Superwedge setup

[astroturf]

Hi Guys

I've just got in from a nite of frustration, in trying to make sense of polar alignment with my LX90 & Superwedge

Some instructions describe setting the tangental arm to Magnetic north, which had me stumped straight off, How does one detirmine the exact compass point for magnetic north? I had it set to true north & it appeared to be well off the SCP & couldn't be adjusted to it

Any help would be appreciated with this & any other points of interest concerning setup

Cheers
Bryan

[GTB_an_Owl]

Hi Bryan

magnetic north can vary depending on your location

i do believe sydney is 11 or 12 degrees different to true north

someone else will tune in and confirm in what direction - but i think it is east (when your looking south ?)

googling should enlighten you a bit more

geoff

[Ric]

Hi Bryan, if you go to the "Projects & Articles" section there are a lot of helpful articles in the "Beginners section" which will help you get started.

I'm starting out with polar alignment myself and found them very helpful with my understanding of what is going on.

Cheers

[GTB_an_Owl]

try this link

http://www.myastroshop.com.au/guides/polar-align-basic.pdf

geoff

[astroturf]

Thanks Guys
Geoff
that website pretty much spells it out,whilst I was searching for the SCP it felt like I was about 12 deg out

Ric
I thought this was going to be relatively easy & pretty much took that approach, however When you realise that you're all alone without the Goto to find Sigma O. It suddenly becomes not so easy LOL

The article "Polar alignment with a wedge in the southern hemisphere" on this site , is very good (thanks to the author) but didn't go into detail as regards magnetic/true south

Anyway, with this new info I shall test the frustration levels this evening

Cheers
Bryan

[Ric]

Hi Bryan, I also found it a good idea to spend a few nights studying Octans with binoculars, finderscope and then through the eyepieces and relating it back to my star charts.

I now find that I have a good feel for the area and finding that faint little beggar called Sigma not as daunting any more. There are still a few other areas to sort out and polish up in polar aligning but at least one hurdle has been cleared.:D

Cheers

[astroturf]

[quote=Ric;322283]Hi Bryan, I also found it a good idea to spend a few nights studying Octans with binoculars, finderscope and then through the eyepieces and relating it back to my star charts.


Hi Ric
Another nite outside with the Wedge Has proven this to be a very good idea

However My main problem all along has been a dicky compass(Meade )
it points to north about 20 deg to the east when fitted to the wedge but when removed, it points to where it should. as my handheld compass does

Maybe the wedge has become magnetized, any idea's?

After lining everything up with the handheld compass (near the wedge) everything looks right but I can't yet find & identify Sigma O

Tonite, I'm going back to Alt/az & goto, to find the little sucker, stare at it for a while & possibly take some images of it for future reference

Cheers
Bryan

[Ric]

Hi Bryan, forget the Meade compass they are $#*%, take it out and put it back in the box. Sorry I should have mentioned this as well.

I read an article about compass's which said that they are only good for the hemisphere that they are built in. I don't fully understand it myself but it's something to do with the way they are magnetised in line with the Earths field.

I use my Brunton geologists compass which has sighting wires in it, that way I can stand away from the scope and sight it in to magnetic north.

Cheers

[5ash]

Hi Bryan i have an LX90 and 1 star alignment under polar mount gives go to to Sigma Octanis.I use the star map attached for the field of view in both the finder and eyepiece. I try to make the finder view match the main map and then the eyepiece view match the inner map .I have a more detailed version of that .
regards philip:)

[QUOTE=astroturf;322238]Thanks Guys

I thought this was going to be relatively easy & pretty much took that approach, however When you realise that you're all alone without the Goto to find Sigma O.

[astroturf]

Thanks Phillip
I've been studying up on my Star charts & I'm becoming a bit more familiar with the area, That's a good image of the 2 FOV's

Ric
there isn't much wrong with the Meade compass when it's not within the wedge assy. I just have to work out an accurate way of setting the tripod up pointing north, whilst keeping the compass away from it
My reasonable quality handheld compass looses it's bearings in a similar fashion when placed within the wedge

Bryan

[aworley]

Hi Bryan,

Its Alex here..... I just bought a standard wedge for my lx90 8".

I assume you've got true sth sorted ..... that is a really important first step - i don't use the meade compass, i use a handheld...however, once I got it sorted, I put markers (in my case cheap steel plates from bunnings) in the ground and reset on those each night...At bargo last sat night, I didn't have the benefit of the steel plates, but still got polar aligned once I had got a good handle on true south (ie without knowing SCP)

I had lots of trouble getting going, but with the steel plates and WCS it is now quick and accurate. Basically, now I use WCS software to get polar aligned because I couldn't locate SCP and soon it will be blocked by the house.....

I follow this setup...

1. Put mount on steel markers (or at bargo, set south at 12 degrees (can't remember if it is east or west of magnetic south - i will check if you want)
2. Got the wedge level using my own bubble level - the one on the standard meade wedge is useless
3. Level the forks and put OTA in 90 degree position
4. Do a two star align - i use canopus and rigel kent
5. Then use WCS software (reversed for southern viewing - this took a bit of doing, but its easy once you know)
6. I get very accurate polar aligning without using SCP and without knowing up/down/left/right - WCS uses drift alignmment to get accurate alignment. It cost me $36 - the best money i have spent.....

Clear skies
Alex

[astroturf]

Hey Alex
Thanks for your tips
How was Bargo on saturday
I'm not sure what WCS is but it sounds good, maybe you could enlighten me

I did finally have some success after working out the fiasco with the built in compass & I have to agree the metal plates sound like a good idea
I'm thinking of putting concrete pads down (3) in the lawn that are perfectly level, I've found that the tripod legs if extended can slip even when tightened especially with the extra weight in the wedge
some sort of threaded adjustment on the tripod extensions might be a good thing too, I'm still thinking about that one

Cheers
Bryan

p.s. I just found WCS I'll give it a go

[mdgodf]

You can find magnetic north for your location here: http://www.ga.gov.au/oracle/geomag/agrfform.jsp

[JimmyH155]

Hi Guys, I totally agree with your comments re compasses and bubble levels - throw them away. I had same trouble on my Meade. I now use a builders level to get the mount level in both directions, and I obtained a hand-bearing compass from a yacht chandler - not cheap, but it is very accurate. Dont try setting up scope too near any large accumulations of metal (old car bodies etc) this will throw out your compass.
On Australian East coast (Brissie) the magnetic variation is 12 degrees EAST. I think it is fairly similar all down the coast, but check out with Met Bureau. Remember old sailors adage "Variation east, steer least, variation west, steer best. " ie for east variation in Brissie, set compass to read 168 degrees (180 - 12) the compass body will then be pointing due south:D