Fast newts, coma, small chips

[Lee]

Hi all
I'm looking at going to a fast newt for imaging, I guess I'm happy with the focal length of my ED80, not happy with the aperture.... I'll probably get a 8" f/4 newt....
I'll probably give it a try without a coma corrector to begin with, as I'm getting an Atik-420, which has a reasonably small chip - should I cough for a Baader now, or does anyone think she'll be right with the small chip???

Is anyone imaging on small chips, fast newt, sans coma corrector???

[CoolhandJo (Paul)]

I think you hould get the Mppc straight away! Small chip or not you may need to crop down even further

[naskies (Dave)]

What type of objects are you planning on imaging? According to my field of view calculator, an 8" f/4 newt with the Atik 420 will give you 1.13''/pixel which is good, but the field of view will be tiny: 30.63' x 23.07'.

Fine for planetary nebulae and small galaxies, but I'd imagine you'd struggle to fit most of the popular nebulae (e.g. Lagoon won't fit, Trifid will be a squeeze) and galaxies (Sculptor Galaxy is 27' long). You'll lose some of the edges of your field of view to dithering and cropping (e.g. drift and field rotation due to polar misalignment).

Something else to consider is that the chip used in the Atik 420 (Sony ICX-274) has a shallow well depth - only 14,000 - which means stars will lose their colour and bloat quickly.

Might be worth checking out some other cameras in a similar price range (or slightly higher) too, e.g. the QHY8L.

[Lee]

I'm happy with the FOV, galaxies/smaller nebs my favourites - I've got the ED80 and a 100mm f/5 achromat for larger nebs....
There is always places to stretch the budget in this hobby.... hopefully the little 420 will keep me happy for a bit!

[Shiraz (Ray)]

sounds like the basis for a good med-hi res system Lee. In good seeing I think that you will need a coma corrector, even with such a small chip. Although the well depth is low, it is compensated for by the extremely low read noise - overall dynamic range is a healthy 71dB - much the same as better known chips like the K8300. regards Ray

[Lee]

Thanks Ray, I've seen some long subs with the 420, very clean, in comparison to my DSI Pro, which is as noisy as a KISS concert....