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## RE: [ASCOM] NOVAS & Kepler documentation?

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• deltaT isn t a constant. It is TT - UT1 but in practice you d probably use some sort of lookup table to adjust for leap seconds in UTC. Here s a definition of
Message 1 of 10 , Nov 5, 2012
• 701 KB

deltaT isn’t a constant. It is TT – UT1 but in practice you’d probably use some sort of lookup table to adjust for leap seconds in UTC. Here's a definition of deltaT and attached is a PDF file full of related definitions that I've collected from various sources.

TT runs a little ahead of UT1 (a refined measure of mean solar time at Greenwich) by an amount known as deltaT = TT - UT1. DeltaT was measured at +65.7768 seconds (TT ahead of UT1) at 0h UTC on 1 January 2009;[8] and by retrospective calculation, deltaT was close to zero around the year 1900. The difference deltaT, though somewhat unpredictable in fine detail, is expected to continue to increase, with UT1 becoming steadily (but irregularly) further behind TT in the future.

Below is one way of computing deltaT

Tim Long

/*

Adapted from AAPlus library by PJ Naughter

Permission was granted to convert the library to C#

This source is modified from PJ Naugters AA+ lib

(http://www.naughter.com/aa.html)

and therefore is covered under his copyright license, which

is as follows:

Purpose: Implementation for the algorithms which calculate the difference between Dynamical Time and Universal Time

Created: PJN / 29-12-2003

History: PJN / 01-02-2005 1. Fixed a problem with the declaration of the variable "Index" in the function

CAADynamicalTime::DeltaT. Thanks to Mika Heiskanen for reporting this problem.

PJN / 26-01-2007 1. Update to fit in with new layout of CAADate class

PJN / 28-01-2007 1. Further updates to fit in with new layout of CAADate class

Copyright (c) 2003 - 2009 by PJ Naughter (Web: www.naughter.com, Email: pjna@...)

All rights reserved.

Copyright / Usage Details:

You are allowed to include the source code in any product (commercial, shareware, freeware or otherwise)

when your product is released in binary form. You are allowed to modify the source code in any way you want

except you cannot modify the copyright details at the top of each module. If you want to distribute source

code with your application, then you are only allowed to distribute versions released by the author. This is

to maintain a single distribution point for the source code.

*/

using System;

using System.Diagnostics;

namespace Tigra.Astronomy.AAOO

{

public class DynamicalTime

{

public DynamicalTime()

{

}

static double[] DeltaTTable =

{

121, 112, 103, 95, 88,  //1620 - 1698

82, 77, 72, 68, 63,

60, 56, 53, 51, 48,

46, 44, 42, 40, 38,

35, 33, 31, 29, 26,

24, 22, 20, 18, 16,

14, 12, 11, 10, 9,

8, 7, 7, 7, 7,

7, 7, 8, 8, 9,   //1700 - 1778

9, 9, 9, 9, 10,

10, 10, 10, 10, 10,

10, 10, 11, 11, 11,

11, 11, 12, 12, 12,

12, 13, 13, 13, 14,

14, 14, 14, 15, 15,

15, 15, 15, 16, 16,

16, 16, 16, 16, 16, //1780 - 1858

16, 15, 15, 14, 13,

13.1, 12.5, 12.2, 12.0, 12.0,

12, 12, 12, 12, 11.9,

11.6, 11, 10.2, 9.2, 8.2,

7.1, 6.2, 5.6, 5.4, 5.3,

5.4, 5.6, 5.9, 6.2, 6.5,

6.8, 7.1, 7.3, 7.5, 7.6,

7.7, 7.3, 6.2, 5.2, 2.7,  //1860 - 1938

1.4, -1.2, -2.8, -3.8, -4.8,

-5.5, -5.3,  -5.6, -5.7, -5.9,

-6, -6.3, -6.5, -6.2, -4.7,

-2.8, -0.1, 2.6, 5.3, 7.7,

10.4, 13.3, 16, 18.2, 20.2,

21.2, 22.4, 23.5, 23.8, 24.3,

24, 23.9, 23.9, 23.7, 24,

24.3, 25.3, 26.2, 27.3, 28.2, //1940 - 1998

29.1, 30, 30.7, 31.4, 32.2,

33.1, 34.0, 35.0, 36.5, 38.3,

40.18, 42.2, 44.5, 46.5, 48.5,

50.54, 52.2, 53.8, 54.9, 55.8,

56.86, 58.31, 59.99, 61.63, 62.97

};

public static double DeltaT(double JD)

{

//Construct a CAADate from the julian day

Date date = new Date(JD, Date.AfterPapalReform(JD));

double y = date.FractionalYear();

double T = (y - 2000) / 100;

double Delta;

if (y < 948)

Delta = 2177 + (497 * T) + (44.1 * T * T);

else if (y < 1620)

Delta = 102 + (102 * T) + (25.3 * T * T);

else if (y < 1998)

