M51 with CPC 1100

[cfpendock]

Here is my first attempt at M51. Taken between clouds using a CPC 1100 and an Atik 4000 camera.

4 x 120second subs each of RGB binned 2x2, 4 x 250secs Luminance (1x1).

Although I am pleased with the image, it is a far cry from what others achieve. My excuses are that there was some light from an adjacent street light, but I am not sure if this accounts for the grainy result. Also the image is badly aligned - the result of some cropping required due to the different exposures being snatched between clouds over a long period of time, and a less than perfect polar alignment.

I also found focusing difficult with the standard Celestron focuser, even using FWHM in Artemis. The image was stacked in DSS and (over)processed in Photoshop.

My questions are:

1. Would auto guiding have helped on such short exposures, or is the blurriness due to focussing or drive error?

2. How much total exposure time is necessary to make a significant improvement in graininess, or could this be due to the street light? It is difficult to understand how some people manage longer exposures with the weather in the UK.

Thanks for looking

Chris

[michael.h.f.wilkinson]

Despite grain, an impressive shot. Given that the CPC is an alt-az mount, I wonder whether autoguiding is the solution. Even with autoguiding, field rotation would occur, I would say.

[ultranova]

Hi Chris, im not sure about the auto guiding bit due to your set up being an alt-az mount, if

it you had a EQ mount i would say yes.

to help with the noise take more pictures the more you take the better the end result,

alaso to the fact you used 2x binning I think im correct in saying this intoduces more noise

you have an incredible amount of detail for such short sub times,

I have just got into the ccd stuff so im still learning

Paul

[cfpendock]

Thanks Paul and Michael.

The scope is mounted on a heavy duty wedge, so it's equivalent to an Eq mount, hence my reference to polar alignment. Interesting in what you say about the binning, Paul. I thought it would save time as I thought the binned exposures were only to provide a colour "wash", the detail being provided by the luminance. Probably I am incorrect about this, but time was of the essence when clouds are about!

chris

[Gina]

Nice colour and reasonable detail - a good result for just a little data Did you really mean 4 subs of 120/250s? I would go for at least 10 subs of each - that will sort out your noise

[KevUU]

Wow, that looks pretty decent to me, especially for 4 subs and under lp

[sologuitarist61]

Smashing image!