Nexstar 5 (older non i model) alignment problem
Posted 11 February 2013 - 06:17 PM
I live in Brazil and I have bought a very good condition Nexstar 5 (gray tube not i version). I am trying to align it using the "2 star alignment" method and the stars Castor and Canopus. The alignment process finishes showing the message "Alignment successful". The problem is that when I request the controller to go to an object the scope slew to the object but aims the scope about 1 or 2 degrees below the desired object. When I ask the controller to go to the alignment stars the scope slew to them correctly.
Does anyone know what may be going on? The scope may be defective? Is there any software bug when using it in the Southern hemisphere?
The alignment location is Latitude: 19º 37' 09" S, Longitude: 43º 13' 37" W.
Posted 11 February 2013 - 07:00 PM
I don't have any experience with the southern hemisphere, but I haven't heard of any problems reported on these forums regarding that kind of error in the southern hemisphere only.
Can you provide some more details about what you're doing? When you say the scope is off by 1-2 degrees, is that for all objects regardless of location in the sky? Does the amount of error get worse as you get farther from the alignment stars? Are the problem targets near the zenith or horizon? Also, were either of the alignment stars near the zenith or horizon?
Posted 12 February 2013 - 05:47 AM
Dan is right in as much as it would help to know more of how you are aligning your Nexstar 5. However, perhaps to guide you a little, you should be observing the following fundamentals:
1) Make sure that your Azimuth GoTo Approach is set to Positive. (The Nexstar 8/11GPS and Nexstar 5i/8i require a Negative setting for use in the Southern Hemisphere but NOT the Nexstar 5).
2) Conversely, ensure that your 'scope's Altitude GoTo Approach is set to Negative. (I think you'll find this to be the default setting).
3) Always move the OTA DOWNWARDS to make the required right angle with the mount arm. Precision here is important. To that end, ensure that both the mount is level with the ground and the OTA is at right angles to the mount arm. Use a bubble level for the purpose.
4) Getting to the starting position for a "Two Star Align" with a Nexstar 5, approach North by pressing the RIGHT arrow button. This will minimise drive gear backlash.
5) Using a medium power eyepiece (EP), ensure that you centre each alignment star with the correct movement. In the case of the Nexstar 5, this should be performed using the RIGHT and UP arrow buttons.
6) You will find it easier to centralise the alignment stars if you throw the 'scope out of focus to produce what looks like a doughnut. Alternatively, use a reticle or cross-haired EP to centralise.
7) Choose alignment stars which have a good angular separation between them. (90-135 degrees is considered ideal and do not choose ones below 20 degrees or above 70 degrees in altitude).
Hoping these "basics", specific to the Nexstar 5, help, but as Dan advised, it would also assist if you provided a little more detail as to what you have done and also importantly, what you settings are with particular reference to your Altitude and Azimuth GoTo Approach and to your method of alignment star centralisation.
Posted 12 February 2013 - 01:08 PM