Sharpcap always shows different coordinates from stellarium

[EBRND]

Hello everybody!

It´s been quite a while that I am struggling to make Stellarium and Sharpcap to work together smoothly, to no avail.

SharpCap and Stellarium show different coordinates for the same object. I´ve already checked backlash and alligment issues and they´re ok.

I manage to plate solve, sync and slew in SharpCap, but the result is always different!

I use the latest versions of Sharpcap, Stellarium, as well as of ASCOM, to operate a Celestron Nexstar SE 6".

I searched the internet and found these reasons for this desynchronization:

1) Time and location: Both software programs use different methods to calculate the position of celestial objects. Stellarium uses the computer's clock and the user's location to display the correct positions of celestial objects in the sky, while Sharpcap may use GPS data or a manually-entered location and time.

2) Coordinate systems: Stellarium uses the equatorial coordinate system, which is based on the celestial equator and the celestial poles. Sharpcap, on the other hand, may use different coordinate systems, such as Altitude-Azimuth or the horizontal coordinate system.

3) Settings: Both programs have various settings that can affect the way celestial objects are displayed. For example, Stellarium allows the user to choose between different star catalogs, while Sharpcap may have different settings for field of view or image orientation.

In other words, seems that I missed completely the nature and usage of SharpCap OR the wedding of this couple is impossible due to a deep never solved incompatibility beetwen the programs OR SharpCap wasn´t made for AltAz telescopes at all...

Both programs suit me well when used independently, but I got really tired of this desynchronization. Can any one suggest:

1) Any other sky map that works better with SharpCap?

2) Any other imaging program that works better with Stellarium?

Thanks in advance

Eduardo

[Menno555]

Hi Eduardo

In Stellarium, where do you look for the coordinates? Stellarium gives multiple coordinates at the same time. For example coordinates based on J2000 and also coordinates based upon JNow.
SharpCap uses J2000, so in Stellarium you should use that too.
Just to be sure, I just did check both with a plate solve of an earlier capture of IC 2574:

Plate solve SharpCap: RA=10:28:18,Dec=+68:25:20 (J2000)
Coordinates Stellarium: RA=10:28:27,Dec=+68:24:42 (J2000)
Coordinates Stellarium: RA=10:30:09,Dec=+68:17:35 (JNow)

As you can see the JNow gives a big discrepantie.
Hopes this helps a bit.

Menno

[admin]

Hi,

actually, it's a bit more complex than SharpCap always using J2000...

SharpCap always uses J2000 for a two main things

1) Co-ordinates of any target that you want to GOTO from the catalog of targets, via the sequencer, etc. This is because catalog co-ordinates listed for objects are almost invariably J2000 based

2) The results of any plate solving application (Astap, Astrotortilla, etc) - again those programs work based on star co-ordinates, which are J2000, so the results are J2000

Now, the next thing is your ASCOM mount. Almost all ASCOM mount drivers work in JNOW co-ordinates. The mount driver can report the co-ordinates it uses, and fortunately most of them correctly report JNOW. SharpCap will believe your mount about the co-ordinates it supports and will convert appropriately - ie if you issue a GOTO a target with J2000 co-ordinates and the mount needs JNOW, it will convert. If the plate solving reports J2000 and the mount needs JNOW, again it will convert.

The co-ordinates shown in the mount control on the right will match the mount's co-ordinate system for consistency with the mount handset/mount specific software.

cheers,

Robin

[EBRND]

Hi Robin

Yesterday I found out that SharpCap shows exactly the same coordinates as the HC and points sharply to the objects. So the issue is certainly with Stellarium. It never matches the coordinates on SharpCap and HC...

[admin]

Hi,

two final things to check

1) Look at both sets of co-ordinates in Stellarium for an object - the 'On Date' ones (JNOW) will most likely match your handset and the readings in SharpCap. The J2000 ones are the ones you would use if you wanted to tell SharpCap to GOTO the object, as they are the published ones in most cases

Capture.JPG (78.87 KiB) Viewed 1212 times

2) If you are using telescope control in Stellarium to make it talk to your mount, set 'Equinox of the date' in the telescope settings and then further down set 'Use stellarium settings' in the 'Source for co-ordinate system' choice.

cheers,

Robin

[EBRND]

Hello Robin

You' ve helped me a lot. Check this out!

https://www.cloudynights.com/topic/8741 ... omsearch=1

Cheers

Eduardo