Published: Oct 18, 2011
Revised: May 11, 2016
If you’re a veteran astroimager please avert your eyes. If you’re new to the sport, please pay attention and realize that the tips I’m going to describe will justifiably annoy the stew out of serious astroimagers and may get you run out of dark sites or banned from private observing parties. And if you are not an astro imager, read on anyway, because the tip will also apply to landscape astrophotographers, too – tip 5, below, that is.
My tips advocate using a green laser pointer. I have purchased several from various sources and they range in price from $5! to $50. The $5 ones are from overseas sellers and honestly the quality isn’t always a high point, but then a recent $40 purchase from Fry’s Electronics was also a dud. Green laser pointers in the 5 milliwatt (5mW) range are extremely helpful for pointing out the night sky to beginners because the beam can be seen for miles. These lasers CAN BE DANGEROUS so DO NOT POINT at people or aircraft. The beam can be seen in the night sky for up to two miles. Pointing at or near airplanes may result in your arrest and prosecution. Just don’t do it!
Interestingly the $25 laser pointer with the “Star Pattern Kaleidoscope Cap“ seems to be the same thing as the $29 version without the cap so save yourself $5 by taking the cap off yourself. The best bargain I’ve seen on a good laser pointer lately is on E-Bay. Search for “Military Grade Green Laser (or lazer)” Be sure to get one with a battery and charger… there are different styles.
As I noted, use of green lasers around serious observers or astro imagers will not be looked upon with favor. You may well ruin their observing and imaging and any budding friendship. If you are confronted and forced to divulge who gave you this dangerous and disrespectful advice please remember my name Neil deGrasse Tyson. 🙂
Green lasers are powerful tools – just like those amazing Jedi light sabers in Star Wars. Listen carefully, recruit and use your force wisely.
When Setting up for Polar Alignment
I point a laser through my polar scope. The beam comes out the front and I can immediately tell if I need to make some serious adjustments to my mount orientation – and in which direction. Since mount alignment is something you generally do in early twilight (as soon as Polaris is visible) the appalled astro imagers may forgive you for using this method when it is not yet dark enough for them to do imaging.
Acquiring Your Target
Finding an object in the sky that cannot be seen with the naked eye, or in the camera viewfinder is greatly aided by a green laser. I check my planisphere (or better yet a more detailed star atlas) to form an idea where in the sky I need to look. For example I may note that my target is equidistant between two bright stars and up a moon diameter. I then sweep that area with binoculars or a finder scope. When light pollution is bad and I can’t easily find the object, I fall back to my trusty Jedi Laser pointer. Here is how:
- Shine the laser through the viewfinder of the camera! Wiggling it around will show the area of the sky that is in the camera’s field of view. I can’t guarantee that no damage will result to your camera – a green laser can wipe out pixels if you point it at the sensor – but that theoretically should not be possible because the mirror redirects the viewfinder to the lens and together with the shutter completely covers the sensor. Be sure your optics (e.g. lens) are focused because if not the laser will be attenuated. You may need to use binoculars to confirm that you’re at the right location in the sky. This method allows two handed single person operation.
- If you don’t want to shine the laser through the view finder: I either hold the laser and the binoculars or I have a friend shine a laser in the vicinity where the target should be. The glowing green light makes finding the direction in the binoculars (or a finder scope) so much easier. Once I find the target with the binoculars, I keep the laser steady and lower the binoculars to see exactly where that green beacon is pointing. I repoint my camera/telescope
- If I am imaging with a zoom lens, I may start zoomed out. I take a trial photo (short, high ISO) and confirm whether my target is present or not. If I can’t confirm it I may again point the laser (using binoculars) while the next image is being captured. I am hunting for the green beacon with my image – adjusting the camera as needed.
- Once I have my target in my shot I can make minor adjustments using the Decl* and RA* on my mount to fix the framing and do not need the laser anymore.
- Oh.. and here is a nifty trick, shine the laser through your viewfinder and wiggle it around… it will trace out the boundary of what is in your shot! Even if you are not doing faint object photography that will be a big help.
*Decl and *RA? What? If these terms are new to you, you might find my Astrophotography 101: Getting Started Without Getting Soaked to be really helpful. Or join me out in the field (Astro 201). See the course list. Many of the classes are webinars and can be attended from the convenience of your computer.
Trying to Decide What to Target?
In the Northern Hemisphere, Andromeda (M31) and the Orion Nebula (M42, or NGC 1976) with its many nearby nebula such as the Horsehead, Running Man, and others should not be passed up. Both are easily spotted with binoculars or even the naked eye in dark sky sites. Don’t expect any of these to give up its glorious color and structure unless you use long exposures and a good camera.
For a great list, see 111 of the brightest deep sky objects article in Sky and Telescope.
If you want to learn to locate objects in the night sky, set up, balance and polar align your mount, and get a start on astro imaging, please consider attending my Astrophotography 101 Webinar and/or Astrophotography 201 Field Practice. If you want to go whole hog on perfecting your astro images, then Astrophotography 301 is what you want!
Again, DO NOT target anything that appears to be moving at all.