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Can I have some members cooling fan solutions please ?

spaceboy

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spaceboy

spaceboy

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The thing that annoys me the most is that I had done all this research 12 months ago and came up with the 80mm 15-31 cfm fan being the ideal size. I had one fitted to the standard rear cell fixings and for the best part although not baffled it did an "OK" job of cooling the mirror. I don know ....... I seemed to throw the idea of just baffling the 80mm out the window. I guess if any thing I can always stick it on the end of a long white pole and get some clean energy for the tent the weekend.

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spaceboy

spaceboy

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i have just done the fan thing - made my baffle etc. when i look through the fan i can see the back of the mirror - should there be a "black out" layer between the fan (attached to baffle) and the mirror?

I know some have attached grills 120mm Aluminum chrome fan Dust Guard grill PC coated fingerguard case fan grill | eBay between the fan and the mirror but I didn't feel the need TBH.

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spaceboy

spaceboy

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Did it come with a metal plate, perhaps, to protect the mirror?

Earlier Helios and blue tube Sky-watcher scopes came with a metal plate over the rear of the primary but this had to be removed every time the scope needed to be collimated. Collimation required you to have handy a screwdriver and allen key. The newer SW's no longer have this plate on the back in favor of having collimation knobs to allow easier collimation with out the need for tools.

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sublime_mick

sublime_mick

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I have the blue tube skywatcher explorer 200 - i removed the back plate and made the baffle to the exact same size as back plate. fan in the middle of baffle/back plate. velcro strips keeping baffle in place however when you look through the fan blades you can see the mirror. just wondering if this small exposure will have an impact on viewing - i like spaceboys post re filtered finger guards. but if there was no impact on viewing i'd leave it - or even just make a cap out of dark cloth to act as a black out and a filter.

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sublime_mick

sublime_mick

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that clarifies it spaceboy. I made mine and could see the back of the mirror through the fan. It was previously covered with a black plate - I thought It must be important to keep the back sealed (and as dark as possible). but id there is no effect with stary light entering via fan then it'll be cool (excuse pun). so the newer models have the back of mirror fully exposed?

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spaceboy

spaceboy

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so the newer models have the back of ?

The mirror is exposed on new OTA's but it dose pay to make a baffle as any light entering the rear of the OTA will effect contrast. This is partly my reason behind this thread as I wanted to improve the air flow from my fan while also reducing the risk of any stray light entering around the mirror cell.

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sublime_mick

sublime_mick

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is partly my reason behind this thread as I wanted to improve the air flow from my fan while also reducing the risk of any stray light entering around the mirror cell.

i'll be making a filter type thing out of weed control cloth I have - it's dark and will also filter out any dust entering the tube. Thanks for all the advice. I based my effort on the work done by skills on this thread. found a thin enough chopping board (which the wife hasn't noticed missing - stole tools from my dad's toolbox - and bob's yer uncle. will get some pics of it up.

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Macavity

Macavity

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Aside: Some "PC" type fans are fairly horrible. Had one seize up in the (modest) cold, recently. Worthwhile getting (replacing with) a nice low noise type with decent bearings? I see CPC-Farnell carry "Papst" axial, DC, ball-bearing ones, I used to fit in my PCs... ;)

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spaceboy

spaceboy

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UPDATE:

First real chance to try out the fan early hours of this morning and it worked remarkably well. In fact so well that I now have some concerns about how quickly it did cool the mirror / OTA. While not exactly the same, if I was to wash a glass in hot water then put it under the cold it would crack. Last night I took the 250PX out from a 20'-23' centrally heated flat into a 6' cold (felt colder Brrr...) and with in around 30 or so minutes I was able to use x250 on Jupiter. 8/10 times I only use the scope at dark sites so the 40 minute drive in a cold car usually helps cool the scope yet I'd still have to wait 30-40 minutes before the views were steady enough for any real magnification. I'm happy with the results even though I did have concerns going OTT on the size of the fan. If anything it was a novelty to turn the fan full up and feel the breeze blowing out the top of the tube.

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