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Celestron Nexstar Plate Solve Routine - skip alignment

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#1 fuadramsey

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Posted 28 May 2020 - 12:07 AM

I am barely figuring out plate solving and got it to work and frame images. It's awesome. 

 

Now I want to skip alignment. I read that you just need to polar align first and then slew to an object, and then plate solve. My question which never really gets addressed is regarding time and location in the handcontrol/PC computer. What is your Nexstar or similar routine? 

 

Do you just use last alignment and then update the time and location in the handcontrol, or do you just use last alignment and then update the time and the nearest city location in the handcontrol. 

 

I guess I'm trying to figure out how important is time and location is for plate solving if you want to skip a 2 star alignment and 3 star calibration.

 

 

Thanks! 

 

I just got back into the "hobby" after about 10 years of not imaging. The software is great, most notably Astro Photography Tools!



#2 oshimitsu

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Posted 28 May 2020 - 12:52 AM

The date and time gives your hand controller a rough starting point so it's fairly important. If you have the date and time off your mount may point to the ground when you tell it to slew. What are you using for plate solving? 

 

I polar align, turn the mount on, skip alignment by choosing quick align and then slew to a bright star so I can set focus. My scope will generally not be anywhere close but that's fine because I can just blind solve and plate solving can do the rest for me.



#3 fuadramsey

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Posted 28 May 2020 - 01:42 AM

I'm plate solving for imaging. I'm just trying to figure out the fastest way to get to imaging.

Incidentally I modified my hand controller to connect via Bluetooth. I'm able to connect and drive the scope via Bluetooth with Sky Safari ( and to my PC via ASCOM). I also found an app that sends the date and time to the hand controller but I think something is off, or I'm doing something wrong.

I have to do more testing to see when I can actually sync the hand controller to my phone via the app.

Ideally I'd like to turn on the scope, set time and location via Bluetooth, use last alignment, and then polar align with PHD2, then do a go to that's somewhat close and plate solve.


Last time I tried that the go to was way off. I'm also very familiar with the alignment process and have excellent go tos. I think the issue this time was the time and location setting I sent via Bluetooth with Scope Friend.

Any tips?

#4 sg6

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Posted 28 May 2020 - 02:13 AM

I'm plate solving for imaging. I'm just trying to figure out the fastest way to get to imaging.

Can I argue the point that you do not want "the quickest way to get to imaging", you want "the best way to get to imaging". And it likely is not the quickest.

 

Would say some alignment is required as the scope has to compensated for tilt - Left/Right and Forward/Back - if the compensation used is wrong then the scope will move incorrectly.

 

Is alignment really that hard?

Takes me 2 minutes, maybe less. Half of mine is done while putting the scope and all the bits out.

It is also a way to check that data is right and everything.

 

Ultimately I will argue that the person that takes 10 minutes to set up and align and get everything as good as reasonable will produce better images.

 

These scopes should be termed semi-auto or semi-computerised. They are not fully by any means.



#5 oshimitsu

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Posted 28 May 2020 - 02:16 AM

Can I argue the point that you do not want "the quickest way to get to imaging", you want "the best way to get to imaging". And it likely is not the quickest.

Would say some alignment is required as the scope has to compensated for tilt - Left/Right and Forward/Back - if the compensation used is wrong then the scope will move incorrectly.

Is alignment really that hard?
Takes me 2 minutes, maybe less. Half of mine is done while putting the scope and all the bits out.
It is also a way to check that data is right and everything.

Ultimately I will argue that the person that takes 10 minutes to set up and align and get everything as good as reasonable will produce better images.

These scopes should be termed semi-auto or semi-computerised. They are not fully by any means.

Plate solving is quicker and more accurate. I literally turn my scope on, quick align to skip the alignment process, slew to a star, blind solve and the scope slews back with the target dead center. If the OP used a starsense it would be the same thing.

Sent from my SM-N976V using Tapatalk

#6 oshimitsu

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Posted 28 May 2020 - 02:23 AM

I'm plate solving for imaging. I'm just trying to figure out the fastest way to get to imaging.

