M83

[ChrisV (Chris)]

This was taken over the two nights before I did the NGC3324 I posted below.

Taken on my GSO 8" F5 newt with an ASI071-MC OSC cooled camera.
Guiding PHD2 with an ASI290MM on a ZWO 200mm guidescope.

It is 46x 5min subs captured with sharpcap. Those from the first night were flat/dark subtracted in sharpcap, and those from the second night were corrected in DSS. Then StarTooled - Startools is fun!! I've cropped off half the image.

What surprised me was that this one with 42 subs (over 2 nights) doesn't seem much better that I got using just 24 subs from the 1st night. But it could just be me processing them differently in startools - I was a bit more savage in trying to pull things out with the 42 sub version.

[that_guy (Tony)]

I've read somewhere that stacking has a diminishing return, that somewhere after 25 or so subs the effects become less and less.

[Benjamin (Ben)]

Looks great! Just learning the processing thing with StarTools and am finding it really approachable (after a few video tutorials), although my fiddling around with it is not particularly organized yet. The ASI071 seems a very nice camera. Did you move to this from a DSLR or just dive in? Curious how much noise you are removing or whether the stacked image is pretty clean to start with.

[luka]

There is a detailed description of the effect of stacking on the noise on the DSS page here.

Simplified, if you double the number of images your SNR goes up by sqrt(2) = 1.41x.
Triple it to get SNR up by sqrt(3) = 1.73x
4x imaging time will get you double SNR.
(SNR = signal to noise ratio)



Chris, the lack of improvement could also be due to quality of data. Perhaps on the 2nd night the seeing was not that great or your guiding was not spot on etc. Also if you are trying to image from light-polluted areas, unfortunately you will never be able to get the faint signals. And you have processed the data from two nights differently... in theory that should not matter but in practice who knows

[ChrisV (Chris)]

Originally Posted by Benjamin

Looks great! Just learning the processing thing with StarTools and am finding it really approachable (after a few video tutorials), although my fiddling around with it is not particularly organized yet. The ASI071 seems a very nice camera. Did you move to this from a DSLR or just dive in? Curious how much noise you are removing or whether the stacked image is pretty clean to start with.

Yes. So much to learn in star tools. Every time I use it I find something else.

I came into this from video astronomy - with small sensor cameras then a dslr. I had been doing 30-60s shots on the dslr - or stacking a few for live viewing in sharpcap.
This camera is much less noisy than my dslr!! The single shots are great on brighter objects. But once you start stretching ...

[ChrisV (Chris)]

Originally Posted by luka

There is a detailed description of the effect of stacking on the noise on the DSS page here.

Simplified, if you double the number of images your SNR goes up by sqrt(2) = 1.41x.
Triple it to get SNR up by sqrt(3) = 1.73x
4x imaging time will get you double SNR.
(SNR = signal to noise ratio)



Chris, the lack of improvement could also be due to quality of data. Perhaps on the 2nd night the seeing was not that great or your guiding was not spot on etc. Also if you are trying to image from light-polluted areas, unfortunately you will never be able to get the faint signals. And you have processed the data from two nights differently... in theory that should not matter but in practice who knows

Thanks. I'll go through my single images. The quality was a bit variable. And I have some guiding issues - still learning how to do that in phd2. There's a big slow sine wave (1-2" peak-to-peak) on the RA guiding - I can see that it's spread my stars in that axis so it must do awful things to the DSOs. So sorting out pec is next. Doing that while the moon is around. I'm trying the inbuilt pec on the cgem, but has anyone used the beta phd2 with the built in pec? I tried it last night and it actually seemed to work after a few cycles.

It's all a massive learning curve.

[rustigsmed (Russell)]

hi chris,

looks good nice capture well done! got to love m83.
I would play with the levels the colour feels a little imbalanced, maybe try and turn the green down and the blue up a tad from the midpoint.

cheers

rusty

[ChrisV (Chris)]

Yes. Its very green. Sure it wasn't that bad before I converted to jpgs. I'm having trouble sorting out the colour thing. I think I'll try and find the video tutorials rather than rage through like a bull in a ... Trouble is - I tend to just fiddle rather than read the manual.

M83. Gotta start somewhere !

[LostInSp_ce]

Fantastic image Chris. The level of detail within M83 is amazing and the intensity of the flares is very nice, complimenting the galaxy perfectly.

[Anth10 (Anthony M)]

Beautiful image, should be proud of this , well done.

[cometcatcher (Kevin)]

That is a great image. I am still deciding which camera to get to upgrade from a DSLR. So keep the images coming.

[ChrisV (Chris)]

Thanks all.
Of what I imagine mono must be much better for AP. I'm using an OSC camera as I also use it for live imaging.

[Benjamin (Ben)]

Originally Posted by cometcatcher

That is a great image. I am still deciding which camera to get to upgrade from a DSLR. So keep the images coming.

I'm convinced!

[glend (Glen)]

Great image Chris. Colour looks fine to me.

[cometcatcher (Kevin)]

Originally Posted by ChrisV

Thanks all.
Of what I imagine mono must be much better for AP. I'm using an OSC camera as I also use it for live imaging.

At present my choice is between either yours or the mono ASI 1600mm cool. So no pressure or anything, but you will help me decide with your images. I think I need both.