Polar alignment

Spacegazer (Alex) · #1 06-01-2014, 11:23 AM

Ok so this is my first post

.
I have been reading astronomy forums for a couple of months now, while I decided which telescope to buy (I must say this was quite difficult because the reviews do not always agree). Forum-wise, and for what I read, I thought this was the best southern-hemisphere forum out there.
As for the equipment, I chose the one in my price range and with the least negative reviews (that I found

): a Celestron Advanced VX mount with an 8" Edge HD OTA. I also bought a few Luminos and Omni eyepieces, an LPR filter and T-ring and adapter for my camera.
Now that I've been out a few nights, I'm really happy with it. Goto is very precise when alignment is good and the mount is very stable. I previously had one of those 1000x refractors. Needless to say, I almost lost my interest in astronomy because of this scope.
Anyway, last night I tried for the first time to use the all-star polar alignment. Here's where my luck ran out. It won't work ... or it may just be my ignorance at work. This is what's happening: I go to a star (not near the celestial pole, nor upward or too close to the east or west). Next, the scope moves away and again toward the star and asks me to center it. I do this and press align. This is where the hand controls "syncs" to this star. Then, it says everything is ok to start with polar alignment and asks to press enter. When I do this, the telescope is supposed to move away and then back but not all the way. This is where I'm supposed to move the scope in alt and/or az manually (without the control) to re-center the star.
But in this last step, the mount moves waaay too much and ends up completely somewhere else. The mount is roughly pointing south (at least as precisely as I can do it with a compass), leveled and the latitude is set to my observing site's latitude.
After reading a bit, I found that the hand control calculates the error after the first alignment (not the polar alignment, the other one). This can be displayed in the hand control. When I do this it says the error in polar alignment is 99º in az and like 40º in alt.
This is impossible. I may be a newbie but I can't be missing the south by that much... Maybe I'm forgetting something?
Any help is appreciated.
Sorry for the long post

seeker372011 (Narayan) · #2 06-01-2014, 05:59 PM

Have you checked the location in the Hand Controller? There may be a glitch there?

mithrandir (Andrew) · #3 06-01-2014, 06:46 PM

There are several things you need to have right, or at least almost right, with an equatorial mount. A GPS either built in or attached simplifies much of it.

If you are using a tripod one leg must be pointed towards the pole and the counterweight shaft will be above it.
Do not trust any levels built in to the mount, at least not without testing them with a real spirit level. It doesn't have to be perfectly level but close helps.
You need to know your latitude and longitude. You can get it off many smartphones if you don't have a GPS. Make sure you get the signs right for both lat and long.
You need to know the time. Again your phone will do if you don't have a GPS (exact time is critical for mobile phones to work). When entering the time make sure you get the UTC offset correct for your location. Don't forget DST. I set my mounts to UTC and ignore local time.
The polar axis has to be running north/south. You can get close with a compass and the correct magnetic variation but this can be completely bollixed by any iron objects nearby. The Solar Noon method is more reliable. I found that the pavers around the pool run almost exactly N/S and E/W so the joins get me close enough.
The polar axis has to point at the pole. The scale engraved on the mount should get you close. I have a digital level that I sit on the dovetail.

Once you've got that down pat the scope's alignment routines should get you up and running reasonable quickly.

Spacegazer (Alex) · #4 08-01-2014, 09:10 AM

Thanks Andrew. I'll try to be more precise next time (when the skies clear...).
I'll go buy a bubble level because so far I've been using the compass iPhone app that has something like a level, but not as precise I suspect.
But I still think there may be something wrong with the hand controller as Narayan suggested because, as I said, the error that the thing calculated was quite large...
If things don't improve I'll contact support. Maybe there's an update or something for the hand controller.
When I find a solution I'll post it here in case someone else has the same problem.

