FORUM DU LOGICIEL PRISM

Ce forum a pour but d'aider les utilisateurs du logiciel PRISM
https://forum.prism-astro.com/

Dérive DEC entête image sur une série d'images

https://forum.prism-astro.com/viewtopic.php?t=1460

Page 1 sur 1

Dérive DEC entête image sur une série d'images

Posté : 27 juin 2016, 21:33
par Marc DELDEM
Bonsoir,

Sur plusieurs sessions, je remarque le problème suivant:
Je fais une série d'un champ, avec auto-guidage (sans dithering) et avec l'AO8 de SBig.
Je fais le prétraitement de la série (addition simple en tentant compte de la rotation).
Je compare ensuite les écarts en translation issus du prétraitement avec les coordonnées RA/DEC de l'entête de l'image.
Il n'y a pas de transformations géométriques appliquées aux images prétraitées.

Voici un exemple qui donne le facteur de translation (DX et DY) issu du prétraitement et la valeur RA/DEC de l'entête de l'image

Code : Tout sélectionner

						                t_KIC	8462852-001.cpa	20h06m15.507s	+44°27'23.83''
Translation	DX=-0.18	DY=0.14		t_KIC	8462852-002.cpa	20h06m15.838s	+44°27'22.18''
Translation	DX=-0.22	DY=0.07		t_KIC	8462852-003.cpa	20h06m16.064s	+44°27'19.81''
Translation	DX=-0.18	DY=0.15		t_KIC	8462852-004.cpa	20h06m16.323s	+44°27'23.92''
Translation	DX=-0.34	DY=0.04		t_KIC	8462852-005.cpa	20h06m16.479s	+44°27'29.09''
Translation	DX=-0.10	DY=0.10		t_KIC	8462852-006.cpa	20h06m16.872s	+44°27'17.51''
Translation	DX=-0.23	DY=-0.08	t_KIC	8462852-007.cpa	20h06m17.030s	+44°27'18.83''
Translation	DX=-0.13	DY=0.14		t_KIC	8462852-008.cpa	20h06m17.438s	+44°27'09.94''
Translation	DX=-0.13	DY=0.06		t_KIC	8462852-009.cpa	20h06m17.730s	+44°27'08.49''
Translation	DX=-0.36	DY=-0.13	t_KIC	8462852-010.cpa	20h06m17.917s	+44°27'07.71''
Translation	DX=-0.18	DY=0.06		t_KIC	8462852-011.cpa	20h06m18.199s	+44°27'03.06''
Translation	DX=-0.27	DY=0.00		t_KIC	8462852-012.cpa	20h06m18.325s	+44°27'02.34''
Translation	DX=-0.23	DY=-0.05	t_KIC	8462852-013.cpa	20h06m18.643s	+44°26'51.42''
Translation	DX=-0.05	DY=0.04		t_KIC	8462852-014.cpa	20h06m19.002s	+44°26'46.76''
Translation	DX=-0.29	DY=0.11		t_KIC	8462852-015.cpa	20h06m19.134s	+44°26'43.89''
Translation	DX=-0.03	DY=0.14		t_KIC	8462852-016.cpa	20h06m19.426s	+44°26'48.40''
Translation	DX=-0.16	DY=0.09		t_KIC	8462852-017.cpa	20h06m19.607s	+44°26'35.54''
Translation	DX=-0.42	DY=0.05		t_KIC	8462852-018.cpa	20h06m20.117s	+44°26'34.71''
Translation	DX=-0.04	DY=0.15		t_KIC	8462852-019.cpa	20h06m20.451s	+44°26'29.81''
Translation	DX=-0.24	DY=-0.12	t_KIC	8462852-020.cpa	20h06m20.772s	+44°26'34.46''
Translation	DX=-0.24	DY=-0.07	t_KIC	8462852-021.cpa	20h06m21.073s	+44°26'30.05''
Translation	DX=-0.30	DY=0.13		t_KIC	8462852-022.cpa	20h06m21.482s	+44°26'24.77''
Translation	DX=-0.65	DY=0.09		t_KIC	8462852-023.cpa	20h06m21.766s	+44°26'24.54''
