Mould Inside Objective Lens Cell?

[Ian McCallum]

Last night, after bringing my Sky-Watcher Startravel 120 achromatic refractor back inside, I noticed some marks on the inside of the objective lens.  I keep my telescopes inside the house, at room temperature. 

The telescope had been outside for a few hours in just below zero temperatures, so I always allow the telescope to 'breath' before putting on the lens caps. This usually takes a few hours.

Is this mould starting to grow on the inside of the telescope? Have I done anything wrong? 🤔. Is it enough of a problem that it could impede any visual observering or imaging? 🤔

The scope is only a few months ago and was bought brand new from Auntie @FLO. 

[Ratlet]

Might it be ice?

I guess it could be but from the lenses I've seen with mold, it tends to be round-ish.  Those look perfectly circular.  I'd leave it till the morning and check again once it has had a good warm up.

My understanding is that the mold on glass takes a long time to grow or really really bad storage.  I can see that the way you've used it could amke it bloom.

[Ian McCallum]

9 hours ago, Ratlet said:

Might it be ice?

I guess it could be but from the lenses I've seen with mold, it tends to be round-ish.  Those look perfectly circular.  I'd leave it till the morning and check again once it has had a good warm up.

My understanding is that the mold on glass takes a long time to grow or really really bad storage.  I can see that the way you've used it could amke it bloom.

I think these are drip of condensation that have dried out. I've been told that leaving the telescope lens covers off to 'breath' when it comes back into the warm house, isn't necessarily the best way. 🙄

[Moonlit Knight]

Dew spots, worry not 

[Moonlit Knight]

3 minutes ago, Ian McCallum said:

I've been told that leaving the telescope lens covers off to 'breath' when it comes back into the warm house, isn't necessarily the best way. 🙄

Personally I take the lens cap off and leave the tube open over night. I leave my eyepiece case open along with my mount case to until the morning. On very occasions objectives collect few and even ice at the zenith. Not sure how many of use would leave that capped and locked away inside a bag or case.

 I do understand the rationale, just not sure how one gets the temperature down slowly and steadily enough to prevent condensation forming with the cap on without turning the objective into a really expensive petri dish

[Ian McCallum]

2 hours ago, Moonlit Knight said:

Personally I take the lens cap off and leave the tube open over night. I leave my eyepiece case open along with my mount case to until the morning. On very occasions objectives collect few and even ice at the zenith. Not sure how many of use would leave that capped and locked away inside a bag or case.

 I do understand the rationale, just not sure how one gets the temperature down slowly and steadily enough to prevent condensation forming with the cap on without turning the objective into a really expensive petri dish

I do exactly the same, leaving both the lens cap and eyepiece cap off, so that any moisture or condensation can evaporate naturally. I leave the scope like this for a few hours (or longer in colder weather). It's always left horizontal whilst this happens or perhaps with the objective lens raised above the level of the focus tube. 

I've got a second hand SW Evostar 120 achromat that I've been using for over a year now and haven't seen anything like that on it. 

[Alkaid]

Definitely dew spots.  Found on most refractors, they will not impede the views.

I have found that bringing a cold  / dewy scope back into a warm habitable room will instantly result in severe moisture problems.   I now bring my scope to a 'halfway house' - I previously used a cold cellar, and after moving home we have an unheated porch which is just as good.  Then when scope has acclimatised to that, I will eventually bring it back into a warm room, caps off.

I once brought a new refractor straight in to a warm family room (after about 3hrs of sub-zero use) and left the caps on.  Next day I found a HORRRENDOUS amount of dried dew spots, in the end I had to gently clean them off using baader wonder fluid. (Not a decision taken lightly either, I refuse to touch lenses unless absolutely necessary).

[Moonlit Knight]

I just cleaned mine, every couple of years is quite enough for me

[Moonlit Knight]

I also throughly dry the outside of the scope with a clean towel (obviously no where near any glass) 

[Moonlit Knight]

I would be very interested hear what others think…

[Which one is Polaris]

8 hours ago, Moonlit Knight said:

I would be very interested hear what others think…

I can't image at home.  I drive out, setup and take apart every night. 

