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Starwiz

CdC and Telescope Alignment

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I've just got Cartes Du Ciel controlling my telescope, but of course the hand controller is no longer connected.

So, my question is - how do I align the telescope now?

The logical way I can think of is to make CdC point to Polaris, then point the scope at Polaris.  Then slew to another object and adjust scope as necessary for a sort of 1 star alignment.

Is this correct or am i barking up the wrong tree?  Is there a better way?

Thanks

John

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Correct, are you using a camera for imaging? If so then platesolving is the best way  very accurate, I use APT and use the pointcraft tool .

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2 hours ago, Starwiz said:

The logical way I can think of is to make CdC point to Polaris, then point the scope at Polaris.  Then slew to another object and adjust scope as necessary for a sort of 1 star alignment.

You can do that - when you have the scope pointing at what it thinks it is looking at then right click on the object in Cdc and tell it it is correct (cant remember the exact phrase to click on).

As bottletopburly says - platesolving is much more accurate.

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I guess I'm a bit old school here. I use CdC but I align the mount using the polar align tool in EQASCOM.

 

 

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Thanks all, for the help.  Much appreciated.

John

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A bit of a mix really but IMO:-

1. Polar align using any method excluding Platesolving. So manually using polar scope and EqAscom as stated above or via something like Sharpcap Pro (£10). Problem is you have to be able to see Polaris 😞

2. Then use Platesolving.

3. If you use EQmod use N point alignment. Platesolving does not solve Slewing accuracy it just gets you to where you want to be and does this with a series of GoTo's. Using N point alignment does allow  good slewing within any triangle created in my experience. Then use ,if required,Platesolve to "dead centre" the object for AP. http://eq-mod.sourceforge.net/eqmod_polaralign.html - If you cant see Polaris Eqmod N point alignment will still work 🙂

Depending on your kit accurate polar alignment will place your slew,IMHO, near (not everytime) and minimise the number of Platesolve generated GoTo's  to be dead centre. 

Another alternative is "Drift Alignment".

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Assuming you have a Skywachter/celestron? mount, I do the following using 1 star alignment:

1) Assure the mount is polar aligned using the mount alignment scope or just visually.

2) Unlock the scope and point the telescope by hand to the celestial pole/Polaris. Lock again.

3) Power on the mount. The mount is now roughly aligned.

4) Slew using the planetarium program to a bright well know star/object.  The scope should  point to the object within maybe 10 degrees. Unlock the mount and center the scope by hand to the star using the finder scope and lock again  (or use plate solving to sync)

 

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Posted (edited)

Never heard of your step 4 before. I use the slew and sync buttons in CdC.  

After polar alignment I:

slew to a bright star using CdC 

step to the eyepiece and centre the star by adjusting the scope using a gamepad (set up with EQMOD)

press sync in CdC

repeat as required. 

Sometimes I just sync to a few stars around the region of the sky I'm imaging. 

 

Edited by Ouroboros
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I sometimes find in cdc that from the home position I have to make sure I choose a star that is no to far away and start to center and sync until I have enough  stars mapped to give me descent accuracy. 

TBH platesolving take all the hassle and time wasted away.

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21 minutes ago, spillage said:

I sometimes find in cdc that from the home position I have to make sure I choose a star that is no to far away and start to center and sync until I have enough  stars mapped to give me descent accuracy. 

TBH platesolving take all the hassle and time wasted away.

What hassle? It takes a few minutes to sync the mount to the stars. I usually do it before it's properly dark just as the brightest stars like Vega, Arcturus etc are coming out. 

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On 14/06/2019 at 09:58, Ouroboros said:

Never heard of your step 4 before. I use the slew and sync buttons in CdC.  

Your method is good as the others. There are three ways to sync it:

  • Unlock the scope, move it manually till the target star is in the finder and to lock it again is a quick way to get it aligned (from 20  or 30 degrees offset) in maybe 20 seconds without the requirement to sync is the mechanical way.  You could use this method with only the mount and no camera or computer available.

or

  • Slew with the control buttons to the target star and sync to it in the planetarium program. (Planetarium program with scope control required)

or

  • Take an image, do the astrometric (plate) solving and sync the mount to the solution.  (Camera, imaging program and solver required)

 

All methods work. I use normally the last one but you need to be fully automated.

 

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Agree with what has been said. I use platesolving with Sharpcap which puts the sync points in EQMOD. I have a list of bright stars at (roughly) 2h intervals at 30-60N which I use as my starting point. That way, I don't have to worry too much about how the scope is positioned on the mount after PA and can still get it within the required max distance for Sharpcap to do its thing.

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Posted (edited)
57 minutes ago, han59 said:

Your method is good as the others. There are three ways to sync it:

  • Unlock the scope, move it manually till the target star is in the finder and to lock it again is a quick way to get it aligned (from 20  or 30 degrees offset) in maybe 20 seconds without the requirement to sync is the mechanical way.  You could use this method with only the mount and no camera or computer available.

or

  • Slew with the control buttons to the target star and sync to it in the planetarium program. (Planetarium program with scope control required)

or

  • Take an image, do the astrometric (plate) solving and sync the mount to the solution.  (Camera, imaging program and solver required)

 

All methods work. I use normally the last one but you need to be fully automated.

 

It was the thought of manhandling an unlocked mount whilst trying to delicately centre a star in the eyepiece within a fraction of a degree that threw me. But maybe I misunderstood the procedure being described. 🙂 

Edited by Ouroboros
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43 minutes ago, Demonperformer said:

Agree with what has been said. I use platesolving with Sharpcap which puts the sync points in EQMOD. I have a list of bright stars at (roughly) 2h intervals at 30-60N which I use as my starting point. That way, I don't have to worry too much about how the scope is positioned on the mount after PA and can still get it within the required max distance for Sharpcap to do its thing.

