The effects of dew?
- Larry 1969
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The effects of dew?
Yet another unsuccessful imaging session... I think this makes 5 in a row... (VERY FRUSTRATING)!!!
I checked all of my apps and conditions should have been good. No clouds or smoke and the dew point was 42F and the projected low was 46F.
Well, it turns out the low reached 40F and the outside of my rig was covered in dew in the morning...
I started my imaging plan after astronomical darkness and finished well before astronomical twilight and here's what I noticed...
My first bunch of frames looked pretty good (at least to me) so I went to bed. I awoke just as the plan finished and the last image displayed appeared much darker and I couldn't see the galaxy (I was imaging M33... Again...). M33 was easily identifiable in my first bunch of subs but I couldn't make it out at all toward the end of the session... Could that be dew formation? My last post turned out to be dew related (at least I think so) but the effect was different... There were several bright stars in that image and they appeared to have halos around them... My view of M33 doesn't have any bright stars near by so maybe dew is darkening the images???
I have the first 5 and the last 5 of my light frames along with a master dark, master flat and master dark flat that I will link to via OneDrive just in case anyone want's to take a look...
https://1drv.ms/u/s!ArYaleH4xdi5gysgiPX ... s?e=DuHqJ4
Thanks!
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
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Re: The effects of dew?
Have you considered using dew heater straps to keep your optical surfaces free of dew? I use one heater strap around the outside of my refractor at the location of the objective lens. I use a second one on my guide scope at the location of the objective. I never have any problems with dew.
You can check with Orion to find out what they recommend for your telescope.
Just FYI.
Steve
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- Larry 1969
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Re: The effects of dew?
I'm looking into shields now. I'm not sure how I would heat my secondary mirror and I'd like to avoid the ridiculous cost of dew controllers.
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
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Eq6-R Pro controlled by APT via EQmod with an OTA mounted mini PC
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- bobharmony
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Re: The effects of dew?
Like you, I am not thrilled about the idea of dew heaters, nor have I figured out a way to protect the secondary, camera sensor, or
Bob
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Re: The effects of dew?
Yeah, dew is a real pia. Bob’ s fan is a really good idea. If you want to go cheap and are a do it yourselfer like me, I made a 8 watt and a 3 watt dew heater with nichrome wire and duct tape. I control it with a single $3 led controller I bought on Amazon. Been using it for over a year and cost under $20 for all (including the tape). Pre made versions aren’t very expensive either. If you are interested, let me know
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Re: The effects of dew?
Another type I'm trying is, again the hoops from JoAnn but this time a couple of wooden strips connecting the two hoops and then wrapping and gluing fabric inside the wooden framing strips and around the hoops.
Both shields are about 12" long.
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- Graeme1858
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Re: The effects of dew?
There's a gradient diagonally and some colour tweaking and sharpening wouldn't go amiss but I just had a quick go. What do you get from your final stack?
As far as dew goes and to quote Jim, it's a pia! I have a heated dew shield but you would never know! I have never felt any change in temperature but it does draw current so something is happening. Having said that, it does work to a degree because the problem is worse when I don't use it. I have a hair drier, so I pause the sequence and use that every 10 minutes on the
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- Larry 1969
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Re: The effects of dew?
That's interesting Bob.bobharmony wrote: ↑Fri Oct 16, 2020 1:32 pm Larry - the thing I notice on dewy nights is that the background gets brighter as the night goes on and dew builds up on the OTA.
Bob
I can't really explain what's going on here... Possibly a few different problems?
I've had several fairly successful sessions in the past with the same capture and processing techniques so I'd like to think it's not operator error...
I'm going to have another go at it this weekend. I'm making a make-shift dew shield right now so we'll see...
Thanks!
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
For imaging:
Orion 8" astrograph 800mm @ F3.9
Eq6-R Pro controlled by APT via EQmod with an OTA mounted mini PC
Tele Vue Paracorr Type 2 coma corrector
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- Larry 1969
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Re: The effects of dew?
Thanks Jim!Juno16 wrote: ↑Fri Oct 16, 2020 1:41 pm Sorry to hear of your woes Larry.
Yeah, dew is a real pia. Bob’ s fan is a really good idea. If you want to go cheap and are a do it yourselfer like me, I made a 8 watt and a 3 watt dew heater with nichrome wire and duct tape. I control it with a single $3 led controller I bought on Amazon. Been using it for over a year and cost under $20 for all (including the tape). Pre made versions aren’t very expensive either. If you are interested, let me know
I'm ok with do-it-yourself projects but have you used this solution on a newtonian scope? How do you heat the secondary?
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
For imaging:
Orion 8" astrograph 800mm @ F3.9
Eq6-R Pro controlled by APT via EQmod with an OTA mounted mini PC
Tele Vue Paracorr Type 2 coma corrector
Altair Hypercam 26C
- Larry 1969
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Re: The effects of dew?
That's far better than my attempts with that data! Did you incorporate my calibration frames?Graeme1858 wrote: ↑Fri Oct 16, 2020 4:54 pm It's so disheartening when things don't go right. But if your first five and last five are anything to go by, I would be quite happy with that!
