an Owl in the moonlight

[derrickf]

We seem to have the worst of the clear nights in the last few weeks - while imagers to the North and East of my location have had some pretty clear conditions the M4 corridor has had generally murky conditions with the odd clear break. This image of M97 has been taken over the last month with high cloud, poor seeing and the moon trying hard to ruin any nominally clear spells.

Anyway enough moaning  image details:

Equipment: TS (GSO) 12" truss RC (2400mm Focal Length) with modified back plate, Mesu200, Atik383L+, Atik EFW2, Lodestarx2 on Atik OAG

Exposure: L=9 x 600s unbinned; R=G=B= 9 x 600s binned 2x2 each filter.

Captured with MaxImDl and processed in Pixinsight.

The image is rather noisy due to the presence of the moon on several of the nights when I collected the data and further due to the relatively short total exposure time but it doesn't look as though I'll be able to add more any time soon based on the weather forecast. Despite that there are still dozens of tiny, faint fuzzies visible in the background.

There was one night where, during a clear spell that lasted for about 90 minutes, the seeing was fantastic (although transparency was not great) and I managed to capture 5 or 6 images where the measured stellar FWHM was sub 2 arc seconds and in2 image2 was below 1.8 arc seconds - this is the reason I bought the long focal length scope - it's just a pity we haven't had many such nights in recent months. Still, it does bode well for the RC and Mesu200 setup if the conditions ever improve again ...

Derrick

[laudropb]

Very nice image.

[cfpendock]

Considering the conditions, that is pretty good, and the stars look fairly tight.  I am intrigued that you shot the Lum at single binning at 2400mm focal length.  It seems to me that your resolution must have been less than half arc second per pixel, and as you have said, the really good seeing was around 2 arc seconds. Could you have effectively increased the time by binning the Lum, and hence possibly reduced the noise a bit?

In any event, it's a nice image - despite the moonlight.

Chris

[PeterCPC]

I totally agree about the sky conditions so you did well with that.

Peter

[derrickf]

34 minutes ago, cfpendock said:

Considering the conditions, that is pretty good, and the stars look fairly tight.  I am intrigued that you shot the Lum at single binning at 2400mm focal length.  It seems to me that your resolution must have been less than half arc second per pixel, and as you have said, the really good seeing was around 2 arc seconds. Could you have effectively increased the time by binning the Lum, and hence possibly reduced the noise a bit?

In any event, it's a nice image - despite the moonlight.

Chris

Hi Chris,

Thanks for your comment; I did consider binning but decided that I would persevere with the luminance unbinned for a couple of reasons: I had just collimated the scope so wanted to verify that I had done so successfully and, I'm not convinced that binning would have helped significantly with the moonlit sky. I did try one binned luminance and the object SNR was not substantially improved but I did have issues with the brighter stars becoming saturated.

Just a point about my point of view on sampling resolution and seeing: in order to properly sample a star we need a pixel scale of FWHM / 3.3 so to critically sample stars in seeing conditions of 1.8 arc-seconds FWHM a pixel scale of 0.54 arc seconds is needed which is pretty close to my unbinned 0.46 arc seconds pixel scale with the Atik383.

 

Regards

Derrick

[derrickf]

51 minutes ago, PeterCPC said:

I totally agree about the sky conditions so you did well with that.

Peter

Thanks Peter,

I can't remember such a long period of dire sky conditions at any time in the last 20 years as we have had in the last couple of years.

 

Derrick

[FranckiM06]

Very nice image

[pyrasanth]

On 2/28/2016 at 16:49, derrickf said:

Thanks Peter,

I can't remember such a long period of dire sky conditions at any time in the last 20 years as we have had in the last couple of years.

 

Derrick

I agree with this. I've been an astronomer for nearly 40 years and the conditions have got steadily worse with dire weather & light pollution everywhere. It does not hold good for the future.

[Astroboy239]

Same here pyarasanth. Actually we have clear skies since a week this shouldn't happen in this month tho. But our biggest problem is the dust in the air acting like clouds. Weather and climate change is changing the seasons. 

 

 

Varad 

[ollypenrice]

That's lovely. I began by enjoying the image and only then read the capture details. I was surprized that this had no OIII or Ha. A super Owl. It does neet a bit of FL, thos one!

Olly

[derrickf]

Thanks Olly,

Just LRGB in this one; it is now badly situated for me to capture more data this year or I would have grabbed some narrowband - maybe next year.

 

Derrick

[Jannis]

Very nice image

[ultranova]

very nicely done indeed,

Having the FL has captured some nice details even if the

conditions were very challenging

well done

Paul