Presumably there's  the advantage of doing all the alignment at the computer screen. Whereas I'm doing it by eye at the scope and then coming back to the laptop (albeit only 4m away) to click the sync button before slewing to another star and walking back to the scope to align on that one.  Lot's of ways to skin a cat as they say. 

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With the plate solving methods do you have to be connected to the Internet for it to work or is the star database downloaded to your computer as part of the plate solving application?  

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10 minutes ago, Ouroboros said:

With the plate solving methods do you have to be connected to the Internet for it to work or is the star database downloaded to your computer as part of the plate solving application?  

No - there are a number of stand alone packages (most use Linux emulation Cygwin) - even one by someone who posted on your thread LOL. 

They are

1. Astrotortilla

2. All Sky Plate Solve (ASPS)

3. Platesolve2

 

Plus others.

Most depend on an Ascom connected mount and download std Astrometry net index's depending on your FOV (19gb max if all downloaded). They do NOT use the internet just required reasonable fast SSD/CPU to do platesolving below 30secs.

Suggest you read a few other threads on SGL especially on the difference between "Blind" and "std" platesolving. 🙂

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@stash_old thanks. Interesting to find out how it works. I seem to have managed so far without it. 🙂 

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I'm having some problems with this.  I set up the scope to point to polaris, then set CdC to the same and in CdC do a right-click - Telescope - Sync Alp:UMi to sync to polaris.

Then I try slewing to another object, but the scope doesn't go where expected.  Also, sometimes it will give a 'below horizon' warning when it is clearly not.

Any thoughts on what the problem might be?

Thanks

John 

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19 minutes ago, Starwiz said:

I'm having some problems with this.  I set up the scope to point to polaris, then set CdC to the same and in CdC do a right-click - Telescope - Sync Alp:UMi to sync to polaris.

Then I try slewing to another object, but the scope doesn't go where expected.  Also, sometimes it will give a 'below horizon' warning when it is clearly not.

Any thoughts on what the problem might be?

Thanks

John 

Might first thought would be to check date, time and location in cdc.

Helen

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My experience is....

From powering on my rig. Point it at a very bright star that I can see in the sky and on CdC. Get the star close enough to center of view. Right click on same star in CdC and Sync with mount. That tells the mount where it is pointing.

Platesolve is much easier if you get it working(Which I highly recommend). I point the scope just to the east of north. Take a 10 second image and plate solve. Depends on lots of things but it plate solves within 10 mins, sometimes 30 seconds but usually 4 mins...Be patient if it does not solve ..Give it 10mins to be sure. Once it's plate solved correctly, I find I can slew most places and plate solve again within a minute and be extremely accurate.

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Posted (edited)
3 hours ago, Star101 said:

"it plate solves within 10 mins, sometimes 30 seconds but usually 4 mins...Be patient if it does not solve ..Give it 10mins to be sure. Once it's plate solved correctly, I find I can slew most places and plate solve again within a minute and be extremely accurate."

I usually solve under 10sec using the local installation. I can understand that people would be reluctant to use plate solving if every solution took minutes to get solved. To speed up solving, you need to have your FOV exactly right in the configuration and  download only the appropriate index files. If not, you will need to go through all index files and there are a lot :) ...There are a couple more tips to speed things up in the documentation.

To get the exact FOV you can do a blind solve and Astrometry.net will tell you. If I use astronomy tool calculator I get 2.49 x 1.66 deg FOV for my setup, a blind solve gives me 2.44 x 1.63 deg FOV. Not a big difference, but it is accurate.

In my case, I only use plate solving. I never do any kind of star alignment, I just sync to the solution when on target. I even use astrometry to get my polar alignment right.

Edited by Vox45
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Thanks all, some very helpful suggestions there, so I was able to look at a few things I hadn't thought of.

I think I've finally got to the bottom of it after much daytime experimentation.

I was aligning CdC exactly with Polaris to polar align the mount.  Polaris of course, isn't in exactly the right position and I think this was confusing the software somehow.  When it actually needs to look directly at Polaris, it has to slew the mount by about 6 hours in right-ascension at the time of the experimentation.

I love this hobby 😀

Now I need to get plate solving working.

John

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On 19/06/2019 at 13:26, Vox45 said:

I usually solve under 10sec using the local installation. I can understand that people would be reluctant to use plate solving if every solution took minutes to get solved. To speed up solving, you need to have your FOV exactly right in the configuration and  download only the appropriate index files. If not, you will need to go through all index files and there are a lot :) ...There are a couple more tips to speed things up in the documentation.
 

If I plate solve with my TS65Q (420mm) It does platesolve quite fast. However, if I platesolve with the C11 (2800mm) It can take its time.  * I think, maybe the FOV is much wider with the TS65Q so generally has many more stars to use! ( guessing!!)*

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Are you restricting the index files the solver uses? The one I use starts with the widest fov and works down to the narrowest, so if I had a very narrow fov and used all the index files it would waste an awful lot of time getting even into the ballpark.

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8 hours ago, Demonperformer said:

Are you restricting the index files the solver uses? The one I use starts with the widest fov and works down to the narrowest, so if I had a very narrow fov and used all the index files it would waste an awful lot of time getting even into the ballpark.

How do I restrict and prioritise the index files?  I've had a look but can't see how to do it.

Thanks

John

 

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