Spacegazer (Alex) · #5 13-01-2014, 05:02 AM

Hi again guys. I've been digging a bit more into this. Apparently All Star Polar Alignment is not currently working in the southern hemisphere.
Bummer really. They shouldn't advertise this mount as fit for astrophotography when you can't polar align it (at least with the included tools - the hand control).
That being said, can anyone suggest any other efficient polar alignment method?
I've bee trying to use the iterative polar alignment tool in Astroplanner. I tried it a bit last night after some observing. I didn't take any pictures though. But as its name suggests, it is iterative. So it takes quite a bit of time...
Oh and after getting it really close to alignment (or so Astroplanner said), I reset the mount and tried another sky alignment from scratch. However, I noticed initial estimations were off, much more so than before. So my second question is, aren't these estimations supposed to become better when the mount is polar aligned? Does this mean that while I thought I was aligning I was actually doing the opposite?
Thanks!

SteveInNZ · #6 13-01-2014, 05:56 AM

ASPA has been working for the southern hemisphere for years. I haven't heard that it stopped working recently.
Since you get good gotos after alignment, I'd suspect an error in sign or direction in either your location or the time. Did you turn the RTC on ?
It may pay to do a factory reset, power the mount down, wait a bit and then start over with new location and time settings.

Steve.

Spacegazer (Alex) · #7 14-01-2014, 11:52 AM

Thanks Steve.
I did many factory resets already... Also the RTC is on. It also keeps time between sessions! Something that I had read it didn't do.
Yeah I read that ASPA was not working in the southern hemisphere when it came out, but it was then fixed in the next update. However, I think it isn't working again.
For these tests, I introduced the coordinates manually because I read there was once a problem with the international database.
These are the "symptoms"

:
- Changing the place using the database to any city in the northern hemisphere, using quick align (default alignment, supposing the mount is perfectly polar aligned) and visualizing the polar alignment (error calculated by the HC) shows 0 alt and 0 az, which is logical. Also identifying the closest named star from the home position (aligned pointing at the celestial pole) yields Polaris as the result.
- When the place is set in the southern hemisphere, using quick align and displaying the polar alignment: 90 az/-69 alt. Also identifying the closest named star to the celestial pole still yields polaris! Even after doing a two star sky alignment!

I think this means it is not just ASPA that's not working. Polaris can't be in the southern hemisphere!
I contacted Celestron support. I'll see what they have to say.
Does anyone have a new Celestron mount and is also having trouble??

SteveInNZ · #8 14-01-2014, 06:44 PM

That's certainly odd. I was going to suggest using Quick Align as a diagnosis tool. I use it for the initial alignment. It works well (for me) and is much quicker than messing about with compasses, etc.
Even the 90 az/-69 alt answer doesn't make sense. With a latitude of -34. I'd expect an error of -124 or 56.
Did you try explicitly entering the Lat and Long ?
What version is the firmware in the hand controller and motor control board ?

Steve.

ilife13 (David) · #9 15-01-2014, 01:58 AM

Alex
I feel your pain. I have had a celestron CG5 GT (Nextstar + hand control) mount for nearly 18 months and have been tempted to throw it in my pool on several occasions. I have tried everything to get a polar alignment and failed. Exactly as you describe your problem. You would be wasting your time contacting Celestron, I have on 3 occasions now and supplied information about my setup, location etc. All I get is a tab to their standard polar alignment procedures. They didn't bother to read my enquiry otherwise they would know it wasn't just me. I have read a posting on another site around 12 months ago in my efforts to find an answer. This particular man had exactly the same problem but when he got no joy from Celestron he took it a step further albeit 6 months later. He managed to contact the head software designer for Celestron and his response was that they have admitted a glitch in polar alignment in the southern hemisphere. I have purchased a computer lead to update my hand control and although there are some changes it still won't work. I am seriously thinking of selling mine to purchase something that actually works. I have significantly more patience than the average person and I am sick of it. My next move may be to try and download an older software version as the new one hasn't fixed it. Most people would have given up on astrophotography by now but I am stupidly stubborn and refuse to let it defeat me.

ilife13 (David) · #10 15-01-2014, 02:14 AM

Alex
The posting I mentioned in my reply was actually IIS from January 2013.
The response from Derik (Celestrons' software engineer) was. "This is now a confirmed bug in all versions of the Nexstar+ when operating in the southern hemisphere. He obviously didn't offer a solution so I assume there wasn't one.