Incidentally I modified my hand controller to connect via Bluetooth. I'm able to connect and drive the scope via Bluetooth with Sky Safari ( and to my PC via ASCOM). I also found an app that sends the date and time to the hand controller but I think something is off, or I'm doing something wrong.

I have to do more testing to see when I can actually sync the hand controller to my phone via the app.

Ideally I'd like to turn on the scope, set time and location via Bluetooth, use last alignment, and then polar align with PHD2, then do a go to that's somewhat close and plate solve.


Last time I tried that the go to was way off. I'm also very familiar with the alignment process and have excellent go tos. I think the issue this time was the time and location setting I sent via Bluetooth with Scope Friend.

Any tips?

I didnt mean "why" are you plate solving, I was asking what software are you using to plate solve. I'm not at all familiar with how you were able to convert your HC to bluetooth.



#7 fuadramsey

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Posted 28 May 2020 - 02:39 AM

I'm using Astro Photography Tools Point Craft utility, near solve routine.

As far as the handcontrol I wired a HC-05 Bluetooth module to the serial line. I installed a switch to turn it on and off so I can use either Bluetooth (visual use control with Sky Safari) or serial wired to USB for guiding.
I don't know how reliable guiding is over Bluetooth and would rather have a solid connection.

Im using a CG-5 and getting solid 5 minute subs with an F5 1500 reflector. I think I'm getting the most out of the mount that I can. I even got some 10 minute subs the other night during a test.

I'll figure it out, the issue is time and I don't have a backyard so I've been going out to the desert and relearning all this again.

#8 ButterFly

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Posted 28 May 2020 - 02:52 AM


I guess I'm trying to figure out how important is time and location is for plate solving if you want to skip a 2 star alignment and 3 star calibration.

It's the difference between blind solving and solving within a radius from the scope's purported RA+Dec.  Solving is just quicker the closer you are to where it starts looking.

 

So with Nexstar scopes, polar align a well leveled mount.  Line up the index well on both axes.  Turn on the mount, set time and location well, then do a quick align.  The smaller the errors inputting the values, and your inherent cone error, the closer a slew is to the target.  In all likelihood, it's small enough to be close enough for quick solves.  Make sure you sync the mount before caibrating PHD2 so PHD2 knows where it is.



#9 fuadramsey

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Posted 28 May 2020 - 10:33 AM

Sounds good, that's pretty much what i've been doing minus the quick align. I'll give that a few more goes and nail down the Bluetooth time/location sync. 

 

I'm just trying to add up all these little things that save a good amount of precious dark sky time so I can relax and have a beer while my scope does the work!

 

Here's where I got most of the info to add Bluetooth to my handcontroller. This has pretty much everything you need to know how to do it.

https://astro.marxra...andMarx2018.pdf

 

Here's an image I got from the CG-5 last weekend. Now i have to relearn processing  . . .

 

 
NGC4631 Whale Galaxy

 

 

 

 

 



#10 fuadramsey

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Posted 28 May 2020 - 11:09 AM

I may have found the issue with the Bluetooth time/date sync!  There's a GMT timezone offset I haven't made in the app Scope Friend. It's under the settings menu/GMT Timezone offset. I guess I didn't set it because right above that setting there's a setting for DST, however I just reread the GMT Timezone Offset setting and it says " . . . This value is independent of the current DST setting!" I updated it, so we'll see.

 

Seems like that will solve my time/location Bluetooth sync operation. I'm going to polar align, then select use last alignment. After that I'll update the time/location via bluetooth and then try a go to. I bet that gets me in the ballpark.



#11 TelescopeGreg

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Posted 28 May 2020 - 03:54 PM

I may have found the issue with the Bluetooth time/date sync!  There's a GMT timezone offset I haven't made in the app Scope Friend. It's under the settings menu/GMT Timezone offset. I guess I didn't set it because right above that setting there's a setting for DST, however I just reread the GMT Timezone Offset setting and it says " . . . This value is independent of the current DST setting!" I updated it, so we'll see.

