Date   

Re: 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. 



Re: PHD2 Guiding for G-11

W. Christopher Moses
 

I see the guiding file, but not the images yet.  What is its name?


Re: Question from a prospective buyer: All Star Polar Alignment

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


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

Can you upload a single sub also, please.



On Sat, Jun 23, 2018 at 3:16 PM, lamb_mark@... [ESPMC-Eight]
 

Chris, 

 
I just added my PHD2 guidelog from the last session.

I also uploaded a JPG photo of my M13 stacked image (7Dmk2, 60s, ISO1600, 144x) which was made from shots over 4 nights.   This will show my egg/triangle stars.

This was stacked with DSS 4.1, using DSS AWB, and initial processing using Ps CS6.  I am a novice with Ps, but bought it last year to sharpen my Eclipse images.  I do NOT have any add-ins, but will probably get them in the near future.  I started with DSS Autosave.TIF, and while it was still 32-bit, had Ps slightly crop the edges, squeeze the histogram at the black point and white point (without clipping any data) to maximize the DR before converting to 16-bit, and slight increased the exposure.  Then I converted to 16-bit, did a minor Curve stretch (RGB), tweeked the Curves in the separate Red, Blue, and Green channels, and then reduced Contrast a little.

This photo is no where near finished, as I am just now starting to play with Ps and do not know what I am doing.

I liked the DSS output better with AWB selected, as the background was MUCH more neutral.  I color sampled 4 point in the background to make it neutral.  I also had DSS "Set Black Point to 0", used AHD Interpolation, and Median Kappa-Sigma Clipping.

I noticed something strange, if I directly pulled in the Autosave.TIF file into Ps, it came as a 32-bit file.  But if I only change the Autosave.TIF name to something descriptive before loading it into Ps, it would go to ACR which would convert to 16-bit.  So I would start with Autosave.TIF into Ps, as I wanted to do what I could in 32-bit, so my 16-bit converted files would fill the entire 16-bit  dynamic range.
 


Re: PHD2 Guiding for G-11

Mark Lamb
 

Chris, 
 
I just added my PHD2 guidelog from the last session.

I also uploaded a JPG photo of my M13 stacked image (7Dmk2, 60s, ISO1600, 144x) which was made from shots over 4 nights.   This will show my egg/triangle stars.

This was stacked with DSS 4.1, using DSS AWB, and initial processing using Ps CS6.  I am a novice with Ps, but bought it last year to sharpen my Eclipse images.  I do NOT have any add-ins, but will probably get them in the near future.  I started with DSS Autosave.TIF, and while it was still 32-bit, had Ps slightly crop the edges, squeeze the histogram at the black point and white point (without clipping any data) to maximize the DR before converting to 16-bit, and slight increased the exposure.  Then I converted to 16-bit, did a minor Curve stretch (RGB), tweeked the Curves in the separate Red, Blue, and Green channels, and then reduced Contrast a little.

This photo is no where near finished, as I am just now starting to play with Ps and do not know what I am doing.

I liked the DSS output better with AWB selected, as the background was MUCH more neutral.  I color sampled 4 point in the background to make it neutral.  I also had DSS "Set Black Point to 0", used AHD Interpolation, and Median Kappa-Sigma Clipping.

I noticed something strange, if I directly pulled in the Autosave.TIF file into Ps, it came as a 32-bit file.  But if I only change the Autosave.TIF name to something descriptive before loading it into Ps, it would go to ACR which would convert to 16-bit.  So I would start with Autosave.TIF into Ps, as I wanted to do what I could in 32-bit, so my 16-bit converted files would fill the entire 16-bit  dynamic range.
 


New file uploaded to ESPMC-Eight

ESPMC-Eight@...
 

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the ESPMC-Eight
group.

File : /User Contributions/PHD2_GuideLog_2018-06-18_221720.txt
Uploaded by : lamb_mark@hotmail.com <lamb_mark@hotmail.com>
Description : Mark Lamb PHD2 Guide Log

You can access this file at the URL:
https://groups.yahoo.com/neo/groups/ESPMC-Eight/files/User%20Contributions/PHD2_GuideLog_2018-06-18_221720.txt

To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398

Regards,

lamb_mark@hotmail.com <lamb_mark@hotmail.com>


Re: Question from a prospective buyer: All Star Polar Alignment

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


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

No problem. Glad to help

On Saturday, June 23, 2018, 10:35:04 AM EDT, lamb_mark@... [ESPMC-Eight] wrote:


 

Chris,


Thanks for all the quick replies; all in the time since I replied early AM and then went on a 3 hr pre-breakfast bike ride!

