UVEX on a Maksutov 127

UVEX on a Maksutov 127

Postby Christian Buil » Wed Jul 17, 2019 4:35 pm

UVEX on a another small telescope (and low cost), a Sky-Watcher Maksutov 127 mm f/11.8 :

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The equatorial mount is a little overdimensioned ...

Who says small telescope says possibility to use a narrow slit. Of course the optical flux is limited by the small aperture, but in return, the resolution power increases (it is a choice).

Tests by using 10 microns wide slit on Vega, with R = 1450 at 550 nm (and R = 1700 at Halpha wavelength) and a 300 l/mm grating + ASI183MM for the visual spectral domain coverage:

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The slit wide on the sky is only 1,37 arcsec. If we adopt a 14 microns slit the angular wide is 1,92 arcsec. The resolution power drop now to R=1200 at 550 nm (R=1400 near Halpha) :

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The Be star QR Vul:

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Symbiotic AG Peg ;

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Of course, no question of take spectra of the magnitude 15 objects with such a small instrument (!!!), however here, the "bright" actual cataclysmic star in Cygnus near magnitude 9.5 - 9.75 by using a 10 microns slit :

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or by using a 14 microns slit (+ a processing method here adapted to oversampled spectra --- the ASI183MM pixel size is only 2.4 microns --- for reduce the noise ("nearly" equivalent to a 2x2 binning)) :

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I really enjoy doing this type of spectrography with a small telescope and a (relatively) low cost spectrograph. This seems to me coherent (it does not exclude other configurations, of course).

It is very specific to spectrography: the product (radiometric resolution i.e. SNR) X (spectral resolution power) result is nearly a constant. If we sacrifice the magnitude, we gain is in spectral resolution power increase.That's what makes science (and education) with very small instruments.

Christian Buil
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Re: UVEX on a Maksutov 127

Postby etienne bertrand » Wed Jul 17, 2019 8:06 pm

Bien pratique, on va pouvoir faire de la spectro même en voyageant autour du monde ;)
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Re: UVEX on a Maksutov 127

Postby James Foster » Wed Jul 17, 2019 11:08 pm

To: Christian,

I shot AG Peg at almost the same date/time as yourself, abiet in LISA IR only(for comparison):
Image

James
James Foster
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
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Re: UVEX on a Maksutov 127

Postby Christian Buil » Thu Jul 18, 2019 9:17 pm

Etienne, c'est un peu ca aussi l'idée, disposer d'une configuration légère pour la manutention !

D'autres exemples de spectres faits avec cette configuration...

A MILES blue standard star, HD207330:

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or P Cyg:

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details:

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Christian
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Re: UVEX on a Maksutov 127

Postby Christian Buil » Wed Jul 31, 2019 8:51 am

Part of Vega spectrum by using UVEX on a Maksutov 127 telescope and 1200 l/mm grating (blaze 400 nm) :

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Resolution of R=3800 is now nearly reatched in the blue (400 nm).

The same night, RR Lyrae spectrum (V=7.5) :

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Because the use of a very small telescope, the system is nearly limited by diffraction phenomena (I can see Airy disk on the slit during guiding). Because diffraction, the practical minimal slit width is here 9.5microns (here I use a 14 microns slit) and the absolute diffraction theoretical limit resolution is R=9800.

Christian Buil
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Re: UVEX on a Maksutov 127

Postby Benjamin Mauclaire » Wed Jul 31, 2019 6:09 pm

Hello Christian,

Voilà un jolie doublet du calcium qui se niche au milieu des raies de Balmer de RR Lyr.
Avec un T 1m, on peut espérer faire des time series de 600-900 s adaptées aux pulsations du cycle de ~13h.

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