Question from a prospective buyer: All Star Polar Alignment


hubbell_jerry@...
 

Hi Joe,

I completely understand your point of view. Most beginners want the equipment to be easy and want to get to the observing part without having to mess with the setup of the equipment. Anything that make the setup easier is most welcome. I understand that beginner mounts from other companies may provide some automation to align the mount, but the G11 is not really considered a beginner mount and requires some knowledge before operating it effectively. There is a polar alignment scope available for purchase, but we don't include that because most of our G11 customers are not beginners and do not want to spend the extra money for a polar scope on the G11.

We have not really done the best job of explaining the power of the 2 and 3-star alignment routine in the ExploreStars application and how to get a basic polar alignment without the use of a polar scope for the G11. Again, very few beginners will buy the G11 as their first German Equatorial Mount. The EXOS 2 mount comes with a polar alignment scope so the user can do a halfway decent alignment. The G11 is a different story.

One of the secrets about the 2 and 3-star alignment routine that I have coded in the ExploreStars application is that it was designed for those who do not or cannot do a decent polar alignment, or even level their mounts very good. The alignment routine is designed to convert the mount's coordinate system to the celestial coordinate system so that the mount points correctly. 

What this means is that the mount could be up to 10-15 degrees off of north and the altitude could be a few degrees off and it won't matter. You could literally look at your horizon and say "that looks about north" and plop your mount down and not bother setting the altitude or level. We have demonstrated this at star parties we have attended in 2016 and since.

The trick though is that when you start the alignment, and the mount slews to the first star, you need to be able to identify that star correctly. Now if you are several degrees off, and you don't know how much exactly, you may pick the wrong star to SYNC on. This would through it off completely. This won't work of course. So even if the alignment routine can handle this much error, it still relies on the user to correctly identify and SYNC on the correct star as selected. This is a bit of a stretch for a beginner unless he is very familiar with the sky.

What we suggest is you use a compass and a level to do a daytime polar alignment that will get you to about 0.5 deg of the NCP if you are careful and practiced. 

The procedure is as follows:

1. Obtain the Longitude and Latitude of your location.
2. Using an online resource such as http://www.magnetic-declination.com/ and http://www.magnetic-declination.com/what-is-magnetic-declination.php to determine your Magnetic Declination.
3. Set up your tripod and level it as close as reasonably achievable.
4. Install your mount on the tripod with the counterweight bar over top of one of the tripod legs pointed north.
5. Using the Magnetic Declination determined in step 2, align your mount to True North by sighting
        at a distant object using the compass and aligning your mount with the object.
6 Install your telescope on the mount.
7. Connect up the PMC-Eight to the mount, power it up and get the ExploreStars working.
8. Once everything is working and ExploreStars is running, go to the coordinate input screen and enter the following coordinates into the RA/DEC:
DEC = your local Latitude Value
RA = your local LMST (as read off the display) - 1 minute
(this puts the telescope on the east side of the pier)
9. This will point the telescope near zenith. Place the level on the top of your telescope across the aperture being careful on to touch the optics.
10.  Adjust the north facing tripod leg to level the top of the telescope so that it is pointing at zenith.
11. Park the mount after getting level and you are ready to do a 2 or 3-star alignment as your mount should have a very good polar alignment at this point.

This is a bit different from using a polar scope, but it has an advantage in that you can do it during the day or night, and it does not require the north star to be seen in case it is blocked by trees.

I will work on creating a knowledge base article from this.

Although this is not quite as fancy as providing an electronic means to do a polar alignment, it does the job for visual observing. If you are doing astrophotography then there are several techniques available that are more precise than using this method or a polar scope that you would want to learn, I use the declination drift method which has the advantage of not having to see the north star also. Although a bit time consuming at first, it can be done in 5-10 minutes if you practice and are consistent when setting up your mount.

There are going to be a lot of things that you are going to want to learn to do where the equipment will not do it for you, especially if you are doing astrophotography. Learning the sky is one of them, as many beginners learn when they discover that you have to be able to identify the stars in the sky to do an alignment. Typically mounts do not align themselves as you know. Doing a polar alignment when you cannot see the north star is another skill that is very useful.

I will put a physical polar alignment function on the list of things to add to the ExploreStars application, but as I said, it will be a few months probably before I can even start to look at this.

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC. 



W. Christopher Moses
 

Just out of curiosity, which mounts in this price class, other than the orions, offer an all sky alignment feature?

Personally, I would rather a mount not have it.  It is just going to raise the cost of the mount and then you are stuck with that solution.  It's like getting a nice GPS touch-screen in a car.  It's not really upgradable, and in a year your phone will do a better job.

Just my opinion, of course.

Chris


joe@...
 

Dear Jerry,

Thank you for all the detailed answers to many of my questions including this one.  I have had nothing but superb experiences with Explore Scientific products, and yet better experiences with the companies customer service. I fear that on this alignment issue, atypically, Explore Scientific has taken its eye off the prize.  

