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markclaire50

Polar alignment without pole star

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I am in the very embryonic stage of planning to do AP and I haven't got an eq mount yet. 

The PLAN is currently to buy an heq5 with rowan belt. BUT, the flattest places in my relatively small back garden are on the patio with house directly blocking North or end of garden where I can see polaris BUT trees behind me would block a swathe of Southerly sky?

So, either way I'm stuffed. The lawn in between these two areas, is of course sloped! Not something I'd like to put a tripod and scope on. 

This means that effectively I can't do both polar alignment with polar alignment scope AND do AP on many Southerly objects. Even in the middle of the lawn, I suspect the tree would block too much. Only on the patio is South reasonably OK. Although I can't see anything north of past WSW or ENE. 

I don't want to be limited to alt az photography, but this is a problem. I've heard of drift methods and computer methods and some mounts having automated systems, etc etc. 

So, any suggestions on this? Am I beyond help? ? If I pay a large sum of money for an eq mount (which I intend to place an 80mm ed on, but also an 180mak for visual/planetary AP) I'D like it to track properly. I know this isn't essential for the planetary AP, but is for fainter dso. 

Please help

Thanks 

Mark 

 

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I'd personally go for being able to see Polaris and image North, West, and East.

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It’s quite straightforward to polar align without the ability to ‘see’ Polaris.  You have mentioned some methods but the easiest for me was to use the Polar Alignment routine in the SynScan handset. As long as you can see 3 well known stars it’s easy to use. You just need to guess where Polaris is initially.

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There are methods of polar aligning using Drift alignment, which you perform in two steps, observing a star move along a reticle eyepiece to confirm that the mount is correctly aligned N/S and for the correct latitude. If you can set your latitude correctly (using the location where you CAN see Polaris), you could mark out where your tripod legs go at the other site to give you a "near enough" position to do the drift align. (Caveat... I've never tried it, so I don't know how easy it is in practice)

http://www.iankingimaging.com/show_article.php?id=11

Alternatively, How sloped is the lawn in between them? Might you be able to place 2 small paving slabs on the lower side of the slope and a third in a shallow hole up the slope so that you can set your tripod level (or alternatively, just shorten that that leg). 

 

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It will be challenging to PA without experience and without Polaris.

If you think, you will need to hide the rig each morning... I don't think it's worth the pain....

However, if you will be able to leave the rig outside permanent, -  it is worth a battle and 100% possible.

You will spend some time adjusting the position, learning PHD2 drift alignment, - but at the end you will manage to do it properly and will be able to have subs 5min or even longer, -  if needed.

Handset does have 3 star PA, but it will not be enough... At the end you will need Laptop, EQMOD, PHD2 to pin point PA.

My first EQ mount position was without Polaris, - it was very difficult and frustrating initially, as I had no one to advice and I had to break through all the ice alone.

If you will be confused, or not sure if you do something correctly, - drop me a line.

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2 hours ago, Gfamily said:

There are methods of polar aligning using Drift alignment, which you perform in two steps, observing a star move along a reticle eyepiece to confirm that the mount is correctly aligned N/S and for the correct latitude. If you can set your latitude correctly (using the location where you CAN see Polaris), you could mark out where your tripod legs go at the other site to give you a "near enough" position to do the drift align. (Caveat... I've never tried it, so I don't know how easy it is in practice)

http://www.iankingimaging.com/show_article.php?id=11

Alternatively, How sloped is the lawn in between them? Might you be able to place 2 small paving slabs on the lower side of the slope and a third in a shallow hole up the slope so that you can set your tripod level (or alternatively, just shorten that that leg). 

 

Thanks. Digging any type of hole would require consultation with a higher power?

But I had wondered if there may be something I could do along those lines. 

 

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3 hours ago, markclaire50 said:

on the patio with house directly blocking North or end of garden where I can see polaris BUT trees behind me would block a swathe of Southerly sky?

Yup, my problem too!

Ian

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2 hours ago, RolandKol said:

It will be challenging to PA without experience and without Polaris.

If you think, you will need to hide the rig each morning... I don't think it's worth the pain....

However, if you will be able to leave the rig outside permanent, -  it is worth a battle and 100% possible.

You will spend some time adjusting the position, learning PHD2 drift alignment, - but at the end you will manage to do it properly and will be able to have subs 5min or even longer, -  if needed.

Handset does have 3 star PA, but it will not be enough... At the end you will need Laptop, EQMOD, PHD2 to pin point PA.

My first EQ mount position was without Polaris, - it was very difficult and frustrating initially, as I had no one to advice and I had to break through all the ice alone.

If you will be confused, or not sure if you do something correctly, - drop me a line.

Thank you. Yes, I have some serious thinking to do on this. I get the distinct feeling that somehow I need to go down being able to PA with polaris, if at all possible. If only my house wasn't in the way. ?

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6 minutes ago, markclaire50 said:

Hi, have you found a solution? 

Currently I have only used an Alt-Az mount ;<). If I decide to invest in an EQ mount then I should need to compromise a bit and move away from the house a little, but at least my garden is on the level. Probably not the answer you wanted to hear! Of course, if you are loaded you might care to look at the TTS-160 Panther mount, an Alt-Az mount with the facility to rotate the scope and thus allow imaging without field rotation!

