Fitted a fan DIY style

[Mart29]

Will try this tonight , don't really suffer from dew on the 200 dob but thought it could make images more stable, at least I have seen posts to that effect. 

So let's try! 

Do you guys leave it on for the session or just at the start?

 

 

[saac]

I've never used a fan myself but I think the idea is to use it before you view/image to reduce the cool down time.  I wouldn't have on when imaging, though I may be wrong. 

Jim 

[Dave scutt]

5 minutes ago, Mart29 said:

Will try this tonight , don't really suffer from dew on the 200 dob but thought it could make images more stable, at least I have seen posts to that effect. 

So let's try! 

Do you guys leave it on for the session or just at the start?

 

 

Is the fan sucking in air or blowing out, not sure if it makes a difference but i was asked that question.

I leave mine on for a couple of hours just to make sure it's cooled down enough before use.

[Mart29]

5 minutes ago, Dave scutt said:

Is the fan sucking in air or blowing out, not sure if it makes a difference but i was asked that question.

I leave mine on for a couple of hours just to make sure it's cooled down enough before use.

The strongest flow is out but they circulate air around the mirror inside   , so both I guess! 

[dweller25]

Here is my DIY Skywatcher solution.

I hand cut a circular mask from thin aluminium scrap and then installed a fan that blew cold air in.

The full size mask allows for maximum cooling efficiency.

I used the 3 locking bolts to hold it in place.

It worked well and was very cost effective.

 

Edited September 24, 2022 by dweller25

[Mart29]

7 minutes ago, dweller25 said:

Here is my DIY Skywatcher solution.

I hand cut a circular mask from thin aluminium scrap and then installed a fan that blew cold air in.

The full size mask allows for maximum cooling efficiency.

I used the 3 locking bolts to hold it in place.

It worked well and was very cost effective.

 

Great job! I may make a mask later on. I put plastic bolts just the hook it in on the sides to remove it easy if it doesn't do great things it can come off.

[CraigT82]

Having a well baffled fan like the one above is a great way to increase the efficiency of the fan which lets you run it at lower speeds to minimises vibration. Saying that though I don’t think I’ve ever seen the vibration effects of a fan running visually, but when hi-res imaging it is very visible, so I make sure to mechanically decouple the fan from the scope on my OTA. 

[Ricochet]

2 hours ago, CraigT82 said:

I don’t think I’ve ever seen the vibration effects of a fan running visually

I can see the movement of air in my 8" dob with the fan running on full speed, it looks the same as thermals from an uncooled scope. In addition, running the fan on full introduces a touch of astigmatism into the primary, so I run the fan on full power before a session and then either turn it down to the minimum speed or off completely when observing. 

[CraigT82]

I also turn fan down to minimum just before observing/imaging, so that it’s just enough to break up the primary boundary layer. I also have it pulling air down the tube rather than pushing air up, I find the airflow within the tube is a bit more orderly that way.