M101 First Dither attempt

[cuivenion]

I only managed a short session unfortunately and had to reduce the exposure time or I'd have run out of imaging time. First attempt with dithering and darks:

12 x 180s

100 x Flats

500 x Bias

26 x Darks

Taken with a GPCAM colour v1 with a Chinon 135mm 2.8 lens, stopped down to 4.6, mounted on an AstroEQ Vixen GP. Guided by a PS3 Eye finderguider. Stacked in DSS and processed in GIMP 2.9 beta. I still haven't come up with a way to reduce the star halo's without it looking artificial so I've just left them as is. My processing skills are pretty basic, just curves and levels really at the moment.

[happy-kat]

Try the trial version of StarTools there is a filter tool for bright halos.

[cuivenion]

Thanks I'll give it a look.

[happy-kat]

Your star shapes are nice but watch you don't clip the black point when using levels. 101 has come out nicely identifiable.

[cuivenion]

Thanks will do. I think one of the main problems is the darks never quite seem to get rid of the amp glow properly so I'm left with a gradiant. Dithering seems to work for the noise but I just need more exposures before it really starts to have a big effect.

[Adam J]

2 hours ago, cuivenion said:

I only managed a short session unfortunately and had to reduce the exposure time or I'd have run out of imaging time. First attempt with dithering and darks:

12 x 180s

100 x Flats

500 x Bias

26 x Darks

Taken with a GPCAM colour v1 with a Chinon 135mm 2.8 lens, stopped down to 4.6, mounted on an AstroEQ Vixen GP. Guided by a PS3 Eye finderguider. Stacked in DSS and processed in GIMP 2.9 beta. I still haven't come up with a way to reduce the star halo's without it looking artificial so I've just left them as is. My processing skills are pretty basic, just curves and levels really at the moment.

What are you dithering with? The standard setting in PHD2 give insufficient movement between frames in my opinion. There is a scaling factor in the set-up. 

[cuivenion]

I'm using this:

http://openphdguiding.org/phd2-dither-app/

I had the maximum dither amount in pixels set to 8. If I had it set any higher the guiding would fail to settle. I'm reading up on APT at the moment that looks like a good piece of software for AP. I usually use Sharpcap but I'm thinking APT may be more suited for the type of imaging I'm doing. Sharpcap is more EAA and planetary imaging focused.

[Adam J]

Cant comment I paid for the pro version of Backyard EOS, it will dither though PHD2 and i am very happy with it.

[alacant]

Hi. A Kodak #8 filter will all but remove the halos. Just remember to balance the blue afterwards. You can also use deconvolution on the blue channel to add the blue back to the central star. Leave the r and g as they are. As happy-kat has recommended for the halos, StarTools also makes the channel separation, decon and colour balance easy too. HTH.