Setting up I take the flattener cap off and put my Nikon Z6ii camera onto the scope as soon as it is safely on the mount.  That is quick, extension tubes still cool, and no condensation forms on the sensor.

I put my objective dew heater on the scope and turn it on, then take the big cap off.  No condensation forms on the lens.

 

At the end of the night I check the objective and put the cap on before I take the heater off.  The cap is a snug fit with felt.  I leave the camera on, taking Darks.  Drive home.

I bring the scope + camera  into the house and put it in the spare bedroom as it is, turn the camera off.  Some condensation forms on the outside, wipe it off after 30 mins.

Next day I take the objective cap and camera off, check no condensation (never is) and leave the caps off for a day or two.

I take the card out of the camera, transfer the Lights, save the first 10 - 15 Darks.

 

I did try taking the objective cap and camera off the scope as soon as I got home and had bad condensation on the objective and camera sensor immediately.  That took a very good cleaning to get them both clear again.  Sensor in particular.  Lesson learned.

 

I am happy to hear of any improvements possible in my workflow.

[Moonlit Knight]

30 minutes ago, Which one is Polaris said:

I am happy to hear of any improvements possible in my workflow.

Me too, to be honest. I was considering posting it as a new topic to look for some kind of consensus, if that was possible. 
 

It would also be interesting to see how people manage other scopes other than refractors. I have owned a couple of dobs, but that over 10 years ago now and I honestly can’t remember what I used to do. 

[Moonlit Knight]

I found this in Sky and Telescope

The most destructive dewing happens when a telescope is in storage. No telescope should be closed up and put away until it is thoroughly dry. Water that has nowhere to escape may attack optical coatings and ultimately etch the glass itself. So may condensation that forms and evaporates repeatedly in a sealed environment over long periods of time.

 

How, you may ask, does water get into an airtight space that was dry when you sealed it? The answer is it was there all along. Air contains water vapor, and if your telescope gets colder than what the dew point was when the air was sealed in, water will condense. This is why so many puzzled telescope owners discover water stains on the inside surfaces of their corrector plates and refractor lenses.

 

Several approaches can prevent this. Don't move a sealed telescope from warm to cold storage. In fact, sealing may be a bad idea altogether. The best telescope covering is cloth, which can "breathe." It keeps dust off while letting water vapor out. And you might want to leave the eyepiece holder covered only with cloth — just enough to keep dust and spiders out.

[Ian McCallum]

I contacted  Auntie@FLO and @Chris emailed back.  He kindly went through what he thought it was, based on years of AP, it boils down to dried in dew spots. so no mould, thankfully.  I'm not sure if removing the whole lens cell from the front of the OTA. to clean the flint glass surface would invalidate the warranty?  I'll not do anything till I know for sure...

[Which one is Polaris]

Well that is good news !!  No mould.

I am not proficient enough to contemplate removing the lens cell.  I don't know about the Warranty, but I would be worried that I would cock up the alignment and quickly spiral into problems I couldn't fix.  I do have a few specks of dust on the inside of the objective but by all accounts it is immaterial so I will ignore them.

[Shed9]

I think I responded to your question on a FB page somewhere Ian. Definitely not mould, it would take far, far longer to develop and looks branch like in appearance. Mould is rarely symmetrical as its organic and besides, even when caught early mould is not that serious either. It's only when mould is left on optics for long periods of time that  it can attack coatings. UV light (even leaving out in the sun), ammonia and hydrogen peroxide will tackle optical fungus, I used to do it all the time with camera lenses. Get a desiccant cap for the focuser and, as advised by others already, keep the transition between temperatures in check.

[Moonlit Knight]

2 hours ago, Shed9 said:

I think I responded to your question on a FB page somewhere Ian. Definitely not mould, it would take far, far longer to develop and looks branch like in appearance. Mould is rarely symmetrical as its organic and besides, even when caught early mould is not that serious either. It's only when mould is left on optics for long periods of time that  it can attack coatings. UV light (even leaving out in the sun), ammonia and hydrogen peroxide will tackle optical fungus, I used to do it all the time with camera lenses. Get a desiccant cap for the focuser and, as advised by others already, keep the transition between temperatures in check.

True

Also an excellent reason to get into white light solar