Dew problems on SWE 150PL Newt

[Planetesimal]

Last Saturday was my first properly dark sky viewing session - I managed to get everything set up while the moon was still under the horizon, and was amazed at the difference it makes to how many stars you can see. I was pleased to note that yes, the milky way is very clear to see right across the sky - I know I'm lucky to have skies as dark as this from my own back garden, which has made me even more determined to continue observing and making the best of it!

The problems struck about an hour or so in - all my optics fogged up with dew / condensation, including the finderscope, the primary, the EPs, everything!

I had to take the whole set-up inside for half an hour to dry out before trying again... So, I'm thinking this is a problem I'm going to have to deal with if I'm going to make a success out of this... I've looked through the forums to find answers but as a beginner I don't really understand what people are talking about on this topic!

I've looked on the FLO site for example, and I just can't picture from the products listed how I'm going to keep the dew off my EPs and finderscope. Will I really need to start modifying the scope by adding fans etc.? Is there an easier solution at this stage?

Anyway, I'd love to hear from anyone who has some suggestions as to how this issue can be tackled!

[wookie1965]

A quick fix is a hair dryer other than that its dew heaters ive only seen them for scopes not for finders you could make your own dew shields out of a camping mat that would help, but not your eyepieces like i said use a hair dryer clear your lens.

[Planetesimal]

A quick fix is a hair dryer other than that its dew heaters ive only seen them for scopes not for finders you could make your own dew shields out of a camping mat that would help, but not your eyepieces like i said use a hair dryer clear your lens.

Thanks Wookie - I see you have the 150P! I intend to upgrade my eyepieces like you've done but I'd better take it one step at a time... The stock 25 mm gets the most use for me at the moment!

So, re dew heaters for the mirrors, what is the usual type of heater used and how are they fitted? I'm a little nervous about removing mirrors at this stage (still waiting for the cheshire collimator to turn up!)...

[wookie1965]

Well im a novice ive not used dew heaters myself ive only used the dew shields with my scope it was the secondary dewing and the finder and now the Telrad i just made dew shields.It will be the same with yours just make a dew shield for your scope and your finder that will sort them out your eyepieces i leave mine in the case open until i use them usually they dont fog up if they do i step back for 30 seconds then its ok again other than that hair dryer. To answer your question the dew heater goes round the front of your scope i think and keeps the air warm so dew cannot form if you look on FLO website they sell them.

[Planetesimal]

Well im a novice ive not used dew heaters myself ive only used the dew shields with my scope it was the secondary dewing and the finder and now the Telrad i just made dew shields.It will be the same with yours just make a dew shield for your scope and your finder that will sort them out your eyepieces i leave mine in the case open until i use them usually they dont fog up if they do i step back for 30 seconds then its ok again other than that hair dryer. To answer your question the dew heater goes round the front of your scope i think and keeps the air warm so dew cannot form if you look on FLO website they sell them.

Cool thanks... I wasn't sure if those heaters were just for the Mak scopes that they're shown with on the FLO site, but sounds like it's just a case of getting the right diameter. So with home-made dew shields for e.g. the finderscope, am I right in thinking this is effectively a layer of insulation adhered to the outside of the tube like a blanket?

And at the risk of putting too many questions in a post (and straying off my own topic!), have you found the telrad useful / worth the investment?

[Velvet]

I have dew heaters on my EP's, finder and telrad and dew shirld on 200p. Nothing like being over to top. But have never had dewing problems.

So i suppose you would call it a success

velvet

[RikM]

I have made a dew shield for the front of the scope and finder out bits of foam camping mat and velcro. That seems to help keep the dew from forming on the secondary mirror and finder. For EP's I keep the cap on when not actually looking through them. This seems to be enough for all but the wettest of nights.

