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Problems with accurate polar alignment!

Andreas

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Andreas

Andreas

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Hello there!

I recently learned how to polar align my mount properly, or well.. maybe not properly since the end-results isn't very good.

With the polar alignment fully aligned, with mount and tube perfectly balanced I only manage to get 1 minute exposures before the stars getting stretched.

I took some pictures and trying to explain as best as I can about how I'm doing when I polar align my mount in hope of that someone might have an idea about what I'm doing wrong.

1. Adjusting the mount-legs until the bubble in the spirit level is placed in the middle

2. Rotating the Date Circle until the index mark is lined up with the zero.

3. Rotating the RA axis so that the pointer points at todays date, (first September for me).

4. Rotating the RA setting circle so that the pointer points at the current time, (16:00 in this case).

5. Rotating the RA axis so that the pointer is ligned up with zero.

6. Using the polar scope to adjust the T-bolts and adjustment knobs until polaris is located in the small circle.

***Image removed by moderator***

After the polar alignment I mount my camera and balance both axis until they're perfectly balanced.

Then I take some test exposures with my camera without any eyepieces, and the stars starts to get stretched after only 1 minute, yippee!

Does anyone have an idea about what I've done wrong?

All help is really appreciated!

// Andreas

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Black Knight

Black Knight

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The first thing I would say is (and this is only my opinion), but while setting circles may be fine for visual use, I don't know that I'd rely on them for imaging purposes. The next thing is, have you checked the alignment of the polarscope reticle? This video by Dion of Astronomy Shed takes you through ensuring the reticle itself is correctly aligned.

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Arushin

Arushin

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The first thing I would say is (and this is only my opinion), but while setting circles may be fine for visual use, I don't know that I'd rely on them for imaging purposes. The next thing is, have you checked the alignment of the polarscope reticle? This video by Dion of Astronomy Shed takes you through ensuring the reticle itself is correctly aligned.

I would agree 100%. In my experience the setting rings will give you a guide for visual but I wouldn't trust them for accurate polar alignment. If you go and look at a road atlas of the UK and measure the width of a motorway for instance on the map, you will find that if you where to scale up the map to life size the road you just measured would be somewhere between 300-500 feet wide (which I am pretty sure it is not in real life). This applies also to the setting circles on your mount. At the scale of say the RA axis of the mount, the best you are going to get is 'somewhere close-ish'. I would certainly check that your polar scope is correctly aligned before anything else. There are much simpler methods of polar alignment that are far less confusing than messing around with the setting circles. Don't forget that even a VERY well aligned mount will start to show star trails after a while if you are not guiding. I can get between 3-6 mins without using the guider if I have spent a reasonable amount of time polar aligning. Have a trawl around on here for Polar alignment methods or PM me and I will send you instructions on how I do it. Good luck.

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skfboiler

skfboiler

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That sounds about right to me. However, you did not mention, but did you have the DA axis pointer at 90 degrees? Also, as far as the polar scope, you said that had Polaris in the small circle, but did you rotate the mounts so that the polar scope reticle, with the Cassiopia and Big Dipper configuraations, match the how they actually configured in the sky that night or close as you can get it?

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Alan_B

Alan_B

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Where can you get the screws that are used to replace the hex adjusting screws shown in the first video. When I adjusted my polar scope fiddling with the supplied screws was a right pain and as a result I got close and left it at that. Having watched the video mentioned above I see that I should be aiming for more accuracy but need to source those screws first

So if anyone out there knows the size & where to get them please post :grin:

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Andreas

Andreas

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The first thing I would say is (and this is only my opinion), but while setting circles may be fine for visual use, I don't know that I'd rely on them for imaging purposes. The next thing is, have you checked the alignment of the polarscope reticle? This video by Dion of Astronomy Shed takes you through ensuring the reticle itself is correctly aligned.

Hi and thanks for the answer!

Very great videos!

When it comes to alignment of the polarscope reticle it should be fine, because I did this one time after that I by mistake freed the map in the polarscope.

What do you use instead of the circles? A guidecamera?

// Andreas

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Andreas

Andreas

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For imaging you really need to be drift aligning. Plenty on the web about it so give it a google.

