What are people using to run fans on dobs

[Jemmo (Adrian)]

Hey guys so I got my son and is has a fan on the back just wondering what you power them with I'll put a pic up. It looks like an av plug. What kind of batteries run them

[Jemmo (Adrian)]

Here's pic

[Lee]

It may be marked on the fan somewhere - probably will be 12V DC though.

[Jemmo (Adrian)]

Yeah it's 12v I just never seen a av plug to run power or how to wire it. First scope with a fan. I do heaps of 4 wheel driving and have a million 12v gadgets wired up which I've done myself. Never seen an av plug haha

[Lee]

DIY. Have used them myself for low voltage/current apps, find the connection 'flaky' at times though...

[raymo]

Chop it off and replace it with whatever connection you prefer.
raymo

[Jemmo (Adrian)]

So I cut the av end off and just added some extra wire and brought myself a 12v battery. My next question is. What sort of chargers do these batteries use. I only have a car work shop charger which has jumper lead ends to clip on the battery which is way too big for this little one

[Jemmo (Adrian)]

Should the fan be drawing air from the back of the mirror or pushing air at it

[AG Hybrid (Adrian)]

Originally Posted by Jemmo

Should the fan be drawing air from the back of the mirror or pushing air at it

You want it drawing air from the back of the mirror.

[jenchris (Jennifer)]

Use some radio shack mini crocodile clips and make up a tiddly wire to the same place as the major league ones are wired to

[Jemmo (Adrian)]

Cheers for help guys

[xelasnave]

Forget the scope what about a fan for the operator

[cathalferris]

Originally Posted by AG Hybrid

You want it drawing air from the back of the mirror.

In general unless you have a specific reason otherwise, you want the fan pushing air onto the back of the mirror. This maximises the heat transfer from the mirror to the air and the cooling effect.

The best setups that I have seen for improving the seeing conditions and the cooling effect on the mirror, is where the fan blows from outside onto the back of the mirror and is baffled off, with a baffle ring above the mirror. This takes exterior air, blows onto the rear of the mirror and the enclosure at the bottom of the tube forces the moving air to the outside edge of the mirror and up into the tube, where the ring baffle forces that moving air across the mirror surface wiping the boundary layer away. The mixed air then moves slowly up through the top of the telescope tube or the mirror box.

If all you are looking for is faster cooldown/thermal stabilisation of the mirror then pointing the fan at the back of the mirror will be sufficient.