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Old 24-11-2009, 10:43 AM
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mental4astro (Alexander)
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Having trouble finding objects in your charts?

Hi all,

This is not an original idea, but one adapted from the 'Telrad finder chart' idea.

Finding objects sometimes can be very difficult, like galaxies and planetary nebulae. Doing this from a light polluted area, like Sydney, the challenge is even more so.

You can use DSC's. I don't have such a unit, nor am I looking at getting them. So I'm stuck with charts.

To this end I've made myself a set of "finder rings" scaled to the charts I use. These are circles drawn onto a sheet of acetate film (overhead projector film) which are then placed over the section of the chart I'm following. These circles serve to surround the field of view seen through the finder scope (or scopes) being used.

To get the scale correct, you will need to sit down with your finder (doesn't need to be mounted onto your scope) along with your atlas, another sheet of acetate film & a fine marker pen. Aim your finder at a bright star rich area of the sky, like the tail section of Canis Major or Scorpius. Using the crosshairs for reference, rotate and move your finder until you have two 'brightish' stars which span the whole of the field of view of the finder without moving the finder. Locate these stars in your chart and mark them on the acetate film (with the film over these stars!)

Next task is to measure this distance with a ruler, half it, and you then have the radius of the circle you need to scribe.

I use two charts during my sessions: The Cambridge Star Atlas, and the Asahi charts I found in the 'Beginners' forum. The Cambridge is a good all-round atlas, while the Asahi charts are highly detailed. I also use two finders on my big dob. To this end I've made two sets of "finder rings" to use with each finder.

I've also uploaded a section of sky pertaining to that surrounding the bright galaxy NGC 253 visible at this time of year, to show the surrounding stars through my 7X50 finder, which I would then use to track down this sucker. A mate of mine had been having trouble locating it. This tool may help a little, hopefully, .
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Last edited by mental4astro; 24-11-2009 at 11:24 AM. Reason: clarification
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Old 24-11-2009, 10:24 PM
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troypiggo (Troy)
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Excellent idea. Thanks for sharing.
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Old 25-11-2009, 10:22 PM
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michaellxv (Michael)
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All I need now is a clear night to go out and make the measurements
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Old 26-11-2009, 10:18 AM
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mental4astro (Alexander)
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First clear night in ages here in Sydney, though first quarter. But I had to make a stand to this challenge of finding a few faint fuzzies from home that I hadn't tracked down before! I loaded the big Odyssey II with the 3" Celestron FirstScope finder I made, a couple of EPs & binos in hand.

First target was NGC 1300 & 1404 in Fornax. Found the chart, placed the circle over it, aimed & looked through the eyepiece... BANG, there they where! Dead centre! I was most surprised that I was able to glimpse these two galaxies through this much maligned little FirstScope! From Sydney & first quarter Moon. I've always said that this little scope is really only a rich field scope, at f/4 and with a spherical mirror.

To make sure this was no fluke, I then had a crack at NGC 1549 & 1553 in Dorado. Same procedure, and looking through the EP, again dead centre. What most intrigued me here was the structure that can be seen in these two galaxies. I'd like to have a crack at them from a dark site.

Last was the PN NGC 1360. This one did prove tricky to spot through the eyepiece, not because of lack of tracking it down, it was there, but a very, very faint puff of smokeiness.

Definately keeping these circles as a permanent feature in my kit now!
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Old 26-11-2009, 12:21 PM
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jjjnettie (Jeanette)
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Ingenious.
You could also put a laminating pouch through the laminator instead of using the sheet of acetate film.
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