Hi Freddie!

Don't you need a reticle eyepiece for drift aligning?

I've actually heard of people that have managed to get 5 min exposures with only polar alignment, but maybe that took all night to do as well.

// Andreas

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JamesF

JamesF

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If you get the polar alignment close with the polar scope then after that you need to get it more accurate using drift alignment. You can do that by eye using an eyepiece with a reticle, but there are also programs such as eqalign that can help do it using a camera.

James

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Black Knight

Black Knight

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Personally I use the really rather excellent EQMod and its built-in PA tool. For drift aligning, I use a camera as James has suggested. For Canon DSLRs, APT has a built-in drift alignment tool (DARV) which works quite well, but there are others such as EQAlign and WCS. WCS has the advantage that it can be used with a webcam if that is all you have.

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Andreas

Andreas

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I would agree 100%. In my experience the setting rings will give you a guide for visual but I wouldn't trust them for accurate polar alignment. If you go and look at a road atlas of the UK and measure the width of a motorway for instance on the map, you will find that if you where to scale up the map to life size the road you just measured would be somewhere between 300-500 feet wide (which I am pretty sure it is not in real life). This applies also to the setting circles on your mount. At the scale of say the RA axis of the mount, the best you are going to get is 'somewhere close-ish'. I would certainly check that your polar scope is correctly aligned before anything else. There are much simpler methods of polar alignment that are far less confusing than messing around with the setting circles. Don't forget that even a VERY well aligned mount will start to show star trails after a while if you are not guiding. I can get between 3-6 mins without using the guider if I have spent a reasonable amount of time polar aligning. Have a trawl around on here for Polar alignment methods or PM me and I will send you instructions on how I do it. Good luck.

Hi again,

Someone else is having a similar problem in another thread and Brantuk has kindly linked this excellent guide http://stevebb.com/p..._alignment.html

Hey and thanks for answers!

I see that it's hard to get long exposures without drift or guide, but before I'll buy a guidecamera, I want to learn how to polar align it properly.

Great site with good information! I think I missed to have the DA axis at 90 degrees, maybe that's why?

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JamesF

JamesF

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EQAlign may be quite fussy about which scopes you use it with. Or perhaps I'm just rubbish at using it. I have tried it with my 127 Mak and whilst it could happily find a star it couldn't get past working out the initial drift angle.

James

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Andreas

Andreas

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That sounds about right to me. However, you did not mention, but did you have the DA axis pointer at 90 degrees? Also, as far as the polar scope, you said that had Polaris in the small circle, but did you rotate the mounts so that the polar scope reticle, with the Cassiopia and Big Dipper configuraations, match the how they actually configured in the sky that night or close as you can get it?

Hi and thanks for the answer!

Yes that's right, I didn't have the DA axis pointer at 90 degrees, so I'm going to test that right now actually!

The polar scope should match with the night sky since that's ( as far as I know) is what the setting circles does?

// Andreas

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Black Knight

Black Knight

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EQAlign may be quite fussy about which scopes you use it with. Or perhaps I'm just rubbish at using it. I have tried it with my 127 Mak and whilst it could happily find a star it couldn't get past working out the initial drift angle.

James

I know many swear by EQAlign .... I just end up swearing at it. I've never managed to get it work properly! :D I'm sure that says more about me than EQAlign though! :D

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Andreas

Andreas

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If you get the polar alignment close with the polar scope then after that you need to get it more accurate using drift alignment. You can do that by eye using an eyepiece with a reticle, but there are also programs such as eqalign that can help do it using a camera.

James

Hi James!

I do neither have a reticle eyepiece or a camera that fits into the polar scope. :(

// Andreas

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Andreas

Andreas

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Personally I use the really rather excellent EQMod and its built-in PA tool. For drift aligning, I use a camera as James has suggested. For Canon DSLRs, APT has a built-in drift alignment tool (DARV) which works quite well, but there are others such as EQAlign and WCS. WCS has the advantage that it can be used with a webcam if that is all you have.

Hey!

I have both canon DSLR and a Neximage webcam, but how do they fit into the polar scope?

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