Scope Acclimatising Issues

[Dragons Egg]

According to 'Scope Doctor' (aka Steve Richards) in February's edition of the Sky at Night magazine, he strongly advises upon returning home after an evening's observation to allow the telescope to re-acclimatise to indoor conditions by keeping all its lens caps off, so enabling any condensation on the mirrors and lenses to evaporate at nature's own pace. This is the procedure I follow myself. Now, however, having recently purchased a TeleVue NP101is refractor, it seems that this advice is no longer appropriate, at least according to the manual that came with the scope. Thus I quote: 'To prevent dew formation when bringing the scope in from the cold, we advise to close the cold scope in its case before bringing it into the warm indoors. Do not open the case until the scope has come up to room temperature.' Is there something especially distinctive about the lenses of TV refractors that requires this opt-out, or am I missing something? (which is more than possible, of course). Incidentally, the advice forwarded in the manual fails to mention whether this procedure includes affixing the lens caps back on to the scope, or not as the case might be. . . which may or may not be important. Hmm. 

Very puzzled. 

Edited March 23, 2020 by GrahamKnott

[mikeDnight]

Hi Graham,

I always take a look at my lens by shining a red torch at it. If its clear of dew, I cap it and bring it into the house. It will stay clear providing I don't uncap it while its still cold.  If however it does have signs of dew on the lens, I'll bring it back into the house uncapped and allow the moisture to evaporate over night. I never wipe dew off as it will disappear by itself over time. It's really important never to cap a dewed lens, or you'll encourage fungal growth. So cap it if its dry and leave it uncapped if its dewed, once the dew has gone you can cap the scope and rest easy. 

Never leave a telescope tube that has ice or moisture on it in its carry case. Once back in the house, always leave it uncased until the tube is dry. If you uncap a cold but clear lens when youve just brought it back into a warm room, it will immediately fog over, and youll need to leave it uncapped until the moisture evaporates. I cant remember my NP101 ever fogging over, but i was always careful to check the lens before i capped it.

You've got a great scope by the way!

 

Edited March 23, 2020 by mikeDnight

[Dragons Egg]

Hi mikeDnight - many thanks for your detailed advice. I'll pay heed to it from now on. Unfortunately, it's come a bit too late for me. To keep it brief, I forgot to uncap the scope one night, and found to my dismay the next morning that the objective lens was covered what looked like dried up condensation marks. I then (very gently) removed these marks, using Baader Wonderfluid and some lint-free Kimwipes, plus a virgin Baader Wondercloth. Having dealt with that issue, I'm now left with a series of faint but seemingly permanent smears across the front of the lens. I could live with that but for the fact that the scope's image quality has now deteriorated markedly. It's become impossible to keep all the stars in a given field of view uniformly focused. Also when I run my viewing eye back and forth across the eyepiece lens, the stars glint and sparkle, and momentarily blur and become unfocused. Quite frankly I'm too alarmed to try and remedy the situation any further. Instead, it now seems that I'll have to get the scope professionally cleaned. . . though in view of the present coronavirus shutdown, it looks as if I'm in for a long wait.    

PS. I've tested the EPs on another scope, and they check out fine.