Polar alignment questions

[FarAndBeyond]

Im a bit confused about some parts of this polar alignment thing, firstly my polar scope has the new Skywatcher 2012-2032 reticule. I have been reading around the internet about it but still feel a bit confused. For example the reticule is not aligned with the RA axis, meaning when the RA axis is perfectly vertical (counterweight rod pointing straight down) the "0" on the reticule clock face is like 20 degrees to the left, and then of course if I place the "0" on the reticule at its top most position at 12 a clock then the RA axis is not vertical. And i guess the RA axis needs to be vertical as a starting point, or am I wrong about that? I read thats often how they are delivered from the factory. So do I need to unscrew and rotate the reticule (and risk loosing the perfect centered position) or is there some other easy way to do the polar alignment with the reticule not vertical? For example the polar align apps when they show the position of polaris on the clock face they count with the clock face being correctly positioned, and I guess the same goes for when using the setting circles?

Also since the view is upside down so when the polaris is placed in its lowest position (6 a clock) on the clock face doesnt that actually mean that its in its highest position in the sky? Or how does that work, I guess the polar align apps count for that?

And then the most crucial question of all... I don´t have any visibility at all to Polaris from my balcony and I would want a long exposure Astrophotography worthy alignment, is that somehow achievable without visibility to Polaris? And I guess as soon as you move the mount the polar alignment is thrown off? I just heard about the SynScan handset having a routine to set the polar alignment? What solutions are there for this problem (if there are any solutions at all that are accurate enough)?

Im sure some of my questions has been asked in other threads, but I wanted to ask the questions my own way, I hope thats okay?

[PeterCPC]

Sharpcap has a PA routine.

Peter

[PhotoGav]

The main thing is that the majority of your questions are irrelevant as you can’t see Polaris from your location, so it doesn’t matter! There are software solutions that will help with PA when you can’t see Polaris, such as Sharpcap and PHD2. Drift alignment will also work. You will have to set up with a good theoretical polar alignment, ie pointing North with your latitude on the altitude scale. Good luck with that.

To answer your other questions: the only reticle alignment that matters is with the RA axis of rotation, ie that it is central in its slot. It doesn’t matter where the counterweight bar is at all, you just rotate the R.A. until the reticle dot is at the correct hour angle to be able to put Polaris in it. The scope & weights end up in some weird positions, but it just doesn’t matter (so long as you don’t hit anything!). Yes, PA apps generally allow for the inverted view.

Good luck and I hope you get polar aligned easily!

[spillage]

If you have a view to the south and west  then you can use drift alignment. This is built into phd2 and you can also run it manually.

[RolandKol]

I had a similar problem, as my house blocked Polaris... 
I tried all kind of tutorials and always failed....

So I did it my way....

1) I leveled an placed the tripot North using the compass on the smartphone, balanced all properly with all the cameras and cables on;

2) Used syncscan smartphone app to enter all details to the EQMOD (or handset) and stellarium;

3) Aligned Finderscope as good as possible;

4) Once dark, slewed to target the Moon and mound missed it;

5) Adjusted Mount ALT and Ra bolts to center the Moon. The mount/tripod was so far off, I had to manually lift it and turn it a bit to get the Moon in the Center. Moon was close to Meridian at that time;

6) So I slewed to a Bright Star in The East (Close to 0 degrees ALT), Used adjustment bolts to target star in the finderscope and later, in the main scope...  

7) Slewd back to the Moon, it has not missed, but was not in dead Center. I presume because 2 or 3 star alignment was not done;

8 ) I did 5 star alignment (synced 5 starts with EQMOD) and did PHD2 calibration close to meridian  and 0 ALT (3 sec exposure); 

9) In the same spot, reduced PHD2 exposure to 1s, started PHD2 Drift Alignment... Took ages... But managed to get "quite Close", but far from perfect;

10) Tried to use PHD2 slew East (or West, do not remember) to do ALT drift alignment (the second part), the tree blocked the view... Found visible area close to the spot PHD2 suggested and did Drift for ALT;

11) Went Back to Meridian (close to 0) and repeated RA Drift alignment... Got a better result than initially, I think I should go back East and repeat ALT drift, but as It took ages already, I skipped;

12) Removed Sync data from EQMOD, did star alignment again and Recalibrated PHD2 with 3sec exposure;

13) Used PHD2 guiding assistant;

14) took around 4 hours in total... reached around 5 min exposure time without star trailing.