Ian

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28 minutes ago, The Admiral said:

Currently I have only used an Alt-Az mount ;<). If I decide to invest in an EQ mount then I should need to compromise a bit and move away from the house a little, but at least my garden is on the level. Probably not the answer you wanted to hear! Of course, if you are loaded you might care to look at the TTS-160 Panther mount, an Alt-Az mount with the facility to rotate the scope and thus allow imaging without field rotation!

Ian

Just checked the panther mount cost. I think I'll get a couple. ????

Dreaming...... ? 

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3 minutes ago, markclaire50 said:

Just checked the panther mount cost. I think I'll get a couple. ????

One for each end of the garden :)

For what it's worth I don't think drift alignment is that hard, but it's probably far more hassle if you have to do it every time you go out.  Could be worth negotiating over the possibility of a permanent pier that you can leave the mount on under a cover?

James

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17 minutes ago, JamesF said:

One for each end of the garden :)

For what it's worth I don't think drift alignment is that hard, but it's probably far more hassle if you have to do it every time you go out.  Could be worth negotiating over the possibility of a permanent pier that you can leave the mount on under a cover?

James

Thanks James. I'm beginning to think limiting myself to North West and East may be best. Do you know the distance that tripod legs on heq5 are when fully spread? 

Another alternative is the az eq mount skywatcher sell. I'd be able to do both visual and AP. Who knows, I could even stick it in the car. Perhaps reason to join astronomy club. They may have a dark site. ??

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4 hours ago, Owmuchonomy said:

It’s quite straightforward to polar align without the ability to ‘see’ Polaris.  You have mentioned some methods but the easiest for me was to use the Polar Alignment routine in the SynScan handset. As long as you can see 3 well known stars it’s easy to use. You just need to guess where Polaris is initially.

+1 this

I don't know about Skywatcher mounts, but the Celestron mounts can polar align using any three stars. It does not need a view of Polaris. It does some wizardry and works out how other stars would move and you adjust your alt/az bolts to centre your chosen star (e.g. something close to meridian).

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I had exactly this problem and with some digging on solar observing polar alignment I figured out a way to do it roughly. Noted here in this thread:

That said, it’s not super accurate. It’s about on par with a decent visual alignment... when it works. The problem is that you are relying on the accuracy of your mounts Goto system. If it’s good then so will your alignment accuracy. On a good day, my EQ3 would give me 10-15s exposures on a 750mm focal length with the ASI290.

I found that the best way is the laser pointer method in that thread. Attach a laser pointer to you mount in a very reliable place. Do an accurate align once then mark where the laser points to. That should get you most of the way there. You can then fine tune depending on your needs.

Much of the time for EAA I align as I described in that post — even when I can see Polaris. That said, for real AP you’ll need something more accurate. 

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6 minutes ago, London_David said:

I had exactly this problem and with some digging on solar observing polar alignment I figured out a way to do it roughly. Noted here in this thread:

That said, it’s not super accurate. It’s about on par with a decent visual alignment... when it works. The problem is that you are relying on the accuracy of your mounts Goto system. If it’s good then so will your alignment accuracy. On a good day, my EQ3 would give me 10-15s exposures on a 750mm focal length with the ASI290.

I found that the best way is the laser pointer method in that thread. Attach a laser pointer to you mount in a very reliable place. Do an accurate align once then mark where the laser points to. That should get you most of the way there. You can then fine tune depending on your needs.

Much of the time for EAA I align as I described in that post — even when I can see Polaris. That said, for real AP you’ll need something more accurate. 

Thanks! I will read that thread. 

Mark 

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Since you said you can view Polaris and around, I recommend using sharpcap for polar alignment. With the free version you can only check your PA error, with the paid version you can polar align really fast with the use of a camera like the asi120mc or maybe even a Webcam if it's compatible and sensitive enough. 

It's well worth the (low) price. 

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Frank,

the free version V2.9 allows PA alignment as well.

 

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Posted (edited)
2 hours ago, Atreta said:

Since you said you can view Polaris and around, I recommend using sharpcap for polar alignment. With the free version you can only check your PA error, with the paid version you can polar align really fast with the use of a camera like the asi120mc or maybe even a Webcam if it's compatible and sensitive enough. 

It's well worth the (low) price. 

Hi. Thanks for your reply. I can only see polaris at the end of my garden but then can't image Southerly objects because next door neighbours trees are in the way too much. To image Southerly objects I need the other ways. It sounds like skywatcher latest software can do this, if I ensure the scope is pointed in roughly the right declination towards polaris. Do you agree? 

Edited by markclaire50

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Posted (edited)
On 05/03/2019 at 04:01, Merlin66 said:

Frank,

the free version V2.9 allows PA alignment as well.

 

Nice, didn't know it allowed too. 

On 05/03/2019 at 04:51, markclaire50 said:

Hi. Thanks for your reply. I can only see polaris at the end of my garden but then can't image Southerly objects because next door neighbours trees are in the way too much. To image Southerly objects I need the other ways. It sounds like skywatcher latest software can do this, if I ensure the scope is pointed in roughly the right declination towards polaris. Do you agree? 