Translation	DX=-0.45	DY=0.25		t_KIC	8462852-024.cpa	20h06m22.338s	+44°26'28.41''
Translation	DX=-0.06	DY=0.11		t_KIC	8462852-025.cpa	20h06m22.993s	+44°26'42.61''
Translation	DX=-0.43	DY=0.19		t_KIC	8462852-026.cpa	20h06m23.369s	+44°26'48.12''
Translation	DX=-0.41	DY=0.10		t_KIC	8462852-027.cpa	20h06m23.792s	+44°26'56.59''
Translation	DX=0.10		DY=0.00		t_KIC	8462852-028.cpa	20h06m24.369s	+44°26'29.58''
Translation	DX=0.20		DY=-0.12	t_KIC	8462852-029.cpa	20h06m24.694s	+44°26'33.99''
Translation	DX=0.06		DY=-0.12	t_KIC	8462852-030.cpa	20h06m24.958s	+44°27'09.66''
Translation	DX=0.09		DY=-0.05	t_KIC	8462852-031.cpa	20h06m25.363s	+44°26'54.40''
Translation	DX=-0.11	DY=-0.34	t_KIC	8462852-032.cpa	20h06m25.595s	+44°26'50.62''
Translation	DX=0.09		DY=-0.16	t_KIC	8462852-033.cpa	20h06m26.030s	+44°26'46.06''
Translation	DX=0.17		DY=-0.14	t_KIC	8462852-034.cpa	20h06m26.551s	+44°26'41.23''
Translation	DX=-0.06	DY=0.02		t_KIC	8462852-035.cpa	20h06m27.053s	+44°26'38.11''
Translation	DX=0.07		DY=-0.17	t_KIC	8462852-036.cpa	20h06m27.251s	+44°26'40.83''
Translation	DX=0.04		DY=-0.06	t_KIC	8462852-037.cpa	20h06m27.675s	+44°26'42.78''
Translation	DX=0.00		DY=-0.18	t_KIC	8462852-038.cpa	20h06m28.122s	+44°26'26.41''
Translation	DX=-0.02	DY=-0.11	t_KIC	8462852-039.cpa	20h06m28.553s	+44°26'22.66''
Translation	DX=-0.12	DY=-0.25	t_KIC	8462852-040.cpa	20h06m29.027s	+44°26'16.33''
Translation	DX=0.08		DY=-0.08	t_KIC	8462852-041.cpa	20h06m29.424s	+44°26'06.16''
Translation	DX=0.10		DY=-0.13	t_KIC	8462852-042.cpa	20h06m29.805s	+44°26'02.73''
Translation	DX=-0.14	DY=-0.13	t_KIC	8462852-043.cpa	20h06m30.128s	+44°26'03.93''
Translation	DX=0.24		DY=-0.09	t_KIC	8462852-044.cpa	20h06m30.574s	+44°26'06.18''
Translation	DX=0.32		DY=-0.16	t_KIC	8462852-045.cpa	20h06m30.859s	+44°26'11.39''
Translation	DX=0.13		DY=-0.10	t_KIC	8462852-046.cpa	20h06m31.142s	+44°26'07.58''
Translation	DX=-0.41	DY=-0.40	t_KIC	8462852-047.cpa	20h06m31.438s	+44°26'09.58''
Translation	DX=0.10		DY=-0.12	t_KIC	8462852-048.cpa	20h06m31.601s	+44°25'53.65''
Translation	DX=0.11		DY=-0.17	t_KIC	8462852-049.cpa	20h06m31.959s	+44°25'50.14''
Translation	DX=-0.21	DY=-0.24	t_KIC	8462852-050.cpa	20h06m32.142s	+44°25'49.73''
Translation	DX=0.00		DY=-0.07	t_KIC	8462852-051.cpa	20h06m32.527s	+44°25'46.17''
Translation	DX=0.21		DY=-0.07	t_KIC	8462852-052.cpa	20h06m32.714s	+44°25'49.20''
Translation	DX=0.10		DY=-0.23	t_KIC	8462852-053.cpa	20h06m33.030s	+44°25'45.79''
Translation	DX=0.06		DY=-0.37	t_KIC	8462852-054.cpa	20h06m33.303s	+44°25'50.45''
Translation	DX=0.38		DY=-0.34	t_KIC	8462852-055.cpa	20h06m33.513s	+44°25'11.00''
Translation	DX=0.63		DY=-0.30	t_KIC	8462852-056.cpa	20h06m33.795s	+44°24'44.11''
Translation	DX=0.30		DY=-0.32	t_KIC	8462852-057.cpa	20h06m33.769s	+44°24'14.86''
