SharpCap and Lunar

[StuartT]

Those of you who use SharpCap for lunar, can I just check that my histo should be set to logarithmic to get the right exposure to be 30-40% ?

Thanks

 

[StuartT]

Any advice anyone? Is this curve looking right for a good exposure? I'm assuming the white bar at the bottom needs to be about 30-40% along the x-axis, but am I right to check the 'logarithmic' box?

Thanks

[Ags]

Unless I am very mistaken, the Logarithmic check box only affects the Y axis, all the useful stuff on the X axis is unaltered.

[The Lazy Astronomer]

1 hour ago, StuartT said:

Any advice anyone? Is this curve looking right for a good exposure? I'm assuming the white bar at the bottom needs to be about 30-40% along the x-axis, but am I right to check the 'logarithmic' box?

Thanks

Checking the logarithmic box just a different way of displaying the histogram information graphically. Check it if you want, it makes no difference to the capture.

There seems to be different approaches to exposure for lunar and planetary imaging, but the best results I've had is by following advice to ignore the histogram, set a high gain and short exposures (around 5ms, but maybe even shorter for the very bright moon). Don't worry if it looks bad on the capture screen, stacking and sharpening will work their magic later!

[The Lazy Astronomer]

Typical, you wait all day for a response then 2 come along at once 😁

[vlaiv]

Yes, forget the histogram and set exposure below 5ms.

Set it to lower if you are over exposing but don't increase if image looks too dim - stacking takes care of that.

Your main concern is to freeze the seeing with short enough exposure to avoid motion blur created by atmosphere.

[StuartT]

1 hour ago, vlaiv said:

Yes, forget the histogram and set exposure below 5ms.

Set it to lower if you are over exposing but don't increase if image looks too dim - stacking takes care of that.

Your main concern is to freeze the seeing with short enough exposure to avoid motion blur created by atmosphere.

Interesting. Thanks. I assumed that the histogram was a guide to correct exposure.

Fortunately, I just looked back at last night's capture (with which I got this image) and see that 

Gain=0
Exposure=0.00492

So I just managed to sneak under your threshold vlaiv 😃

[vlaiv]

1 hour ago, StuartT said:

Interesting. Thanks. I assumed that the histogram was a guide to correct exposure.

Fortunately, I just looked back at last night's capture (with which I got this image) and see that 

Gain=0
Exposure=0.00492

So I just managed to sneak under your threshold vlaiv 😃

Another important point - you want to raise gain so that your read noise drops.

At least gain of 100+ (maybe even 350).

Also - check out AutoStakkert!3 instead of Registax for stacking of planetary images - newer and better. Registax is good for wavelet sharpening and basic post - like channel align / white balance and so on.

[StuartT]

20 minutes ago, vlaiv said:

Another important point - you want to raise gain so that your read noise drops.

At least gain of 100+ (maybe even 350).

Also - check out AutoStakkert!3 instead of Registax for stacking of planetary images - newer and better. Registax is good for wavelet sharpening and basic post - like channel align / white balance and so on.

That's interesting. I have been using zero gain becuase I thought you lose dynamic range at higher gain levels. Is that not right?

I have clear sky tonight also, so I am going to try higher gain (which will allow me to use nice short exposure times). Thanks

Yes, I used to use Autostakkert3 for stacking, but I found that Registax does a very slightly better job (comparing directly with the same images and the same wavelet sharpening settings)

Edited January 18, 2022 by StuartT

[vlaiv]

9 hours ago, StuartT said:

That's interesting. I have been using zero gain becuase I thought you lose dynamic range at higher gain levels. Is that not right?

Dynamic range is something you get from stacking and should not be concern in single exposure. Even stack of two images will have 40% higher dynamic range compared to single image - let alone stack of several hundred of subs.