Okay, it's a stupid thread title, but I've had that song stuck in my head, so I figured I'd share the joy around.
It's coming into winter down in Melbourne, and I'm wondering just how much fuss people make about dew heaters and the like.
You can get heaters for pretty much everything - cameras, eyepieces, secondary and primaries, but I'm playing with a couple of new scopes now and I'm trying to gauge whether I've just been lucky.
I mean, I've had observing sessions shut down by dew that was all over my computer, but never on my optics (except for when I accidentally exhale too close to the eyepiece - oops!) but I can't see how a dew heater would help this as my breath is more humid than the surrounding air which effectively drops the dew point on anything I breathe on.
I get that the entire length of the tube acts as a dew shield with the dob. Keeping fans running probably helps too, since heat exchange is more efficient with the moving (warmer) air than radiating off to the cold dark depths of space so the net effect is a warmer scope.
So, in your opinion, what are the important surfaces to protect from dew in terms of likelihood of it dew-stroying your observing or photography session?
I'm especially interested to hear from ppl who are in Melbourne or go up to the LMDSS. Or people that are finding they have to use those little dew heaters on their sensors, which seems like overkill to me, but what dew I know, right? Does anyone *really* have to put a dew heater on a secondary? I suspect by the time the secondary dews up you'd be in for a pretty uncomfortable session anyway, so does it really matter if you have to pack it up?
I dunno, dew can get pretty evil here in Canberra. I do a few things to help mitigate it.
1. I hard wax all my scope tubes (Turtle Wax Super Hard Shell). Yep, you bet, it makes the dew run off instead of pooling. I have gone out and seen my FSQ-85 with rivulets running off - I kid you not! I even hard wax my mounts, and make sure I leave wax residue in any gaps leading to the electronics to help water-tight those areas. Overkill? Not in my opinion. I reapply a new coat EVERY morning after a dew session after the scope has dried off. I don't pick the scope up by the tube anyway, so it's not going to slip out of my hands.
2. I put dew straps behind the objective as well as another on the dewshield itself. Sure, the one located behind the cell wards off dew from the lens (OK, sorry, I only am talking refractors as my VC-200L doesn't dew up!), but I found that dew was developing on the tip of the dewshield as well as the small baffle inside the dewshield on the FSQ. So, I now have another strap positioned over the baffle.
3. I put dew straps also on the guidescope objective. It's a necessity.
4. I do NOT EVER assemble the scope during night. My rig is ALWAYS assembled for how it is when imaging. This maintains a sealed system, so dew won't develop on CCD windows, flatteners, reducers, filters. I have had them dew up before, so I learned my lesson.
5. Heaters on sensors/CCD windows - haven't had a need because of the above.
The only times I have had to end a session due to dew was because I had NOT put on the dew heater straps because I was too blase, thinking "Nah, not going to dew tonight". When I have been out at Yass last winter, I had frost all over the scope and mount (a prior incarnation of Takahashi - I've had a few ), but because I had the heaters on, the glass was clear and I kept going (was NOT fun packing it up! HAD to wear gloves)
And another thing I found entirely beneficial was keeping a few chemical hand warmers handy - they VERY quickly de-fog EP's you have accidentally breathed on and don't use up battery. They also keep your pockets and hands warm in the interim . I have even strapped one onto the dewshield once when the old battery I had karked it in the field.
I have significantly less issues with dew at Heathcote (other side of Heathcote to the site you’re referring to) than in Melbourne. In Melbourne I set up on grass in my backyard, some nights the dew isn’t too bad but other nights... I gave up using my newts in Melbourne as without a dew heater on the secondary it could dew over not too long after the primary (12”) finally cools down.
The dew shield on my 4” is quite short so I put a strap on that otherwise it would dew over pretty quickly and I’ve recently started using eye piece heaters. Even when I didn’t look through the EP’s they would dew over!
My c9.25 dews up like there's no tomorrow in my backyard in melbourne without a dew shield and dew heater. I haven't had much dewing of the eyepieces and if i do I change to another and bring the dewy one in the garage for a little bit till it dries up
I found that putting aluminium foil tape over the external surfaces helped a lot. This reflective material stops everything from heading for -30C due to radiative cooling from the sky - with an extension to the tube, the scope stays close to ambient inside and out and a little bit of fan forced airflow over a 2w heater and into the base of the OTA does the rest. Have also found that using an al foil shield around the focuser/filter wheel helps. Rarely have any dew problems on the scope, but everything else ends up dripping wet - part of the fun of being by the sea..
For comparison, when I first got the scope, dewing with the native CF finish was so bad that some of the internal paint dissolved in the layer of water and dripped down the inside of the tube and a bit on the mirror - modified tube doesn't look CF sexy anymore, but dew is really no longer an issue at all.