[wookie1965]

The Telrad was the best investment you can download all the Telrad maps print them off i have started by printing the ones off im going to look at that night then laminate them got the laminator and sleeves from Wilkinson's £14 odd pence heres a list of places to download from. http://www.solarius.net/Pages/Articles/dbArticle.aspx?artid=messier_finders

http://www.utahskies.org/deepsky/caldwell/charts/caldwellTelrad.htm

http://www.astro-tom.com/messier/messier_finder_charts/messier_maps.htm

[Planetesimal]

I have made a dew shield for the front of the scope and finder out bits of foam camping mat and velcro. That seems to help keep the dew from forming on the secondary mirror and finder. For EP's I keep the cap on when not actually looking through them. This seems to be enough for all but the wettest of nights.

I'm trying to picture how the dew hield fits to the scope... Is it basically a piece of foam mat rolled up into a tube so it fits around the front few inches of the OTA? I guess you'd have to cut out the bits where the focusser and the finderscope bracket / telrad mount sit? Which makes me think it would be a permanent fixture on the tube...

Is there a guide to making one of these things somewhere on the internet?

[RikM]

Oh it's ever so complicated

You cut a strip of foam mat (I bought one from Asda for £1.50) long enough to wrap around the OTA with a bit of an overlap and wide enough so that it sticks out about 1.5x the aperture. E.g. the one for my 150P once rolled up is about 30cm long held together with sticky backed velcro tabs so it's a nice snug fit. It fits onto the tube as far as the focuser and I cut slots for the spider bolts.

[bish]

I've always used a dew shield and 12v hair dryer, works a treat. I now have a dew heater as the hair dryer makes quite a bit of noise - fine for star parties but not great for the neighbours.

[RikM]

I've always used a dew shield and 12v hair dryer, works a treat. I now have a dew heater as the hair dryer makes quite a bit of noise - fine for star parties but not great for the neighbours.

How/where have you fitted your dew heater? I have thought about getting heaters (just for the SGL starparties, because they are a bit damp being next to the river) but could never work out how to fit them without getting wires in the optical path.

[Planetesimal]

How/where have you fitted your dew heater? I have thought about getting heaters (just for the SGL starparties, because they are a bit damp being next to the river) but could never work out how to fit them without getting wires in the optical path.

Thanks for posting the picture, I understand now! The Asda roll mat looks like it'd be worth a try for starters - certainly a lot cheaper than those fully controlled heated jobs!

My garden is heavy clay, so it holds water and turns into a swamp after rain and generates a very damp environment, so it'll be fingers crossed that the home-made job will be enough...

Have to say I'm jealous of the diagonal finderscope and that focusser (is it the stock 2" crayford?). My accessory list is getting longer by the day - still, at least the rellies will know what to buy me for Chrimbo this year!

[RikM]

Standard 2" Crayford with an Orion self centring adaptor Quite a nice chunk of glass in it though

I find the right angle finder so much easier to look through than the straight through type. Coupled with a Rigel or Telrad illuminated zero power finder it's a great combination.

[wookie1965]

heres mine the shield is a bit too big but it does the job.

[RikM]

I had originally made mine a bit longer but it kept catching the wind (and ruining subs when imaging using an eq3-2) so I trimmed it a bit.

[wookie1965]

Up to now ive been lucky and as ive not delved in to the realms of astrophotography yet i will keep it this long, where i view from in my garden ive got my gym behind me and a six foot fence in front of me so im quite shaded away from the wind.

[Planetesimal]

Standard 2" Crayford with an Orion self centring adaptor Quite a nice chunk of glass in it though

I find the right angle finder so much easier to look through than the straight through type. Coupled with a Rigel or Telrad illuminated zero power finder it's a great combination.

I hear you! I've already got neck-ache looking through the straight-through finder, particularly from trying to find objects high up. I think a right-angle finder and a telrad will definitely be going on that wish list.

[moriniboy]

I use 2 ep's and keep one warm in my pocket whilst using the other one

[Planetesimal]

I use 2 ep's and keep one warm in my pocket whilst using the other one

Good suggestion, thanks! I finally got my Baaders cleaning fluid through yesterday, so had a great session cleaning all the gubbins off the lenses. Now if only the sky would clear so I could actually use the blighters...