exposure/frame rate question???

[northcanadian]

Hi folks:

I understand the frame rate and exposure rate should be same when imaging. However when imaging a dim Saturn can the exposure rate be increased and gain decreased for more contrast and histogram fill? Is that kosher or correct?

Thanks and clear skies

Roger

[lensman57]

Hi folks:

I understand the frame rate and exposure rate should be same when imaging. However when imaging a dim Saturn can the exposure rate be increased and gain decreased for more contrast and histogram fill? Is that kosher or correct?

Thanks and clear skies

Roger

Hi,

That is not strictly true, if all parameters are operating within specification you should be able to divide 1000 by exposure to get the frame rate ie: 25 ms exposure will give you 40 FPS and 20 ms will give you 50 FPS but life is seldom so simple. With my ASI120 mc on an SW 100 ED and televue powermate 2.5x I need to push the gain to about 85% to get about 15 FPS for Saturn. Without the barlow 30~35 FPS is possible. A lot also depends on the computer itself as downloading large raw files at 30 fps does take some processing power . So long as you can push the gain up a reasonable amount to keep the frame rate high you should not worry about the noise as theoretically a large number of frames for satcking should get rid of a lot of noise, the moral of the story is that the more sensitive the chip the better the outcome, as you have a reasonably low gain for a reasonably high FPS and this means cleaner images.

Regards,

A.G

[jambouk]

Gain at 85% seems very high, but i agree, with a 2x barlow or powermate in the system, Saturn is very dim on my chip too (also 120MC), but i also had a diagonal in the set up when i did it, and plan to try without next time. I think i was put off doing any recording with the gain that high, but maybe i should just give it a go.

How long are you imaging Saturn for each time?

James

[lensman57]

Gain at 85% seems very high, but i agree, with a 2x barlow or powermate in the system, Saturn is very dim on my chip too (also 120MC), but i also had a diagonal in the set up when i did it, and plan to try without next time. I think i was put off doing any recording with the gain that high, but maybe i should just give it a go.

How long are you imaging Saturn for each time?

James

Hi ,

I do about 4000 frames, set Pipp to use about 2500~3000 and then stack about 70% AS!2 and then Registax.

Regards,

A.G

[moxican]

I use firecapture for my recordings. I've just got my ASI120MC and I didn't have the chance to try it out, but I did image Saturn a few times with DBK21. What I realized is that it is not only the settings that effected the frame rate. Whatever the settings were Firecapture kept dropping frames for me and everything was slagish. A good trick would be also that after you are ready to start recording zoom out on the preview vindow. It will let things flow quicker.