Regards
Graeme
What software did you use? Mine were so poor I discarded them...
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
For imaging:
Orion 8" astrograph 800mm @ F3.9
Eq6-R Pro controlled by APT via EQmod with an OTA mounted mini PC
Tele Vue Paracorr Type 2 coma corrector
Altair Hypercam 26C
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Re: The effects of dew?
Current Equipment:
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- Larry 1969
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Re: The effects of dew?
I'm ok with spending a bit on the heater itself if necessary but there has to be a reasonable controller (even a DIY controller)...
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
For imaging:
Orion 8" astrograph 800mm @ F3.9
Eq6-R Pro controlled by APT via EQmod with an OTA mounted mini PC
Tele Vue Paracorr Type 2 coma corrector
Altair Hypercam 26C
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Re: The effects of dew?
Current Equipment:
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Scope: 130mm f7 APO
Cam: ASI071mc-pro
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Re: The effects of dew?
Larry 1969 wrote: ↑Fri Oct 16, 2020 5:24 pm Did you incorporate my calibration frames?
What software did you use?
Larry
All three calibration frames dropped into
Regards
Graeme
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- Larry 1969
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Re: The effects of dew?
Thanks. That's interesting. I couldn't get much out of it inGraeme1858 wrote: ↑Sat Oct 17, 2020 7:36 am
All three calibration frames dropped into DSS with the light frames and left to get on with it. Then Curves and levels stretched in Gimp.
Regards
Graeme
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
For imaging:
Orion 8" astrograph 800mm @ F3.9
Eq6-R Pro controlled by APT via EQmod with an OTA mounted mini PC
Tele Vue Paracorr Type 2 coma corrector
Altair Hypercam 26C
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Re: The effects of dew?
I am liking this... but the only electrical resistance heater wire I've found required buying a spool of 100 feet. Any idea where one might get a smaller amount.
Edit: I guess I hadn't really explore Amazon - but I went to electronic supply places. I wonder if something like this: https://www.amazon.com/Kanthal-A1-Gauge ... B07CHSG169 might work? I could make a snake like layout of wire on the secondary and use a temperature resistive glue to hold it in place.
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- Larry 1969
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Re: The effects of dew?
I've never dealt with dew before. Maybe because my old
I'm having some trouble understanding the purpose of the "controller"... Is it just a variable resistor used to adjust the temp of the heater?
If so, why not just run it on "high" all the time with no controller?
I like the resistance wire idea but how do you run it along the spider vane without it affecting your image? (diffraction spikes)
Larry
10" Skywatcher collapsible goto dob, various EP's and a Celestron StarSense auto align.
For imaging:
Orion 8" astrograph 800mm @ F3.9
Eq6-R Pro controlled by APT via EQmod with an OTA mounted mini PC
Tele Vue Paracorr Type 2 coma corrector
Altair Hypercam 26C
- Lady Fraktor
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Re: The effects of dew?
The controller is for power regulation and adjusts the temperature.Larry 1969 wrote: ↑Sun Oct 18, 2020 6:07 pm This is getting interesting.
I've never dealt with dew before. Maybe because my old dob was collapsible and I never used a shroud so I was open all the time? It was never an issue.
I'm having some trouble understanding the purpose of the "controller"... Is it just a variable resistor used to adjust the temp of the heater?
If so, why not just run it on "high" all the time with no controller?
I like the resistance wire idea but how do you run it along the spider vane without it affecting your image? (diffraction spikes)
Larry
You only want 1-2° above the dewpoint to keep the optics dry without causing heat waves or heating the glass to much.
UlteriorModem (Tom) had a tutorial on how to make your own dew heaters if you do not want to buy ready made ones.
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Re: The effects of dew?
AFA as the spider vanes is concerned: I intend to put a connector at the back of the mirror to the middle of the vanes. Then I can connect power to it only when needed. But thin electrical (insulated) wire well taped to the vanes should not really do too much to enhance the spikes.
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- UlteriorModem
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Re: The effects of dew?
LOL I tired to follow the link to that article I did on that 'other' forum and of course the forum is pretty much dead 'database error'. I guess Guss just holds the URL for the hell of it. Wish I had saved that article somewhere.Lady Fraktor wrote: ↑Sun Oct 18, 2020 7:41 pm UlteriorModem (Tom) had a tutorial on how to make your own dew heaters if you do not want to buy ready made ones.
Anyhow the original article is still available here. He even outlines how to make one for the diagonal.
https://www.dewbuster.com/heater-resistors.html
Also I just got a new diagonal holder with a built in dew heater from Protostar. He has a very elegant solution. Uses two of the vanes as conductors! No internal wiring visible! It does however require some 'special' attention to the mounting to insulate the vanes from the
https://www.fpi-protostar.com/s4vmnts.htm
Current Equipment:
Mount: Celestron CGX-L
Scope: 130mm f7 APO
Cam: ASI071mc-pro
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