Having trouble making accurate alignments?

[ILoveKnowledge]

Hi all! I have a Celestron Nexstar 8SE telescope and I even bought the GPS unit for it! For some reason with deep space objects away from the immediate planets, I have trouble accurately centering the three stars during the alignment procedure and while near space objects such as the planets work well with the "GoTo" hand controller, the deep space objects always seem to be slightly off. Do you have any tips or hints on what I should do? Also, if the objects are slightly off, what is the best way to find the objects? Use a star map? I was hoping that with my GPS skysync unit my alignments would be completely on target. It is a little frustrating. All tips and hints would be highly appreciated.

Thanks in advance!

[DirkSteele]

A GoTo mount lives and dies by the accuracy of the initial star alignment so it is crucial that you centre those stars as best you can. When the scope is roughly aligned on one of the stars, reduce the slewing speed right down so when you use the arrow keys on the hand control you can gently move the stars to the very centre of the field. When you say the "targets are sligtly off" what do you mean? The reality of most GoTo mounts is that they will place the object of interest in a low power eyepiece, but not always smack bang in the middle of field of view, and certainly not if you are using one with a narrow field of view. As a personal point (though I am using an older Nexstar 11 GPS) I tend to favour the 2 star alignment process over the 3 star so you might look to try that as well.

In case you are unfamiliar with how to calculate magnification and field of view, the following formula will help you. Generally when I slew from one object to another, I will use an eyepiece with at least 0.8^o field of view. Especially if I am moving from one side of the sky to the other, rather than objects that are near to each other.

Magnification = Telescope focal length / eyepiece focal length (your telescope has a focal length of 2032mm). So in your scope that 81x magnification with the supplied eyepiece.

Field of View = (eyepiece field stop diameter / Telescope focal length) x 57.3 OR Apparent Field of View of Eyepiece / Magnification.

The field stop diameter or apparent field of view of the eyepiece that came with your scope may well be included in the instruction manual. I cannot be sure but I assume it is a regular plossl eyepiece which typically have a 50^o apparent field of view, so in you scope it will give a true field of view of 0.61⁰. The reality is it probably should be enough but if you don't have any other eyepieces you might want to consider an investment in at least a couple more (one high power for planets and one lower power than the one supplied with the 8SE).

Clear skies,

Matthew

[Tom123]

I agree - initial alignment is king.

I use a widefield eyepiece (hyperion 21mm) and a illuminated reticule eyepiece (I have a Meade Astrometric, skywatcher do far cheapers ones) for my alignment procedure. Find the star with the widefield, then refine with the reticle (depending on what i'm doing i use 1-point or 3-point alignment but that's with a heq5 not a nexstar). Usually gets the object into the fov of my hyperion or camera. But then again, if you're viewing DSOs you don't necessarily want the object dead centre anyway

[earth titan]

As is cone error!

[Carbon]

I find it a lot easier to center de-focused stars in the eye piece during the alignment procedure.

[alan potts]

I have the LX 200 12 inch and I don't aways get objects in the exact center, I think that is asking a bit much, I am happy with them being in the field of view at Mag x80. I do believe they get better as the evening goes on, it's almost as if they learn after you have made corrections.

Alan.

[tingting44]

i like the sound of the illuminated recticile eye piece!!! as with my eye pieces i never really know where dead center is, and just press ok when i think its dead center lol, i have to get one of these illuminated recticile eye pieces i think, AWSOME! i am quite new to this but think i have found a hobby for life

[ILoveKnowledge]

thx for the replies! I just ordered a "Meade MA 12mm Illuminated Reticle Astrometric eyepiece 1.25 Inch Wireless" and should receive it in the next couple of days and let you know how it goes! Thanks so much for all the tips and advice!

[erigby]

I'm new to Astronomy and new to the forum, I bought my 8SE a couple of weeks ago but have only had accessories 2 days including the skysync. As stated i'm new to this but i'll give a few pointers on what i've found so far:

Firstly I noticed the skysync chord easily wraps around the mount when operating the scope so the first think I did was take the longer strap and wrap it around the fork arm rather than the leg so the skysync goes with the scope, this way you can rotate your scope 360deg all day, i'll come up with a more permanent solution later.

Align your finderscope accurately on a distant land based object, I used a nearby obstuction light on a nearby skyscraper, these are easy to identify as they flash but are very small to help with accurate alignment. Spend time doing this it pays off, my starpointer has been spot on everytime up to now.

For aligning i'm fortunate enough to have an iphone with the starwalk app, I use this to find suitable stars to use the 2 star align (Not Auto 2 star) and manually enter the name of the stars i'm aligning.

When fine tuning the star align, always move to each star in the same direction i.e right and down for the final alignment of both stars, this will help eliminate offset due to backlash in the gears. Also leave the star out of focus, this gives you a bigger object to center. I have a 8-24mm zoom lens which is also useful as you can locate the star then zoom in to make it as big as possible to centre.

I noticed after a bit of use it seems to go out of sync, all I do here is turn the unit off and on and restart the alignment process. Although its annoying it gives you practice doing the alignment, i'm just hopeing the consistancy gets better over time.

I've got all the gear required to mount a camera now and am just waiting on my D5100, hopefully ther'll be a good pic in the top left soon.