Let's get down to basics. The G-11/PMC-8 is a polar scope-free mount with a computerized go-to control system so alignment is a basic function that is poorly addressed.  It seems to me that the development priorities for this product need to be revisited. The very help,  much appreciated, work-around suggestions that have been posted demonstrate the resourcefulness of the community of early adopters, but it is not the Explore Scientific style to bring an unfinished product, whatever its potential, to market. Buyers who spend in excess of $3000 have a right to expect that the mount+controls will provide all basic functions, including alignment.

The amount of thought you have already given to coding the all star alignment, and the solution that you've outlined suggests that you may privately agree. What message should be my take-away as potentially interested owner?

Joe Izen


Robert Hoskin <r_hoskin@...>
 

Indeed.  I am really not a fan of the subscription model, but with Robin, I'm happy to give it a couple of years before getting torqued about it.  He's doing a great job...



From: "Michael Fulbright mike.fulbright@... [ESPMC-Eight]"
To: ESPMC-Eight@...
Sent: Friday, June 22, 2018 6:02 PM
Subject: Re: [ESPMC-Eight] Re: Question from a prospective buyer: All Star Polar Alignment

 
Robin is doing so much development at the moment I also don't mind supporting his effort.  I really think he is trying to build a all around image acquisition solution and can't wait to see what it will be like in year or two. 

Michael Fulbright

On 6/22/2018 5:56 PM, 'W. Christopher Moses' chris_moses@... [ESPMC-Eight] wrote:
 
Oh...I didn't realize that.  I have the pro version.  Even if they charge $15/year it is worth it for me.  I really like the program.  Their PA routine is great and the new smart histogram looks great.

On Friday, June 22, 2018, 5:53:06 PM EDT, Steve Siedentop sdsiedentop@... [ESPMC-Eight] wrote:


 
No, I believe SharpCap is on a subscription model as well.

-Steve 

On Fri, Jun 22, 2018 at 5:47 PM chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 
Are you referring to TSX?  It is not cheap.  And the subscription is $100/year, for the pro version. Plus you have to buy the camera add-on in order to image with it.

I'm not sure if it is really worth the money or not...it is nice.





W. Christopher Moses
 

If it comes out as good as his current stuff, he has a real winner.


Michael Fulbright
 

Robin is doing so much development at the moment I also don't mind supporting his effort.  I really think he is trying to build a all around image acquisition solution and can't wait to see what it will be like in year or two. 

Michael Fulbright

On 6/22/2018 5:56 PM, 'W. Christopher Moses' chris_moses@... [ESPMC-Eight] wrote:
 
Oh...I didn't realize that.  I have the pro version.  Even if they charge $15/year it is worth it for me.  I really like the program.  Their PA routine is great and the new smart histogram looks great.

On Friday, June 22, 2018, 5:53:06 PM EDT, Steve Siedentop sdsiedentop@... [ESPMC-Eight] wrote:


 
No, I believe SharpCap is on a subscription model as well.

-Steve 

On Fri, Jun 22, 2018 at 5:47 PM chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

Are you referring to TSX?  It is not cheap.  And the subscription is $100/year, for the pro version. Plus you have to buy the camera add-on in order to image with it.


I'm not sure if it is really worth the money or not...it is nice.



W. Christopher Moses
 

Oh...I didn't realize that.  I have the pro version.  Even if they charge $15/year it is worth it for me.  I really like the program.  Their PA routine is great and the new smart histogram looks great.

On Friday, June 22, 2018, 5:53:06 PM EDT, Steve Siedentop sdsiedentop@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:


 

No, I believe SharpCap is on a subscription model as well.

-Steve 

On Fri, Jun 22, 2018 at 5:47 PM chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

Are you referring to TSX?  It is not cheap.  And the subscription is $100/year, for the pro version. Plus you have to buy the camera add-on in order to image with it.


I'm not sure if it is really worth the money or not...it is nice.


Michael Fulbright
 

You can get a lifetime subscription for Sharpcap for much less than a pole master.  If you already have a setup with a camera supported by Sharpcap it is a much better solution imho.

I use Sharpcap to polar align with these camera/telescope combinations:

- ASI120MM-S and 50mm guide scope @200mm focal length (FOV ~ 2 deg)
- ASI1600MM and 70mm imaging scope @ f/4.8 (FOV ~3 deg)
- ASI1600MM and 8 inch f/4 imaging Newtonian (FOV ~1.5deg)

I really don't see a scenario if you have a imaging or guiding setup with a degree FOV or larger where you'd need to spend money on a pole master.  I'd invest the money in your guiding solution instead.

Michael Fulbright

On 6/22/2018 5:42 PM, Steve Siedentop sdsiedentop@... [ESPMC-Eight] wrote:
 
I believe the catch is the pricing is a subscription.  If you already have a camera that will work with it, it’s definitely cheaper in general than a Polemaster.