Was VERY happy and was prepared to Kill anyone who touched the mount!

 

[Donkeiller]

8 hours ago, FarAndBeyond said:

Im a bit confused about some parts of this polar alignment thing, firstly my polar scope has the new Skywatcher 2012-2032 reticule. I have been reading around the internet about it but still feel a bit confused. For example the reticule is not aligned with the RA axis, meaning when the RA axis is perfectly vertical (counterweight rod pointing straight down) the "0" on the reticule clock face is like 20 degrees to the left, and then of course if I place the "0" on the reticule at its top most position at 12 a clock then the RA axis is not vertical. And i guess the RA axis needs to be vertical as a starting point, or am I wrong about that? I read thats often how they are delivered from the factory. So do I need to unscrew and rotate the reticule (and risk loosing the perfect centered position) or is there some other easy way to do the polar alignment with the reticule not vertical? For example the polar align apps when they show the position of polaris on the clock face they count with the clock face being correctly positioned, and I guess the same goes for when using the setting circles?

Also since the view is upside down so when the polaris is placed in its lowest position (6 a clock) on the clock face doesnt that actually mean that its in its highest position in the sky? Or how does that work, I guess the polar align apps count for that?

And then the most crucial question of all... I don´t have any visibility at all to Polaris from my balcony and I would want a long exposure Astrophotography worthy alignment, is that somehow achievable without visibility to Polaris? And I guess as soon as you move the mount the polar alignment is thrown off? I just heard about the SynScan handset having a routine to set the polar alignment? What solutions are there for this problem (if there are any solutions at all that are accurate enough)?

Im sure some of my questions has been asked in other threads, but I wanted to ask the questions my own way, I hope thats okay?

Your mistake was buying an EQ mount in the first place.

Never underestimate their innate hostility.

 

[RolandKol]

13 hours ago, Donkeiller said:

Your mistake was buying an EQ mount in the first place.

Never underestimate their innate hostility.

 

He wants to image DSO,

He had no other option in this stage of technology... 

[michael8554]

If imaging DSO's can I assume you will image one target per night ?

Then don't bother with star alignment to enable you to easily goto multiple targets per night !

Instead concentrate on polar aligning to not worse than 5 arc mins.

Then SYNCH on a star close to your target, then goto your target.

Michael 

[Thalestris24]

Hi

The Synscan hand controller has a routine for doing Polar Alignment without needing to be able to see Polaris. Drift alignment is another option if you can see either east or west, and south. I for one can only see east so point the mount north with the aid of a true north compass app. Then I drift align to the east using phd2's drift align tool and adjust alt. It doesn't matter if my Az is out slightly since I'm imaging to the east and a small az error doesn't cause a problem. If you can keep your focal length short and your exposures short, PA errors are less of an issue. The new-ish cmos cameras encourage you take lots of short exposures rather than a relatively few long ones (I must get one!).

Louise

[FarAndBeyond]

I have visibility between about 70° East to 160° South (clockwise). So no visibility towards North and not towards West. So does that mean that I can not do drift alignment? My scope is at 1000 mm focal length (Explorer 200P-DS).

It sounds as there are a few ways to do reasonable tracking without a proper polar alignment (Polaris visibility), but to me it sounds as if they are not perfect (i.e. comparable to a real polar alignment) and that they also are time consuming, but maybe im wrong? I actually don´t mind if it takes some time, especially if the time consuming part doesn´t need to be done at every observation (provided the mount hasn't been moved)?. But its nice to know that there are options for us people who doesn´t have Polaris visibility. My goal is to have good enough tracking to be able to do Deep sky photography (not yet though), i.e. good tracking for the exposure times which are needed for this kind of photography.

Thalestris24 was mentioning CMOS cameras taking several shorter exposures, in comparison to a CCD which take fever long exposures I guess, which ive also read about online. So one could say in other words that generally a CMOS doesn´t need high tracking accuracy for as long time as a CCD camera, meaning it will have to track accurate for a shorter time than with a CCD? Or am I wrong about that thought?

