Cooling fans ...... do more than just cool ?

[John]

I've been reading an interesting thread on the Cloudynights site about cooling fans and newtonian scopes. Many of the posts express the view that strategically placed fans don't just speed up the cool down of the scope but also, when left running, deliver improvements to planetary and double star viewing because of the effect they have on i) the boundary layer of air adjacent to the mirror and ii) any currents of warmer air within the tube.

Obviously you need to find fans and a fitting method which does not introduce any vibrations to the scope if you are to view with the fans running but, according to the posters, this is perfectly possible and the benefits are noticable.

I've not really bothered with a fan or fans for cooling the newts that I've owned but I wonder if anyone of SGL has and observes with them running ?.

[stev74]

This is very interesting, I've also heard that for planetary viewing leaving a fan on can be beneficial. Although I keep my scope out in the shed so cool down time isn't an issue. I was thinking about adding a fan for this reason, so I'd also be interested in any feedback from other members?

Well I've got to do something during the Summer months, already on the cards is flocking, cleaning the primary and some TLC for the EQ5.

Cheers

[dweller25]

I have a fan installed in my 8" F/6 Newt, I always keep it running during high power planetary observing, the benefits are tremendous - easily proved by just turning the fan off. Best £5 I ever spent.

[zhgutas]

I too have always wondered about the vibration issues.. This site, for example, offers suspending a fan on some rubber bands to eliminate vibration, though it's not quite "my style" I like things "looking good" when I eventually take a plunge and do some DIY.. Would be interesting to hear what way do people mount their fans, and how well that works

Marius

[brianb]

You can get a far better improvement by using an oversize tube made of insulating material (or lined with expanded polystyrene sheet, or cork) rather than a "tight" tube made of metal tube. Fan cooling is useful but if the scope is properly cooled then (a) cooling currents don't exist ( any residual currents are confined to the outside 1/2 inch of the tube, if this is outside the light beam then no issues.

You don't see wooden tubes, or oversize insulated metal tubes, much these days because of weight & size issues. This is a pity, the performance advantages are considerable.

[Astro_Baby]

Old newts often had thin cork insulation I recall from years ago. I fitted a fan on my 8" F5 which way oversized to give fastest possible cool down. I fitted a variable power control so it can be trimmed back to just enough to keep air moving if needs be and disrupt any tube currents or boundary layers.

I saw a noticeable improvement in my newt on short viewing sessions where the scope, left to its own devices, probably would not have been cool enough.

I got a super slick motor and I cant see any vibrations in the view even with the fan running flat out. That may be because its installed on a steel plate thats heavy enough to hold the fan solid. Its also a low vib/silent fan. I cant think most small fans though would create much vibration if securely anchored down becasue of the weight of the tube.

[Macavity]

For computer cases, I always used to replace the standard fans with:

Welcome to ebm-papst in the UK

And also under-run the voltage, via speed controller. Nerdy or what?

[Moonshane]

my dob has such a fan - see http://stargazerslounge.com/members-equipment-gallery/97917-dob-has-landed.html and scroll down.

I find that it definitely helps with cool down but cannot say it massively helps with the view - I have often turned off the fan once cool to no detriment. I have not yet observed through a summer though and maybe this is when it matters most?

I can say that my views of Saturn have been excellent and I can split most doubles

cheers

Shane

[nitram100]

Jahmanson, i have an OO Europa 10" F4.8 like yourself and i added 3 cooling fans to the rear, it improved my planetary performance quite considerabley, i actually found it difficult to spot the Cassini Division before adding the fans, afterinstalling them and leaving them for 15 minutes the cassini is easy as is the GRS.

I do leave them running sometimes when viewing and don't notice any vibration, probably because i put small rubber O rings on the bolts.