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Drying off lenses?

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#1 57bel

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Posted 22 January 2020 - 02:05 AM

Hello,

I have been taking my telescope out for around 6 hours each night, in a relative cold environment and dew seems to accumulate on the mirrors before I can put it away. Is it true I should leave it uncovered to dry off the mirrors before I put it away? I have read online this is the proper thing to do, but a professor told me to just wipe them down (removing both mirrors and recrollminating about once a month). It is a celestron 130 eq newtonian. Any input is welcome I am mainly just looking for more opinions. My understanding is the less you touch the mirrors the better. I would also assume the same is true with eyepieces, so I keep them in my fanny pack in between uses and wipe those down with an eyeglass microfiber cloth. Any and all opinions welcomed,

-57bel



#2 greenstars3

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Posted 22 January 2020 - 02:52 AM

57bel "My understanding is the less you touch the mirrors the better. I would also assume the same is true with eyepieces," 

 

Yes!

 

Please do not wipe them down.

You should simply let them dry out in the house, if you wipe them off you may trash the mirrors and eyepieces with very fine scratches that will scatter light and seriously degrade the image you are trying to see. Cover the scope with a clean sheet while stored inside to keep the dust down while it dries. When dry and stored for a period of time I use a shower cap on both ends of my solid tube newtonian. you should only need to take out your mirrors to wash them. Check your collimation each time you set it up to get the best views you can, you will get better at it as you do it and it will not be the chore that it is in the beginning.

 

Robert

 

edit: the only thing that I touch my eyepieces with is a Q tip, and then lightly after wetting them with distilled water or if needed isopropyl alcohol to clean them

Just let them dry out and then put the caps back on  


Edited by greenstars3, 22 January 2020 - 02:59 AM.


#3 havasman

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Posted 22 January 2020 - 04:35 AM

Never "wipe down" a mirror! Your strategy is better. Best is to prevent dew via active dew control using dew strips and controller.

 

And better than your microfiber cloth for your eyepiece lenses are Kimwipes, a lab grade lint free paper product available cheap on-line or at office supply stores. Eyepiece coatings are more robust than mirrors or refractor lenses. They are best cleaned with isopropyl alcohol on a Kimwipe or untreated q-tip and finished with a breath and a Kimwipe. If you're only cleaning an eyepiece lens that has been fogged or dewed, a breath and a Kimwipe is all you need. Use a Kimwipe ONCE and toss it. That avoids the problem with those cloths. They're only clean once - the 1st time you use 'em.



#4 phillip

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Posted 22 January 2020 - 07:46 AM

In and out of doors is a delema on condensation of mirrors. Definely don't touch them! My best option todate is I keep it in my car trunk, temp ready as well for Observation! Amazingly it holds alignment rather well. 

 

I May buy back a former XT8 I sold as a  upcoming observor could use it. Had loads of condensation. Still performs but will eventually properly clean it, again never wipe the mirror!

 

XT10, XT8


Edited by phillip, 22 January 2020 - 07:47 AM.


#5 JoshUrban

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Posted 22 January 2020 - 09:09 AM

Oh yeah, just let 'em sit and warm up.  They'll LOOK really gunky after a while, but still, it'll take a while before that messes with the view.  When it comes time to clean the mirrors (which would be a LONG time), there's a whole process that involves gentle soaking, distilled water, alcohol, but no wiping.  At the end of the day, a dirty mirror is better than a scratched one (ruined one, that is), and it takes a lot of dirt to degrade the view.  (Never look at it with a flashlight - done that, and that's a good way to freak oneself out!)   



#6 Paul J

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Posted 22 January 2020 - 09:10 AM

Living in Scotland dew is a perennial issue, especially on the corrector of my EdgeHD.  From the outset, my approach to residual dewing and condensation when bringing the scope indoors was to leave the optical surfaces alone and allow moisture to evaporate.  I now augment this approach by applying the dust cover outside prior to bringing the scope indoors.  This approach avoids thermal shock to the optical surfaces and consequent sudden condensation, by trapping the ambient observing temperature between the dust cover and the optics.  The scope is then allowed to come to indoor ambient temperature.  I can’t remember exactly where I picked up this little pearl of wisdom, but I believe it may have been from the Astro-Physics web-site.

 

- Paul


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#7 tog

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Posted 22 January 2020 - 10:01 AM

"...but a professor told me to just wipe them down..." Sometimes profs have no idea what they are talking about. His school is probably footing the bill for his equipment. Listen to the advice from the folks here. 


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#8 happylimpet

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Posted 22 January 2020 - 10:04 AM

Your professor is an uninformed lunatic.



#9 phillip

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Posted 22 January 2020 - 11:58 AM

Sounds like the professor isn't a John Dobson, famed sidewalk Astronomer! You simply don't wipe down a mirror. They perform quite well with abit of dust. 

 

Plenty of information on the proper way to clean a telescope mirror. Take Heed! 


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#10 banjaxed

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Posted 22 January 2020 - 12:58 PM

As the mirror is usually the most expensive item in a telescope it pays to treat it properly IMO.


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#11 JOEinCO

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Posted 22 January 2020 - 03:22 PM

.....a professor told me to just wipe [the mirrors] down.....

Those who can, do. Those who can't, teach. lol.gif lol.gif 


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#12 JOEinCO

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Posted 22 January 2020 - 03:26 PM

.......And better than your microfiber cloth for your eyepiece lenses are Kimwipes.....Use a Kimwipe ONCE and toss it. That avoids the problem with those [microfiber] cloths. [Microfiber cloths are] only clean once - the 1st time you use 'em.

Yep. Havasman is dead-right. The popularity of microfiber cloths amazes me.

 

"Let take a piece of fabric and wipe our optics with the same thing over and over and over....shocked.gif confused1.gif 


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#13 charlesgeiger

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Posted 28 January 2020 - 06:37 PM

After many years at this hobby, I would agree with a couple things mentioned above.  I would also add something.

With any type of telescope with a corrector or lens in front, you need a dew shield.  If you can afford a dew controller and heater get one.  As one person above said, If your scope is outside, cold, and not dewed up, cap the end (lens/corrector) end.  If there is a lot of dew on the tube, gently wipe it down before bringing in.  Leave scope out of box, capped, and then check the lens after it has been indoors for at least an hour.  (Or you can leave it to the next morning). Take the cap off and if you have any dew, use a hair dryer to evaporate it.  Do not put the hair dryer on high or direct the heat directly (like an inch) from the lens.  You will see any dew evaporate.  Then recap and call it good.  Do not put any type of cloth on the surface of a lens/corrector/mirror. 

Eyepieces: When outside, see if they are fogged up, if not cap them and put them into your eyepiece case.  You can use the same method as above after they have been in the house for awhile.  Remove the caps, if you see any dew, use the hair dryer to evaporate.  Again, do not use anything (like a hanky or rag on the surface.  If you see eyelash oil on the lenses, wait until you have time and then use a small bit of alcohol to clean.  Do not use acetone as it will destroy and plastic.  Kimwipes to use gently (dab) on the surface with alcohol...do not allow any liquid to wick under surface of eye lens...going deeper, use reagent grade isopropyl alcohol (92+ percent you can get at a pharmacy) as the others leave streaks.  Again, keeping dew off by evaporating is the best way and the air from the hair dryer will blow away dust/lint.  

If you need to fully clean the optics, which should be no more than once per year, you can find several recommendations on how to do it and what to use...

Charlie




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