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So you've bought a big scope, more than likely been taken in by the Dob brigade (we are pretty persuasive ;-) ) and after a couple of sessions in the garden looking at Jupiter, Orion, and the moon you're scratching your head trying to find other targets??! Is that decision to favour a manual 'better' scope over GOTO starting to haunt you? Don't despair, star hopping is about practice and it becomes easy quite quickly. When I started I went through the same contrasting emotions and thought I might of bitten off more than I could chew, when I started star hopping I'd end up wandering off in the wrong direction and spending ages looking at the wrong object. I think one of the most confusing things for the new telescope owners is matching up sky maps with the inverted (and sometimes horizontally) flipped views through the telescope. The 30 min you spend now reading this and setting up Stellarium and learning the technique will make life easier for you (hopefully) in the long run. It will be a little awkward/time consuming the first time while you set everything up, but once that's done it won't need to be done again and this (imo) becomes a very quick and efficient method.

So to star hop easily you'll need the following:

  • Stellarium (Newest version 0.11.4 - download for free)
  • Clear skies
  • Patience
  • Telescope

Method

The method I use is to draw a line in Stellarium (using the angle measure tool - we'll get to that in a min) from the nearest naked eye object to my target I can find through my telescope. I then use the 'Ocular' plugin on Stellarium to simulate exactly what I should be seeing through my EP, I then 'walk' along the drawn line counting off the stars until I get to my target...it's that simple! No more wandering off in the wrong direction! For this demonstration I'll use M42 in Orion as our a target, as it’s something that’s easy to find, but this technique will work for any object

Preparation

The first thing is a one off setup of your 'virtual' scope in Stellarium (if you've already done this then skip onto the next section). In Stellarium go to the 'configuration settings' (or press F2) and select 'plugins', you should see an option for the 'Ocular’ plugin, click on that. This is where you store all the info about your scope and EP's. Make sure you have 'load at startup' selected on the front screen of ocular plugin before we proceed.

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Next we'll input our telescope information, click on 'telescope', in here enter in the specs of your scope, the aperture is the diameter of your mirror, and focal length is how 'long' your scope is (we'll skip over the technical definitions for now). If you haven't a scope or are unsure and want some figures to use, we'll use my Dob as an example test scope.

Aperture – 254 mm

Focal Length – 1200 mm

Make sure you have mirror flip 'vertically' selected and depending on your scope also select 'horizontally', you can easily change the horizontal option if it turns out you don't need it. This is done to ensure the view through the virtual scope is orientated the same as your scope.

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Next we move onto EP's, click on the 'Eyepieces' tab and enter in the information for you EP's in there, if you're unsure what your 'aFOV' (actual field of view) is then Google your EP and a retailer will likely have specifications listed. Entry level plossls and 'kit' EP's tend to have an aFOV of approx. 50-55 degree, you won't go far wrong putting in a value between them if you can't find your EP's aFOV specification. The focal length will be written on the side of your EP, It may be just a number written on its own. List all your EP's into here; it saves time adding them in future. Don’t worry about at this point entering a value for ‘Field Stop’. I tend to name my EP's by the manufacturer and EP size...as before a couple of examples to use if you need:

Name - Skywatcher 38 mm

Focal length - 38

aFOV - 70

Name -Celestron X-Cel Lx 7mm

Focal length - 7

aFOV – 60

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That's all your scope and EP's set up….. still with me?? Go back to the front of the plugins page and make sure the ‘angle measuring’ tool is configured to load at startup.

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Close off Stellarium and reload it up (sometimes it needs to do this to register changes you've made). Now we can finally get onto the star hopping. Bring up M42 on screen, either via the search box (F3) or zoom onto it manually. Zoom out enough that you can see Orion’s Belt. Make sure you have M42 selected by clicking on it, press 'spacebar' to centre the object; do not click on any other object (whatever you click the simulated view will go straight to).

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Now select the 'angle measuring' tool from the bottom task bar:

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'Draw' a line from the nearest bright star that you can see with a naked eye - in this case go for the left star (Alnitak) in Orion’s Belt.

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With your 'real' telescope locate this star through your viewfinder, telrad etc, and using your lowest powered EP (i.e. a 32 mm, 38mm etc...not 5mm!!) get this star in view, focused and central. Back to Stellarium, (making sure M42 is still selected) press Ctrl-O to bring up your 'virtual' scope, you should see it zoomed in on M42, cycle through the eyepiece tab at the top right until you get to the one you're using in your 'real' telescope.

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Now using your keyboard arrow keys 'walk' along the drawn line in Stellarium from M42 until you reach Alnitak, this is your starting star for the real thing.

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Now compare this virtual view with the view through your telescope, you should see the stars all roughly match up in view, if the orientation is wrong bring up your telescope configuration (as detailed earlier) and select/deselect the horizontal or vertical flips as required, after each change shut down and startup Stellarium (once you've got it right you'll never need to do it again), it can be a little trial and error but eventually you'll have everything roughly orientated the same way (I can never get it bang on 100%). If you can see more than appears in the image first check to make sure you have the right EP selected, or go back and increase the aFOV value in increments of 1 degree until matched, again save. If the stars look too bright in Stellarium or there's too many bring up the 'Sky & Viewing' options (F4) and reduce absolute/relative scale options (top left) until you find the closest match, also try and try and get your light pollution level set, start off with a value of around 3 and work from there.

gallery_15857_2308_26055.jpg

Now you are fully configured between scope and Stellarium, the overwhelming majority (i.e. 90%) of what you've just read will not be applicable next time you go out.