My 7Dmk2 has 4.08 micron pixels, so I am imaging at 1.2"/px.


Re: PHD2 Guiding for G-11

Mark Lamb
 

Chris,

Thanks for all the quick replies; all in the time since I replied early AM and then went on a 3 hr pre-breakfast bike ride!

My 7Dmk2 has 4.08 micron pixels, so I am imaging at 1.2"/px.


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

DO you happen to know the pixel size of the camera?  I'll crunch some numbers and see what sort of exposure time you can do with different PA errors before seeing any trailing.

Also, what are you using to process the images: photoshop, pixinsight?

Thanks,
Chris

BTW - feel free to give me a call if you like.  Sometimes typing all this can be tedious and error-prone.  Just send me a direct email and I'll send you my number.

On Saturday, June 23, 2018, 6:25:33 AM EDT, lamb_mark@... [ESPMC-Eight] wrote:


 

Chris,


My imaging camera is a Canon 7Dmk2, APS-C DSLR, it is attached to my 2" focuser with a single extension tube and compression collar.  I try to keep this collar tight (3 thumb screws), but it is not the most rigid connection.  It would be nice if there was a locking, bayonet-type mount for my 2" T-adapter.  

What are pinched optics?

I have NOT done a star test.  What is it?

Thanks!


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

I thought that heard that polar alignment of 1' was typically good using a polar scope, but that PoleMaster could get better alignment much faster.

That would be very good.  So good I wouldn't count on getting it that low very often.  Even 2" is tough sometimes.

Ohhhh....I see. You mean 1' not 1".  Sorry, it's early and my coffee hasn't kicked in yet. 1' probably is good using a polar scope.  I would expect PM to much more accurate than squinting on your hands and knees at tiny dots of light.

My 10-15" is 4x as accurate as 1'.  I do not know how I can get PM any more accurate, though getting the cursor on the exact center of the stars IS a challenge as they bounce about quite a bit (seeing?).

Just use PoleMaster and you will be fine.  Don't worry about Phd2's numbers. I'm not sure I've ever seen mine down to 2" in PhD2.

No matter which 3 methods you use, you will get three different answers.

This isn't just a PMC-8 thing.  My old iEQ45 behaved the same way and my friends iEQ60ec does also.

It's as if slewing the scope introduces some mysterious movement in the PA.  Now, I would expect a tiny change due to hanging cables, loose parts, etc but not the giant ones everybody observes when comparing PM to PhD2.

I've spent a lot of time on this issue.  I have one remaining test to run - using AstroTortilla to calculate PA at the location of the target. ( AT can calculate the PA error at any point in the sky very quickly.) Then I would like to see what PhD2 says at the same point in the sky.  In fact, I would like to run AT at multiple points over the sky and see how much different the PA is.  This is, basically, creating a mount model.  I'm still looking into automating it, but it shouldn't be too bad if I can find one chunk of code I need.

I've been meaning to post a thread over on CN about this.  I'll post the link when I do.

You seem to be doing great.  You have learned a lot really fast! Congrats.

Chris


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

Pinched optics are when the screws holding the lenses in place are too tight and very slightly deform the lens.

A star test is a simple way of determining the optic quality of a setup.  I could describe it, but it is probably easier to just google "star test telescope." There are numerous articles and videos.
Its a really quick procedure and is worth learning.


Re: PHD2 Guiding for G-11

Mark Lamb
 

Chris,

I thought that heard that polar alignment of 1' was typically good using a polar scope, but that PoleMaster could get better alignment much faster.

My 10-15" is 4x as accurate as 1'.  I do not know how I can get PM any more accurate, though getting the cursor on the exact center of the stars IS a challenge as they bounce about quite a bit (seeing?).