Translation	DX=0.33		DY=-0.32	t_KIC	8462852-058.cpa	20h06m33.818s	+44°24'08.06''
Translation	DX=0.59		DY=-0.05	t_KIC	8462852-059.cpa	20h06m33.953s	+44°24'21.49''
Translation	DX=0.59		DY=-0.03	t_KIC	8462852-060.cpa	20h06m34.062s	+44°24'29.76''
Translation	DX=0.23		DY=-0.07	t_KIC	8462852-061.cpa	20h06m34.085s	+44°24'59.15''
Translation	DX=0.06		DY=-0.55	t_KIC	8462852-062.cpa	20h06m34.200s	+44°25'21.78''
Translation	DX=0.41		DY=-0.29	t_KIC	8462852-063.cpa	20h06m34.508s	+44°25'14.21''
Translation	DX=0.39		DY=-0.36	t_KIC	8462852-064.cpa	20h06m34.528s	+44°25'04.26''
Translation	DX=0.54		DY=-0.35	t_KIC	8462852-065.cpa	20h06m34.674s	+44°24'58.82''
Translation	DX=0.41		DY=-0.21	t_KIC	8462852-066.cpa	20h06m34.691s	+44°24'56.49''
Translation	DX=0.35		DY=-0.38	t_KIC	8462852-067.cpa	20h06m34.853s	+44°24'53.93''
Translation	DX=0.45		DY=-0.37	t_KIC	8462852-068.cpa	20h06m35.018s	+44°24'51.67''
Translation	DX=0.23		DY=-0.29	t_KIC	8462852-069.cpa	20h06m35.298s	+44°24'49.73''
Translation	DX=0.24		DY=-0.36	t_KIC	8462852-070.cpa	20h06m35.468s	+44°24'56.39''
Translation	DX=0.28		DY=-0.18	t_KIC	8462852-071.cpa	20h06m35.708s	+44°24'54.31''
Translation	DX=0.45		DY=-0.15	t_KIC	8462852-072.cpa	20h06m35.920s	+44°24'52.40''
Translation	DX=0.25		DY=-0.27	t_KIC	8462852-073.cpa	20h06m36.158s	+44°24'50.45''
Translation	DX=0.59		DY=-0.19	t_KIC	8462852-074.cpa	20h06m36.395s	+44°24'51.82''
Translation	DX=0.00		DY=-0.39	t_KIC	8462852-075.cpa	20h06m36.427s	+44°24'50.08''
Translation	DX=0.21		DY=-0.51	t_KIC	8462852-076.cpa	20h06m36.448s	+44°24'49.58''
Translation	DX=0.64		DY=-0.14	t_KIC	8462852-077.cpa	20h06m36.671s	+44°24'48.22''
Translation	DX=0.47		DY=-0.38	t_KIC	8462852-078.cpa	20h06m36.641s	+44°24'45.12''
Translation	DX=0.41		DY=-0.13	t_KIC	8462852-079.cpa	20h06m36.731s	+44°24'43.85''
Translation	DX=0.26		DY=-0.51	t_KIC	8462852-080.cpa	20h06m36.821s	+44°24'44.92''
Translation	DX=0.13		DY=-0.32	t_KIC	8462852-081.cpa	20h06m36.777s	+44°24'40.44''
Translation	DX=0.48		DY=-0.28	t_KIC	8462852-082.cpa	20h06m37.306s	+44°24'39.60''
Translation	DX=0.25		DY=-0.36	t_KIC	8462852-083.cpa	20h06m37.373s	+44°24'33.19''
Translation	DX=-0.04	DY=-0.46	t_KIC	8462852-084.cpa	20h06m37.615s	+44°24'43.64''
Translation	DX=0.07		DY=-0.47	t_KIC	8462852-085.cpa	20h06m37.686s	+44°24'36.85''
Translation	DX=0.38		DY=-0.30	t_KIC	8462852-086.cpa	20h06m38.087s	+44°24'25.10''
Translation	DX=0.94		DY=-0.69	t_KIC	8462852-087.cpa	20h06m38.259s	+44°24'32.55''
Translation	DX=0.57		DY=-0.78	t_KIC	8462852-088.cpa	20h06m38.361s	+44°24'36.71''
Translation	DX=0.50		DY=-0.66	t_KIC	8462852-089.cpa	20h06m38.495s	+44°24'36.45''
Translation	DX=1.04		DY=-0.73	t_KIC	8462852-090.cpa	20h06m38.891s	+44°24'36.32''
Translation	DX=0.75		DY=-0.67	t_KIC	8462852-091.cpa	20h06m39.019s	+44°24'26.70''
