Polar Alignment software help

[lifeonmars]

Hello everyone,a question from a beginner,i have downloaded the polarscope alignment software by Dr J Dale and its seems very straightforward,but I notice the download consists of three parts

1. Polarfinder

2.readme

3. Reticule

What do I need the reticule for?,isn`t the same information on the four printable polar scope views can anyone explain who knows what they are doing.Thanks in advance for all your help.

[Cornelius Varley]

Don't delete that file. The reticule.bmp is part of the program when you run the .exe

Peter

[mallorcasaint]

The reticule file is the graphic that is overlaid to disply the position of the Pole Star.

[lifeonmars]

Thank you very much for your help with that ,it never even crossed my mind it was a graphic overlay,might get the hang of

computers one day.The trouble with me I am a bit of a Dinosaur but now its clear!! Many thanks

[JamesF]

This is for getting the correct rotational alignment of your polar scope?

James

[mallorcasaint]

It is a tool to help you polar align the scope by using the polar scope.

[JamesF]

Ah, yes, I found it. Looks like the idea is that once you have your polar scope aligned with the RA axis then to get the marker on the reticle in the correct position for Polaris you use the program to print the position of Polaris relative to the centre of the polar scope reticle, set your time and date rings to the correct time and date and rotate the polar scope until the Polaris ring is in the same position?

I do that by setting the time and date rings to midnight on 1st November, which is when Polaris is furthest south of the NCP. I then rotate the polar scope until the Polaris ring is at the bottom (because the polar scope inverts the image). Lock it in position and job done, no software required I usually make sure it's really at the bottom by aligning the centre of the reticle with something that is vertical, then turning the polar scope so the centre of the Polaris ring is also aligned with the same vertical, beneath the centre spot.

James

[lifeonmars]

Some interesing stuff coming out here jamesf interesting how you set the time and date rings to midnight on the first of november when polaris is furthest south of the celestial pole,do you leave your scope set up all the time in an observatory or am i missing something here.There seems to be many variations on how these things can be set up.

Is there a almanac or database somewhere that tells ypu transit times on different dates?

[JamesF]

I have an EQ3-2 with a polar sope that gets moved around on a regular basis. Aligning the polar scope only needs to be done once, though, and can be done during the day (it's probably easier if you do). I assume that's what you're trying to do?

James

[lifeonmars]

Hi James

Yes thats what I would be doing but i think I get bogged down by thinking i have to set it up at every observing session from scratch,so when you set up the 1st of november settings would i be right in saying you are actually pre calibrating the polar scope to the mount.

Whats your procedure when you go out to observe ,the reason i ask I have read the procedure on the astro baby site which is very comprehensive but seems a bit long winded.

The other problem I have I like to know the reason I am doing something and not just follow a procedure parrot fashion,and I must admit it its a bit tricky getting my head around it but thnks very much for your help!

[JamesF]

There are several steps involved.

The first is to make sure the polar scope is aligned with the RA axis of the mount, so that when the RA axis is rotated the polar scope stays pointed in exactly the same place. This is usually done with three grub screws or knurled screws. It's easiest done during the day.

The next is to account for the fact that Polaris doesn't quite coincide with the North Celestial Pole and as a result over the course of a year appears to rotate around it. So depending on the time and date Polaris will actually be in a different position relative to the NCP. That's what the above program is for -- finding out what position Polaris is in relative to the NCP at any given time and date. You can do this adjustment during the daytime, too. You just need to find out where Polaris will be at a given date and time (in GMT), rotate the RA axis until the time and date rings read the same, then rotate the polar scope so the circle that represents Polaris is in the correct position relative to the spot or cross in the centre of the reticle (which is the NCP). Getting that alignment perfect isn't so simple though, and because I know the position of Polaris at midnight on 1st November is always at its highest above the NCP, in the polar scope it must appear to be lowest below the NCP (because of the image inversion in the scope). So I rotate the RA axis unti the time and date rings read midnight on 1st November, then turn the polar scope until the Polaris ring is directly below the NCP by lining them both up with something in the distance that I know to be vertical.

Once that is done you're in a position to polar align the mount whenever you use it. To do that, with the scope off the mount set the latitude scale roughly right on the mount, and line it up by eye with Polaris. Rotate the RA axis until the time and date rings read the current time and date (in GMT) and lock the clutches. Then find Polaris in the polar scope eyepiece and using only the alt and az adjustment screws, move the mount so that Polaris is in the ring on the reticle. Mount up the scope, check the reticle once more and you're done.

