Tuesday, May 19, 2015

How to find stuff without GOTO - Starhopping

Star Hopping  (Not Star Hoping!)

So you bought a manual scope to give you more aperture.  But now you have to learn how to point it to actually find stuff to see.  Where do you start?

First you'll need some good star maps.  See my other article -  Star Map Blog

Update 12/2022

I wrote an app to help teach the skill of star hopping!


You need to learn some of the major constellations to get yourself oriented in the sky.  A planisphere can really help with that.  You turn the wheel until it matches the current date/time and it shows you the constellations and brighter stars that are visible.


Some people take the planisphere out and spend time learning the night sky to that level of detail, others just jump right in to trying to locate things and use the planisphere to get started.  That choice is up to you.

Now you need to locate the object you want to see on your starmap.
Say you want to find M57, the Ring Nebula, in the constellation Vega.

Here's the star chart from freestarcharts.com:

M57 is a planetary nebula in the constellation Lyra.   Vega is a very bright star (5th brightest in the night sky) and so makes an easy starting point.

NOTE: The first thing to do (and the thing I did NOT know to do when starting out) is to get your chart aligned so that the orientation of the stars matches the view in your finder scope.  The triangle of stars near Vega make an easy target for this.  Turn your chart until the triangle of stars matches up with your view in the eyepiece.

Hopefully you have a RACI finder (Right Angle Correct Image).  If you do, the view on the chart will match the view in your finder scope.  You probably have around a 5° field of view in your finder, so you get an idea of how many stars you should see based on the scale of degrees on the right side of the border of the star chart above.   Many people actually make a wire ring or clear plastic disk the size of their finder scope FOV so they can lay it on paper to visualize what the finder should show.  Or if you are using electronic charts, you can make a circle that matches your finder or even eyepiece sizes.

If you don't have a RACI, or are looking through the eyepiece and are using paper charts, then you'll have to do the mental gymnastics of flipping the charts.   Look up which way it flips for your type of scope (as refractors, CATs and newtonians/dobsonians all have a different view).  If you're using electronic charts, you should be able to flip the star chart display itself.



Now that you have your star chart aligned you should be able to get oriented between your finder and your chart.   Now look for patterns of stars to help you on your path to your target.  I realize that this one is pretty darn simple, but don't rush it.  Learn to see the patterns and follow along.

I find a pattern of stars and move the scope until I get them near the edge of my finder, then look for the next set.  For instance the star at the bottom left of the triangle with the star Vega (in the upper right) has 2 other stars forming a smaller triangle.



NOTE: Another skill that comes with time is getting used to matching up the finder stars to the chart stars.   Depending on your chart, finder, light pollution, transparency, etc the stars will not match up exactly, so you have to learn which stars are "important" and which ones to ignore.   Trying to find the brighter stars and ignoring the rest will help.

Now if you put that triangle of stars on the edge of your finder moving away from Vega, you should find the bright star Sheliak.  Now you're almost there.  Move the center of your finder 1/3 of the way between Sheliak and Sulafat and switch to your eyepiece.  You'll want a mid magnification eyepiece as the ring nebula is rather small and you should see a "fuzzy star" in the eyepiece.   Center it and up the magnification and you're there!

NOTE:  For practice after enjoying the view for a few minutes, I go back to my starter star and do the hop again.   Now that I'm oriented and know the route better, it's much easier the 2nd time and reinforces the skills and helps the learning process.

Trainer: I made a web app to help in starhop training.   Use the information above and see if you can make the hops needed to get the DSO in view!

StarHop Trainer

Conclusion

Star Hopping is a skill.   It takes a while to develop.   It will be frustrating at times for sure, but it gets easier with time and practice.   To get up to speed quicker, take your time and figure out the hops and the patterns, even if you can "get to the target" quicker.   Then repeat the star hopping one or more times after you've had your first view.   That reinforces the skills much quicker than hopping to a new target.   After a few months of doing that, I was pretty confident.   Now after 2 years, I can find things accurately and confidently, including things like faint comets, which aren't even on the charts.
Posted by at No comments:
Subscribe to: Posts (Atom)