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Astrometric (plate) solving on your phone, ASTAP for Android

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#1 han.k

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Posted 13 October 2021 - 05:24 AM

The ASTAP command-line solver has been compiled for Android. Binaries are available at SourceForge. An app around it would be required to make it useful. Are the any volunteers who interested in creating such an app?

 

Below a screenshot of a test in the Android emulator BlueStacks

 

Han

 

astap_for_android.png


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#2 jrschmidt2

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Posted 13 October 2021 - 08:14 AM

I'm trying to imagine the workflow here.  Where would the images come from, given that (aside from ASI Air app?) What would one do with the resulting platesolve data?  This would seem really useful if there were an EAA + ASCOM app for Android that it could be integrated into.

 

Writing an app that simply selected an image from the user's phone and then platesolved it would be easy.  But I guess I don't see the utility of that.



#3 han.k

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Posted 13 October 2021 - 10:29 AM

Using the ASIair would not make sense. It is more a replacement.

 

One possibility would be to transfer the images from a DSLR camera to the phone. Solving could give the user information where the DSLR camera is looking at.

 

At the moment I don't foresee a direct control loop to slew the mount to a desired position. 

 

If it possible to capure stars with the phone camera and solve the image you could consider other applications. But  since this will take a few seconds, I don't think that is a pratical application compared with the almost instant response of the gyro sensors of the phone.

 

Han


Edited by han.k, 13 October 2021 - 10:30 AM.


#4 tjay

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Posted 13 October 2021 - 06:34 PM

I wonder if it could be used in combination with the gyro sensors on the phone to do something similar to what the Celestron StarSense Explorer scopes do...



#5 han.k

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Posted 14 October 2021 - 04:40 AM

Looking to some StarSense videos, the solving seems to be done in the keypad or in the camera itself but not in the phone. I had the impression StarSense takes about 10 seconds to solve. That is not a problem if there is a control loop back to the telescope and you can sync and slew the telescope with the correct amount of degrees to target.

 

If you would use a phone solver as feedback for a Dobson and correct the mount manually then the solving should be quick. By correcting manually you would easilly overcorrect or undercorrect and it will require some manual push and pulls to be on target. So solving should be quick in the range of one or two seconds. Using ASTAP in the phone that will be possible if the initial start postion is found by blind solving or gyrosensors. Then follow up solving will be fast. But the image taking and transport should fast as well. Wat you could consider it to feed the phone camera with more photons and use that as the input sensor. So put the phone behind a viewfinder or one of the phone-camera-lenses available.  Lens opening 10 mm or better.

 

 

Han



#6 tjay

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Posted 14 October 2021 - 05:29 PM

Looking to some StarSense videos, the solving seems to be done in the keypad or in the camera itself but not in the phone. I had the impression StarSense takes about 10 seconds to solve. That is not a problem if there is a control loop back to the telescope and you can sync and slew the telescope with the correct amount of degrees to target.

 

If you would use a phone solver as feedback for a Dobson and correct the mount manually then the solving should be quick. By correcting manually you would easilly overcorrect or undercorrect and it will require some manual push and pulls to be on target. So solving should be quick in the range of one or two seconds. Using ASTAP in the phone that will be possible if the initial start postion is found by blind solving or gyrosensors. Then follow up solving will be fast. But the image taking and transport should fast as well. Wat you could consider it to feed the phone camera with more photons and use that as the input sensor. So put the phone behind a viewfinder or one of the phone-camera-lenses available.  Lens opening 10 mm or better.

 

 

Han

Han,

 

The StarSense Explorer scopes have a right angle mirror mount for phones to allow the camera to point at the sky without having the screen of the phone at a difficult to use angle.  The phone platesolves, and you can use the scope as a push to.  There are no motors on those scopes.

 

https://www.youtube....h?v=3Hb0x-IdeDs



#7 han.k

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Posted 15 October 2021 - 01:14 AM

Okay clear. There are two systems:

 

1) "StarSense", system with a camera and a motorized scope

2) "StarSense Explorer" using a smartphone and a mirror for a manual scope.

 

The "StarSense Explorer" seems to be based on a combination of the phone gyroscope-sensors and a fine calibration on the brightest stars visible in the phone camera. That is an interesting approach. Is simplifies the solving and could use only one (brightest) star detected to calibrate.

 

https://www.youtube....h?v=oWbGQgDffVg

 

Using a solver only will require more visible stars in the aquired image to detect star patterns. So I assume an lens opening of maybe 10 mm minimum.  As a test I will put my phone behind a viewfinder and see if it can pick up enough stars for a solve.

 

Han

 

"StarSense", system

StarSense-1.jpg

 

"StarSense Explorer"

star_sensor_explorer-2.jpg

 



#8 han.k

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Posted 15 October 2021 - 02:14 PM

The test with a smart phone behind a 7x50 was disappointing. Field of view is small due to the small lens opening. Didn't get enough stars.

 

Pointing a Galaxy S10 to the zenith collected about 20 stars but the quality is relative poor. Even nova.astrometry.net can't solve them:

http://nova.astromet...247602#original

 

Transfering images wireless from a DSLR camera to the phone for solving seems technical a better solution.



#9 lambermo

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Posted 17 October 2021 - 10:12 AM

That is great news ! And the second plate solver for android to my knowledge (SkEye Cam being the other one).

It shows using the phone camera is doable, but with a tripod.

I'll be following your efforts with great interest.



#10 han.k

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Posted 17 October 2021 - 01:48 PM

That is interesting SkEye.

 

I will continue investigating solving a smartphone image.This should possible for modern high end smartphones as soon something like 20 stars are a visible. It will require some adaptations of the current ASTAP solver which is much more tuned for small fields-of-view. This all without extending the exposure time by integrating or gyro information.

 

I would be interested in night-sky images taken by a smartphone for testing.

 

Han




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