I find this interesting. Reflective tape would reflect heat *away, wouldn't it? I would have thought it would *accelerate the cooling of the scope past the dew point? I believe you that it works, I'm just grappling with the how? (and then thinking of doing something similar :-)
I recall that Allan L had a theory that using one of those reflective "Space Blankets"/ survival blankets, would work very well at keeping condensation off of his dob. I think the idea of slowing thermal loss to the cold night sky is exactly right. Keep the scope warm and cosy. I invisage a new must have accessory, a "Telescope Cosy" - a heated reflective shroud that keeps just enough heat in your setup to avoid the dreaded Dew. Dew Not be without one.
I have so far found that the $30 delivered dewstraps I ordered in from China months ago work perfectly well - the scope will have dew running off it in rivulets, and the glass will still be fine. And no need for a controller - they have 3 position switches built in - on/off, low and high. I have never had to use high yet.
I notice myastroshop now sells the exact same offerings too. MUCH cheaper than the others, and work just fine.
I have so far found that the $30 delivered dewstraps I ordered in from China months ago work perfectly well - the scope will have dew running off it in rivulets, and the glass will still be fine. And no need for a controller - they have 3 position switches built in - on/off, low and high. I have never had to use high yet.
I notice myastroshop now sells the exact same offerings too. MUCH cheaper than the others, and work just fine.
I grabbed some from China as well......elastic Velcro to attach, various sizes, run from USB, have an adjustable temperature dial built in the cord....they work amazingly and were 22 delivered.
For less than the cost of a single name branded dew strap i’ve Kitted out 2 x telescopes and 2 x guidescopes with no name ones
I have so far found that the $30 delivered dewstraps I ordered in from China months ago work perfectly well - the scope will have dew running off it in rivulets, and the glass will still be fine. And no need for a controller - they have 3 position switches built in - on/off, low and high. I have never had to use high yet.
I notice myastroshop now sells the exact same offerings too. MUCH cheaper than the others, and work just fine.
I'm interested; where abouts did you come upon these cheap dew straps? Was it an ebay thing? Alibaba?
I grabbed some from China as well......elastic Velcro to attach, various sizes, run from USB, have an adjustable temperature dial built in the cord....they work amazingly and were 22 delivered.
For less than the cost of a single name branded dew strap i’ve Kitted out 2 x telescopes and 2 x guidescopes with no name ones
I opted for the 2.2mm plug version. These cost a tad more. I just added on my own cig to 2.2 female plugs and voila.
Going to order a few more for the VC200L and MAYBE an EP version too.
As long as you're shaded from the night sky you'll be alright. The only time dew is an issue for me is when I point the scope right up. The C11 with its larger glass corrector is the worst so I run a lot of heat through the corrector cell from the get go and try to keep it in temperature all night. Other smaller aperture scopes are less of an issue but I have multiple dew straps and run them all night. When I use lenses I wrap them in socks (like my finders) and shove eBay hotties in there. That gives me ~8h of heat and does the job. No power required. For the laptop I have an astro tent so I keep it covered all the time. The only half opened is the half where the telescope tripod is. To stop the dew on the tent roof I lay rags on it (old curtains) and peg them around the tent frame. When they're soaked I put dry ones on. That happens only on really wet nights. Usually I keep the same set for the whole night.
Marc that brings up an interesting topic, "getting it under cover" protection for imaging gear, hubs, laptops etc when away from you usual location. Upcoming QLd Astrofest for example. What is the current thinking on pop-up structures, be they tents, gazebos, toilet cubicles, flys, etc? How big is too big? Respecting the space required by others setting up nearby and not cutting off altitude angles. There was a recent comment about a certain well known IIS member who has a " gazebo that can be seen from space". Minimalism or maximum covered area?
I put my stuff out totally uncovered or shielded. Even the laptop. The laptop has been the only issue (dew on screen) and I have not found a very effective solution yet (since I have one of those cold touch cooled laptops lol). Towels, cut out boxes etc no benefit I have seen. Might buy a heater strip for the monitor!
Marc that brings up an interesting topic, "getting it under cover" protection for imaging gear, hubs, laptops etc when away from you usual location. Upcoming QLd Astrofest for example. What is the current thinking on pop-up structures, be they tents, gazebos, toilet cubicles, flys, etc? How big is too big? Respecting the space required by others setting up nearby and not cutting off altitude angles. There was a recent comment about a certain well known IIS member who has a " gazebo that can be seen from space". Minimalism or maximum covered area?
There is a varierty of tents ranging from single shower cubicle size up to bigger structures but there is only one taj mahal. My tent has probably a 1.8m x 1.8m foot print so it's in the medium range. There are bigger wider tents.
- I've had a few 
), but because I had the heaters on, the glass was clear and I kept going (was NOT fun packing it up! HAD to wear gloves)