Translation	DX=0.70		DY=-0.85	t_KIC	8462852-092.cpa	20h06m39.200s	+44°24'14.93''
Translation	DX=0.65		DY=-0.91	t_KIC	8462852-093.cpa	20h06m39.296s	+44°23'48.66''
Translation	DX=1.33		DY=-0.91	t_KIC	8462852-094.cpa	20h06m39.499s	+44°23'35.96''
Translation	DX=1.04		DY=-0.66	t_KIC	8462852-095.cpa	20h06m39.722s	+44°23'13.86''
Translation	DX=0.79		DY=-0.77	t_KIC	8462852-096.cpa	20h06m39.963s	+44°23'14.35''
Translation	DX=0.62		DY=-0.53	t_KIC	8462852-097.cpa	20h06m40.145s	+44°23'08.73''
Translation	DX=0.26		DY=-0.87	t_KIC	8462852-098.cpa	20h06m40.290s	+44°23'13.91''
Translation	DX=0.84		DY=-0.83	t_KIC	8462852-099.cpa	20h06m40.567s	+44°23'14.59''
Translation	DX=0.50		DY=-0.85	t_KIC	8462852-100.cpa	20h06m40.675s	+44°23'15.48''
Translation	DX=0.73		DY=-0.67	t_KIC	8462852-101.cpa	20h06m40.792s	+44°23'13.60''
Translation	DX=0.60		DY=-0.86	t_KIC	8462852-102.cpa	20h06m40.916s	+44°23'14.71''
Translation	DX=0.87		DY=-0.90	t_KIC	8462852-103.cpa	20h06m41.003s	+44°23'15.85''
Translation	DX=0.82		DY=-0.48	t_KIC	8462852-104.cpa	20h06m41.009s	+44°23'13.23''
Translation	DX=0.43		DY=-0.72	t_KIC	8462852-105.cpa	20h06m41.282s	+44°23'27.97''
Translation	DX=0.51		DY=-0.88	t_KIC	8462852-106.cpa	20h06m41.343s	+44°23'29.38''
Translation	DX=1.03		DY=-0.96	t_KIC	8462852-107.cpa	20h06m41.655s	+44°23'26.13''
Translation	DX=0.48		DY=-0.92	t_KIC	8462852-108.cpa	20h06m41.986s	+44°23'12.42''
Translation	DX=0.86		DY=-0.78	t_KIC	8462852-109.cpa	20h06m42.318s	+44°23'08.93''
Translation	DX=0.35		DY=-0.86	t_KIC	8462852-110.cpa	20h06m42.737s	+44°23'20.73''
Translation	DX=0.71		DY=-0.78	t_KIC	8462852-111.cpa	20h06m43.096s	+44°23'12.21''
Translation	DX=0.42		DY=-0.80	t_KIC	8462852-112.cpa	20h06m43.347s	+44°23'12.93''
Translation	DX=0.41		DY=-1.02	t_KIC	8462852-113.cpa	20h06m43.545s	+44°23'14.78''
Translation	DX=0.78		DY=-0.67	t_KIC	8462852-114.cpa	20h06m43.944s	+44°23'54.81''
Translation	DX=0.63		DY=-1.01	t_KIC	8462852-115.cpa	20h06m44.143s	+44°23'56.74''
Translation	DX=0.60		DY=-1.33	t_KIC	8462852-116.cpa	20h06m44.438s	+44°23'36.03''
Translation	DX=0.34		DY=-1.02	t_KIC	8462852-117.cpa	20h06m44.694s	+44°23'21.42''
Translation	DX=0.70		DY=-0.65	t_KIC	8462852-118.cpa	20h06m45.113s	+44°23'12.07''
Translation	DX=0.29		DY=-1.04	t_KIC	8462852-119.cpa	20h06m45.562s	+44°23'24.49''
Translation	DX=0.49		DY=-1.22	t_KIC	8462852-120.cpa	20h06m45.946s	+44°23'25.20''
Translation	DX=-0.17	DY=-0.98	t_KIC	8462852-121.cpa	20h06m46.360s	+44°23'23.33''
Translation	DX=-1.05	DY=-1.03	t_KIC	8462852-122.cpa	20h06m47.881s	+44°23'20.31''
On voit que le facteur de translation est au maximum 1 pixel.
Or j'ai une dérive de 4' en DEC.
Avec un échantillonnage de 1.25"/pixel, une dérive de 4' en DEC correspond normalement à 192 pixels.
Il y a donc un problème.