Star Hopping

Now all you have to do is walk your way down the line drawn and match up the stars with the view as you go along. It’s that simple!! You can apply this technique to find any object.

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Note:

Stellarium - You will need to deselect the angle measure tool to re-enable dragging of the sky by mouse

Stellarium – Press Ctrl-O to exit out of the ocular view

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So you've bought a big scope, more than likely been taken in by the Dob brigade (we are pretty persuasive ;-) ) and after a couple of sessions in the garden looking at Jupiter, Orion, and the moon you

We've been astronomying for over a year now used stellarium and had no idea you could do such things with it. Fantastic advice. Thank you.

Hey thanks, the oculars setting was pretty confusing on the older verison of Stellarium I had as it was very hit and miss what it saved, it caused no end of confusion and grief!! The night mode is muc

I've been a great advocate of Stellarium for the last couple of years and never knew it had such powerful features, thanks very much.

BTW when I tried to configure the ocular plug-in the way you suggested I didn't get the options when I clicked on ocular in the plug in menu. However by using "Alt+O" a pop up menu appears that includes "Configure Oculars" which I used to add my scope and eyepiece details.

Once again thanks for taking the trouble to document this.

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Make sure you have mirror flip 'vertically' selected and depending on your scope also select 'horizontally', you can easily change the horizontal option if it turns out you don't need it. This is done to ensure the view through the virtual scope is orientated the same as your scope.

On this point, I believe that for a Newt, or a refractor or SCT/Mak used "straight through" both flips should be enabled, which has the same effect as a 180 degree rotation. For a refractor or SCT/Mak used with a star diagonal it is only horizontal flip that's wanted, not vertical (assuming the eyepiece is pointing upwards).

@Astro Imp: The controls in the top right don't always appear. There's an option in the Ocular plugin config to have them or not.

Edited by cantab
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I've been a great advocate of Stellarium for the last couple of years and never knew it had such powerful features, thanks very much.

BTW when I tried to configure the ocular plug-in the way you suggested I didn't get the options when I clicked on ocular in the plug in menu. However by using "Alt+O" a pop up menu appears that includes "Configure Oculars" which I used to add my scope and eyepiece details.

Once again thanks for taking the trouble to document this.

Yes that's right, I think it's the same on all versions of Stellarium, you just click configure and go through to the Telescope/EP area.

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On this point, I believe that for a Newt, or a refractor or SCT/Mak used "straight through" both flips should be enabled, which has the same effect as a 180 degree rotation. For a refractor or SCT/Mak used with a star diagonal it is only horizontal flip that's wanted, not vertical (assuming the eyepiece is pointing upwards).

@Astro Imp: The controls in the top right don't always appear. There's an option in the Ocular plugin config to have them or not.

I get so confused with all the flips!! Mine's probably wrong but it's what lines up with what I see through the scope close enough. I think because the night sky rotates is always tricky to get it orientated bang on but you can get it within a couple of degrees after fiddling with them.

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@Astro Imp: The controls in the top right don't always appear. There's an option in the Ocular plugin config to have them or not.

s

They're not there on the front screens in ocular view on earlier versions of Stellarium but in the latest version 0.11.4 they're added in.

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s

They're not there on the front screens in ocular view on earlier versions of Stellarium but in the latest version 0.11.4 they're added in.

I uploaded version 0.11.4 to make sure I had the latest version before I started trying this and it didn't have the features you describe but I got there in the end including the controls in the top right.

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Alan...make sure it's the right version of stellarium thats loading up, you'll probably need to delete the old one off your system. When I installed the new version my desktop shortcut kept on opening up the old version until I deleted it from my system. If you've installed a new version and the old one is deleted you'll need to put in yr GPS coordinates. Only other thing I can think if its not that, is making sure all the boxes are ticked for it to load at startup.

Hope this helps

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How about "Sod it all, use a goto." :grin: :grin: :grin:

I think with a lot of new owners alignment issues it can result in 'go near' rather than GOTO, it's quite easy to use this technique with a tracking scope, if anything it'll make it even easier as the objects won't move whilst your looking between scope and screen. A lot of GOTO users can get stuck for objects to go off hunting once they're done with the Messier list etc, it's win win.

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Being a star hopper for many years, I do agree that your method is a good one except for two faults. First, to what magnitude stars do you count? Observing conditions may not be what the program shows. Second, you have to take the PC out with you when using the method or maybe writing down the counts of stars as you hop with the scope?

Though your method is a good one, I would still advise observers to get a good star atlas (several are available for free on line and printable such as this site) then picking the LP EP you will use, do an actual FOV measurement on a star near the celestial equator by letting the star drift across the FOV and timing (in seconds) its passage (across the center of the FOV). Take this number and divide by 240. the answer is your EPs actual FOV in degrees.

Then, using a circle template or compass, draw FOVs from the pilot star to the object on the atlas page.

The only problem (to get used to) is practicing moving your FOV in the right direction from the pilot star, as your method does as well as mine.

The main difference between the two methods is with mine, only a single atlas page (with several star hops on it) has to be taken outside. And NO chance of a PC or other app crashing or experiencing other electronic malfunctions.

But I applaude your efforts in this effort to promote star hopping, which skill every observer should have under his/her belt :grin:

Edited by Mr Q
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