About the comment that my mistake was to buy a EQ mount in the first place....of course it was not a mistake. How else should I learn if I dont have a mount in front of me? One can do all the reading in the world (which I have done quite a bit before I purchased the mount, and yes even the thin manual as well) but that doesnt compare to having access to the physical mount, and also thats part of the fun to learn as you go. I like a challenge, and when there are good forums around that helps a great deal with the learning as well.?

[spillage]

Have a look here. I guess I have always drifted south, west but east is also a viable option. 

[Thalestris24]

Hi

If you can see south and east you  can drift align. Whereas  ~180 deg south is ideal, 160 deg will probably still be doable for adjusting az. At 1000mm you'll need to autoguide also. It is possible to do live stacking with SharpCap Pro - something I've been dabbling in myself lately :). However, it relies on having a sensitive (high qe camera) that can grab images in matters of seconds and stack and align them as you go. A focal reducer will help by reducing your focal length. Still, the more accurately you can polar align the better, generally - especially at longish focal lengths like 1000mm. AP is generally easier with shorter focal lengths. Most dso targets are quite big so benefit from a large fov. Even good camera lenses can take excellent images and can paired with a particular camera to give a desired fov. Some of the best images I've done have been taken with a 200mm fv vintage smc Takumar

Louise

[RolandKol]

You will manage to get 5min exposures. 
Just do not expect to do it perfectly from the very first time...

Without experience and without Polaris, - it is a real challenge.

But as your scope will stay in the balcony without disturbance, - you will be able to adjust and increase accuracy as you learn.

Just,

to make a good start and make following adjustments easier (as I mentioned before), - level the mount as good as you cant and balance with all the cables and cameras as perfect as possible

keep in mind, if camera is on the scope in around 3'oclock/or 9 o'clock (this is the standard position of the eyepiece for observing), it shifts the center of the gravity of the scope and the rig is not balanced.

The best position for the cam is around 6'oclock or, if you afraid to lose it, around 12 o'lcock.

[Aldebaran5]

Phew, just glad I can see Polaris from my location

Keith

[Thalestris24]

13 minutes ago, Aldebaran5 said:

Phew, just glad I can see Polaris from my location

Keith

Drift aligning is straightforward and easy enough!

Louise

[RolandKol]

3 hours ago, Thalestris24 said:

Drift aligning is straightforward and easy enough!

Louise

Yep, especially with a help of PHD!
however, it is also a very time-consuming exercise!

[Thalestris24]

17 minutes ago, RolandKol said:

Yep, especially with a help of PHD!
however, it is also a very time-consuming exercise!

Yes, the PHD2 tool is very helpful though you either need a phd2-compatible camera or a guide scope. It shouldn't take more than about 10-15mins to get a reasonably good PA (it is an iterative procedure). If you have a permanent setup then you only need to check PA occasionally, providing you don't move anything. Even without PHD2 to help, it can be done with an eyepiece (I believe!).

Louise

[FarAndBeyond]

Well I don´t have a view direct south, more like 20 degrees to the East of south direction.

I was playing around with the Polar align Pro app which I just bought, to be honest it gives me even more questions. For example since my Skywatcher 2012-2032 reticule is not aligned properly with the vertical axis the app said there is a way to "set zero position", one is then suppose to look at the SynScan HC at the "show information"(?) in Utility function and the R.A info there and then slew to the R.A position that the app gives. Well when I slew in the R.A direction (left/right) the R.A numbers is not changing unless I first slew in the DEC direction (up/down), then if I have first slewed in DEC direction and after that slew in only the R.A direction the R.A value changes, but not if I start out with slewing in R.A. Also when I slew in the DEC direction the R.A numbers are changing as well. 

Also, its the same thing with the Alt/AZ information, it always shows 360 degrees as a starting point and my Altitude, and if I start with slewing left or right the Azimuth value is not changing, however if starting with Altitude slewing first and then slew in the Azimuth direction only then the Azimuth value changes, exactly like with the R.A/DEC info. And same thing here that while slewing in DEC the Azimuth value changes at the same time.

Why would the R.A value change when slewing only in DEC, or the Azimuth value while slewing only in Altitude, since the actual R.A axis is obviously not moving when slewing only in DEC? And why wouldn't the R.A or Azimuth value change when slewing in those directions until I have first slewed in the DEC/Altitude direction?

The only thing that changes values at all times and independently is the third information option, AX1 and AX2. Also, when I try moving/"slewing" in DEC/Alt in a planetarium program the R.A/Az values are not changing however?