 

Seems like that will solve my time/location Bluetooth sync operation. I'm going to polar align, then select use last alignment. After that I'll update the time/location via bluetooth and then try a go to. I bet that gets me in the ballpark.

If you are moving the mount between imaging sessions, I'd recommend using Quick Align instead of Last Alignment, so that you start from a consistent, neutral mapping of the sky.  If nothing else, it's one less variable that could be a problem at some random time.

 

I'm also assuming by "Celestron Nexstar" you are NOT talking about the SE mounts (Alt / Az), but about the GEM-types.  So, an AVX or similar.  I have an AVX.

 

I'm using a different toolset than you at the mount, but this is my "quickest path to beer".  Do a good job at polar alignment - take your time there to be precise - then turn on the mount.  The mount should remember both the location from last time, and know what time it is.  If not, you probably haven't enabled the internal battery.  It's in the Utility menu.

 

Using the hand controller, slew to a bright star near your intended target, and get the camera in focus.  Since the mount will likely miss the star, get it centered in the camera's field of view.  With the hand controller, add that star in as an alignment star.  This gets the internal alignment pretty close.

 

I then look up the target in my mount-control software (CCDciel in my case), and use it to slew to the target.  What it does is command the mount to move, then takes a verification image.  That gets plate solved and sync'd to the mount.  It's going to be off a bit, so a second slew is automatically done, imaged, and solved.  That is almost always dead on target.  Fire up the autoguider, calibrate if you have to, and you're off to imaging!



#12 fuadramsey

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Posted 28 May 2020 - 05:16 PM

"path to beer" I love that.

 

Cool, I'll start using Quick Align. I like that option better since I always start at the exact index marks and a good polar alignment. 

 

I use a CG-5 , you know, the coffee grinder. It has the Nexstar hand control. 



#13 fuadramsey

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Posted 01 July 2020 - 11:17 AM

Well, I got if figured out and have ran this several times and my path to beer is pretty quick now . . . about 1/2 hour.

 

Here's how I get my CGEM II ready to image.

 

 

  1. Level and point the mount North using a compass (keeping magnetic declination in mind).
  2. Balance the mount and OTA with all gear on it, and get the DSLR focus  close using liveview or looking through the viewfinder. -just a quick in the ballpark focus.
  3. Set the mount up with the polar scope using the circle in the polar scope and placing Polaris in the correct position. I don't rotate the RA, I just use an app that shows where Polaris should be on the circle for that time/location. This is helpful so I can load up and balance my scope with all the gear (camera, guidecam, cables) during light.
  4. Do a polar alignment with SharpCap. Still don't need the mount on. 
  5. Put the mount back on the index marks. Connect the mount to Celestron's CPWI program and update the time and location when it prompts me. Then I do a quick align. No star alignment needed.
  6. Connect APT to the mount and DSLR and do a GoTo++ to a bright star. This will get me pretty close to the item I go to, and then APT will take a photo, and plate solve and center the item in my DSLR. It'll take a couple times to do it and it runs by itself and is pretty quick and it's like magic.
  7. I'll adjust my focus using a Bahtinov mask and the Bahtinov tool in APT using live view while I'm on this bright star.. This is pretty quick too.
  8. After I'm all set, I'll just do a GoTo++ in APT to the item I want to image. Make sure to press sync the mount when prompted. This basically does a one star alignment on the item you just framed/plate solved.
  9. I start PHD2 and connect my mount (using CPWI) and guidecam. I'll run the guide assistant and apply the suggestions. I believe this should be run once a night or if the seeing changes. I apply the recommended adjustments. 
  10. I then start imaging. I do this with APT and a script. I can tell it to image one object and then go to another and capture that and park the scope, and then hibernate the computer. 

And finally I have a beer. Last couple of times the path to beer was about 1/2 hour. After that I'll do some visuals and hang out! 

 

enjoy!



#14 TheHarvester

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Posted 01 July 2020 - 02:28 PM

Now, all you need to figure out is why you have bad taste in beer.




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