If your polar scope reticle isn't illuminated then you may find it hard to see. Shining a red torch at an angle down the open end of the polar scope can sometimes help. I've made an illuminator for my EQ3-2 using some bits of waste water pipe and an LED which helps enormously.

Knowing it's Polaris you're looking at through the polar scope and not some other star is a knack. Obviously it's not going to work particularly well if you use another star If you've got it reasonably close by eye though, Polaris should be the brightest star you can see.

James

[lifeonmars]

Thanks a million James for that explanation must have took you a while to right it all up,it makes a lot more sense to me now and really appreciate you taking the time to explain it in more simple terms,I will have a good read of it ,and weigh it all up.I hope you dont mind if I come back and ask more questions if i get stuck but many thanks.I am amazed at how friendly and helpfull this forum is!!!

[JamesF]

No problem. I type fast

James

[KJ Dalley]

Thanks a million James for that explanation must have took you a while to right it all up,it makes a lot more sense to me now and really appreciate you taking the time to explain it in more simple terms,I will have a good read of it ,and weigh it all up.I hope you dont mind if I come back and ask more questions if i get stuck but many thanks.I am amazed at how friendly and helpfull this forum is!!!

I would also like to acknowledge that very useful set of instructions from James on Polar Alignment.

I tried polar alignment last night (first clear night in ages!). I did a very basic method and got amasing results but anything that I can do to improve the accuracy is going to make it even better.

Many Thanks

Kev

[JamesF]

You are most welcome

James

[daz]

You know what... I've never 'got' the date method of doing PA - until now!!

Trouble is, all the date numbers have rubbed off of my mount, but James' explanation made it really clear!!

[lifeonmars]

Hi Again a question for James who kindly gave me a very good explanation of polar Alignment on my HEQ5..one thing I am struggling with, I have followed your instructions and set the date and time circles to read 12 oclock on the 1st of november ie the upper transit point of Polaris,and then to turn the actual polarscope so the representation of polaris on the etched reticule is at 6 oclock how do I turn the Polarscope?, rather than use the rotation of the ra axis to move polaris around the etched circle till it reaches 6.0clock.Hope i am making sense.

[JamesF]

Perhaps it's clearer to explain by doing things in a slightly different order, and perhaps I didn't adequately explain some steps.

Around the polar scope, next to the date circle is a ring with a white index mark on it. Loosen the grub screw that locks it in place. This ring is what keeps the rotational alignment of the polar scope., It's probably easiest to do this first because it's a pain if the screw ends up underneath when you want to adjust it. Rotate the RA axis until the Polaris indicator is at the bottom, and lock the RA axis. The date ring should still spin freely, so turn that so the time and date rings indicate midnight on 1st November. On the inside of the date ring you should find a small longitude scale that reads something like E..20..10..0..10..20..W. Without allowing the date ring to rotate any further, spin the ring with the index mark around to align with the zero point and lock it. That's it.

When you want to align with Polaris at the start of an evening you align the zero point on the longitude scale with the index mark once more, by turning the date circle. Next turn the entire RA axis (I usually do so by turning the counterweight bar) so the date circle aligns with the correct time (in GMT) and lock it. Check the date circle hasn't moved relative to the index mark as it can drag a little sometimes. Then adjust alt and az so Polaris is in its marker on the reticle.

I do all my adjustment with the scope off the mount, and then give it a final check after mounting the scope. It's much easier and puts less stress on the adjustment mechanism if you don't have the weight of the scope on it at the time.

James

[lifeonmars]

hi James Thanks very much for that further explanation I will give that a try sounds like this is second nature to you,but I have not had much time due to work commitments up until now so to get my teeth into it,and have the battle is knowing what should move freely and what is actually adjusting something.I think I undid that grubscrew but it wouldn`t move, is it on a screwthread or is the only thing holding it in situ the grubscrew?

I must say I really appreciate your help with this its really good that people are so helpfull on this forum.

Many many Thanks Frank

[JamesF]

To the best of my recollection the index ring is free to spin once the grub screw is undone. The screw in question is just a bit further around from the index mark as far as I recall. I don't think there are two, but it might be worth checking

James

[lifeonmars]

Hi james

Thanks for that James will give that a check

Many Thanks Frank