Imaging with the Atik 414 EX

[astro mick]

Hi Folks.

This is a section of the Pelican Nebulae.It will be completed in Narrowband when I can get back out.But I,m really impressed with the sensitivity of this camera.

This H-Alpha image is the result of just 10x300 secs,with Flats applied.Normaly I would shoot at least 24 at this exposure.

This camera is so easy to get up and running,with great software and drivers.I normally use Starlight cameras,which are really good,but let down by their software and drivers,which can be quite difficult to install.

Mick.

[nightster]

It hard for me to believe that this kind of detail can be produced by an amateur. The portion near the center right has an almost 3D feel, lots of depth.  Can't wait to see more.

[D4N]

That is really nice, may I ask what the rest of the setup was?

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[astro mick]

Thanks Jeff,thanks Dan.

It was taken with an Altair Astro 72ED Scope,with a x0.8 Focal Reducer.

Mick.

[Davey-T]

Very nice Pelican Mick, really stands out, in some images it's difficult to distinguish it from the background.

Dave

[toxic]

nice image there mick.

what scope was used with the 414ex

[Davey-T]

According to FLO,s new app your'e under sampling ?

It says chuck the .8 reducer and use 2X Barlow

Dave

http://stargazerslounge.com/topic/245060-imaging-camera-telescope-suitability-calculator/#entry2663206

[Chris]

Fantastic Mick, and I'm pleased you're liking the Atik

@ Dave - I think the only downside to under sampling is lack of resolution, but on the flip side it increases sensitivity ( I think this is right?).

Lots of detail in this image

[Davey-T]

Fantastic Mick, and I'm pleased you're liking the Atik

@ Dave - I think the only downside to under sampling is lack of resolution, but on the flip side it increases sensitivity ( I think this is right?).

Lots of detail in this image

Yes I use WO 110 FLT, Atik 4000 .8X f/r which is theoretically under sampling but works fine for me, might be nice to have just a flattener but I'd rather under sample and have round stars at the corners.

Apologies to Mick for thread drift

Dave

[astro mick]

Thanks guys. 

But undersampling/oversampling, I have,nt a clue what your talking about.

Mick.

[D4N]

As I understand it under sampling is when you have insufficient resolution at your image scale to provide the level of detail you want. For us this is generally star shape and nebulosity.

Over sampling is when you have far more resolution at your image scale than seeing will allow you to image at.

Over sampling in itself isn't harmful to the image but without excellent seeing conditions you won't be optimal for your equipment.

Under sampling can cause stars to appear square rather than round but may be a necessary evil if you want a wide FOV, it will also reduce detail in nebulosity but this should be less obvious. Stacking techniques like drizzle and dithering can help rectify this somewhat.

It may be worth noting that planetary work is generally horrendously over sampled compared to deep sky but then they also throw away the vast majority of their subs when they stack so the short exposure times can catch the moments of truly good seeing.

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[astro mick]

Cheers Dan.

But I don't think I will worry to much about it.

Mick.

[Davey-T]

Hi Mick,

Sampling is assessed using the Nyquist sampling criterion used in hifi systems etc that says that when sampling a wave the sampling frequency should be two times higher than the highest frequency present in the original. So music on CDs is 44Khz around twice the human hearing frequency of 20Khz.

Ideal Nyquist imaging calls for a pixel size half the diameter of the diffraction disc defined by it's FWHM this is critically sampled because it has just enough pixels to capture all the available detail.

Images sampled with pixels larger than the FWHM are undersampled, images sampled with more than two pixels across the core of the diffraction disc are over sampled.

Much of this is a hang over from original CCD  imaging with large (18 / 27micron) pixels and long focal length scopes so not worth getting too obsessive about.

As imaging in the UK limited by the seeing which gives an Airy disc far larger than the ideal the best way is to experiment to see what works in the real world.

Dave