Est-ce que d'autres utilisateurs (Prism 10.1.13.187) ont ce même problème ?
Est-ce lié à l'utilisation de l'AO8 dans le guidage ?

Si quelqu'un a une idée.
Marc

Re: Dérive DEC entête image sur une série d'images

Posté : 03 juil. 2016, 02:47
par Cyril Cavadore
Si tu guides et que tu as des rappels en DEC, sur la carte du ciel tu vas voir lentement deriver ton pointeur, et aussi la coordonnée qui va aller dans l'image.
Donc pour moi ca ne me choque pas.

Re: Dérive DEC entête image sur une série d'images

Posté : 03 juil. 2016, 12:21
par Marc DELDEM
Salut Cyril,

Sur l'image 1 qui sert de référence pour faire l'addition de toute la série, j'ai comme coordonnée de centre d'image 20h06m15.507s +44°27'23.83''.
Et sur la dernière image de la série, j'ai comme coordonnée du centre d'image 20h06m47.881s +44°23'20.31''.
Or la translation nécessaire pour cette dernière image pour l'aligner sur la première n'est que de 1 pixel (Translation DX=-1.05 DY=-1.03).

Donc j'ai une dérive en DEC (axe Y) de plus de 4 minutes d'arc et seulement 1 pixel en translation pour l'addition (1 pixel valant 1.25 seconde d'arc).

A mon avis il y a un soucis et surement lié à l'AO8.

Marc

Re: Dérive DEC entête image sur une série d'images

Posté : 04 juil. 2016, 00:06
par Cyril Cavadore
Ah oui, je vois, parce que c'est l'AO qui fait bouger l'image et pas le monture .... donc la coordonnée centrale est celle de la monture, pas d'une quelconque astrometrie.

Re: Dérive DEC entête image sur une série d'images

Posté : 03 mai 2017, 23:14
par Marc DELDEM
Bonsoir Cyril,

Je remonte ce sujet, car cela fait 1 mois que je n'utilise plus l'AO8 et le problème persiste.

Voici un exemple où c'est une séquence de poses unitaires de 120s guidée en ASCOM pulse guide, SANS AO8.
Je guide avec le second capteur de la SBIG ST8.

