From: Alan Friedman <alan@greatarrow.com>
Date: September 26, 2005 11:36:55 AM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Re: M2 from Los Angeles - dew
I hear you on the unattended issue - I live and observe in downtown Buffalo, NY. I have neighbors who chain their wicker porch furniture!
I think that a dewshield is a necessity with a catadioptric scope or refractor. I have the old simple version Kendrick system - limited adjustments amount to on and more on. This is enough dew tech for my purposes. I wrap the strip around the outside of the dewshield about 1/3 of the way out from the lens and leave it on low from the beginning of the session. There seems to be minimal adverse effects to the figure of the optic from this approach. Inadequate cool-down and general seeing issues are much more substantial problems. Try to avoid the hairdryer thing if you can. The scope will be quite dry if put away in the closed case - you can check it the next day to be sure.
Alan
On Sep 26, 2005, at 1:20 PM, Tim wrote:
Alan:
My setup is a little complicated. We live on a hilltop, and though my "back yard" is kind of
isolated from the outside world, where I set my scope up is visible. So I prefer not leaving
it unattended for any length of time. I keep the C-8 in my basement shop, which stays
pretty cool during the day, but is probably 10 degrees warmer than the outside air in the
morning. This scope can't see the eastern sky, though, because of the house. So, as we
overtake Mars and switch to "daylight wasting's time" toward Halloween, I think I'll move
back to my other scope...
My other scope for planetary, the Nexstar 925, is in my roof, where I can leave it set up
alone. I close it off from the house with doors beneath the scope, but I haven't had the
opportunity to be certain that thermals aren't still a problem. Vibration is only a problem
when my son and his friends are running up or down the stairs below!
Since both these scopes are SCTs, I'd be interested in hearing your thoughts about the
Kendrick system and how it might affect planetary definition. I'd prefer not to use a blow
drier, also, but I'm not sure I'm ready to spend a few hundred bucks on the temperature
controllable Kendrick system. I could also try a dewshield, but the opening around my
9.25" is so tight it might hit the sides if I slew too close to the horizon.
-Tim.
--- In Astro_IIDC@yahoogroups.com, Alan Friedman <alan@g...> wrote:
> When I shoot Mars I usually set-up the evening before to let my scope
> cool completely. I leave it with caps on covered by a tarp and go to
> sleep, setting the alarm to get up for mars (somewhere between 2:00 and
> 3:30 at the moment.) Things may have gotten dewy outside but the optics
> will be dry. If I am going to be up all night I always set up a
> Kendrick dew system. But for a couple of hours of imaging near dawn I
> wrap a layer of foam around my dewshield - this is will delay the
> formation of dew quite effectively.
>
> Dew is a drag. It deposits airborne contaminants on the corrector which
> requires more frequent cleaning. I almost never use a hair dryer.
> Blasting warm air at the optics will generally ruin the figure of the
> glass for the balance of the observing session. At the end of the
> imaging session I cover the scope and put it away in the case (which
> has been left closed) and let the scope return to ambient temperature
> slowly.
>
> Best -
> Alan
>
>
>
> On Sep 25, 2005, at 6:53 PM, Milton Aupperle wrote:
>
> > Hi Tim;
> >
> > Very nice shot for a first time out doing DSO's with Astro IIDC.
> >
> > I think you'll be impressed with the increased sensitivity your goingÂ
> > to get with Mars imaging, as the larger pixels give you about 40%Â
> > more light per pixel than the ApLux gathers. You can use less gainÂ
> > and/or run at higher frame rates, which will help improve S/N.
> >
> > I can sympathize with the dew problems. When I was on holidays IÂ
> > tried imaging the day after it had finally stopped raining (3 daysÂ
> > worth). The scopes optics would "dew up" after 5 minutes and the onlyÂ
> > way to briefly clean them was with the hair dryer at max. However toÂ
> > make matter worse, when I checked the optics with a flash light forÂ
> > how dewed they were, a bazillion little gnats and moths would land onÂ
> > the optics and get stuck there. After 45 minutes of screwing around IÂ
> > finally packed it in for the night. After another day of sunnyÂ
> > conditions all the dew was gone and the dessert like climate inÂ
> > Saskatchewan allows me to image all night with none of those problemsÂ
> > at all.
> >
> >
> > TTYL..
> >
> > Milton J. Aupperle
> > President
> > ASC - Aupperle Services and Contracting
> > Mac Software (Drivers, Components and Application) Specialist
> > #1005 - 815 14th Avenue. S.W.
> > Calgary Alberta Canada T2R0N5
> > 1-(403)-229-9456
> > milton@o...
> > www.outcastsoft.com
> >
> >
> > On 25-Sep-05, at 10:17 AM, Tim wrote:
> >
> > > Folks:
> > >
> > > I uploaded a file into the DSO area this morning. It's a stack ofÂ
> > > ten 20" exposures taken with
> > > my new Pt. Grey Flea camera (the camera is actuallly smaller thanÂ
> > > the Mogg 1 1/4" adapter
> > > with the 0.6 FR lens).
> > >
> > > I experimented for about 3 hours last night with various DSOÂ
> > > objects. I would have shot Mars
> > > as well, but was set up in the back yard, and our house is 40'Â
> > > tall, so it didn't rise above the
> > > roof before I started to fade! Too bad, too. The seeing wasÂ
> > > pretty good, though the dew was
> > > moderate. I don't have a dew heater, so I had to use a blow dryerÂ
> > > every 20 minutes or so. I
> > > thought the clouds would roll in by morning, but they didn't.
> > >
> > > Anyway, I am amazed at the quality of the images from the Flea. Â
> > > Dark frame subtraction in
> > > Astro IIDC works very well, too. If anything, I found that takingÂ
> > > these sample DSO images
> > > with the flea was orders of magnitude easier than my "first nightÂ
> > > out" with my Meade DSI Pro.
> > > And the image quality is much better, too.
> >
> >
> >
> > YAHOO! GROUPS LINKS
> >
> > â–ª Â Visit your group "Astro_IIDC" on the web.
> > Â
> > â–ª Â To unsubscribe from this group, send an email to:
> > Â Astro_IIDC-unsubscribe@yahoogroups.com
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> > Service.
> >
> >
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