New Member - Question on Winter Observing

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LukeMule97
Posts: 10
Joined: Sun Feb 14, 2021 3:12 pm

New Member - Question on Winter Observing

Post by LukeMule97 »

Hi All, hope everyone is having a great day! New to MAS and wondering if I might be able to ask if there is anyone who could help me out with understanding which equipment I would need to observe outside in the Minnesota winter cold. My family and I have a Celestron Newtonian 8" reflector and are all very much newbies to the telescope and astronomy world. We've been able to see a few things through our window but are hoping to get the scope outside and really learn how to use it. We've heard a dew shield or a lens warmer will be something to use for winter observing but we aren't sure where to start in terms of looking for one to buy or if there is a specific kind we need to be looking for. Would anyone know what we might want to look into in for winter observing equipment/gear? Thank you very much for taking the time!

Luke
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SEmert
Posts: 1794
Joined: Mon May 31, 2004 2:48 pm
Real Name: Steve Emert
Location: White Bear Lake, MN

Re: New Member - Question on Winter Observing

Post by SEmert »

Hi Luke, and welcome to the MAS!

Well, right now it's pretty brutal so personal protection is even more important than keeping the scope defrosted. In addition to multiple layers, stock up on some of those disposable hand warmers to put in the toes of your boots and in your mittens.

For the scope, if it's on a computerized mount, be sure to have a good battery to drive it, as battery power wanes with lower temps.

Since yours is a Newtonian, you're in a bit of luck that your primary mirror is pretty well protected down at the bottom of the OTA. The secondary may get some dew or frost, but since it's facing down toward the primary instead of up to the sky it should work for some time before frosting up. I've installed a dew heater wire on the back of mine, but that's because mine is a more open truss Dob and also I'm a bit paranoid about it.

Your biggest dew and frost problems will be on the finder and the eyepieces. You can keep it simple and do periodic de-dewing by using a hair dryer, although that isn't very convenient as you are continually stopping to de-dew or defrost the surfaces. If you're near an AC outlet and have a long enough extension cord you can use a regular hair dryer. If you're out in the field and only have battery power, you can get a little 12V dryer normally intended for camping. Scope Stuff used to have them, but they appear to be gone now. Amazon has them. https://www.amazon.com/Portable-Car-Sty ... 753&sr=8-8
Be aware, those little 12V hair dryers aren't all that great, though.

For something a little more practical, there are resistive dew heaters that can be installed on your scope. They attach around the finder and around the eyepieces using Velcro. Again, Scopestuff has them, as well as the larger retailers like Orion, OPT and Astronomics. http://www.scopestuff.com/ss_dnot.htm Caution, the commercial dew heaters are fairly high wattage and need dew heater controllers to make the heat adjustable. You only need the eyepiece or finder to be warmed a few degrees to keep the dew and frost off optical surfaces.

If you are handy with electronic components, you can make your own dew heaters using resistor ladders. This site has instructions. https://www.dewbuster.com/heater-resistors.html

Barring all the electrical stuff, you can also use the chemical hand warmers to keep finders and eyepieces dew free. Just use a rubber band to lash one to the side of the eyepiece or finder. And keep the eyepieces you are not currently using warm in your pocket.

Oh, and if the mount and OTA gets all dewed or frosted up, don't fret. Just bring it inside after your observing session and wipe it down a little and let it dry naturally from there. It'll be fine. In the summer when my stuff gets all wet from dew, I just spread it out on the driveway in the sun the next morning and let it dry. Of course, do your best to dry off optical surfaces right away. Don't trap dew on lenses by putting the dust covers on and leaving them!

Hope that provides a good starting point.
Steve Emert
MAS Membership Coordinator
12.5" f/4.7 Obsession Clone Homemade Truss Dob, sometimes equipped with Celestron StarSense Explorer app
Celestron C8 SCT OTA on AVX GEQ mount
Astro-Tech AT72 ED Refractor OTA usually on Explore Scientific Twilight 1mount or tripod with Benro geared head
Celestron 5" SCT OTA on Synta AZ-4 or Explore Scientific Twilight 1 Alt-Az Mount, usually equipped with StarSense Explorer app
Orion 150mm Mak OTA and Orion EQ-G computerized mount
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SEmert
Posts: 1794
Joined: Mon May 31, 2004 2:48 pm
Real Name: Steve Emert
Location: White Bear Lake, MN

Re: New Member - Question on Winter Observing

Post by SEmert »

For more ideas and resources, pull down the BSIG meeting presentation I posted last February on telescopes and accessories.
viewtopic.php?f=5&t=11473
Also, look through the web links we have in the BSIG forums for more ideas and free/low cost resources available on the web:
viewtopic.php?f=5&t=4726

Also, what type of finder do you have on your 8" Celestron Newtonian? If just the stock 6x30 optical finder, I suggest augmenting it with either a Telrad finder or a Rigel QuikFinder or even a red dot finder (sometimes also called a "Mars finder" - since it projects a red spot). https://www.telescope.com/Orion/Orion-E ... p/7228.uts or http://www.scopestuff.com/ss_rdp1.htm

These "zero power" finders often make it much easier to find Solar system and brighter deep sky objects than the "soda straw" view through the small stock finder scope.
Steve Emert
MAS Membership Coordinator
12.5" f/4.7 Obsession Clone Homemade Truss Dob, sometimes equipped with Celestron StarSense Explorer app
Celestron C8 SCT OTA on AVX GEQ mount
Astro-Tech AT72 ED Refractor OTA usually on Explore Scientific Twilight 1mount or tripod with Benro geared head
Celestron 5" SCT OTA on Synta AZ-4 or Explore Scientific Twilight 1 Alt-Az Mount, usually equipped with StarSense Explorer app
Orion 150mm Mak OTA and Orion EQ-G computerized mount
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Dale Smith
Posts: 433
Joined: Sat Dec 23, 2006 1:11 pm
Location: Plymouth, MN

Re: New Member - Question on Winter Observing

Post by Dale Smith »

You might also click on Quick Links in the upper left of the forum screen and do a search of past posts using terms like dew, heater, etc.

I found putting a shower cap over the base of my Dob helps delay fogging of the primary mirror by preventing ground level air from getting through the gap between mirror and tube.

One technique I have used a few times on really cold nights is to grab my biggest pots and kettles about an hour before I am going to leave, boil several gallons of water, pour it into plastic milk jugs and put them into a portable cooler (the type you would fill with ice and six-packs for a picnic in the summer). The insulation of the cooler will keep the water warm until the following morning. Great place to stick your hands for a quick warm up. I once accidently exhaled on an eyepiece on an extremely cold night. It instantly frosted over and was too cold for the frost to melt and evaporate. A minute in the cooler evaporated the frost.

If you make your own dew heater be sure to test it prior to going into the field. A guy I knew in Virginia built a home brew heater for his Dob tube. A little while into his next observing session he smelled smoke and found that the inside of his scope was on fire.
LukeMule97
Posts: 10
Joined: Sun Feb 14, 2021 3:12 pm

Re: New Member - Question on Winter Observing

Post by LukeMule97 »

Hi Steve and Dale,

Thank you both so much for taking the time to read and help me with this post/question! This is great to hear and will take a peek at the forum links you've mentioned for some good options to keep those eye pieces and secondary mirror warm. I'm very excited to get it outside and start learning, thanks so much again!
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