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How long to allow cool down between subs?

Adrian23

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Adrian23

Adrian23

Posted
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Just a quick question. I'm just starting out in AP, using a Canon 500d with a SW 80 ed DS Pro on a Celestron VX mount. I'm unguiding so I'm shooting between 60 sec and 90 sec light frames.

How long should I be leaving between each sub to allow my camera to cool down ?

Adrian

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brantuk

brantuk

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Twenty or thirty seconds should be more than enough depending on the temperature outside. If it's cold 15secs may be enough. That's what I used with my 1000D during moderate temperatures in autumn. Hth :)

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jgs001

jgs001

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Posted

If I'm using my intervalometer, 10 seconds, if I'm using full computer control, as long as the dither and settling time takes... I've never measured it, but it can't be that long. This is using my 450d.  Like Roger, I've never noticed any problems.

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ronin

ronin

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I think the simple rule is: The same length of time as the exposure.

And just before everyone screams it's far too long that came from the last SGL imaging day at Bedford. :grin: :grin: :grin:

Most cameras these days have rubber bodies and that will keep the heat in, so eventually it will build up.

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jambouk

jambouk

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2 seconds here, but i'm still trying to find my feet with DSO stuff and limited to 30 second exposures anyway.

Would doing your darks at the end of the run when the sensor is hot help as the "erroneous data introduced by the hot sensor" would then be maximum and this could subsequently subtracted from the data subs?

Jd

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Luke

Luke

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When I started off I used to leave as long an interval as the exposure, because I had heard that advice given somewhere. So, five minute gaps for my five minute subs. I then noticed lovely images from folks using a very small gap, so I experimented one night leaving very short gaps. It was not very scientific, but to my eyes I could not see any difference between the short gap and long gap subs, apart from I had almost twice as many shots when using a short gap.

I wondered whether perhaps the long gap advice was more relevant for older cameras :confused: That was just my own findings with my 450D, not terribly scientific, always best to test for yourself and see what works for you. I think I ended up leaving 15 second gaps (perhaps even shorter would have worked, I think I just picked that out of thin air as being not very long), though that was a while ago and these days I mostly do solar and lunar imaging with a video camera.

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Alien 13

Alien 13

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I have just looked at my shooting timer sequence again and i do have either a 2 or 10 second delay in there after the mirror lockup so it goes something like this.

Initial 6 second delay > mirror lockup > 2 or 10 second delay > shoot sub >  repeat.

Alan

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TractionMan

TractionMan

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Very interesting thread to read. But what if you're shooting images to make a time-lapse? Then it wouldn't be such a good idea to allow to much of a gap between the images right? I mean, if the gaps are to long, the video will look rather jerky and end up looking more like stop motion than time-lapse. I might be totally wrong here though.

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jambouk

jambouk

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It depends what you are time lapsing... The ones I've done of star trails, the exposures have been 20-30 seconds and the gaps 2-5 seconds; so most of the jerkiness comes from the subs and not the gaps.

Jd

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Jonk

Jonk

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Hmmm...interested in this too.

I'm wondering if there's a simple way to have a small fan cooling the electronics whilst an exposure is not taking place? i.e control from whatever is controlling the camera (APT, BYEOS, Intervalometer etc...)

Main issue with this is blowing dust / flies etc into the sensor housing if it's in the wrong place.

Maybe a small 12v PC fan or similar?

I'm going to have a good think about this....

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jambouk

jambouk

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Luke, do you have noise reduction turned on? If so, the camera will automatically take a dark frame of the same duration as the data frame and subtract it from the data frame, removing hot pixels and evening out some variation in the sensor. The sensor is still working during that second 10 seconds so will not be cooling down, but will be heating up even more. Most people turn this fiction off, as they do all their dark frames together and subsequently subtract them at the processing stage.

Dave - yes all sensors generate heat. This is why most astro CCDs are "cooled". Some people even build mini cooling boxes to house their DSLR camera body in.

Jonk - if using a DSLR i suspect it is difficult to get the "cooling" to the sensor as it is housed deep within the camera. But people try. Might be easier just to buy a factory made cooled CCD camera, or accept the sensor gets warm and use plenty of dark frames to compensate for this.

Jd

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