{

int Index = (int)((y - 1620) / 2);

Debug.Assert(Index < DeltaTTable.Length);

Debug.Assert(Index >= 0);

y = y / 2 - Index - 810;

Delta = (DeltaTTable[Index] + (DeltaTTable[Index + 1] - DeltaTTable[Index]) * y);

}

else if (y <= 2000)

{

int nLookupSize = DeltaTTable.Length;

Delta = DeltaTTable[nLookupSize - 1];

}

else if (y < 2100)

Delta = 102 + (102 * T) + (25.3 * T * T) + 0.37 * (y - 2100);

else

Delta = 102 + (102 * T) + (25.3 * T * T);

return Delta;

}

}

}

-----Original Message-----
From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On Behalf Of Roger
Sent: 05 November 2012 12:52
To: ASCOM-Talk@yahoogroups.com
Subject: [ASCOM] NOVAS & Kepler documentation?

Hi,

I'm hoping someone can point me to a location of current NOVAS and Kepler documentation (ASCOM implementation). It would really help with the troubles I'm having trying to get NOVAS working.

Google returns a few hits which lead me to this page:

http://www.ascom-standards.org/Help/Developer/html/

However the above seems inaccurate. For example the DeltaT property of planets is described as being optional however I find that I must set a value, but don't know what value is relevant for a given planet or minor planet.

So, indication seems to be that the documentation I've found doesn't match the NOVAS version I have. I believe I have the most recent version, downloaded recently from http://www.ascom-standards.org/Downloads/ScriptableComponents.htm

Thanks,

Roger.

------------------------------------

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• Roger, Tim Long responded to your previous email from 10/28. Rick Burke ... From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On Behalf Of
Message 2 of 10 , Nov 5, 2012
Message
Roger,

Tim Long responded to your previous email from 10/28.

Rick Burke
-----Original Message-----
From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On Behalf Of Roger
Sent: Monday, November 05, 2012 7:52 AM
To: ASCOM-Talk@yahoogroups.com
Subject: [ASCOM] NOVAS & Kepler documentation?

Hi,

I'm hoping someone can point me to a location of current NOVAS and Kepler documentation (ASCOM implementation). It would really help with the troubles I'm having trying to get NOVAS working.

Google returns a few hits which lead me to this page:
http://www.ascom-standards.org/Help/Developer/html/

However the above seems inaccurate. For example the DeltaT property of planets is described as being optional however I find that I must set a value, but don't know what value is relevant for a given planet or minor planet.

So, indication seems to be that the documentation I've found doesn't match the NOVAS version I have. I believe I have the most recent version, downloaded recently from http://www.ascom-standards.org/Downloads/ScriptableComponents.htm

Thanks,
Roger.

• Thanks Tim, but I don t see anything in that documentation for NOVAS or Kepler. I ve looked in the contents, index and searched for NOVAS and kepler
Message 3 of 10 , Nov 6, 2012
Thanks Tim, but I don't see anything in that documentation for NOVAS or Kepler. I've looked in the contents, index and searched for "NOVAS" and "kepler" without success. The only reference search finds to NOVAS is in the change log for what's new in each version. Am I missing something? I have the most recent version of ASCOM.

Thanks,
Roger.

--- In ASCOM-Talk@yahoogroups.com, "Tim Long" <Tim@...> wrote:
>
> If you've installed the ASCOM developer tools, then you should have some
> documentation installed locally on your start menu.
>
>
>
>
>
> -----Original Message-----
> From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On
> Behalf Of Roger
> Sent: 05 November 2012 12:52
> To: ASCOM-Talk@yahoogroups.com
> Subject: [ASCOM] NOVAS & Kepler documentation?
>
>
>
> Hi,
>
>
>
> I'm hoping someone can point me to a location of current NOVAS and
> Kepler documentation (ASCOM implementation). It would really help with
> the troubles I'm having trying to get NOVAS working.
>
>
>
> Google returns a few hits which lead me to this page:
>
> http://www.ascom-standards.org/Help/Developer/html/
> <http://www.ascom-standards.org/Help/Developer/html/>
>
>
>
> However the above seems inaccurate. For example the DeltaT property of
> planets is described as being optional however I find that I must set a
> value, but don't know what value is relevant for a given planet or minor
> planet.
>
>
>
> So, indication seems to be that the documentation I've found doesn't
> match the NOVAS version I have. I believe I have the most recent
> version, downloaded recently from
> http://www.ascom-standards.org/Downloads/ScriptableComponents.htm
> <http://www.ascom-standards.org/Downloads/ScriptableComponents.htm>
>
>
>
> Thanks,
>
> Roger.
>
>
>
>
>
>
>
> ------------------------------------
>
>
>
> For more information see http://ASCOM-Standards.org/
> <http://ASCOM-Standards.org/> .
>
>
>
> To unsubscribe from this group, send an email FROM THE ACCOUNT YOU USED
> TO SUBSCRIBE(!) to:
>
> ASCOM-Talk-unsubscribe@yahoogroups.com
> <mailto:ASCOM-Talk-unsubscribe@yahoogroups.com>
>
>
>
> Yahoo! Groups Links
>
>
>
> http://groups.yahoo.com/group/ASCOM-Talk/
> <http://groups.yahoo.com/group/ASCOM-Talk/>
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• Sorry for it appearing that I ignored Tim, Rick, I just don t see a message from him regarding my October 28th message. Perhaps you could post me a link. I do
Message 4 of 10 , Nov 6, 2012
Sorry for it appearing that I ignored Tim, Rick, I just don't see a message from him regarding my October 28th message. Perhaps you could post me a link. I do see two replies to this more recent thread from Tim.