Re: PHD2 Guiding for G-11

Mark Lamb
 

Chris,

My imaging camera is a Canon 7Dmk2, APS-C DSLR, it is attached to my 2" focuser with a single extension tube and compression collar.  I try to keep this collar tight (3 thumb screws), but it is not the most rigid connection.  It would be nice if there was a locking, bayonet-type mount for my 2" T-adapter.  

What are pinched optics?

I have NOT done a star test.  What is it?

Thanks!


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

If you have a PhD2 log file that has a session in it that is more than about 30 min, upload it to the file section.


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

"Is this a reasonable polar alignment?  Should I also have PHD2 do drift align?"

8"-15" is pretty lousy.  Most sources will tell you to shoot for 2" or under.  In reality, the accuracy you need depends on a number of factors, including your arcsec/pixel, the relative location of the guide scope, the exposure time, etc.  I can send you the math if you really want it.

But, as I mentioned before.  I don't pay attention to PhD's reported value any more.  I get a good PA with PoleMaster or Sharpcap and that's it.

(Incidentally, I'm working on some math and software that, among other things, should help explain and quantify the discrepancy between PM and PhD2.)

So, as long as your PM results look good, I would stick with it.

I'm sure someone will disagree, and I welcome other points of view.  I've spent a lot of time playing with multiple software packages and their measure of PA.  I would like to hear other peoples experiences.


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

With respect to the image's star shapes - A few things:

1. What is your main imaging camera?
2. Triangular or diamond-shaped stars usually mean pinched optics in my experience.
3. Have you done a star-test?

I am no expert, by any means.  I would really recommend posting them to a  CloudyNight forum, either Beginner CCD/CMOS Imaging or DSLR Imaging.  Whichever is appropriate.  

If you want to dig into the nitty, gritty details of star shapes and optical issues, the definitive work seems to be:



It is easily approachable if you have any sort of technical background.


Re: Question from a prospective buyer: All Star Polar Alignment

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.





Re: PHD2 Guiding for G-11

W. Christopher Moses
 

Huh...I just sent a long response and it appears to have vanished into the ether. I'll retype it after dinner.


Re: PHD2 Guiding for G-11

W. Christopher Moses
 

Hi,
So here is my interpretation of some some of your questions and results.
In no particular order:

1. Can anybody give me setting recommendations?
Only kind of.  To truly share exact settings, your scopes, cameras, etc would have to be identical.  However, here are some things I have found generally useful:

A. I'm still experimenting with hysteresis and PPEC. It looks to me like PPEC usually gives better results.  I would give it a try - keep in mind that its results will get better with time.
B. Two seconds is pretty low. I would expirement with 3-5.  I usually find that 3 or 4 works best for me.

2. Polar alignment results
I've given up paying much attention to PhD2's PA calculation.  It varies too much.  I can have a perfect PA in both PM and SharpCap and PhD2 will tell me I'm way off.  I have some ideas about what is causing this, but that is another subject.
Once you get a good PA with PM, I would stick with it.  Of course, you will need to rerun it each night even if you haven't moved your equipment. 

3. Where to Calibrate PhD2
People are split on this. Some say you should calibrate on your subject, some say you should calibrate close to the equator.  The docs say the latter, so that is what I do.

4. RA Osc:
From the manual:
The 'RA Osc'  value shows the odds that the current RA move is in the opposite direction as the last RA move.  If you are too aggressive in your guiding and over-shooting the mark each time, this number will trend toward 1.0.  If you were perfect and not over- or under-shooting and your mount had no periodic error, the score would be 0.5  Taking periodic error into account, the ideal value would be closer to 0.3 or 0.4.  If this score gets very low (e.g. 0.1), you may want to increase the RA aggressiveness or decrease the hysteresis.  If it gets quite high (e.g. 0.8), you may want to adjust aggressiveness/hysteresis in the opposite direction. 


So, it sounds like your RA Osc is pretty good.  Personally, I try to keep mine pretty close to .5. Maybe I should experiment with getting the value lower.

4. Total RMS:
A Total RMS error of 1-1.5 is high.  On bad nights I'll get 1 or a touch over. On good nights I can get 0.5"-0.7"

I'll try to answer in more detail later, but I have to run right now.

8921 - 8940 of 10082