Frame Rates for Planetary imaging

[Purplehayze104]

Hi All

just wanted to ask as not done much when it comes to planetary/solar imaging with a cam, ill be using a QH5YL-II mono but would like to know, is there a sort of minimum frames per second i should be aiming for or is it a case of as more the merrier,

any help be appreciated

regards

john

[ronin]

Sure this came up a couple of weeks back, the "answer" was sort of 15-30fps.

You need to get a decent amount of light on the webcam per frame, but without overloading it.

Too fast and the light collection goes down and the data goes up, and then you need to get the data off the camera and onto the laptop.

And I think the sort of area was 15-30fps, as the best.

[oldpink]

depends on the subject and if you barlow or not
I can run 200+fps on jupiter but Mars & saturn I can drop to as little as 15 FPS

just to have a decent image
I normally go with the histogram to give me an optimum rate

[Purplehayze104]

arh ok so really bit of experimentations needed then depending on target

thanks for your replys

regards

john

[Stu_2011]

For my Imaging source DFK 216 camera on my CPC925 I can easily run 60 FPS on a Jupiter, even with a x3 barlow. Saturn and Mars are a bit dimmer so 20-30 frames seems about the normal. I have a Mono QHY5L-II but not used it yet.

If you use SharpCap adjust the exposure so that you get 80-90% Histogram fill and should be about the right brightness for a good capture.

Have a play, it's quite easy really once you have a basic set-up sorted.

Sent from my iPad using Tapatalk

[Purplehayze104]

thanks for the reply

used ezplanetary the other day for some sun shots but recorded as fits files, waste of time an effort, looking into sharpcap & firecapture

[akjudge]

Assuming that you will be stacking the images, the "right" frames per second depends on the exposure length.  Ideally, you want the frames per second to be the same as, or a multiplier of, the exposure length, with the frames per second NEVER producing more frames per second than the exposure time produces in the same second.  For example, if you use 30 fps, then the exposure should be 1/30 sec or 1/60 sec.  If you use 30 fps and use 1/15 sec exposure, every other frame will be a duplicate of the previous frame.  At 30 fps there will be 30 unique frames in one second, but with an exposure of 1/15 sec, there will be only be 15 unique frames in one second -- meaning 15 duplicates per second at 30 fps.

I hope my explanation makes some sense.  The best way to determin the "right" frames per second is to use the histogram as suggested above, adjusting the frames per second so there are no duplicates at the chosen exposure rate.

Jim

[riklaunim]

Assuming that you will be stacking the images, the "right" frames per second depends on the exposure length.  Ideally, you want the frames per second to be the same as, or a multiplier of, the exposure length, with the frames per second NEVER producing more frames per second than the exposure time produces in the same second.  For example, if you use 30 fps, then the exposure should be 1/30 sec or 1/60 sec.  If you use 30 fps and use 1/15 sec exposure, every other frame will be a duplicate of the previous frame.  At 30 fps there will be 30 unique frames in one second, but with an exposure of 1/15 sec, there will be only be 15 unique frames in one second -- meaning 15 duplicates per second at 30 fps.

Most planetary cameras except TIS cameras have fluid framerate - you get what exposure and (USB) bandwidth allows. So you can't set 60 FPS and use 1/30 sec exposures. That what TIS has

I keep the framerate no slower than 30 FPS for nice and big planets. Imaging with dark/specific filters changes that (like methane band or UV), but for RGB or broadband filter no slower than 30 FPS. Mars or Jupiter around 60 FPS, while Saturn struggling around 30 FPS

[Purplehayze104]

thanks for the advice, akjudge you explained it very well i understand wot you mean will give that a go next time i manage to get some clear sky , riklaumin will take that advise on board to

all comments hits an tips are very much appreciated.

regards to you all

john

[Pete Presland]

i have never heard of "duplicated images" surely the frame rate selected is irrelevent, its the exposure that controls the frame rate.

[akjudge]

I use an Imaging Source Camera (DMK21) that has independant frame rate settings and exposure settings.  Since the frame rate is adjustable, it is not "irrevelent".  It is independant of the exposure rate.  The two of them must be coordinated to avoid issues such as duplicate images.

[Pete Presland]

I use an Imaging Source Camera (DMK21) that has independant frame rate settings and exposure settings.  Since the frame rate is adjustable, it is not "irrevelent".  It is independant of the exposure rate.  The two of them must be coordinated to avoid issues such as duplicate images.

agreed but which one is dominant, i have a feeling its the exposure rate.

[akjudge]

agreed but which one is dominant, i have a feeling its the exposure rate.

It depends...  If the frame rate is greater than the exposure setting, the frame rate is dominant.  For example, if the exposure setting is 1/2 sec and the frame rate is 30 fps, then each frame will get "photons" for 1/30 sec -- not the exposure setting of 1/2 sec.  So in this case the frame rate controls.  If the frame rate is less than the exposure setting, the exposure setting is dominant.  For example, if the exposure setting is 1/60 sec and the frame rate is 30 fps, then each frame will get "photons" for 1/60 sec even though the frame length is 1/30 of a second long.  So in this case the exposure setting controls.

[Pete Presland]

thanks for the explanation that certainly makes perfect sense. so does the camera sit idle so there are no "duplicated images" in the first method, or does it try to mantain the frame rate?