Regards,
Roger.

--- In ASCOM-Talk@yahoogroups.com, Rick Burke <astroman133@...> wrote:
>
> Roger,
>
> Tim Long responded to your previous email from 10/28.
>
> Rick Burke
> -----Original Message-----
> From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On
> Behalf Of Roger
> Sent: Monday, November 05, 2012 7:52 AM
> To: ASCOM-Talk@yahoogroups.com
> Subject: [ASCOM] NOVAS & Kepler documentation?
>
>
>
>
> Hi,
>
> I'm hoping someone can point me to a location of current NOVAS and Kepler
> documentation (ASCOM implementation). It would really help with the troubles
> I'm having trying to get NOVAS working.
>
> Google returns a few hits which lead me to this page:
> http://www.ascom-standards.org/Help/Developer/html/
>
> However the above seems inaccurate. For example the DeltaT property of
> planets is described as being optional however I find that I must set a
> value, but don't know what value is relevant for a given planet or minor
> planet.
>
> So, indication seems to be that the documentation I've found doesn't match
> the NOVAS version I have. I believe I have the most recent version,
> downloaded recently from
> http://www.ascom-standards.org/Downloads/ScriptableComponents.htm
>
> Thanks,
> Roger.
>
• Now realising the ASCOM documentation is in windows help format not on the web I searched and see now there s help files in... C: Program Files Common
Message 5 of 10 , Nov 6, 2012
Now realising the ASCOM documentation is in windows help format not on the web I searched and see now there's help files in...

C:\Program Files\Common Files\ASCOM\NOVAS
C:\Program Files\Common Files\ASCOM\Kepler

Thanks for making the link to windows help for me to think to look here. This is going to help enormously.

Working mostly in Java, JS and HTML I just assumed API documentation would be web based.

Regards,
Roger.

--- In ASCOM-Talk@yahoogroups.com, "Roger" <rog1@...> wrote:
>
> Thanks Tim, but I don't see anything in that documentation for NOVAS or Kepler. I've looked in the contents, index and searched for "NOVAS" and "kepler" without success. The only reference search finds to NOVAS is in the change log for what's new in each version. Am I missing something? I have the most recent version of ASCOM.
>
> Thanks,
> Roger.
>
> --- In ASCOM-Talk@yahoogroups.com, "Tim Long" <Tim@> wrote:
> >
> > If you've installed the ASCOM developer tools, then you should have some
> > documentation installed locally on your start menu.
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On
> > Behalf Of Roger
> > Sent: 05 November 2012 12:52
> > To: ASCOM-Talk@yahoogroups.com
> > Subject: [ASCOM] NOVAS & Kepler documentation?
> >
> >
> >
> > Hi,
> >
> >
> >
> > I'm hoping someone can point me to a location of current NOVAS and
> > Kepler documentation (ASCOM implementation). It would really help with
> > the troubles I'm having trying to get NOVAS working.
> >
> >
> >
> > Google returns a few hits which lead me to this page:
> >
> > http://www.ascom-standards.org/Help/Developer/html/
> > <http://www.ascom-standards.org/Help/Developer/html/>
> >
> >
> >
> > However the above seems inaccurate. For example the DeltaT property of
> > planets is described as being optional however I find that I must set a
> > value, but don't know what value is relevant for a given planet or minor
> > planet.
> >
> >
> >
> > So, indication seems to be that the documentation I've found doesn't
> > match the NOVAS version I have. I believe I have the most recent
> > version, downloaded recently from
> > http://www.ascom-standards.org/Downloads/ScriptableComponents.htm
> > <http://www.ascom-standards.org/Downloads/ScriptableComponents.htm>
> >
> >
> >
> > Thanks,
> >
> > Roger.
> >
> >
> >
> >
> >
> >
> >
> > ------------------------------------
> >
> >
> >
> > For more information see http://ASCOM-Standards.org/
> > <http://ASCOM-Standards.org/> .
> >
> >
> >
> > To unsubscribe from this group, send an email FROM THE ACCOUNT YOU USED
> > TO SUBSCRIBE(!) to:
> >
> > ASCOM-Talk-unsubscribe@yahoogroups.com
> > <mailto:ASCOM-Talk-unsubscribe@yahoogroups.com>
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> > http://groups.yahoo.com/group/ASCOM-Talk/
> > <http://groups.yahoo.com/group/ASCOM-Talk/>
> >
> >
> >
> > Individual Email | Traditional
> >
> >
> >
> > http://groups.yahoo.com/group/ASCOM-Talk/join
> > <http://groups.yahoo.com/group/ASCOM-Talk/join>
> >
> > (Yahoo! ID required)
> >
> >
> >
> > ASCOM-Talk-digest@yahoogroups.com
> > <mailto:ASCOM-Talk-digest@yahoogroups.com>
> >
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> > <mailto:ASCOM-Talk-fullfeatured@yahoogroups.com>
> >
> >
> >
> > ASCOM-Talk-unsubscribe@yahoogroups.com
> > <mailto:ASCOM-Talk-unsubscribe@yahoogroups.com>
> >
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> >
> >
> >
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> > ExchangeDefender Message Security: Click below to verify authenticity
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> >
>
• Hi All, Â  The IVideo simulator that I have been working on is now in a stable and completed stage. I have tested it only within C# and need some help from
Message 6 of 10 , Nov 6, 2012
Hi All,