Is this how it supposed to be? Maybe I haven't grasped this thing? Very confusing to me? 

P.S. Maybe I should add that the above is without doing a star alignment, and directly after power on, I haven't tried to look at the information after star alignment, but I guess it will be no difference in how the R.A/DEC information is showed on the Synscan?

 

[Thalestris24]

Hi

Sorry, I can't help with the app you're using. Although being 20 deg away from due South isn't ideal, you should still be able to drift align - it might just take a few iterations. The point of being able to aim due South (close as possible to the Meridian) and due East (at about 30 deg Alt) is to be able to adjust Az and Alt as independently of one another as possible. Programs like Astrotortilla (really a platesolving app) aim to aid polar alignment based on an inbuilt tool which uses a single star (not Polaris). See here for the principles behind this. However, aligning using two axes independently of one another is naturally better. As I mentioned, I personally am unable to see South and only image to the East. After much deliberating, angst, and thinking about the problem I realised I could get away with just pointing my mount North/South (with the aid of a true north compass app or magnetic compass with a true north adjustment) and then doing a partial drift align only to the East, i.e. only adjusting Alt. Since you are lucky enough to be able to see to about 160 deg, you can still use that to adjust Azimuth. Then Adjust Alt by pointing due East followed by going back to check/readjust Az. I use the PHD2 drift align tool - by skipping the initial adjust Az and just adjusting in Alt. The tool makes drift aligning very visual and easy to do. Because I only image to the East a small error in Az is of little consequence. See here for a (somewhat mathematical) discussion of Polar Alignment error. It all sounds complicated but once you've done the drift alignment a few times you'll wonder what all the fuss was about!

Louise

[FarAndBeyond]

On 31/12/2018 at 14:37, Thalestris24 said:

Hi

Sorry, I can't help with the app you're using. Although being 20 deg away from due South isn't ideal, you should still be able to drift align - it might just take a few iterations. The point of being able to aim due South (close as possible to the Meridian) and due East (at about 30 deg Alt) is to be able to adjust Az and Alt as independently of one another as possible. Programs like Astrotortilla (really a platesolving app) aim to aid polar alignment based on an inbuilt tool which uses a single star (not Polaris). See here for the principles behind this. However, aligning using two axes independently of one another is naturally better. As I mentioned, I personally am unable to see South and only image to the East. After much deliberating, angst, and thinking about the problem I realised I could get away with just pointing my mount North/South (with the aid of a true north compass app or magnetic compass with a true north adjustment) and then doing a partial drift align only to the East, i.e. only adjusting Alt. Since you are lucky enough to be able to see to about 160 deg, you can still use that to adjust Azimuth. Then Adjust Alt by pointing due East followed by going back to check/readjust Az. I use the PHD2 drift align tool - by skipping the initial adjust Az and just adjusting in Alt. The tool makes drift aligning very visual and easy to do. Because I only image to the East a small error in Az is of little consequence. See here for a (somewhat mathematical) discussion of Polar Alignment error. It all sounds complicated but once you've done the drift alignment a few times you'll wonder what all the fuss was about!

Louise

Thanks for the info, I have read it and I will have to look into that more carefully, but after reading it seems a bit complicated, maybe it isn't, but there were some mathematical calculations etc. that confused me a bit. Maybe it isn't so hard once you learn it and understand how it works?

[Thalestris24]

1 hour ago, FarAndBeyond said:

Thanks for the info, I have read it and I will have to look into that more carefully, but after reading it seems a bit complicated, maybe it isn't, but there were some mathematical calculations etc. that confused me a bit. Maybe it isn't so hard once you learn it and understand how it works?

Hi

You don't need to know the maths - just the principles and the procedure.

Louise

[kens]

There is a good explanation of the theory  without maths at https://astrocamera.net/equipmnt/p-align/driftaz.htm

The upshot is that a given amount of PA error, the star will drift that amount over a period of 6 hours. It is not linear and an error in Azimuth (left-right) is dominant  near the meridian. An error in altitude is dominant neat the horizon. This is exploited in drift alignment. If you can't see near the horizon then the altitude drift is less important. The great thing with drift alignment is that it is a "what you see is what you get" method. If you don't see any drift in the part of the sky that is visible to you then you are good to go.