Celestial navigation

[Sharaf Z. Muhanna]

Hi Dustin,

I’m new to the astronomy field, and after obtaining the RA and DEC from an image, I’m unsure how to compute the latitude and longitude from them. Is it possible to use Astrometry.net for this, or would you recommend a different approach?
I would appreciate any guidance or recommendations you can share.  

Thanks 

[Dustin Lang]

Hi,

You can try searching this group for previous posts on the topic.  I think it has been covered before.

To go from RA,Dec to lat/long, you need the time and probably the alt/az of the image.  Nothing in the Astrometry.net package deals with time -- you would need to use something else, perhaps astropy or some other software, to do that.

cheers,

dustin

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[Shen Ming]

If you're using a telescope, I think you need write the telescope pointing info (altaz) and time into the same fits header.

If you're doing some integrated navigation with IMU-like modules, please refer to this paper:

Autonomous positioning utilizing star sensor and inclinometer - ScienceDirect

[Sharaf Z. Muhanna]

Hi Dustin,

I’m using the API to calculate the RA/DEC for about 3,000 images, but the process is very slow. How can I use your solution to speed up the calculations? Do you have any recommendations?

[Sharaf Z. Muhanna]

Hi bubu
I am using camera

On Thursday, December 4, 2025 at 12:48:52 AM UTC bubu...@gmail.com wrote:

[Dustin Lang]

Hi Sharaf,

Can you send a link to an example of the images you are solving?  We can probably recommend settings to speed things up.

cheers,

dustin

To view this discussion visit https://groups.google.com/d/msgid/astrometry/998bd9cf-6858-44c2-b663-b7da38fd2659n%40googlegroups.com.

[Bryan]

When you say 'very slow.'  how long is a single image taking to solve?

Are you using the online version of astrometry.net?  Installing it locally and using that allows more options in setting the tuning parameters and is MUCH faster.

Bryan

[Sharaf Z. Muhanna]

[Sharaf Z. Muhanna]

it take around 5 minutes for each image and I have 3,000 images

[Eric SIBERT]

Dustin was asking you for a link to the online solving like:

https://nova.astrometry.net/user_images/14239354#original

Looking at your pictures, they don't seem to be real sky pictures. It
may disturb the solver, especially when trying to order stars by
magnitude. What kind of treatment did you applied?


Eric


"Sharaf Z. Muhanna" <muhann...@gmail.com> a écrit :

> On Monday, December 8, 2025 at 2:31:00 PM UTC dstn...@gmail.com wrote:
>
>> Hi Sharaf,
>>
>> Can you send a link to an example of the images you are solving? We can
>> probably recommend settings to speed things up.
>>
>> cheers,
>> dustin
>>
>>
>> On Mon, Dec 8, 2025 at 7:28 AM Sharaf Z. Muhanna <muhann...@gmail.com>
>> wrote:
>>
>>> Hi Dustin,
>>>
>>> I’m using the API to calculate the RA/DEC for about 3,000 images, but the
>>> process is very slow. How can I use your solution to speed up the
>>> calculations? Do you have any recommendations?
>>> On Thursday, December 4, 2025 at 12:48:52 AM UTC bubu...@gmail.com wrote:
>>>
>>>> If you're using a telescope, I think you need write the telescope
>>>> pointing info (altaz) and time into the same fits header.
>>>>
>>>> If you're doing some integrated navigation with IMU-like modules, please
>>>> refer to this paper:
>>>> Autonomous positioning utilizing star sensor and inclinometer -
>>>> ScienceDirect

>>>> <https://www.sciencedirect.com/science/article/abs/pii/S0263224118308005>

>>>>>> <https://groups.google.com/d/msgid/astrometry/9e422448-7d26-4f0f-b771-4c19f50f1c58n%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>>>> .

>>>>>>
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>>> You received this message because you are subscribed to the Google Groups
>>> "astrometry" group.
>>> To unsubscribe from this group and stop receiving emails from it, send an
>>> email to astrometry+...@googlegroups.com.
>>>
>> To view this discussion visit

>>> https://groups.google.com/d/msgid/astrometry/998bd9cf-6858-44c2-b663-b7da38fd2659n%40googlegroups.com
>>> <https://groups.google.com/d/msgid/astrometry/998bd9cf-6858-44c2-b663-b7da38fd2659n%40googlegroups.com?utm_medium=email&utm_source=footer>
>>> .

>>>
>>
>
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[Dustin Lang]

Hi,

These are very wide-field, so if you set the "--scale-units degwidth --scale-lower 30" it should run a bit faster.

Or, for these wide-field images, you will not need very many index files to work well -- the "4100-series" should work great -- https://data.astrometry.net/4100/ .  There are some instructions on how to use Docker to run locally, at  https://github.com/dstndstn/astrometry.net

cheers,

dustin

[Sharaf Z. Muhanna]

  I built the real-world simulation, and I captured these images from it  

[Sharaf Z. Muhanna]

  The field of view for my images is 50 degrees. The issue now is that I need to obtain the RA/DEC for all 3,000 images, but the API key request takes time and the website’s server has crashed.  

[Astro Keith]

I would suggest using Tetra3 instead. With large fields of view it should solve in fraction of a second.

You would need to build a local copy and generate a suitable index database file (the utility is built in)

But your images do look very strange - do they actually represent real sky? I cannot identify a single asterism or constellation.