The IVideo simulator that I have been working on is now in a stable and completed stage. I have tested it only within C# and need some help from people that know how to use scripting languages to try the simulator and see if it works okay for them.

You can download and build the simulator from http://svn.teamserver.tigranetworks.co.uk/svn/ASCOM-Contrib/ASCOM.Simulator.Video/trunk with the user and password being both: guest

There is a 40Mb video file as part of the project so your update will take a few minutes to complete.

Please report any issues you spot at http://jira.teamserver.tigranetworks.co.uk

I would also appreciate if you can send me your script examples of handling the array of pixels returned by the IVideoFrame written in the language you have used so I can include it in the documentation.

Regards,

Hristo Pavlov
Sydney, Australia

• Hi Tim, Thanks for that. I have since found a DeltaT method in ASCOM.ASCOM_Astrometry.NOVAS3 It seems there s several different implementations of NOVAS in
Message 7 of 10 , Nov 6, 2012
Hi Tim,

Thanks for that.

I have since found a DeltaT method in ASCOM.ASCOM_Astrometry.NOVAS3

It seems there's several different implementations of NOVAS in ASCOM, or perhaps just different versions, but I'm having trouble grasping the placement of these different NOVAS resources in the ASCOM sysytem.

I have ASCOM V6.0 installed and also downloaded:
- NOVAS 2.1.1 from: http://www.ascom-standards.org/Downloads/ScriptableComponents.htm
- Kepler 1.0.1 from the same above URL

I have three sets of documentation on-disk:
1) C:\Program Files\ASCOM\Platform 6\Docs\PlatformHelp.chm
2) C:\Program Files\Common Files\ASCOM\NOVAS\NOVASRef.chm
3) C:\Program Files\Common Files\ASCOM\Kepler\Kepler.chm

None of the above contain any information about the "DeltaT" method, or ASCOM.ASCOM_Astrometry, yet I do indeed have access to the DeltaT method of ASCOM.ASCOM_Astrometry.NOVAS3 method when using it in VB.

The DeltaT method is documented in the NOVAS3 available from this page:
http://www.ascom-standards.org/Help/Developer/html/N_ASCOM_Astrometry_NOVAS.htm

So.... I'm confused as to:
a) how ASCOM_Astrometry.NOVAS3 (which according to above documentation is an implementation of v2 NOVAS) relates to the NOVAS 2.1.1 downloaded from the URL above
b) why there seems to be help on the ASCOM site for this other NOVAS3 object but no mention of it in the platform help downloaded. My versions are messed up maybe? or it's just not documented there?

Perhaps someone can shed some light on this for me.

By the way, I have had the achievement of my first ever calculation of a comet's Alt & Az using ASCOM NOVAS + Kepler tonight, that's a nice step forward and accomplishment for the night.

Thanks,
Roger.