Ci-dessous, j'extrais la position RA/DEC de l'entête de l'image brute, non traitée (image écrite par Prism après l'acquisition):
Diotima (423)-2.cpa 12h26m49.268s +11°24'43.65''
Diotima (423)-3.cpa 12h26m49.128s +11°24'49.11''
Diotima (423)-5.cpa 12h26m48.789s +11°24'47.75''
Diotima (423)-6.cpa 12h26m48.587s +11°24'50.12''
Diotima (423)-9.cpa 12h26m47.888s +11°24'53.54''
Diotima (423)-10.cpa 12h26m47.809s +11°24'55.88''
Diotima (423)-11.cpa 12h26m47.535s +11°24'52.66''
Diotima (423)-13.cpa 12h26m47.038s +11°24'50.33''
Diotima (423)-14.cpa 12h26m46.768s +11°24'56.67''
Diotima (423)-15.cpa 12h26m46.537s +11°24'44.49''
Diotima (423)-16.cpa 12h26m46.239s +11°25'02.86''
Diotima (423)-17.cpa 12h26m46.004s +11°24'56.29''
Diotima (423)-18.cpa 12h26m45.824s +11°24'48.85''
Diotima (423)-19.cpa 12h26m45.586s +11°24'53.60''
Diotima (423)-20.cpa 12h26m45.414s +11°25'02.12''
Diotima (423)-21.cpa 12h26m45.183s +11°24'58.46''
Diotima (423)-22.cpa 12h26m44.797s +11°24'55.10''
Diotima (423)-23.cpa 12h26m44.794s +11°24'56.30''
Diotima (423)-24.cpa 12h26m44.686s +11°25'01.20''
Diotima (423)-25.cpa 12h26m44.538s +11°24'56.87''
Diotima (423)-26.cpa 12h26m44.585s +11°24'58.11''
Diotima (423)-27.cpa 12h26m44.470s +11°25'02.86''
Diotima (423)-28.cpa 12h26m44.203s +11°25'00.88''
Diotima (423)-29.cpa 12h26m44.297s +11°24'58.88''
Diotima (423)-30.cpa 12h26m44.426s +11°25'00.32''
Diotima (423)-31.cpa 12h26m44.224s +11°24'59.08''
Diotima (423)-32.cpa 12h26m44.221s +11°24'56.63''
Diotima (423)-34.cpa 12h26m43.544s +11°24'54.44''
Diotima (423)-35.cpa 12h26m43.659s +11°24'56.99''
Diotima (423)-36.cpa 12h26m43.522s +11°24'57.43''
Diotima (423)-37.cpa 12h26m43.623s +11°24'52.49''
Diotima (423)-39.cpa 12h26m43.370s +11°23'50.54''
Diotima (423)-40.cpa 12h26m43.483s +11°24'51.86''
Diotima (423)-41.cpa 12h26m43.226s +11°24'53.87''
Diotima (423)-42.cpa 12h26m43.226s +11°24'47.73''
Diotima (423)-43.cpa 12h26m43.075s +11°24'48.72''
Diotima (423)-44.cpa 12h26m42.794s +11°24'47.81''
Diotima (423)-45.cpa 12h26m42.784s +11°24'48.42''
Diotima (423)-46.cpa 12h26m42.614s +11°24'46.29''
Diotima (423)-48.cpa 12h26m42.264s +11°23'39.93''
Diotima (423)-49.cpa 12h26m41.959s +11°24'39.38''
Diotima (423)-50.cpa 12h26m41.814s +11°24'42.01''
Diotima (423)-51.cpa 12h26m41.667s +11°24'35.02''
Diotima (423)-52.cpa 12h26m41.602s +11°24'46.40''
Diotima (423)-53.cpa 12h26m41.559s +11°24'41.17''
Diotima (423)-54.cpa 12h26m41.389s +11°24'38.96''
Diotima (423)-55.cpa 12h26m41.321s +11°24'37.17''
Diotima (423)-56.cpa 12h26m41.102s +11°24'34.83''
Diotima (423)-57.cpa 12h26m41.062s +11°24'30.08''
Diotima (423)-58.cpa 12h26m40.882s +11°24'36.28''
Diotima (423)-59.cpa 12h26m40.778s +11°24'31.94''
Diotima (423)-60.cpa 12h26m40.503s +11°24'30.42''
Diotima (423)-61.cpa 12h26m40.331s +11°24'33.87''
Diotima (423)-62.cpa 12h26m40.208s +11°24'30.09''
Diotima (423)-63.cpa 12h26m40.093s +11°24'25.79''
Diotima (423)-64.cpa 12h26m40.075s +11°24'26.03''
Diotima (423)-65.cpa 12h26m39.780s +11°24'19.43''
Diotima (423)-66.cpa 12h26m39.704s +11°24'26.50''
Diotima (423)-67.cpa 12h26m39.550s +11°24'23.45''
Diotima (423)-68.cpa 12h26m39.416s +11°24'19.73''
Diotima (423)-69.cpa 12h26m39.275s +11°24'20.24''
Diotima (423)-70.cpa 12h26m39.013s +11°24'17.80''
Diotima (423)-71.cpa 12h26m38.955s +11°24'15.51''
Diotima (423)-72.cpa 12h26m38.840s +11°24'13.09''
Diotima (423)-73.cpa 12h26m38.746s +11°24'16.47''
Diotima (423)-74.cpa 12h26m38.368s +11°24'08.12''
Diotima (423)-75.cpa 12h26m37.990s +11°24'03.66''
Diotima (423)-76.cpa 12h26m37.695s +11°24'03.81''
Diotima (423)-77.cpa 12h26m37.320s +11°24'03.77''
Diotima (423)-79.cpa 12h26m36.773s +11°23'53.20''
Diotima (423)-80.cpa 12h26m36.521s +11°23'50.20''
Diotima (423)-81.cpa 12h26m36.218s +11°23'48.33''
Diotima (423)-82.cpa 12h26m36.078s +11°23'45.41''
Diotima (423)-83.cpa 12h26m35.754s +11°23'43.10''
Diotima (423)-84.cpa 12h26m35.303s +11°23'44.74''
Diotima (423)-85.cpa 12h26m35.282s +11°23'40.84''
Diotima (423)-86.cpa 12h26m35.044s +11°23'36.92''
Diotima (423)-87.cpa 12h26m34.644s +11°23'38.73''
Diotima (423)-88.cpa 12h26m34.202s +11°23'40.88''
Diotima (423)-89.cpa 12h26m33.878s +11°23'33.22''
Diotima (423)-90.cpa 12h26m33.615s +11°23'38.00''
Diotima (423)-91.cpa 12h26m33.082s +11°23'33.19''
Diotima (423)-92.cpa 12h26m32.836s +11°23'33.63''
=> On peut donc voir une dérive en RA et une dérive très significative en DEC.
J'ai un champ de 32'x22' en RAxDEC et j'ai un échantillonnage de 1.25" par pixel.
En DEC, c'est plus important du fait de la mise en station imparfaite je pense.
Début: 12h26m49.268s +11°24'43.65''
Fin: 12h26m32.836s +11°23'33.63''
Cette séquence a été guidée.
La mise en station n'est pas parfaite mais suffisante pour guider sans problème particulier.