By other ways you mean placing the mount on another area? 

You're right, there is a function on the synscan controller(maybe you will have to update the controller firmware to enable this) that allows you to do a polar alignment after you do a two star alignment,  but you'd have to at least pointed towards northern celestial pole to be easier when you make the PA routine. 

From there you can choose from a list of stars that the controller shows you.  I don't remember if it's accurate for AP.  I can give it a try again and compare with sharpcap to see if the alignment is good or not and tell you. 

 

 

Edited by Atreta
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Posted (edited)

The easiest solution to that problem is making an artificial TNP (True North Pole).

It doesn't make the initial polar alignment any easier, but all subsequent alignments will be (almost) standard.

The accuracy depends only on the distance from the scope to the artificial Polaris and repeatability of the tripod configuration.

I'm sure you have already guessed how it works:

  1. Find the perfect place for your tripod, so it's convenient to use and the distance to the house wall in the North direction is maximal (every inch counts).
  2. Polar align using the drift method (SynScan method will be most likely insufficient for the AP accuracy, it meant for the visual tracking).
  3. Confirm that you are truly aligned making some test images you are planning.
  4. Assuming the result is satisfactory, start marking the resulting geometry:
    1. Mark tripod legs positions on the floor so you can put them back again exactly as they are now.
    2. Mark tripod legs length as they are extended now (if not fully extended) so you can reproduce their length.
    3. Mark tripod legs, so you can be sure the same legs are going into the same marks.
    4. Mark whatever else could move the polar axis in your EQ mount. 
  5. Finally, focus your polar finder on the wall of the house and mark the position of the true celestial pole (having a buddy helping with that would be the easiest).

After the takedown, just match all your markings at set up and finally tweak the residual errors per the Polar finder instruction, just skip the Polaris timing steps as you have the TNP which is not affected. 

Edited by AlexK
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2 hours ago, Atreta said:

Nice, didn't know it allowed too. 

By other ways you mean placing the mount on another area? 

You're right, there is a function on the synscan controller(maybe you will have to update the controller firmware to enable this) that allows you to do a polar alignment after you do a two star alignment,  but you'd have to at least pointed towards northern celestial pole to be easier when you make the PA routine. 

From there you can choose from a list of stars that the controller shows you.  I don't remember if it's accurate for AP.  I can give it a try again and compare with sharpcap to see if the alignment is good or not and tell you. 

 

 

Thanks Atreta

That would be interesting if you have time. 

Mark 

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1 hour ago, AlexK said:

The easiest solution to that problem is making an artificial TNP (True North Pole).

It doesn't make the initial polar alignment any easier, but all subsequent alignments will be (almost) standard.

The accuracy depends only on the distance from the scope to the artificial Polaris and repeatability of the tripod configuration.

I'm sure you have already guessed how it works:

  1. Find the perfect place for your tripod, so it's convenient to use and the distance to the house wall in the North direction is maximal (every inch counts).
  2. Polar align using the drift method (SynScan method will be most likely insufficient for the AP accuracy, it meant for the visual tracking).
  3. Confirm that you are truly aligned making some test images you are planning.
  4. Assuming the result is satisfactory, start marking the resulting geometry:
    1. Mark tripod legs positions on the floor so you can put them back again exactly as they are now.
    2. Mark tripod legs length as they are extended now (if not fully extended) so you can reproduce their length.
    3. Mark tripod legs, so you can be sure the same legs are going into the same marks.
    4. Mark whatever else could move the polar axis in your EQ mount. 
  5. Finally, focus your polar finder on the wall of the house and mark the position of the true celestial pole (having a buddy helping with that would be the easiest).

After the takedown, just match all your markings at set up and finally tweak the residual errors per the Polar finder instruction, just skip the Polaris timing steps as you have the TNP which is not affected. 

Hi Alex 

Thank you for this very useful method!

Mark 

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No problem! Just forgot to mention, that in case your polar finderscope doesn't provide the TNP reticle to mark on the wall, then just use the Polaris marker after setting the time position to some fixed easily reproducible value (e.g. zero).

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Hi Mark,

I faced your problem last night when setting up my equipment at a very dark campsite in Dumfries an Galloway.  I was just setting alignment via the polar scope when the clouds rushed in :( but there were a few stars visible to the south so I had to complete the task with drift alignment using PHD2. 

I only went for one iteration of each axis but that was good enough or 2 minute subs with less than half a pixel movement in either axis between subs.

My advice is place your scope where you will get the images you want, learn drift alignment, as Olly Penrice would say, it is the gold standard.  

If you set up your scope at the bottom of the garden you should be able to get your altitude setting pretty well set up as long as you make sure it is levelled first.  Move it up to your patio or location of choice, relevel, use a compass to align with north and then play with drift alignment. A nice feature of PHD 2 is that you can make some notes as you align and it will remember these for your next session. For AZ ,I record which alignment bolt to tighten depending on whether the slope is positive or negative.  For altitude adjustment I record which direction the star should move according to the sign of the drift.

HTH

Andy

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