Spectro avec C11 ?

[etienne bertrand]

Pour gagner des photons je réfléchis à passer à un C11 pour l'Alpy et le Lhires avec monture EQ6, qu'en pensez vous ? ça va être trop lourd pour bien marcher ? ou ça passe ? Pour l'instant j'ai un C8, ça marche parfaitement mais il faut poser longtemps, le but est d'avoir un meilleur signal possible avec la configuration voir d'atteindre les étoiles Be à magnitudes 10.

[Ken Harrison]

Etienne,
The C11 is a popular choice for spectroscopy and fits well on an NEQ6pro mount.
I use the Spectra-L200 plus ATik 314L on my C11 controlled by a Lodestar guider, using EQMod and CdC.

Mainsail Obs 001s.jpg (64.74 KiB) Viewed 6874 times

Mainsail Obs2 009s.jpg (61.95 KiB) Viewed 6874 times

[Andrew Smith]

Etienne, just remember SN scales with diameter so the gain may not be as big as investing in a new camera(s) with a lower read noise, higher QE than your current one?

Just a thought.

Regards Andrew

[etienne bertrand]

Thanks Ken for the photo, i think C11 is a good/best for the EQ6.
Andrew, i use a Atik414EX so it's a good last CCD. The diametre is interesting i think with the same materiel for have a better SNR.

[Francois Teyssier]

Bonjour Etienne,
Une autre façon d'envisager le probleme : la qualité de l'autoguidage
Diamètre, qualité, réglage et focalisation du telescope = plus de photons
Autoguidage (monture) = plus de photons dans la fente
François

[Ken Harrison]

I find the slit guiding capabilities of AstroArt to be very good. PHD2 is always a good fall back.
Ken

[Robin Leadbeater]

Etienne, just remember SN scales with diameter

The improvement can be even less than that for a slit spectrograph depending on seeing and slit width because of the larger star image. When I went from the VC200L to the C11 I had to increase the slit width in the LHIRES from 23um to 35um and lose resolution to get the full advantage of the larger aperture.

For fast low resolution spectrographs like the ALPY or LISA, I think Christian has the right idea. A fast, large aperture Newtonian is ideal. Better than an SCT with a focal reducer which can give give problems with chromatic aberrations. They can be good value too if you avoid those with flat field correctors (which is not needed). They are big though so you need space and a stable mount.

Cheers
Robin

[Andrew Smith]

For fast low resolution spectrographs like the ALPY or LISA, I think Christian has the right idea. A fast, large aperture Newtonian is ideal. Better than an SCT with a focal reducer which can give give problems with chromatic aberrations. They can be good value too if you avoid those with flat field correctors (which is not needed). They are big though so you need space and a stable mount.

Cheers
Robin

Yes I found my 300mm Newt went well with my LISA. I did try for an 400mm F5 Newt but it was just too big for my observatory. Going to a 400mm ODK was not such an issue for a fiber fed echelle spectrograph but even the I use a 75 micron hole reduced to 50 micron fiber.

Regards Andrew