Si je fais une addition des images, alors le décalage entre les images et la première image (la référence) est:
Translation :-0.18079, 0.24478
Translation :0.079712, 0.15269
Translation :0.16315, 0.24078
Translation :0.34576, 0.19434
Translation :0.30096, 0.26214
Translation :0.3446, 0.23303
Translation :0.21039, -0.51944
Translation :0.37158, -0.00054932
Translation :0.27902, -0.71628
Translation :0.37903, -0.25555
Translation :0.44208, -0.56206
Translation :0.2504, -0.33511
Translation :0.7373, -0.21603
Translation :0.65045, -0.36719
Translation :0.62149, 0.3187
Translation :0.48218, 0.97513
Translation :0.53415, 0.64716
Translation :0.42773, 0.39136
Translation :0.65985, -0.071686
Translation :0.37787, -0.35095
Translation :0.67657, 0.12048
Translation :0.5636, 0.47577
Translation :0.75018, 0.12311
Translation :0.75397, 0.040771
Translation :0.56226, 0.31708
Translation :0.62671, -0.30554
Translation :1.1852, -0.5007
Translation :0.96558, 0.20755
Translation :0.96802, 0.45441
Translation :-1.17, -0.83447
Translation :-0.98456, -2.6808
Translation :-0.88303, -1.2889
Translation :-1.0068, -0.64758
Translation :-1.0391, -0.45471
Translation :-0.85608, -0.71442
Translation :-0.44269, -0.86411
Translation :-0.62158, -1.0919
Translation :-0.4754, -1.096
Translation :-0.9505, -2.0161
Translation :-0.43073, -0.89822
Translation :-0.7984, -0.98083
Translation :-0.83368, -0.79889
Translation :-0.010925, -0.97768
Translation :-0.69183, -0.57092
Translation :-0.42773, -0.89172
Translation :-0.59283, -0.53845
Translation :-0.2489, -0.78607
Translation :0.10638, -1.0018
Translation :-0.46002, -0.64148
Translation :-0.53375, -0.49609
Translation :-0.58899, 0.30096
Translation :0.29333, -0.15927
Translation :-0.22272, -0.41275
Translation :-0.20459, -0.52264
Translation :0.45502, -0.099937
Translation :-0.35553, -0.49579
Translation :0.53967, -0.066315
Translation :0.50677, -0.21469
Translation :0.031036, -0.92563
Translation :-0.59448, -0.18567
Translation :0.55139, -0.69968
Translation :0.37292, 0.32263
Translation :0.92078, -0.2562
Translation :0.11743, -0.60446
Translation :0.39819, 0.6279
Translation :0.80933, 0.3674
Translation :0.21454, -0.70065
Translation :0.42899, -0.69955
Translation :0.76929, 0.60074
Translation :0.55072, -0.60913
Translation :0.79587, -0.95013
Translation :1.2944, 0.30081
Translation :0.79407, 0.1987
Translation :0.78558, -0.68634
Translation :1.1392, 0.62308
Translation :1.2705, 0.14536
Translation :1.0952, 0.48859
Translation :0.76828, -0.815
Translation :1.2042, -0.62003
Translation :0.99582, -0.28033
Translation :1.2655, -0.40268
Translation :1.2013, -0.37616
=> On voit que le décalage ne dépasse pas les 2 pixels, sachant que j'ai 1.25" par pixel.

