#1  
Old 14-09-2009, 09:49 PM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,185
Dew on lens

I have a 68mm (18-35mm) Pentax lens that I would like to use to do widefield. How do you guys keep your lens dry on your DSLRs? Dew shield? Heaters?
Reply With Quote
  #2  
Old 14-09-2009, 10:05 PM
DavidU's Avatar
DavidU (Dave)
Like to learn

DavidU is offline
 
Join Date: Jul 2007
Location: melbourne
Posts: 4,719
Seen this?
http://www.telescopeplanet.co.uk/Vie...e=PON08J000042
Reply With Quote
  #3  
Old 14-09-2009, 10:09 PM
erick's Avatar
erick (Eric)
Starcatcher

erick is offline
 
Join Date: Dec 2006
Location: Shoalhaven Heads
Posts: 8,469
By using a 2" or 3" heating strap. I can recommend the Dew-Not straps. With some form of controller, of course. I just built another one for about $30.
Reply With Quote
  #4  
Old 14-09-2009, 10:11 PM
jjjnettie's Avatar
jjjnettie (Jeanette)
Registered User

jjjnettie is offline
 
Join Date: Feb 2005
Location: Far Far Away
Posts: 16,726
I just use the hair dryer in between shots, but that Kendrick unit looks like it's the go. I want one.
Reply With Quote
  #5  
Old 15-09-2009, 05:17 AM
CoombellKid
Registered User

CoombellKid is offline
 
Join Date: May 2006
Posts: 2,590
Having had the same problem myself. I went the slightly more expensive
way and brought another Thousand Oaks dew controller and dew strap.
I went this way because I have the same system on my dob and it
works beautifully. It has four independant channels so it can be
expanded and used on my 20x80's which I also find needs a bit of dew
control.

That Kendricks unit above looks alright too, probably works out about the
same price as the system I'm using above.

Cheers,CS
Reply With Quote
  #6  
Old 15-09-2009, 07:47 AM
dugnsuz's Avatar
dugnsuz (Doug)
to baldly go...

dugnsuz is offline
 
Join Date: Aug 2005
Location: Hahndorf, South Australia
Posts: 4,200
I use the Kendrick MicroFirelite Controller and two 3" heater straps (Camera lens and Guidescope) - works well. Approx $150AU for entire setup.
http://www.kendrickastro.com/astro/index.html
Gave up using the hairdryer after I read it tends to blast hot dust onto your multicoated lens surface!!!
Doug

ps...and the irony of me using a hairdryer isn't lost on me either!!!!!
Reply With Quote
  #7  
Old 15-09-2009, 07:59 AM
RB's Avatar
RB (Andrew)
Moderator

RB is offline
 
Join Date: Aug 2005
Posts: 21,995
Marc I assume you already have a dew controller so all you need is a 2" or 3" strap like Eric and Doug suggests.
I highly recommend it and that's what I use, along with a hood too.
I never shoot without it because the dew forms so quickly on camera lenses.
Reply With Quote
  #8  
Old 15-09-2009, 08:22 AM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
3" - 4" Dew strap on the 17-40 works a treat.

However be careful if using a larger one. While needing a dew strap at Duckadang I borrowed on off The h0ughinator, but it was a bit big (meant for a 10" scope ). So I wrapped it around a couple of times and set it going. It was a fairly heavy dew so I set it about 3/4 (lots of glass on the 17-40). I came back later to check only to find dew on it. Or what I thought was dew.

The moisture was ...on the inside!!!!! I had turned the strap up too high and it had driven all the moisture in the lens onto the coolest surface, the inside of the lens itself, just like a boiling kettle and a window. Pity I couldn't have vented the lens at the same time and then perfectly sealed it. I wouldn't have had to worry about fungus on the insides after that.
Reply With Quote
  #9  
Old 15-09-2009, 08:24 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,185
Thanks all for the tips & links.
Reply With Quote
  #10  
Old 15-09-2009, 08:29 AM
RB's Avatar
RB (Andrew)
Moderator

RB is offline
 
Join Date: Aug 2005
Posts: 21,995
Quote:
Originally Posted by [1ponders] View Post
While needing a dew strap at Duckadang I borrowed on off The h0ughinator, but it was a bit big (meant for a 10" scope ). So I wrapped it around a couple of times and set it going.
LOL Paul, the reason Houghy uses a 10" strap on his setup is that he usually has 5 or 6 wide angle lenses/cameras side by side, he simply wraps it around them once.

Reply With Quote
  #11  
Old 15-09-2009, 08:35 AM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
I thought the size of it for a widefield lens was to scare the cloud cover away over Newcastle via thermal converction.
Reply With Quote
  #12  
Old 15-09-2009, 08:41 AM
RB's Avatar
RB (Andrew)
Moderator

RB is offline
 
Join Date: Aug 2005
Posts: 21,995
Quote:
Originally Posted by [1ponders] View Post
I thought the size of it for a widefield lens was to scare the cloud cover away over Newcastle via thermal converction.


Ah yes you're right, I remember him mumbling something about it having a dual purpose.
Reply With Quote
  #13  
Old 15-09-2009, 08:47 AM
erick's Avatar
erick (Eric)
Starcatcher

erick is offline
 
Join Date: Dec 2006
Location: Shoalhaven Heads
Posts: 8,469
Quote:
Originally Posted by [1ponders] View Post

The moisture was ...on the inside!!!!!
So, what next? Did you throw the lens away? How did you get the internals dry again?
Reply With Quote
  #14  
Old 15-09-2009, 08:50 AM
[1ponders]'s Avatar
[1ponders] (Paul)
Retired, damn no pension

[1ponders] is offline
 
Join Date: Nov 2004
Location: Obi Obi, Qld
Posts: 18,778
I turned the heat down Eric. Nothing I could do about moisture on the inside. I haven't seen any evidence of it since under 'normal' dew strap operation.
Reply With Quote
  #15  
Old 15-09-2009, 08:53 AM
erick's Avatar
erick (Eric)
Starcatcher

erick is offline
 
Join Date: Dec 2006
Location: Shoalhaven Heads
Posts: 8,469
Thanks Paul.
Reply With Quote
  #16  
Old 15-09-2009, 10:36 AM
montewilson's Avatar
montewilson (Monte)
Registered User

montewilson is offline
 
Join Date: Apr 2007
Location: Sydney
Posts: 374
Hi Marc - Prevention is better than a cure. Dew straps are great, make your own, don't buy one unless you are really rich.

The secret however is to also get an old sock (thick ones are best) and cut a hole in the toe area and put that over the lens after you have attached the heater. You will loose less heat from around the lens body and therefore need less heat to keep the dew off.

Call me for more information.
Reply With Quote
  #17  
Old 15-09-2009, 11:27 AM
multiweb's Avatar
multiweb (Marc)
ze frogginator

multiweb is offline
 
Join Date: Oct 2007
Location: Hinchinbrook
Posts: 18,185
will do
Reply With Quote
  #18  
Old 15-09-2009, 12:48 PM
leon's Avatar
leon
Registered User

leon is offline
 
Join Date: Apr 2006
Location: ballarat
Posts: 10,813
Have to agree with that one Dougie.

Leon
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 07:20 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Celestron Australia
Advertisement
Lunatico Astronomical
Advertisement
NexDome Observatories
Advertisement
OzScopes Authorised Dealer
Advertisement
Meade Australia
Advertisement
Bintel
Advertisement
SkyWatcher Australia
Advertisement
Astronomy and Electronics Centre
Advertisement