heartache and trouble but at the same time it can sometimes trick you into a night of observing the ever famous “Cloud Nebula”. A future blog post will cover how to use the CSC and what it means. Until then, thanks for reading and clear skies!
Will Y.
