Do more lights mean a better image???

[batema (Mark)]

Hi,

I'm just wodering if you took five lots of 5 min lights with similar darks would you get a better image if you took 10 or more lights of the same time with darks and stacked them. Or is there a maximum number you should take and any more is not really going to make a difference?

Mark.

[spearo (Frank)]

I think the more the merrier,
I personally wouldn't worry about going past 20 shots.
Software now significantly assists in in the process too
cheers
frank

[RB (Andrew)]

The more you can stack the better.
What this does is increase your signal to noise ratio and allow you to stretch the data more.

[Gama]

The more light you can muster up the better. This will bring your data to a point where you can easily play with it. Thus the fiasco with the Helix image from Jase vs "The rest of them" in terms of quality data.

You should use a master dark to remove your noise from your lights.

Theo

[Matty P (Matt)]

The more subs the better but as a minimum go with at least 10 x 5 minute subs.

[Terry B]

The total exposure time is the critical value. Multiple short frames compared to less longer frames with the total exposure being the same will have more noise. You aim to take as long an exposure as you can manage and as many of then as you can be bothered.
There is a limit to this though as you have to approximately double the exposure to go 1 mag deeper. When this is reaching days of exposure I think most would give up.

[batema (Mark)]

Terry I'm assuming that is without having a break. Thankyou all for the advice. I have never really taken more than seven so I'm up for a big one tomorrow night weather permiting. thanks
Mark

[Terry B]

Originally Posted by batema

Terry I'm assuming that is without having a break. Thankyou all for the advice. I have never really taken more than seven so I'm up for a big one tomorrow night weather permiting. thanks
Mark

I'm not sure what you mean by without a break. You can add images taken over multiple nights or all taken at once. It doesn't matter but every time you readout the camera you add noise to the image so less readouts means less overall noise. This has to be offset against the potential loss of a long exposure from poor tracking, airplanes etc. I use 5 to 10 min subs as my compromise. Others use longer depending on their ability to guide etc.

[batema (Mark)]

Terry, If you take them over a number of nights would you have to take them when the object is at the same elevation the following evenings???

[Terry B]

Originally Posted by batema

Terry, If you take them over a number of nights would you have to take them when the object is at the same elevation the following evenings???

No, but the seeing is poorer closer to the horizon. Also stars appear to get redder as you get closer to the horizon. This is called "extinction" but I don't think that it would make much difference if you are just taking pretty pics. It is very important if you are measuring the magnitude (photometry)of stars.