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Thermal Issues and Fans Successes

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#151 Project Galileo

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Posted 04 January 2013 - 11:38 AM

I sealed up the rear of my LB16...

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...added a Mauro Da Lio baffle...

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...installed one of these super cool fans as a sucking fan with silicon gaskets and neoprene vibration barriers that doesn't show vibration at any speed or magnification...

Posted Image Posted Image

...and control fan speed with one of these.

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In this picture you can see how hard this fan sucks at 73 cfm. The sides of the shroud are being sucked in against the truss poles with the top cover in place. In the huge space of the LB16's tube it easily turns over the air very rapidly and creates a wonderful laminar flow and very clean image. Just like others have reported it all works almost magically. I don't believe I need a side fan. This single set up works great for the size and thickness of mirror I have. I am now a believer in active cooling and boundary layer removal.

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#152 rlmxracer

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Posted 04 January 2013 - 01:53 PM

Clean looking setup P Galileo. I just made the mistake of looking for the quietest 120mm fan I could find. Well I found out how they got it so quiet... it ony flows 40cfm which is not even close oh well. One good thing I found while removing the stock fan I had to remove my primary. I checked the center spot and it was off center by almost 2mm.
Now I just need a fan that flows more air.

#153 Bob S.

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Posted 04 January 2013 - 02:38 PM

Very nice installation of that sucking fan on the 16" LB Doc! I think one of the potential advantages to our sucking systems is that we are using a pretty homogeneous body of air taking it in from the top. Someone mentioned to me that mixing different kinds of air for frontal boundary layer fans and rear fans is a potentially less optimal strategy than pulling in the air source for the entire primary mirror from one air mass. Not much data on this but it intuitively makes sense. Bob

#154 Tom and Beth

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Posted 04 January 2013 - 04:09 PM

http://www.newegg.co...N82E16835118217

This one controls 2 fans.


Nice. Not very expensive either. They could be attached with Velcro to the OTA or Dob mount. I'd rather go with something like this than try rigging up my own pots.

The only concern for me would be finding adapters for the power supply and fans, or cutting and splicing to the leads I already have. Some folks seem to be able to do this in their sleep. I don't have much prior experience, so I have to figure it out step by step.

Mike


If you're using computer fans, they often have a connector, yes? This speed control (and there's literally dozens of them to choose from) will attach using that connector. All that's left then is wiring to the battery (or power supply) and that's usually a positive and negative lead.

Some of these fan controllers are better than others, and one can find them on Ebay, Amazon, Newegg and the like. One could even buy a 5 way unit and also power little lights, for a tripod, or map reader...all it takes is removing the circuit card from a computer bay adapter and drilling holes in your scope.

I owe all this to somebody here on CN who posted a pic of one of these.

#155 azure1961p

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Posted 04 January 2013 - 06:51 PM

Nevy,

By some percentage sure but in all practical purposes no. These filters are highly cavetized - you can see through them. Perhaps that's the difference, if you can't see thru it its too dense. I wouldn't bother with a rear filter but again at public outtings chicken wire across the back would safe guard from kids unknowingly -- "!!!!"

In your own backyard I think it's a personal call - right now my boundary dies t have the ac filter. I might use simple window screening cut out and mounted over the intake. The rear fan - ill never bother covering lest it's an outreach deal and I haven't done one in a good ten years. I miss it actually.

Pete

#156 Scanning4Comets

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Posted 04 January 2013 - 07:50 PM

If you're using computer fans, they often have a connector, yes? This speed control (and there's literally dozens of them to choose from) will attach using that connector. All that's left then is wiring to the battery (or power supply) and that's usually a positive and negative lead.

Some of these fan controllers are better than others, and one can find them on Ebay, Amazon, Newegg and the like. One could even buy a 5 way unit and also power little lights, for a tripod, or map reader...all it takes is removing the circuit card from a computer bay adapter and drilling holes in your scope.

I owe all this to somebody here on CN who posted a pic of one of these.


I cannibalized a comp fan with a three way switch on it and have it on the back of my mirror. I used to just have it on elastics over the open mirror, but now have it enclosed.

Note the micro switch for changing between low, medium and high speeds as circled.