--- In ASCOM-Talk@yahoogroups.com, "Tim Long" <Tim@...> wrote:
>
> deltaT isn't a constant. It is TT - UT1 but in practice you'd probably
> use some sort of lookup table to adjust for leap seconds in UTC. Here's
> a definition of deltaT and attached is a PDF file full of related
> definitions that I've collected from various sources.
>
>
>
> TT runs a little ahead of UT1 <http://en.wikipedia.org/wiki/UT1> (a
> refined measure of mean solar time at Greenwich) by an amount known as
> deltaT <http://en.wikipedia.org/wiki/DeltaT> = TT - UT1. DeltaT was
> measured at +65.7768 seconds (TT ahead of UT1) at 0h UTC
> <http://en.wikipedia.org/wiki/UTC> on 1 January 2009;[8]
> <http://en.wikipedia.org/wiki/Terrestrial_Time#cite_note-7> and by
> retrospective calculation, deltaT was close to zero around the year
> 1900. The difference deltaT, though somewhat unpredictable in fine
> detail, is expected to continue to increase, with UT1 becoming steadily
> (but irregularly) further behind TT in the future.
>
>
>
> Below is one way of computing deltaT
>
> Tim Long
>
>
>
> /*
>
> Adapted from AAPlus library by PJ Naughter
>
> Permission was granted to convert the library to C#
>
>
>
> This source is modified from PJ Naugters AA+ lib
>
> (http://www.naughter.com/aa.html)
>
> and therefore is covered under his copyright license, which
>
> is as follows:
>
>
>
> Purpose: Implementation for the algorithms which calculate the
> difference between Dynamical Time and Universal Time
>
> Created: PJN / 29-12-2003
>
> History: PJN / 01-02-2005 1. Fixed a problem with the declaration of the
> variable "Index" in the function
>
> CAADynamicalTime::DeltaT. Thanks to Mika
> Heiskanen for reporting this problem.
>
> PJN / 26-01-2007 1. Update to fit in with new layout of CAADate
> class
>
> PJN / 28-01-2007 1. Further updates to fit in with new layout
> of CAADate class
>
>
>
> Copyright (c) 2003 - 2009 by PJ Naughter (Web: www.naughter.com, Email:
> pjna@...)
>
>
>
> All rights reserved.
>
>
>
> Copyright / Usage Details:
>
>
>
> You are allowed to include the source code in any product (commercial,
> shareware, freeware or otherwise)
>
> when your product is released in binary form. You are allowed to modify
> the source code in any way you want
>
> except you cannot modify the copyright details at the top of each
> module. If you want to distribute source
>
> code with your application, then you are only allowed to distribute
> versions released by the author. This is
>
> to maintain a single distribution point for the source code.
>
>
>
> */
>
> using System;
>
> using System.Diagnostics;
>
>
>
> namespace Tigra.Astronomy.AAOO
>
> {
>
> public class DynamicalTime
>
> {
>
> public DynamicalTime()
>
> {
>
> }
>
>
>
> static double[] DeltaTTable =
>
> {
>
> 121, 112, 103, 95, 88,
> //1620 - 1698
>
> 82, 77, 72, 68, 63,
>
> 60, 56, 53, 51, 48,
>
> 46, 44, 42, 40, 38,
>
> 35, 33, 31, 29, 26,
>
> 24, 22, 20, 18, 16,
>
> 14, 12, 11, 10, 9,
>
> 8, 7, 7, 7, 7,
>
>
>
> 7, 7, 8, 8, 9, //1700
> - 1778
>
> 9, 9, 9, 9, 10,
>
> 10, 10, 10, 10, 10,
>
> 10, 10, 11, 11, 11,
>
> 11, 11, 12, 12, 12,
>
> 12, 13, 13, 13, 14,
>
> 14, 14, 14, 15, 15,
>
> 15, 15, 15, 16, 16,
>
>
>
> 16, 16, 16, 16, 16,
> //1780 - 1858
>
> 16, 15, 15, 14, 13,
>
> 13.1, 12.5, 12.2, 12.0,
> 12.0,
>
> 12, 12, 12, 12, 11.9,
>
> 11.6, 11, 10.2, 9.2,
> 8.2,
>
> 7.1, 6.2, 5.6, 5.4, 5.3,
>
> 5.4, 5.6, 5.9, 6.2, 6.5,
>
> 6.8, 7.1, 7.3, 7.5, 7.6,
>
>
>
> 7.7, 7.3, 6.2, 5.2, 2.7,
> //1860 - 1938
>
> 1.4, -1.2, -2.8, -3.8,
> -4.8,
>
> -5.5, -5.3, -5.6, -5.7,
> -5.9,
>
> -6, -6.3, -6.5, -6.2,
> -4.7,
>
> -2.8, -0.1, 2.6, 5.3,
> 7.7,
>
> 10.4, 13.3, 16, 18.2,
> 20.2,
>
> 21.2, 22.4, 23.5, 23.8,
> 24.3,
>
> 24, 23.9, 23.9, 23.7,
> 24,
>
>
>
> 24.3, 25.3, 26.2, 27.3,
> 28.2, //1940 - 1998
>
> 29.1, 30, 30.7, 31.4,
> 32.2,
>
> 33.1, 34.0, 35.0, 36.5,
> 38.3,
>
> 40.18, 42.2, 44.5, 46.5,
> 48.5,
>
> 50.54, 52.2, 53.8, 54.9,
> 55.8,
>
> 56.86, 58.31, 59.99,
> 61.63, 62.97
>
> };
>
>
>
>
>
> public static double DeltaT(double JD)
>
> {
>
> //Construct a CAADate from the julian day
>
> Date date = new Date(JD, Date.AfterPapalReform(JD));
>
>
>
> double y = date.FractionalYear();
>
> double T = (y - 2000) / 100;
>
>
>
> double Delta;
>
> if (y < 948)
>
> Delta = 2177 + (497 * T) + (44.1 * T * T);
>
> else if (y < 1620)
>
> Delta = 102 + (102 * T) + (25.3 * T * T);
>
> else if (y < 1998)
>
> {
>
> int Index = (int)((y - 1620) / 2);
>
> Debug.Assert(Index < DeltaTTable.Length);
>
> Debug.Assert(Index >= 0);
>
>
>
> y = y / 2 - Index - 810;
>
> Delta = (DeltaTTable[Index] + (DeltaTTable[Index + 1] -
> DeltaTTable[Index]) * y);
>
> }
>
> else if (y <= 2000)
>
> {
>
> int nLookupSize = DeltaTTable.Length;
>
> Delta = DeltaTTable[nLookupSize - 1];
>
> }
>
> else if (y < 2100)
>
> Delta = 102 + (102 * T) + (25.3 * T * T) + 0.37 * (y -
> 2100);
>
> else
>
> Delta = 102 + (102 * T) + (25.3 * T * T);
>
>
>
> return Delta;
>
> }
>
>
>
>
>
> }
>
> }
>
>
>
> -----Original Message-----
> From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On
> Behalf Of Roger
> Sent: 05 November 2012 12:52
> To: ASCOM-Talk@yahoogroups.com
> Subject: [ASCOM] NOVAS & Kepler documentation?
>
>
>
> Hi,
>
>
>
> I'm hoping someone can point me to a location of current NOVAS and
> Kepler documentation (ASCOM implementation). It would really help with
> the troubles I'm having trying to get NOVAS working.
>
>
>
> Google returns a few hits which lead me to this page:
>
> http://www.ascom-standards.org/Help/Developer/html/
> <http://www.ascom-standards.org/Help/Developer/html/>
>
>
>
> However the above seems inaccurate. For example the DeltaT property of
> planets is described as being optional however I find that I must set a
> value, but don't know what value is relevant for a given planet or minor
> planet.
>
>
>
> So, indication seems to be that the documentation I've found doesn't
> match the NOVAS version I have. I believe I have the most recent
> version, downloaded recently from
> http://www.ascom-standards.org/Downloads/ScriptableComponents.htm
> <http://www.ascom-standards.org/Downloads/ScriptableComponents.htm>
>
>
>
> Thanks,
>
> Roger.
>
>
>
>
>
>
>
> ------------------------------------
>
>
>
> For more information see http://ASCOM-Standards.org/
> <http://ASCOM-Standards.org/> .
>
>
>
> To unsubscribe from this group, send an email FROM THE ACCOUNT YOU USED
> TO SUBSCRIBE(!) to:
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• Roger, There is a Windows help file called ASCOM Developer Help that is installed along with the ASCOM Developer Components. It should be accessible from your
Message 8 of 10 , Nov 6, 2012
Message
Roger,