-Steve

On Fri, Jun 22, 2018 at 5:08 PM chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

Sharpcap PA is Nice!  I'm trying to decide if I prefer it to the PoleMaster.  It's certainly cheaper, $15 vs $250



Steve Siedentop
 

No, I believe SharpCap is on a subscription model as well.

-Steve 

On Fri, Jun 22, 2018 at 5:47 PM chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

Are you referring to TSX?  It is not cheap.  And the subscription is $100/year, for the pro version. Plus you have to buy the camera add-on in order to image with it.


I'm not sure if it is really worth the money or not...it is nice.


W. Christopher Moses
 

Are you referring to TSX?  It is not cheap.  And the subscription is $100/year, for the pro version. Plus you have to buy the camera add-on in order to image with it.

I'm not sure if it is really worth the money or not...it is nice.


Steve Siedentop
 

I believe the catch is the pricing is a subscription.  If you already have a camera that will work with it, it’s definitely cheaper in general than a Polemaster.

-Steve

On Fri, Jun 22, 2018 at 5:08 PM chris_moses@... [ESPMC-Eight] <ESPMC-Eight@...> wrote:
 

Sharpcap PA is Nice!  I'm trying to decide if I prefer it to the PoleMaster.  It's certainly cheaper, $15 vs $250


W. Christopher Moses
 

Sharpcap PA is Nice!  I'm trying to decide if I prefer it to the PoleMaster.  It's certainly cheaper, $15 vs $250


r_hoskin@...
 

Joe,

If your C14 has a guidescope, and if you can see Polaris, then Sharpcap can help you perform a PA, without additional hardware. 

Without getting into the weeds, it leverages guidescope images from the Polaris area and platesolving, to measure misalignment and show you how to adjust your mount into alignment in real time.  Only takes a few minutes, and it's an inexpensive software subscription.

- Bob
 


hubbell_jerry@...
 

It is possible to use the ExploreStars alignment transform matrix coefficients (shown by turning on Show Alignment Data under Settings Preferences) to calculate the offset in Altitude and Azimuth of the mount. 

The technique would involve calculating the offset in ALT/AZ and then pointing the mount to a bright star adjusting for the calculated offset values. Then you would manually move the ALT/AZ controls to center the star and that would be it. Once you have manually adjusted the ALT/AZ then you would clear the alignment since you have now physically aligned the mount.

Pretty straight forward. I have worked on that math before but would need to refresh my memory and work on a spreadsheet version of the calculation to test it out. Unfortunately, I don't know when I would be able to spend time on it since I have probably 6 other priorities that I am working on currently 

If anyone is interested in working on this, here is the reference paper I used to create the Alignment function in the ExploreStars application. 


If you are interested in taking on this project (not easy!) I would suggest getting familiar with the equations and then derive a method to convert the transform coefficients to an offset in ALT/AZ coordinates. I use an open source library to do the matrix transform calculations called MathNet Numerics:


This really simplifies the work. I have this on my TODO list but I probably won't be able to get it done for a few months yet.

Thanks

Jerry Hubbell
Director Electrical Engineering
Explore Scientific, LLC.

---In ESPMC-Eight@..., <joe@...> wrote :

Celestron's competing CGX mount eschews  a polar scope in favor of their much-touted, "exclusive" All Star Polar Alignment 


    https://www.celestron.com/pages/all-star-polar-alignment


Celestron certainly deserves kudos for a clever idea which I understand works very well.  Celestron doesn't share its code, but the idea is sufficiently general that it shouldn't be patentable.  Is a PMC-8 implementation in the works?  


Every go-to scope manufacturer with sufficient compute power in their scope's processors should be able to implement the idea.  I think it will be common in the near future.  


A PMC-8 implementation affects the choice of whether to purchase an expensive ~$240 Losmandy G-11 scope accessory.


(Thanks for the responses to my many questions!)


W. Christopher Moses
 

You can use astrotortilla, which is free, or use TheSkyX - I think their PinPoint model works with all mounts.

Frankly, I would rather have the requirement of a view of Polaris than of the equator. Of couse, my fov isn't great.


joe@...
 

Celestron's competing CGX mount eschews  a polar scope in favor of their much-touted, "exclusive" All Star Polar Alignment 


    https://www.celestron.com/pages/all-star-polar-alignment


Celestron certainly deserves kudos for a clever idea which I understand works very well.  Celestron doesn't share its code, but the idea is sufficiently general that it shouldn't be patentable.  Is a PMC-8 implementation in the works?  


Every go-to scope manufacturer with sufficient compute power in their scope's processors should be able to implement the idea.  I think it will be common in the near future.  


A PMC-8 implementation affects the choice of whether to purchase an expensive ~$240 Losmandy G-11 scope accessory.


(Thanks for the responses to my many questions!)