Wedge alignment

Hi Guys,
Im engaged in the near impossible task of trying to solo wedge align a 11 inch celestron nexstar GPS.
I was wondering had anyone attempted this before that could give me some tips. I know wedge aligns are a
poor and frustrating substitute for a polar mount but alas funds dont stretch that way at present
The instructions that came with the scope dont seem to apply anymore since I upgraded the firmware to 4.40
Here is my method at present:

1: Set up scope with wedge in place. Adjust wedge to 53 degrees latitude.(no real indicator on wedge is its 53 +/- 5 degrees)
2: Aim roughly at Polaris with one tripod leg pointing at polaris
3: Level wedge so bubble is in center of level
4: Power on scope and select EQ North align
5: Match Alt indicators on fork limbs
6: Find meridian by rotating scope 360 clockwise. (this is a pretty rough guess all things considered, does it matter much ?)
7: Perform EQ auto align, select and align on 2 stars.

Now this method gives a rough and ready alignment and tracking. It doesnt point exactly at anything but its never too far off. When left alone things stay roughly centred for 10 minutes or so. What should the next step be ? Should I ask it to goto a known star in the south say, then perform fine adjustments to centre that star using the wedge and then realign it ? Or should I go straight to drift aligning ? I had a quick go with drift aligning the last night but without fine controls (thats another kit - thank you celestron ! ) it looks like its going to be impossible. I am in the process of trying to order the fine control kit off the internet but in the mean time Id like to have the best alignment methods straight in my head before heading out. I have some parts for autoguiding ready - a meade dsi auto guider, losmandy rings and counterweights but Im trying to source a cheap refractor. I assume drift aligning has to be near perfect for autoguiding to help ? Thanks

Its been a while since I polar aligned my wedged alt-az mount but I have a vague recollection of drift alignment being about the only way of getting good results. But, if you are moving the telescope at all, you'll need to go though the whole process each night. That said, once you have a few under your belt, it becomes easier and quicker.

I've never autoguided but my understanding that precise polar alignment is *not* critical - but it helps of course.

I don't know anough about the Nexsatr to comment on your steps I'm afraid...

FWIW

Dave

I got a wedge recently for my 9.25 celestron, but haven't tried to get it accurately polar aligned yet.

If you have things centered for 10 minutes or so thats pretty good, that's better than mine so far certainly! One thing that was confusing me with the Nexstar eq alignment process is that it's not clear (to me anyway!) whether once aligned the Dec motor is still compensating for poor alignment. What I haven't managed to find in the Nexstar menus is a "Don't try and align, just turn the RA motor on" option.

A friend suggested that for accurate drift alignment I should try using a webcam and phd ( www.stark-labs.com/phdguiding.html ) to determine the drift. I hope to try that some night soon, but first I need to work out how to ensure that just the RA motor is running. Online references not matching with more recent firmware doesn't help matters.

Cheers,
~Al

Since it was clear(ish) tonight I tried aligning the Celestron way. At the end Jupiter was still in the crosshairs of a 12mm eyepiece after 20minutes - granted not the same bit of Jupiter but still.

The process I used was as follows, but there are several variations online suggesting where the alignment stars should be in the sky.
1. Set up the wedge and tripod roughly polar aligned.
2. Perform a 2 star eq align.
3. My second alignment star happened to be in the south around the celestial equator. If your's isn't then goto one that is, hit Identify, and then the nextar should know what you are looking at for the next step.
4. Go to the main menu and hit the Align Button.
5. Scroll till you get to 'Polar Align' and select that.
6. Select Mount align and follow the instructions.
- Basically it will ask you to center the star using the hand controller first. Then it will slew to where it thinks the star should be and you use the alt & az controls _on the wedge_ (not the hand controls) to center the star in the eyepiece.

It was starting to cloud over at that point, and my DIY dew heater wasn't able to keep up with the frost that was starting to form on the corrector plate so I'll try phd another night!

Cheers,
~Al

Hi Guys, thanks for getting back to me.
I have managed to get a latitude adjuster in place so can now adjust the latitude a bit. Thanks albertw,
Unfortunately my handset does not have an identify button and the software is old so I dont think it has the polar
align command. The handset is also as upgraded as it can be, as far as I know that particular version of the handset
cannot be upgraded anymore When I have 2 star align done and I press align all I get is replace X alignment star.
But having said that If I do the 2 star align and send it to a target - andromeda say, it near centers it anyway. Should
I then adjust the screws to centre it and not realign or centre a target - Deneb perhaps and then realign ? I have
a starshoot autoguider. I just realised the last night that its own autoguider function is dodgy and doesnt work. So
I am trying a shoestring USB guider which moves the scope a bit anyway. New plan is:

1: Get the 2 star align working
2: Perform manual drift align using an illuminated crosspiece
3: Use autoguider with USB guiding
4: Hope for the best.

Will see how that works. Let me know how you get on with your set up.

Hi,
I've owned and used a wedge for the past 13 years with my scope in a dome, its a Meade not a Celestron so I cant be of any help with your scopes menus, but
general wedge alignment is universal between scopes,

First thing you do is make absolute sure that the tripod/mount is level, no mount can be truly polar aligned if its not level..
2, placing the scope on the mount, point the scope parallel, as exact as you can to the scopes forks at a rough polar position, there is a dial on my declination axis that tells me the tube is at 90 degrees (although I'd never absolutely trust it), don't know if your scope has that.
3, If you have a mirror lock on your scope, engage it.
4, Put in an eyepiece and using only the latitude and longitude controls on the wedge, point the scope (looking through the scopes eyepiece with a good map\starrynight) at your best estimation of there the pole is.
5, now rotate the scope in RA manually and see if the FOV rotates correctly, rotation should be centered in the FOV, if it isn't then goto step 6, otherwise goto step 7,

6, This is where things could become difficult depending on whats going on. It could mean the scope is not perfectly parallel to the forks, Adjust the declination of the scope and longitude\latitude (to recenter to the pole) til you get as centered a rotation as you can in the FOV. If you cant lock the primary mirror, then mirror flop could make it impossible to get this exactly right and a best approximation is the best you'll be able to do (cos the mirror could move shift due to flop as you rotate the RA axis manually). Also, a loose secondary could also thwart you here aswell in the same manner. If your OTA is not sitting perfectly square in its forks, then you'll never get polar align exact.

7, That's it, your mount is as polar aligned as your gonna get it without using drift methods to adjust. Run your scope star alignment procedure you have in the hand controller. Most controller software can compensate for a slightly off polar alignment situation, so dont spend half the night getting an exact polar alignment unless you have a reason for it.

If you're doing only observing, then a wedge is really not necessary and will only add to your workload of setting up the scope and makes it more vulnerable to wind/vibration, I'd only bother if imaging or in a permanent setup tbh.

Hope this helps