Cooling fans

[AstroStokie]

Hi all

I’ve read a bit about putting your scope out maybe half an hour before observing to cool it down, and also about some dobs having cooling fans. Is it possible to buy these separately, and is it worth it? My 8” looks like it has holes so that something could be added, but can’t find where you would get one online. 

Any advice, please? 

[Ricochet]

All you need is a 12V PC cooling fan, available fairly cheaply online. buying one with decent bearings is a good idea to lower vibration but you should also mount the fan in such a way so that vibrations are not transmitted to the telescope. My solution was to replace the screws holding the mirror cell to the tube with longer ones so that hair bands could be looped over them. Connection of the fan to the bands is via P clips, available from a DIY store.

 

To power it you will need a 12V power source. If you're already running electrical components you might have one, otherwise a lithium polymer battery will do the job. You will however, have to do a bit of diy as the battery will have a 12V jack and the fan will have a fan connector. You may also want to add a controller at some point so that you can vary the fan speed.

[pregulla]

Or you can use a USB power bank and a boost converter to get 12v to your fan. Something like this I guess will be good enough to power a fan.

[Carbon Brush]

Cool down time depends on scope size, construction and mirror thickness. It is not a fixed time.

Knowing your scope type will help other to give specifics, from experience.

A much simpler option than fans, if you can do this, is to put the scope outside, or in an unheated place, before you want to view.

For example, put the scope in a shed or garage for a couple of hours before use. It will at least part way to being at outside temperature.

If your scope is warm, then the optics may not be that well aligned and you may get warm air currents in the tube.
But this only matters when you push the magnification. Again, how much of a problem depends on the scope type.

Hope this helps, David.

[kirkster501]

I have also deployed the cooling fan method on my 12 inch mirror and it works quite well.  You want the fan blowing air ONTO the back of the mirror so make sure the fan is the right way round or else you are sucking air from the mirror and it will not be nearly as effective.

 

 

[AstroStokie]

That’s great...thanks ??