=> J'insiste donc sur le fait qu'il y a un problème pendant la phase de guidage.
En particulier, la position écrite dans l'entête de l'image, si c'est la position que Prism croit être du télescope, alors il y a un problème pour toutes les valeurs de limites de pointage ou de seuil de déclenchement d'une action.
Car Prism va se tromper en cherchant à savoir si la limite est atteinte ou pas.
Je pense par exemple au retournement au méridien dans l'observation automatique ou bien a des limites d'angles horaires également dans l'obs auto.


Marc

Re: Dérive DEC entête image sur une série d'images

Posté : 14 sept. 2017, 21:32
par Marc SERRAU
J'expérimente ce phénomène chez moi et l'ai vu sur le TJMS de Buthiers lors de série de poses longues.
Etrange...

Re: Dérive DEC entête image sur une série d'images

Posté : 14 sept. 2017, 22:02
par Cyril Cavadore
Si il y a des rappels en DEC sur un sens, et continus, le système de contrôle de telescope va avoir son delta qui derive, car il incrémente ou décrémente le DEC dans le firmware de la monture.
La il semble que ca corrige dans un sens ou dans un autre, si tu peux mettre ca dans un plot ?
En tout cas, et en AUCUN cas, Prism ne fait des calculs de RA/DEC, l'info provient du driver ASCOM.
Heures au format UTC+02:00
Page 1 sur 1

Développé par phpBB® Forum Software © phpBB Limited

Traduit par phpBB-fr.com