Viewing objects using azimuth and alt

[BryansBelt]

Sorry if this has been answered somewhere, but I couldn't find anything. I am very new to telescoping and am trying to understand the "azimuth" use. Forgive my stupidity! If my scope is polar aligned north and Saturn is currently at 33 alt and 189 az, to find it I would turn my scope's azimuth dial which rotates the scope and put it at 189. Correct? Then as far as altitude goes, I've read a bit about using your hand, etc to find altitude.

Again, sorry if this is way basic for everyone, but dark is coming and I'm anxious to find some things tonight!!

[Gazabone]

Hi,

Not sure what setting circles you have on your mount. I have recently modified my Dobsonian to use alt az coordinates and I'm very pleased to say I'm using them very successfully. There was a very good article in S@N mag a couple months ago.

My "setting circles" are effectively a compass rose in the base and a magnetic inclinometer on the OTA. How I use them is to centre a bright star near my "faint target", dial in the azimuth coordinate in the base which I take from stellarium and then move the OTA until the pointer is pointing to the correct coordinate on the compass rose and raise/lower the scope until the inclinometer reads the desired altitude. I tend not to bother checking the altitude of my bright reference star, it just wastes time, especially as the targets move quite quickly.

The key is to ensure your mount is level to start with. In theory, once you've calibrated the azimuth once, it shouldn't need changing until you move the mount but I find if I rotate in azimuth more than about 30 degrees, it benefits from re calibrating (an easy 15 second job so not an issue). If you have a "manual" altitude setting circle, you'll need to calibrate that to your bright reference star too (or invest in a digital inclinometer with a magnetic base!)

The other hint I would give is to not hang around as you're dialling in or moving the scope to your faint target. Someone very kindly suggested I set stellarium 2 minutes fast but personally I find I'm more accurate with keeping it to real time.

Take a look at stellarium, it's useful to see how quickly objects move depending whereabouts in the sky they are; something close to NCP hardly moves at all but something low on the South horizon goes like the clappers. An eq mount copes with this automatically but alt az coordinates don't.

Hope you get it sorted, it's a lovely easy way to find targets, personally I think you'll learn the sky more quickly than using a goto set up, the only thing is you will need to use stellarium or similar so you know what the correct coordinates are at the precise time you need them.

[BeanerSA]

I'm confused too. What sort of telescope do you have? Is it a dobsonian, or something on an equatorial mount?

[BryansBelt]

Sorry. I thought my scope had a 360 deg dial to rotate the entire scope, but it doesn't. I have an Orion 130ST. Brand new to using one and just trying to figure it out.

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[Dave In Vermont]

No need to apologize! Answering people's questions is what SGL is all about for the greater part. Please feel free to ask away!

+1 on Stellarium. Stellarium is a very large planetarium/star-charting software-program. And one of the very best (many would say the best) available. Set your location and time-zone, and it will show you realistic charts of what's up in your sky. I suggest downloading the large instruction manual - as well as viewing the Wiki instruction-guide- and the program itself. It has so many features that I'm always finding a new one or three. And it's 100% FREE.

Here you go:

http://www.stellarium.org/

And the Wiki instruction guide:

http://www.stellarium.org/wiki/index.php/Stellarium_User_Guide

And one that's not as up-to-date but can be downloaded to your computer:

http://barry.sarcasmogerdes.com/stellarium/stellarium_user_guide-new.pdf

So take your time and relax. Soon you'll know the sky and get some real use from your scope. One caveat though: Astronomy is addictive!

Enjoy,

Dave

[BeanerSA]

Sorry. I thought my scope had a 360 deg dial to rotate the entire scope, but it doesn't. I have an Orion 130ST. Brand new to using one and just trying to figure it out.

In theory, you would actually want to use the values of RA (Right Ascension) and Dec (Declination) with your equatorial mount. Any star chart or book will have celestial coordinates for sky objects listed as RA/Dec. Then you would take those values, and use your setting circles to point the scope towards the object you are looking for.

The reality is, that setting circles on low end mounts, are next to useless, and star hopping is a much better way to find your object, and then you would use your slow motion controls to keep the object in your eyepiece.

This video explains the problem of setting circles nicely.

Educate yourself a bit by having a look at some of the Eyes On The Sky introductory videos

https://www.youtube.com/user/eyesontheskyDOTcom

[michael.h.f.wilkinson]

+1 for star hopping. Even in a slightly more upmarket mount like the Vixen Great Polaris I have, getting the setting circles to work properly is such a pain I have never bothered with them. I just use a good finder scope and star hop. It has bagged me over 800 deep sky objects to date (I have been stargazing for a long time), so it can't be far wrong

[ronin]

I think this is a correct quick explanation.

If the mount is EQ (Sounds like it is not) then you would rotate the setting circles to read a value that is dependant on both your location and the time, then point the scope to the RA/Dec of the object. Getting the circles to the correct position/value for your location is a bit of a black art.

For Alt/Az I believe you set the Values of 0 = horizontal and South and the other to vertical or Azimuth.

You then need the Alt/Az of the object at that time and for your location and aim the scope at those corodinates. Something like Stellarium supplies these.

On an EQ the RA+Dec of the object remains constant hower the circle itself has to rotate dependant on the time, on the Alt/Az the circles remain fixed but the position of the object is constantly moving.

As mentioned in general the circles are not overly accurate, however they do direct you to the correct area of the sky within reason. I suppose that they are computer generated and printed items are more accurate then we give them credance for. The biggest aspect is setting them up correct and knowing what to do.