Should camera be cooled before focusing?

[Adam1234]

Something I've not thought of until now but the thought just popped up into my head. When using a cooled astronomy camera (eg ASI1600mm pro), should it be cooled before focusing, or does it not matter? 

Normally, my order business when setting up the equipment is:

- Take mount and scope out before it gets dark to cool down sufficiently, position and balance mount/scope

- once dark enough, polar align

- focus on bright star eg deneb 

- frame target

- cool camera while calibrating PHD2

- image 

 

Adam

[symmetal]

It doesn't really matter as camera cooling doesn't tend to make the sensor move backwards or forwards and so the focus won't change. 🙂 However, if the outside temperature cools significantly between focusing and imaging, the focus of the whole imaging train may well change, so having autofocus, I tend to leave focusing as the last item on the list before starting imaging.

Alan

Edited September 20, 2020 by symmetal

[Adam1234]

Cool, thanks Alan. I didn't think it would affect focusing, but thought maybe if the cooler chucked heat out into the focus tube, or something, but I guess this gets expelled from the back of the camera by the fan.

If I could name one thing about astrophotography that I find the most annoying, it's focusing! Such a pain in the neck, but one of the most important things! I think I'll invest in an autofocuser towards the end of the year...

[symmetal]

I suppose if you're imaging near vertical then the heat from the camera cooler is rising past the scope but unless it's running full blast I doubt it has much affect. 🙂. Having an anti-dew heater on the sensor protect window does release a bit of heat into the tube but it gets blocked by the filters and field flattener etc. so again I wouldn't think it's significant. My ASI6200 glass heater consumes about 300mA so that's 3.6W of heat being released.

Once you've got an auto-focuser you'll soon realise how handy it is, as you just focus on your target rather than a bright star, and it will run auto-focus again automatically if the outside temperature changes by a preset amount.

Alan