David

Spacegazer (Alex) · #11 15-01-2014, 02:12 PM

Thanks David! At least I know it's not just me! And that I'm not going crazy because of missing the south or something like that!
I am a very patient person as well, but since I just got the scope like a month ago, I still have some left

.
However, I think I'll channel it toward some external way of polar alignment, because, after trying it myself, going through every option in the HC (many people say Celestron's HC's are quite complex, but by now I know pretty much every single menu, etc. there is and what it does) and your testimony, it would just be useless to keep losing time trying to find some magical fix.
Besides, I can only go out a couple of nights a week (Saturdays and maybe Fridays) since work takes up almost all my time during working days.
I think I'll stick to this iterative alignment technique in this Astroplanner software and see how it goes... But in the end it depends on the ability of the scope to do a precise sky align and if this is also glitched (which I hope it isn't) it still won't work...
By the way, I haven't received anything from Celestron yet. Just an acknowledgement.
I'll post something when I try in more depth the iterative alignment.
What else have you tried to align yours? Maybe the polar alignment scope? It is still no good for me since the celestial pole is blocked at my main viewing site...

SteveInNZ · #12 16-01-2014, 06:22 AM

If you have a webcam, EQAlign is an excellent drift alignment tool. I use it with my SP mount which just has a simple RA tracking motor.
It suggests which stars to use (but you can pick others) and then when it's done, it tells you use the alt or az adjustment to move the star into the circle on the screen.
It takes about the same amount of time as the 2+4 and ASPA on the Celestron mounts to get an alignment suitable for unguided photography.

Steve.

Spacegazer (Alex) · #13 18-01-2014, 11:57 AM

Thanks Steve. I didn't know that one. I'll try it when I get a webcam which I think will be soon.
Just wanted to post here, in case it's useful for anyone, that Celestron support answered that there is a firmware bug and that ASPA is not working for the southern hemisphere in the Nexstar+ HCs. It is in older ones, but they said those don't have RTC and meridian sweep.
They also said they were working on a fix, but who knows how long that could take...

allan gould · #14 20-01-2014, 12:30 AM

Alignmaster works brilliantly in the southern hemisphere but you will need ASCOM and a laptop connection to implement this.
Allan

Tony_ (Tony) · #15 22-01-2014, 11:07 PM

I have a CG-5 mount (which I don't use anymore) and a CGEM. The ASPA works well on both of them. I use a laser through the polar axis to get a rough alignment (tonight was within 7') then I use the aspa. Apart from Periodic error most nights I get virtually 0 drift over 2-3 hours, then some nights too much drift.
Firstly it is best to use 2 alignment stars - must be west of the meridian in the southern hemisphere. I then use at least 3 calibration stars (usually 4) which must be in east of the meridian. Then do the polar alignment.
If the first alignment star isn't in the finderscope then your initial alignment was too far out (but as long as its not too far out it doesn't matter). Make sure everything is tight before starting the process.
The more precise you have your location set the better.

Regards,
Tony.

mmollerza · #16 06-04-2014, 11:31 PM

I'm in South Africa and recently took the plunge and acquired an AVX mount. I've been coming across this problem too and came across this discussion while googling for a solution. Has there been any development in solving this issue, or should I return the mount and get my money back. Without accurate polar alignment I might as well go back to my clock drive and drift alignment.

wolodo · #17 28-10-2014, 06:56 AM

man , i have the solution for Advanced VX sothern hemispher!!i from chile
use Software NextRemote for ASPA!!!! then turn off , and align 2+4 star align used hand control.....easy!!!!