Cookie consent

AstroBin saves small pieces of text information (cookies) on your device in order to deliver better content and for statistical purposes. You can disable the usage of cookies by changing the settings of your browser. By browsing AstroBin without changing the browser settings, you grant us permission to store that information on your device.

I agree
Contains: 
Jupiter 2019-05-02: Capture Parameters Comparison, 





    
        

            Darren (DMach)

Jupiter 2019-05-02: Capture Parameters Comparison

Acquisition type: Lucky imaging

Technical card

Resolution: 1200x600

Date:May 2, 2019

Time: 03:35

Focal length: 5600

CMI: 92.30

CMII: 198.40

CMIII: 158.10

Seeing: 3

Transparency: 8

Locations: Home, Singapore, Singapore

Data source: Backyard

Description

Edit/disclaimer: your mileage may (indeed, almost certainly will) vary, depending on your specific setup (example: I'm using a one-shot colour cam) and locations/conditions (example: seeing is generally consistent and rarely poor where I live).

The test below is not intended to recommend ideal settings for others ... that's not feasible! Rather, it is simply intended to be an account of the testing I'm currently performing for my specific setup. :)
=======================================================================

On a night of fair to good seeing and reasonable transparency, I decided to run a series of tests to narrow in on the optimal capture parameters for my current setup (C11) and processing workflow (recently incorporating WinJUPOS re-rotation).

The tests here were intended to explore the trade-off between:

Capture time for each sub-stack
- Shorter capture time (60s): Less blurring of details in each sub-stack due to the rapid rotation of Jupiter, but less frames = lower overall signal-to-noise ratio.

- Longer capture time (90s): More frames = improved signal-to-noise. Possible blurring of details, but multiple accounts (such as this one by Christophe Pellier) suggest that AutoStakkert is capable of handling rotation in videos up to 2 minutes long.

Frame rate/exposure time
- Higher frame rate (83fps): Less blurring of details due to seeing effects, but requires higher gain = lower overall signal-to-noise ratio.

- Slower frame rate (66fps): Lower gain = improved signal-to-noise, but possible blurring of details due to seeing effects.

The original intent was to test more parameters (e.g. 60s @ 66fps plus some 120s tests) but unfortunately the session was cut short by clouds.

A note on the choice of FPS: advice I have received from multiple sources is that 50fps or more is generally sufficient to "freeze" the seeing. Seeing was good but not great, so I settled for 66fps. The "high" frame rate I chose (83fps) represents the maximum frame rate my aging laptop can handle for SER captures. (Given the "at least 50fps" advice, it makes sense to me to acquire SER files with "high speed" turned off.)

Stacking and processing workflows were kept as identical as possible to facilitate direct comparison. I also pushed the sharpening a little further than I normally would, so as to emphasise the details.

The differences between the images are unsurprisingly minor ... but then incremental improvements in detail are what I'm after! On close observation, detail is best in the middle image (90s @ 83fps) as evidenced by the clearer outline of Oval BA and sharper small, dark spots in the NN & NNN temperate belts (these regions of interest marked in the rev B image).

The results suggest to me that having more frames from which to choose for stacking is ultimately better, as long as the signal-to-noise per frame is not overly compromised.

This agrees with previous testing on my 6SE where I found that, as long as I kept the gain at or below 300 for the ASI290MC, noise per frame was manageable. The difference is that both signal/contrast and detail on the 6SE was ultimately aperture-limited, so there were limiting returns in pushing the frame rate higher as this usually required a gain of >300.

WinJUPOS can clearly handle a small amount of rotation, although shorter captures may still be best in some circumstances (e.g. moon transits).

This is of course a single test, however ... :)

Comments

Author

DMach
Darren (DMach)
License: None (All rights reserved)
1212
Like

Revisions

  • Final
    Jupiter 2019-05-02: Capture Parameters Comparison, 





    
        

            Darren (DMach)
    Original
  • Jupiter 2019-05-02: Capture Parameters Comparison, 





    
        

            Darren (DMach)
    B

B

Regions of interest for detail determination highlighted in red, along with an interesting barge formation (in yellow) in the SEB which has been developing over the past month or so.

Histogram

Jupiter 2019-05-02: Capture Parameters Comparison, 





    
        

            Darren (DMach)