Had a bit of spare time on my hands with the cloud and rain over the last few days.
Decided to mod the newt and attach a mirror fan.
Made use of the useless back plate which normally seals the back of the SkyWatcher 8" and attached a computer fan and Dork Smith 12v variable speed drill unit.
Also wired a socket to power the unit from a cigarette lighter adaptor plugged in to my 17aH powertank.
Came up OK, if I say so myself
Looking forward so seeing the result when it's working on the scope.
problem is there are not enough wires hanging off and shards of metal for cutting your hands on!
seriously mate, you need too go back to "she'll be right" classes and make your projects more slap dash.
I am consoling asimov as we speak, he is having a hard time coming to grips and clean and tidy you have been. This is really unfair Matt, think of your mates next time!!!
Just took the plain (uncut) circular back plate to a friend's place who has a drill press and we used a circular metal cutter.
Of course, I'd pre-measured and marked the plate for the fan hole (72mm radius) and collimation screw holes at the edge (180 degrees apart).
Also had to drill holes for securing the fan to the back plate, but that was all there was to it. Pretty simple, actually... when you've got access to the right tools or a mate with a "Bloke's Palace" for a shed!!
Got a few small breaks in the cloud last night between 7-30 and 9pm.
Had the fan on full blast for about half an hour before and turned it to 1/3 speed during observing and all I can say is WOW!!!!!
Even with very average seeing and Jupiter at only 30 degrees above the horizon I could very clearly see a difference in the view. More subtle detail visible.
But the real difference was noticeable when I slewed to stars. Never had them quite so pin-sharp before, even in the 5mm Vixen LVW (200x). Could even make out the one or 2 fainter diffraction rings around the focused stars.
Alpha Cent and Acrux both very crisp.
If that's what they look like in average conditions I can't imagine what I'll get in good to very good seeing
I'm shocked. Honestly. I didn't think a mirror fan would make such a difference on a 8" scope.
fully recommend spending $30 + $5, get a digital temp sensor with dual sensors from dork smith and for the $5, some thermal paste and stick the sensor at the end of the wire 1/2 up the side of the primary mirror.
that way, you will kno for sure when your primary is within a degree of ambient.
next trick is to see if you can split antares into its blue brother. needs great collimation, good seeing and ambient mirror. it is a good test!
Matt, if you've got a way to cool the primary then the best images will be had with the primary cooled *and* no airflow in the tube to cause currents - i.e. with the fan off and the bottom of the tube closed off.
But if the mirror is not quite cooled to ambient then you'll have to leave the fan running to keep breaking up the boundary layer and/or leave the tube open at both ends to help circulate air.
You should try some experiments...run the fan flat out for a few hours and then switch it off entirely for a test. If the primary has cooled down to ambient then all the air trapped in the tube will become stationary, and Nice Views will result :-)
If the fan arrangement you have now isn't enough to properly cool the mirror (and you have to go the temperature sensor route to really find this out) then you can go for the peltier-assisted cooling without too much hassle and that will certainly do the job.
I'll get a hold of one of those temp sensors and do as you suggest. It's the next logical step on the path you've already well and truly sprinted down!
Where do I get thermal paste, by the way?
And I'll accept that antares challenge, even though I'm only shootin' with an 8". Should be do-able, right?
Also, good advice Bird. I'll try it next clear night flat out ... and then turn it off when it's time for viewing/imaging.
And I'll accept that antares challenge, even though I'm only shootin' with an 8". Should be do-able, right?
dork smith should have it or jaycar i know does!
i used my 5mm lv vixen with the 10" and asimov has done it with the 5" or 6" refractor so i reckon you should be able to.
the main thing here is to know when has the ambient stopped dropping. Canberra sounds alot like tasmania in terms of moderate days, coool cool nights. so knowing the ambient temp is crucial for where you live
Nope, my scope has nothing in that area Although at the moment it's permanently setup on the lawn with the platform aligned, the scope on top and a cover over the whole thing. So it's cooling down from the moment the sun goes down
So first step is the thermometer to tell the difference (if any) in temperature between the mirror and ambient, then a cooling fan, then a peltier.