There is a Windows help file called ASCOM Developer Help that is installed along with the ASCOM Developer Components.  It should be accessible from your Start Menu.  Look under ASCOM Namespace for documentation on the ASCOM NOVAS and Kepler classes.

Rick Burke
-----Original Message-----
From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On Behalf Of Roger
Sent: Tuesday, November 06, 2012 8:52 AM
To: ASCOM-Talk@yahoogroups.com
Subject: [ASCOM] Re: NOVAS & Kepler documentation?

Hi Tim,

Thanks for that.

I have since found a DeltaT method in ASCOM.ASCOM_Astrometry.NOVAS3

It seems there's several different implementations of NOVAS in ASCOM, or perhaps just different versions, but I'm having trouble grasping the placement of these different NOVAS resources in the ASCOM sysytem.

I have ASCOM V6.0 installed and also downloaded:
- NOVAS 2.1.1 from: http://www.ascom-standards.org/Downloads/ScriptableComponents.htm
- Kepler 1.0.1 from the same above URL

I have three sets of documentation on-disk:
1) C:\Program Files\ASCOM\Platform 6\Docs\PlatformHelp.chm
2) C:\Program Files\Common Files\ASCOM\NOVAS\NOVASRef.chm
3) C:\Program Files\Common Files\ASCOM\Kepler\Kepler.chm

None of the above contain any information about the "DeltaT" method, or ASCOM.ASCOM_Astrometry, yet I do indeed have access to the DeltaT method of ASCOM.ASCOM_Astrometry.NOVAS3 method when using it in VB.

The DeltaT method is documented in the NOVAS3 available from this page:
http://www.ascom-standards.org/Help/Developer/html/N_ASCOM_Astrometry_NOVAS.htm

So.... I'm confused as to:
a) how ASCOM_Astrometry.NOVAS3 (which according to above documentation is an implementation of v2 NOVAS) relates to the NOVAS 2.1.1 downloaded from the URL above
b) why there seems to be help on the ASCOM site for this other NOVAS3 object but no mention of it in the platform help downloaded. My versions are messed up maybe? or it's just not documented there?

