I was at Jaycar yesterday, (love that store) and they have USB notebook coolers going for just $13.
Seeing how my 8" doesn't have a cooling fan, I thought this would be a very cheap alternative.
Only takes a little ingenuity to attach to the back of the scope.
The actual fan is approx 6" in diameter, compare that to the ditzy little ones that usually ship with newts.
The big bonus though is that it's powered by USB. No batteries!!! An who doesn't take their lappy out onto the field?
The actual fan component can be easily removed from the outer frame by undoing 4 small screws.
I think I'll attach 4 velcro tabs (soft fuzzy side) using the screws and fashion a belt for the ota out of more velcro (hard scratchy side). Then it will just be a matter of patting it into place.
Did I explain that well enough?
Suggest that you take the opportunity to "seal up" the end of the dob so the air from the fan doesn't bounce back off, but is forced around the mirror and up the tube. Folks seem to think that this restricts dew formation on the primary. Seemed to achieve that in my 12".
Suggest that you take the opportunity to "seal up" the end of the dob so the air from the fan doesn't bounce back off, but is forced around the mirror and up the tube. Folks seem to think that this restricts dew formation on the primary. Seemed to achieve that in my 12".
I agree with Eric here. I did the Scott tannehil mod on my 12" GSO
and found it eliminated dew formation on primary and secondary and significantly reduced time to cool the primary compared to a fan cooling the back of the mirror. Its a very easy mod. You can feel the airflow coming out of the front of the scope. I found that I didn't have to mount the fan on Velcro as vibrations were negligible with the standard GSO fan, so I just put the neoprene membrane around it. But if you have to install a fan, its a very simple way to do it. The whole job, including putting the baffle in front of the primary took only about 20-30 minutes.
The scope that I now have doesn't get dew on the primary. Tim, its maker, reckons that this is due to the large mass of the mirror. I've always thought that the way the mirror box directs airflow from the fan across the front of the primary was a factor. I became convinced of this at Snake Valley on Saturday. Peter Batchelor's 16" LB primary with dew guard and shroud was covered with dew and mine was clear as a bell with no shroud. I don't think Peter's primary had less mass than mine, just a fan that only blows on the back of the mirror.
I recently purchace a fan for my DOB as it already has the holes to take a fan. It is a bit more expensive but I couldn't be bothered pulling things apart, may last a bit longer too.
I check the holes line up. From one hole to the next is 72mm so the 80mm fan seemed to be fine. The next will be to check vibration but I expect I will only use it as an initial cooldown than continuos operation.
From what I imagine a lot of configurations are to force air into the tube and with airflow this would create an enourmous amount of turbulence inside with the mirror. The best way IMO would be reverse and suck it out. I am not sure whether there maybe some other vortices at work in the other direction but it would almost likely suck all the dust out as well without swirling air inside. Cool air can still be drawn in from the top of the tube though away from any possible ground dust.
Although I haven't had any practicle experience on this was just a note. More information would go down well from all the more experienced users cheers.
I recently purchace a fan for my DOB as it already has the holes to take a fan. It is a bit more expensive but I couldn't be bothered pulling things apart, may last a bit longer too.
I check the holes line up. From one hole to the next is 72mm so the 80mm fan seemed to be fine. The next will be to check vibration but I expect I will only use it as an initial cooldown than continuos operation.
From what I imagine a lot of configurations are to force air into the tube and with airflow this would create an enourmous amount of turbulence inside with the mirror. The best way IMO would be reverse and suck it out. I am not sure whether there maybe some other vortices at work in the other direction but it would almost likely suck all the dust out as well without swirling air inside. Cool air can still be drawn in from the top of the tube though away from any possible ground dust.
Although I haven't had any practicle experience on this was just a note. More information would go down well from all the more experienced users cheers.
Malcolm, my understanding is that a major issue affecting seeing from the scope itself is a boundary later of warm air at the front of the primary and that breaking this down with a flow of air across the face of the mirror enhances seeing. I'd be curious to see whether suction would achieve this. I suppose you could reverse the polarity of the fan connections to make it spin the other way.
, but my inverter has a usb outlet.
Keep trying, you'll get there one day.
Photo?
