How can u Polar Align when u can't see the sky?

[Robert_T]

Sorry, if you're looking for answers so am I.

I have an Autostar GoTo LXD75 mount and a backyard that allows no view of either east or western horizon below about 60deg and southern and northern horizon below around 40deg. How can I polar align?

Yes, I know the obvious one, get off my fat you know what and move, but I'm looking for something else. From what I've read drift aligning really needs stars near the horizon as well as straight up?

Would a GPS help? Maybe a polar aligment dance, hell at this stage I'll try anything

[JohnH]

Well a compas will help, that and having a level mount with the latitude accurately set. This will help you get close. As you have a autostar goto mount you can the use the iterative goto method:

http://www.covingtoninnovations.com/astro/iterating.pdf

That is written for N hemisphere of course, use a bright start as close as you can to the S.Pole as your ref point in place of Polaris.

Once you have a good alignment park you scope, mark the tripod leg positions and your ALT/AZ settings. Next session put the tripod in the same spot, align all your marks and off you go...

[[1ponders] (Paul)]

Get in contact with Sharnbrook (Mike) he won a DIY section at astrofest one year with an amazing little invention for polar aligning during the day using the sun. You need to have access to MS Excel for his calculations but from memory his technique was very accurate.

Alternatively get a piece of dowel about 1 meter long and insert it into the polar alignment scope tube (assuming you don't have a polar alignment scope). It will need to go all the way through so you will need to cut a "bung" with a hole dead center to fit the dowl, at the "front" end of the RA Axis. Try to get it as orthagonal as possible to the RA axis. Now cut a right angle triangle out of 12 mm ply with one angle equal to your latitude. Place this on your dowel with "your angle" towards the top, and put a level on top. Adjust altitude until level is...well..level

Next get your compass and use the dowel as an extension to the RA axis to line your compass up on. 11.5 deg east of magnetic south is what you want. Then check your altitude again.

It helps if you tripod head is already level, but this really isn't essential.

If you do a couple of iterations of checking elevation and azimuth this way you can get pretty damn close. Try to get your triangle as accurate as possible. Ply may not be the best but it's cheap, if you have a more accurate material go for it.

Once you have this setup you should be close enough for autoguiding to deal with the worst of it.

[Zuts]

Hi,

That sounds like my backyard.

(1) To polar align the ra axis you dont point straightup, you point at the interesection of the meridian and the celestial equator. Basically from the home position rotate the EQ head 90 degrees left so it is horizonal. Then rotate the scope so it is a right angles to the eq head and pointing north.

A few degrees either way to find a star is fine. Your backyard should allow this.

(2) Usually you would do the dec axis by finding an east or west star about 20 degrees above the horizon. 60 degrees may be too much, but if you get the ra axis right then you should still see some drift due to dec error and can correct for this.

(3) Basically you have my problem. Even after polar aligning i can rarely do a 2 or 3 star align as all the stars a obscured by trees. Even if i could there are so many trees there is nothing interesting to take a photo of. Of course if you dont want to take a photo you really dont need a good polar alignment. A rough one will do followed by a two star align.

(4) Anyway, I just use my backyard to pactice things like drift alignment, guiding, new software etc. Then when it all made sense I went out to the local park where at least i could see things.

The diagrams here really helped me get started http://www.asignobservatory.com/driftalignment.aspx

Cheers
Paul

[Robert_T]

[quote='[1ponders];328858']

Alternatively get a piece of dowel about 1 meter long and insert it into the polar alignment scope tube (assuming you don't have a polar alignment scope). It will need to go all the way through so you will need to cut a "bung" with a hole dead center to fit the dowl, at the "front" end of the RA Axis. Try to get it as orthagonal as possible to the RA axis. Now cut a right angle triangle out of 12 mm ply with one angle equal to your latitude. Place this on your dowel with "your angle" towards the top, and put a level on top. Adjust altitude until level is...well..level

Next get your compass and use the dowel as an extension to the RA axis to line your compass up on. 11.5 deg east of magnetic south is what you want. Then check your altitude again.

It helps if you tripod head is already level, but this really isn't essential.
quote]

Thanks Paul, this is nicely "agricultural" and so makes good sense to me. I do have a poar alignment scope, but I can probably pull that out for all the good it does me. I'll give this a go.

Might be worth then combining with the Goto technique that John (thanks too John) mentions below

[Robert_T]

thanks other Paul, that's a great link. Sounds like i should at least be able to drift align my RA from here. nice one

Originally Posted by Zuts

Hi,

That sounds like my backyard.

(1) To polar align the ra axis you dont point straightup, you point at the interesection of the meridian and the celestial equator. Basically from the home position rotate the EQ head 90 degrees left so it is horizonal. Then rotate the scope so it is a right angles to the eq head and pointing north.

A few degrees either way to find a star is fine. Your backyard should allow this.

(2) Usually you would do the dec axis by finding an east or west star about 20 degrees above the horizon. 60 degrees may be too much, but if you get the ra axis right then you should still see some drift due to dec error and can correct for this.

(3) Basically you have my problem. Even after polar aligning i can rarely do a 2 or 3 star align as all the stars a obscured by trees. Even if i could there are so many trees there is nothing interesting to take a photo of. Of course if you dont want to take a photo you really dont need a good polar alignment. A rough one will do followed by a two star align.

(4) Anyway, I just use my backyard to pactice things like drift alignment, guiding, new software etc. Then when it all made sense I went out to the local park where at least i could see things.

The diagrams here really helped me get started http://www.asignobservatory.com/driftalignment.aspx

Cheers
Paul

[g__day (Matthew)]

Trial PEMPro from CCDWare (and or ping its author an e-mail) - it might help with its polar align wizard - maybe!

[JohnH]

If you want software assistance with drift alignment GuideMaster is free and has Polar Alignmment routines.

http://www.guidemaster.de/index_en.asp

WCS is designed specially for it:

http://wcs.ruthner.at/index-en.php

OR with PHD or K3 turn the graphing on - it is easier to see the drift quickly than via the ep.

Too much information!

[ozstockman (Mike)]

Hi Rob,

You might want to try a digital inclinometer to adjust your latitude. I am using one which I bought from here .
This little device will tell you how accurate your mount latitude scale. If it's not accurate you can adjust it to be perfect using it.

Then with a compass you can point your mount to true South and I guess that's all you need. The only problem here is to find an accurate compass which won't cost you a lot. Cheaper compasses don't seem to me to be accurate at all. I have at least three including one digital built in watch and they never point to the same direction.

P.S. Using my digital inclinometer I found out that latitude scale on my EQ6 mount inaccurate and when it has 37 degree mark on scale it actually sets 35 degree angle.

cheers,

Mike

[Ian Robinson]

Try using other stars as they transist (and your setting circles, can you get altaz reading from your handset ??) together with a compass (and the offset magnetic north) , come to think of it , probably don't need transitting star for this.

You'll need a package or set of tables that gives the altaz for the chosen "aligment stars" so you can compare your alignment and make the appropriate south alignment adjustments ((east or west) assuming your mounts angle of the dangle for your latitude and levelling is right ).

That is one way I used to it when I had a similar problem with horizons.
I knew nothing about drift alignment at the time.

--- I'd move the scope to somewhere that gives me a clear shot at the SCP , it's easier.

[ving (David)]

wcs (as mentioned earlier) works rather well. it took me 20 mins to get good alignment on my first use.

[Robert_T]

Thanks Guys, phew considering I thought I had no options, I am now pretty well swamped with ideas... something here should work