Perhaps someone can shed some light on this for me.

By the way, I have had the achievement of my first ever calculation of a comet's Alt & Az using ASCOM NOVAS + Kepler tonight, that's a nice step forward and accomplishment for the night.

Thanks,
Roger.

--- In ASCOM-Talk@yahoogroups.com, "Tim Long" <Tim@...> wrote:

>
> deltaT isn't a constant. It is TT -
UT1 but in practice you'd probably
> use some sort of lookup table to
adjust for leap seconds in UTC. Here's
> a definition of deltaT and
attached is a PDF file full of related
> definitions that I've collected
from various sources.
>
>
>
> TT runs a little ahead
of UT1 <http://en.wikipedia.org/wiki/UT1> (a
> refined measure of mean solar time at Greenwich) by an amount known
as
> deltaT <
href="http://en.wikipedia.org/wiki/DeltaT">http://en.wikipedia.org/wiki/DeltaT> = TT - UT1. DeltaT was
> measured at +65.7768 seconds (TT ahead of UT1) at
0h UTC
> <
href="http://en.wikipedia.org/wiki/UTC">http://en.wikipedia.org/wiki/UTC> on 1 January 2009;[8]
> <
href="http://en.wikipedia.org/wiki/Terrestrial_Time#cite_note-7">http://en.wikipedia.org/wiki/Terrestrial_Time#cite_note-7> and by
> retrospective calculation, deltaT was close to zero around the
year
> 1900. The difference deltaT, though somewhat unpredictable in
fine
> detail, is expected to continue to increase, with UT1 becoming
steadily
> (but irregularly) further behind TT in the future.
>
>
>
> Below is one way of computing deltaT
>
>
Tim Long
>
>
>
> /*
>
> Adapted from
AAPlus library by PJ Naughter
>
> Permission was granted to convert
the library to C#
>
>
>
> This source is modified
from PJ Naugters AA+ lib
>
> (
href="http://www.naughter.com/aa.html">http://www.naughter.com/aa.html)
>
> and therefore is covered under his copyright license, which
>
> is as follows:
>
>
>
> Purpose:
Implementation for the algorithms which calculate the
> difference between
Dynamical Time and Universal Time
>
> Created: PJN /
29-12-2003
>
> History: PJN / 01-02-2005 1. Fixed a problem with
the declaration of the
> variable "Index" in the function
>
> CAADynamicalTime::DeltaT. Thanks to Mika
> Heiskanen for
reporting this problem.
>
> PJN / 26-01-2007 1. Update to fit in
with new layout of CAADate
> class
>
> PJN / 28-01-2007 1.
Further updates to fit in with new layout
> of CAADate class
>
>
>
> Copyright (c) 2003 - 2009 by PJ Naughter (Web:
www.naughter.com, Email:
> pjna@...)
>
>
>
>
All rights reserved.
>
>
>
> Copyright / Usage
Details:
>
>
>
> You are allowed to include the
source code in any product (commercial,
> shareware, freeware or
otherwise)
>
> when your product is released in binary form. You
are allowed to modify
> the source code in any way you want
>
> except you cannot modify the copyright details at the top of
each
> module. If you want to distribute source
>
> code
with your application, then you are only allowed to distribute
> versions
released by the author. This is
>
> to maintain a single
distribution point for the source code.
>
>
>
>
*/
>
> using System;
>
> using
System.Diagnostics;
>
>
>
> namespace
Tigra.Astronomy.AAOO
>
> {
>
> public class
DynamicalTime
>
> {
>
> public DynamicalTime()
>
> {
>
> }
>
>
>
> static double[]
DeltaTTable =
>
> {
>
> 121, 112, 103, 95, 88,
>
//1620 - 1698
>
> 82, 77, 72, 68, 63,
>
> 60, 56, 53,
51, 48,
>
> 46, 44, 42, 40, 38,
>
> 35, 33, 31, 29,
26,
>
> 24, 22, 20, 18, 16,
>
> 14, 12, 11, 10,
9,
>
> 8, 7, 7, 7, 7,
>
>
>
> 7, 7, 8,
8, 9, //1700
> - 1778
>
> 9, 9, 9, 9, 10,
>
>
10, 10, 10, 10, 10,
>
> 10, 10, 11, 11, 11,
>
> 11,
11, 12, 12, 12,
>