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#157 nevy

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Posted 04 January 2013 - 08:12 PM

Nevy,

By some percentage sure but in all practical purposes no. These filters are highly cavetized - you can see through them. Perhaps that's the difference, if you can't see thru it its too dense. I wouldn't bother with a rear filter but again at public outtings chicken wire across the back would safe guard from kids unknowingly -- "!!!!"

In your own backyard I think it's a personal call - right now my boundary dies t have the ac filter. I might use simple window screening cut out and mounted over the intake. The rear fan - ill never bother covering lest it's an outreach deal and I haven't done one in a good ten years. I miss it actually.

Pete

Ok , thanks for clarifieing that , I wouldn't use one myself as I find the mirror accumulates a bit of dust from normall use after a few sessions anyway even without the fan running , but I have got one of those metal finger guards on the fan , I know from experience that if a finger was to accidentally touch the fan it won't cut my finger tips off as it would just stop the fan from turning but I would be more worried about bending or distorting one of the blades and causing it to vibrate.

#158 Sarkikos

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Posted 05 January 2013 - 01:26 PM

Project Galileo,

...and control fan speed with one of these.

Posted Image


A picture may be worth a thousand words, but sometimes you need more than just seven words to explain a picture. :poke: :grin:

What is this thing, what type of connectors does it have on both ends, how do you use it, where do you get it?

Mike

#159 Sarkikos

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Posted 05 January 2013 - 01:38 PM

I see this thread has come to the usual controversy between fans that suck and and fans that blow. :shrug:

:grin:
Mike

#160 nevy

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Posted 05 January 2013 - 01:49 PM

Project Galileo,

...and control fan speed with one of these.

Posted Image


A picture may be worth a thousand words, but sometimes you need more than just seven words to explain a picture. :poke: :grin:

What is this thing, what type of connectors does it have on both ends, how do you use it, where do you get it?

Mike

That looks like it could be very usefull as I have two scopes with fans so it could be used on either scope to mess with the fan speeds , it would save the trouble of fitting pots to both scopes , come on spill the beans where do you get such a device :-).

#161 Sarkikos

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Posted 05 January 2013 - 01:50 PM

Project Galileo,

...added a Mauro Da Lio baffle...


Here is an interesting quote from that thread:

Vortex

In a tube, a rear fan also creates a vortex which scrubs and lifts much of the boundry layer away too.

At least it does in my 10" f/5.



So that vortex I saw in the defocused image through my 8" f/6 Dob might be a good thing? Perhaps it needs to be modified or enhanced somehow to improve its effectiveness.

Mike

#162 Sarkikos

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Posted 05 January 2013 - 01:53 PM

nevy,

That looks like it could be very usefull as I have two scopes with fans so it could be used on either scope to mess with the fan speeds , it would save the trouble of fitting pots to both scopes , come on spill the beans where do you get such a device :-).


Exactly. The less after-market cutting, splicing and wiring I have to do the better!

:grin:
Mike

#163 MessiToM

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Posted 05 January 2013 - 02:10 PM

This thread has got me cruising for fans. Check out this 110cfm fan at "low" rpm even
http://www.frozencpu...m_VIPER_PWM_...

$9 4 fan controller!
http://www.ebay.com/...k-Aluminum-P...

#164 MessiToM

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Posted 05 January 2013 - 02:29 PM

O guys..........now I have a new project..

#165 MessiToM

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Posted 05 January 2013 - 02:39 PM

nevy,

That looks like it could be very usefull as I have two scopes with fans so it could be used on either scope to mess with the fan speeds , it would save the trouble of fitting pots to both scopes , come on spill the beans where do you get such a device :-).


Exactly. The less after-market cutting, splicing and wiring I have to do the better!

:grin:
Mike


I use something similar for dew busting. Its just a 12volt cigarette adapter with variable voltage outputs. Mine was from radioshack

#166 Sarkikos

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Posted 05 January 2013 - 02:52 PM

I'll have to start looking for those. There are a lot of neat off-the-shelf gizmos in the 12-volt Universe!

Mike

#167 azure1961p

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Posted 06 January 2013 - 12:38 AM

Detail on Ganymede. :john:

Bionic eyes? :lol:


Not at all. At least 8/10 seeing and preferably about 400x though you can see it with less. It's an uncompromising kind of feature that demands a steady image. I've tried with 7/10 which is still good seeing but its too soft at the magnification needed to show some albedo here.

