Dispersion A/px too big?

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Dispersion A/px too big?

Postby Ari Siqueira » Thu Dec 23, 2021 2:58 am

Bonjour à tous sur ce forum.

J'ai essayé de comprendre comment obtenir une valeur de dispersion autour de 4 à 6 A/pixel avec le matériel suivant :
1. Meade SCT 203 mm f/6.3 ou f/10
2. Caillebotis de transmission SA-100
3. Caméra CCD mono IS DMK 41AU02.AS (1 280 x 960 pixels - 4,65 µm)

Je n'ai obtenu des valeurs de dispersion proches des 4-6 A/px que lorsque ma distance réseau-capteur était comprise entre 66 et 76 mm.

Est-ce que je me trompe ?

Je serai très reconnaissant à quiconque commentera cela, s'il vous plaît.

Le tiens,

Ari Siqueira
Ari Siqueira
 
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Re: Dispersion A/px too big?

Postby Robin Leadbeater » Fri Dec 24, 2021 12:09 am

Hi Ari,

If you use the calculator
https://www.rspec-astro.com/calculator/
this confirms that you will get 6A/pixel with a spacing of 77mm
If your seeing is 3 arcsec, the theoretical resolution (star image size x dispersion) is 38A at f10 or 24A at f 6.3 but in practise the aberrations due to the converging beam will likely limit the resolution

At this dispersion the spectrum including the zero order only just fits in the camera frame (useful for wavelength calibration) and if you try to get a higher dispersion (lower A/pix) than this by increasing the distance you will not be able to fit the spectrum and zero order

I suggest starting by running at f6.3 with a spacing of ~65mm. This will give a dispersion of 7.2A/pix which will allow room to fit the spectrum and zero order and give a theoretical resolution of ~30A

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
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