> 12, 13, 13, 13, 14,
>
> 14, 14,
14, 15, 15,
>
> 15, 15, 15, 16, 16,
>
>
>
> 16, 16, 16, 16, 16,
> //1780 - 1858
>
> 16, 15, 15,
14, 13,
>
> 13.1, 12.5, 12.2, 12.0,
> 12.0,
>
>
12, 12, 12, 12, 11.9,
>
> 11.6, 11, 10.2, 9.2,
> 8.2,
>
> 7.1, 6.2, 5.6, 5.4, 5.3,
>
> 5.4, 5.6, 5.9, 6.2,
6.5,
>
> 6.8, 7.1, 7.3, 7.5, 7.6,
>
>
>
> 7.7, 7.3, 6.2, 5.2, 2.7,
> //1860 - 1938
>
> 1.4,
-1.2, -2.8, -3.8,
> -4.8,
>
> -5.5, -5.3, -5.6, -5.7,
>
-5.9,
>
> -6, -6.3, -6.5, -6.2,
> -4.7,
>
>
-2.8, -0.1, 2.6, 5.3,
> 7.7,
>
> 10.4, 13.3, 16,
18.2,
> 20.2,
>
> 21.2, 22.4, 23.5, 23.8,
>
24.3,
>
> 24, 23.9, 23.9, 23.7,
> 24,
>
>
>
> 24.3, 25.3, 26.2, 27.3,
> 28.2, //1940 - 1998
>
> 29.1, 30, 30.7, 31.4,
> 32.2,
>
> 33.1, 34.0, 35.0,
36.5,
> 38.3,
>
> 40.18, 42.2, 44.5, 46.5,
>
48.5,
>
> 50.54, 52.2, 53.8, 54.9,
> 55.8,
>
>
56.86, 58.31, 59.99,
> 61.63, 62.97
>
> };
>
>
>
>
>
> public static double DeltaT(double
JD)
>
> {
>
> //Construct a CAADate from the julian
day
>
> Date date = new Date(JD,
Date.AfterPapalReform(JD));
>
>
>
> double y =
date.FractionalYear();
>
> double T = (y - 2000) / 100;
>
>
>
> double Delta;
>
> if (y <
948)
>
> Delta = 2177 + (497 * T) + (44.1 * T * T);
>
> else if (y < 1620)
>
> Delta = 102 + (102 * T) + (25.3
* T * T);
>
> else if (y < 1998)
>
> {
>
> int Index = (int)((y - 1620) / 2);
>
> Debug.Assert(Index
< DeltaTTable.Length);
>
> Debug.Assert(Index >= 0);
>
>
>
> y = y / 2 - Index - 810;
>
> Delta =
(DeltaTTable[Index] + (DeltaTTable[Index + 1] -
> DeltaTTable[Index]) *
y);
>
> }
>
> else if (y <= 2000)
>
>
{
>
> int nLookupSize = DeltaTTable.Length;
>
> Delta
= DeltaTTable[nLookupSize - 1];
>
> }
>
> else if (y
< 2100)
>
> Delta = 102 + (102 * T) + (25.3 * T * T) + 0.37 * (y
-
> 2100);
>
> else
>
> Delta = 102 + (102 * T)
+ (25.3 * T * T);
>
>
>
> return Delta;
>
> }
>
>
>
>
>
> }
>
> }
>
>
>
> -----Original Message-----
>
From: ASCOM-Talk@yahoogroups.com [mailto:ASCOM-Talk@yahoogroups.com] On
> Behalf Of Roger
> Sent: 05 November 2012 12:52
> To:
href="mailto:ASCOM-Talk%40yahoogroups.com">ASCOM-Talk@yahoogroups.com
>
Subject: [ASCOM] NOVAS & Kepler documentation?
>
>
>
> Hi,
>
>
>
> I'm hoping someone can point me
to a location of current NOVAS and
> Kepler documentation (ASCOM
implementation). It would really help with
> the troubles I'm having
trying to get NOVAS working.
>
>
>
> Google returns a
few hits which lead me to this page:
>
>
href="http://www.ascom-standards.org/Help/Developer/html/">http://www.ascom-standards.org/Help/Developer/html/
>
<http://www.ascom-standards.org/Help/Developer/html/>
>
>
>
> However the above seems inaccurate. For
example the DeltaT property of
> planets is described as being optional
however I find that I must set a
> value, but don't know what value is
relevant for a given planet or minor
> planet.
>
>
>
> So, indication seems to be that the documentation I've found
doesn't
> match the NOVAS version I have. I believe I have the most
recent
> version, downloaded recently from
>
href="http://www.ascom-standards.org/Downloads/ScriptableComponents.htm">http://www.ascom-standards.org/Downloads/ScriptableComponents.htm
>
<http://www.ascom-standards.org/Downloads/ScriptableComponents.htm>
>
>
>
> Thanks,
>
> Roger.
>
>
>
>
>
>
>
>
------------------------------------
>
>
>
> For more
information see http://ASCOM-Standards.org/
>
<http://ASCOM-Standards.org/> .
>
>
>
> To unsubscribe from this group, send an
email FROM THE ACCOUNT YOU USED
> TO SUBSCRIBE(!) to:
>
>
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>
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