Pete

#168 Scanning4Comets

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Posted 06 January 2013 - 02:50 AM

I'll give it a try, LOL! Maybe I'll get lucky and see the footprints on the moon too.

#169 Asbytec

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Posted 06 January 2013 - 03:57 AM

Maybe I'll get lucky and see the footprints on the moon too.


If you do, report back. I wanna try it. :)

#170 Sarkikos

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Posted 06 January 2013 - 09:27 AM

Pete,

Detail on Ganymede. :john:

Bionic eyes? :lol:


Not at all. At least 8/10 seeing and preferably about 400x though you can see it with less. It's an uncompromising kind of feature that demands a steady image. I've tried with 7/10 which is still good seeing but its too soft at the magnification needed to show some albedo here.


I've caught albedo features on Ganymede during excellent seeing but have never seriously tried to tease them out, much less attempt a drawing. That probably requires higher magnification than I like to use on a scope that does not track.

But I have gone up to 600x for Mars when it was at about 6 arcsec just to see what could be seen, and had good results. Didn't attempt a drawing, though. Ganymede is appreciably smaller at about 1.5 arcsec. So Ganymede's apparent diameter is about 4 times smaller than Mars when I was viewing that planet. With steady seeing, though, I should be able to tease out gross albedo markings.

I always resolve the Galilean Moons as disks. That is no problem for a decent 10" Dob.

Mike

#171 Scanning4Comets

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Posted 06 January 2013 - 12:21 PM

Of course I can see the moons as discs, as I did during Oct 25th....but to see DETAIL on one of the moons? Gimme a break. :roflmao:

All the power to you.....Something isn't adding up here.

#172 Sarkikos

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Posted 06 January 2013 - 01:29 PM

Seeing gross albedo markings isn't exactly seeing a lot of detail. You can probably see a lot more "detail" with your naked eyes looking at the Moon than moderate-sized amateur scopes can see on Ganymede in excellent seeing. I don't see this as incredible, but just a big bother to do if you don't have tracking on your scope.

Mike

#173 azure1961p

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Posted 06 January 2013 - 04:57 PM

Markus,

It's not unheard of for a good medium aperture scope to pull this off. Here's a link where one (of several) did a drawing of Ganymede details on a recent night of excellent seeing. http://www.cloudynig...5606142/page...

Too, one observer seemed go do even a little better with a 6" Maksutov.

The key is excellent seeing. I've never pulled it off with 7/10 but 9/10 seeing yes. Also Io if compared to Europa shows a subtle ovular shape, a diffraction effect caused by the brighter equatorial zone versus the dimmer polar regions.

Ganymede s surface features for me need unusually good seeing had here in Connecticut only in the summer. Io tho just 1.2" wide to Ganymedes 1.7" curiously shows the effects of its equatorial zone in just 6/10 seeing.

As far as albedo details on the other moons not counting Io it would seem to be substantially more difficult due to the smaller angular size of the features and inherent lower contrast.

It all adds up - but it takes unusually good observing conditions. And again that's without fans running. I'd imagine the probability now would seem to go up a picketing point or two.

Pete

#174 Scanning4Comets

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Posted 08 January 2013 - 12:20 PM

Just wondering something here,

Would it be ok to use a 9 volt battery on my 12 Volt fan? I tried it and the fan spins....but I am wondering if the battery will get too hot and malfunction over time? :question:

#175 Starman1

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Posted 08 January 2013 - 12:25 PM

Just wondering something here,

Would it be ok to use a 9 volt battery on my 12 Volt fan? I tried it and the fan spins....but I am wondering if the battery will get too hot and malfunction over time? :question:

The lower voltage reduces the fan speed and the battery won't last more than one night (spoken from experience). The battery won't overheat--it just won't last very long.
The standard "D" cell lasts a lot longer, and 8 of them in series should last several full nights.
However, I use a 12V 8 amp-hour deep-cycle rechargeable for 3 fans, and it needs recharging after one night, so just be aware of the limitations of batteries when running fans. Some 12V fans are small and run fairly slow and consume little power. Others push a lot of air and consume a lot of power.






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