Polar alignment of Celestron Nexstar SE

roboh (Mark) · #1 31-07-2010, 09:50 PM

G'day everybody,i'm new to all this and i wanted to ask anyone about polar alignment on a Celestron Nexstar SE.They tell you how to do it in the manual but its writen for the northern hemisphere and (maybe i'm really stupid or something) i just cant seem to get it right for here in Melbourne.The scope is good but i wanna do some astrophotography and i'm still getting a lot of drift.Can anyone help please,i'd really appreciate it.

renormalised (Carl) · #2 31-07-2010, 10:01 PM

Not really the sort of cope to do anything by the way of astrophotography accept for shots of the Moon and the planets. Unless you have it on an EQ mount.

roboh (Mark) · #3 31-07-2010, 10:17 PM

As i said,i'm just a beginner and i wanna use what i have at the moment.I've taken some pretty good shots unguided but i'd like to take some longer exposures thats why i wanna know how to polar align it.

renormalised (Carl) · #4 31-07-2010, 10:32 PM

If you want to polar align it, you can't because the mount that you have it on is an alt-az mount. It can track in altitude (declination if you will) but not in right ascension, which means it can't follow an object across the sky in sync with the Earth's rotation. That's why if you try and go for longer than 30secs to a minute with any exposures, you will see the stars in your pictures begin to rotate. That is due to those stars moving in RA across the line of sight of your scope. In order to be able to take long exposure shots, you need an EQ or equatorial mount, which will also track the stars in RA, allowing you to lock onto a star and follow it across the sky in sync with the Earth's rotation.

The Moon and the planets, because they're bright, can be imaged quite quickly, without any trailing occurring. Having your scope on an alt-az mount in this case doesn't really matter. But to try and get a photo of anything else but the very brightest of DSO's (Deep Sky Objects) will only result in disappointment. That's why an EQ mount is essential for that type of photography.

The only way you could get around it would be to buy a field derotator. They're not cheap and unless they're top quality you will not be able to run exposures for more than a couple of minutes at a time. They need to be very accurate and your mount needs to be accurate also in its pointing ability.

roboh (Mark) · #5 31-07-2010, 10:36 PM

ok,thanx mate,it says in the manual that you can polar align it for astrophotography,i'm just doing something wrong.

MikeyB (Michael) · #6 31-07-2010, 11:33 PM

Hi, Mark - welcome to IIS.

The method you want is termed "EQ North/South Alignment" in Michael Swanson's excellent but somewhat outdated The NexStar User's Guide book. If you PM me your email address, I'll send you a scan of the relevant couple of pages.

First thing is, you need a wedge - does your mount have this built-in? If not, they can be bought separately for $399 for the 6 & 8SE from Andrews.

There's also an online video here: Polar Alignment for Wedge-Mounted Scopes

renormalised (Carl) · #7 31-07-2010, 11:43 PM

Or a wedge...yeah. Late at night...should've thought of that as well

Either way, EQ mounted.

roboh (Mark) · #8 01-08-2010, 12:02 AM

thanx everybody for your help,its much appreciated but now i have another problem,how do i find the south celestial pole? we don't have a clear star like they do in the northern hemisphere but theres gotta be a way

LeeSMaz (Lee) · #9 09-08-2010, 04:09 PM

Have a skywatcher mak127 goto-az.

Tracking is an issue, trying to work out.
Else will connect to the laptop for better
tracking.

Just need a wedge. 33 degrees or so.

Cheers.
Lee.

Allan_L (Allan) · #10 13-08-2010, 12:12 AM

Quote:

Originally Posted by roboh

G'day everybody,i'm new to all this and i wanted to ask anyone about polar alignment on a Celestron Nexstar SE.They tell you how to do it in the manual but its writen for the northern hemisphere and (maybe i'm really stupid or something) i just cant seem to get it right for here in Melbourne.The scope is good but i wanna do some astrophotography and i'm still getting a lot of drift.Can anyone help please,i'd really appreciate it.

Hi Roboh, or Mark,

Is your scope a Nexstar 4 SE ?

Because they DO have a equatorial wedge builtinto the standard tripod.
If this is the case, most of the forgoing posts are irrelevent.

I do have one, and I have polar aligned it, and Ican share your pain, it is very counter intuitive. I actually changed the direction it was pointing four times I think during the process before getting it right.

And when you do get it right, it works quite well.
But be prepared for anyone who sees it to be telling you you have it pointing the wrong way, because it looks to be.

If your nexstar SE is a 5, 6, or 8, then I think you need to buy the optional wedge as mentioned earlier. And I have been told a de-rotator will not work on a Celestron alt az goto.

Depending on your answer, I will continue, after reminding myself how I finally did it. But I do recall that it did not require finding south celestial pole, as the computer worked that out from the two or three star alignment process. and it was very accurate.

roboh (Mark) · #11 09-10-2010, 01:27 AM

Thanx Allan,yeah,its the 4SE with the built in wedge.I do everything the the manual tells me to but when it comes time to do a wedge align there is no wedge align in the HC menu but it says its there in the manual.I have the latest firmware upgrade but its still not there.Any tips would be handy,Thanx

MikeyB (Michael) · #12 09-10-2010, 09:06 PM

If your manual is the 2006 version (check the back cover), later upgrades to the hand control software have replaced Wedge Align with All-Star Polar Alignment. See the Hand Control Version 4 Users Guide for info.

roboh (Mark) · #13 10-10-2010, 07:38 PM

Thanx for that Mickey,i wondered what i was doing wrong and they gave me the wrong manual(slaps head).