[SAS] Fwd: Finding faint things with star charts

  • From: cave8@xxxxxxxxxxx
  • To: sas@xxxxxxxxxxxxx
  • Date: Wed, 4 Mar 2015 17:58:50 +0000 (UTC)

I thought some of you might be able to use this info 

----- Original Message -----

Dear Fellow Astronomer, 

I've been hearing from people who've had trouble using star charts to find 
Comet Lovejoy with binoculars. (By the way, Lovejoy is still in good view .) 
This gets to the problem of how does anyone learn to find faint things in the 
sky using charts with binoculars? Or a telescope for that matter? 

Some figure it out by trial and error, but that's the hard way. A few tricks 
make for huge shortcuts in mastering this. 1) First: know how big your view is. 
To compare what you see in binoculars (or the finderscope on the side of a 
telescope) with what's printed on your chart, you have to know how much sky - 
how much of the chart - your binoculars are showing you. In other words: what's 
the binocular's true field of view? For 7-power binoculars, the view is 
probably about 7° wide. For 10-power binoculars, it's probably about 5° wide. 
You don't have to know exactly, but you should have a general idea. Now get out 
your charts. I'll assume you have the Pocket Sky Atlas . because it's 
super-popular, handy and fairly cheap, and just about ideal for binoculars and 
small telescopes because it shows stars to as faint as magnitude 7.6 - about 
the limit of typical binoculars and good finderscopes. Look on the sides of the 
charts. There's a degree scale running down the sides. This shows declination 
on the map (like latitude on Earth), but it also shows you how big your 5° 
field of view appears on the map! On the Pocket Sky Atlas , 5° is 1 inch wide. 
That's probably a lot smaller than you imagined your binoculars showed. It's 
much smaller than most constellations. That's why you see so little of a 
constellation at a time! Remember this size. Maybe draw it on the inside of the 
front cover so you'll always have it handy. The star patterns on the charts 
that fit into that size circle are the star patterns you'll see in your field 
of view. 

2) Which way is up? On star charts, celestial north is up. On the sky, 
celestial north is always the direction toward Polaris, the North Star. No 
matter at what angle that is from wherever you're looking. You do need to know 
how to spot Polaris. Once you do, you'll know which way is celestial north from 
wherever you're looking. Turn your chart around so its top matches that 

3) Start from a naked-eye landmark near the object you're hunting for. You need 
to know at least a few constellations. (There's an excellent naked-eye 
constellation map in the center of each month's Sky & Telescope The 
constellations provide starting points for zeroing in on the exact point where 
a faint thing on your chart should be. On the chart, working from a starting 
point you know to your faint target, look for star patterns - triangles, kite 
shapes, whatever - marking the path. In choosing these patterns, use the 
brightest available stars that will fit in your field of view. Now, with the 
binoculars (or your telescope's finder), work your way along this trail, 
matching the chart with what you see, step by step. This is called 
"star-hopping." If you get lost, start over. You'll get the hang of it. And 
then you'll know how to do it for the rest of your life. You'll discover that 
when you know the exact point in your field of view to examine, it's amazing 
how much deeper you can see. And how much more confident you'll be that you've 
indeed found what you were looking for. 

I hope you'll use these tips to help you enjoy the Comet Lovejoy, while you 
still can! 

Alan MacRobert 
Senior Editor, Sky & Telescope 

P.S. One reason binoculars are nice is they show a view that's right-side up 
and also is not mirror-imaged. Some telescopes and finderscopes show views that 
are upside-down or tilted, and/or are mirror-imaged. 

This email was sent to: cave8@xxxxxxxxxxx by F+W 10151 Carver Road, Suite 200, 
Blue Ash, OH, 45242 USA 
One-Click Unsubscribe | Manage Subscriptions | Update Profile | Forward to a 

Other related posts:

  • » [SAS] Fwd: Finding faint things with star charts - cave8