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Celestron 925 - Don't leave outside. . .

TerryW

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TerryW

TerryW

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Hi,

I was leaving my Celestron 9.25 XLT outside overnight due to sheer laziness. It developed moisture inside that I removed by genrly warming the OTA with a fan heater and attaching a computer fan to draw out the warmed and moist air.

I wasn't sure when the moisture inside had developed so by way of experiment I attached the OTA to my mount and left it under its telescope cover over night last night (1 night only).

To my horror it now has trickles of water on the inside of the objective lens and is full of moisture again. It even has trickles down the inside of the tube.

I am writing this to warn anyone planning to leave a Celestron 925 outside overnight about the consequences. My scope is now going through the drying process again. It will survive. . . .

Terry.

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TerryW

TerryW

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All that moisture... I'd be worried about developing fungus.

I'll be watching out for that. I can get the inside bone dry which should (I hope) prevent any fungus growth and it won't be going out again. If Jupiter starts to get a green tinge I'll know that fungus is growing:D

I emailed Martin at FLO to see if he has instructions for taking the objective lens off. It can't be difficult. Plus the sealing is awful as can be seen in the photo.

post-15622-1338777062_thumb.jpg

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TerryW

TerryW

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Should you get that much moisture in the first place? After all you could be out observing all night. Wondering if their is a fault somewhere.

andrew

Interesting question that. . . The objective seal is ill fitting. It overlaps that leaving a gap between the sealing ring and glass. I'll see what the manufacturer says.

Thanks for that.

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ScubaMike

ScubaMike

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probably a dumb question....

but did you have the sealing stopper in the eyepiece end when you left it out?

I can't see how so much moist air would get inside the tube.

It's obviously more than just the air already in there, so there must be some airflow from somewhere.

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TerryW

TerryW

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I had my graticule eyepiece in the diagonal. My suspicion (and it is only that) is that the objective lens' sealing ring has been fitted poorly. It overlaps in one place which means that the fixing ring has a gap. See photo around the area with the text "9 1/4 (235mm)" near the bottom.

The cover is from Green Witch and very substancial. When I have been observing lately (about 9pm to 11pm) it has been very wet indeed. My chair, table and laptop have been literally dripping wet.

PS I always dry the front-cover off before it goes back on.

Terry

post-15622-133877706219_thumb.jpg

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Astronut

Astronut

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Mine's been like that since day 1 and it's never been left outside (excepting starpartys). It had a moisture/grease stain on the inside of the corrector plate when I first got it.

Not sure if I should mention this here but it's been back to David Hinds via FLO twice now for cleaning and the stain is still visible. They had the cheek to charge FLO the second time even though it was still under guarantee saying it was my fault!

Needless to say I'm very reluctant to store it in an outside shed, although this would save alot of time setting up.

I haven't really got the time to take it apart myself and from what I've read it's a tricky and time consuming procedure. I'd like to have a go sometime next year when the guarantee expires as I'd like to flock the inside of the tube.

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TerryW

TerryW

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Gee, don't theifs round your way like £1200 nickable pieces of kit then? Respcecfully, what are you thinking leaving such a valuable object outisde like that? !! :icon_salut:

It is the dog and shotgun that discourages the thieves. . . .

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TerryW

TerryW

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Mine's been like that since day 1 and it's never been left outside (excepting starpartys). It had a moisture/grease stain on the inside of the corrector plate when I first got it.

Not sure if I should mention this here but it's been back to David Hinds via FLO twice now for cleaning and the stain is still visible. They had the cheek to charge FLO the second time even though it was still under guarantee saying it was my fault!

Needless to say I'm very reluctant to store it in an outside shed, although this would save alot of time setting up.

I haven't really got the time to take it apart myself and from what I've read it's a tricky and time consuming procedure. I'd like to have a go sometime next year when the guarantee expires as I'd like to flock the inside of the tube.

Martin's strong advice is to leave well alone and that the overall performance won't be affected. I trust his judgement but I am one of those flaming retentive soles that just gets "nagged" by imperfections. I'll do my best to leave it alone but know I'll eventually cave-in and clean it.

Thanks for the "heads-up". I have accepted that the mess is my fault so it will be up to me to fix it. How hard can it be? or are those the famous last words.

I did make a real stupid mistake of taking my Meade eyepiece apart for cleaning. I jumbled up the internal lens and found that even Meade don't keep a diagram of how they are arranged. I eventually bought a book on eyepiece design and followed the 5 piece drawing and I was home and dry.

Terry

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Ags

Ags

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If you do take it apart, note the orientation of the corrector plate v the mirror - I believe they are oriented to minimize wavefront errors, so it would not be good to put the corrector plate back rotated by 90 degrees, for example.

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TerryW

TerryW

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If you do take it apart, note the orientation of the corrector plate v the mirror - I believe they are oriented to minimize wavefront errors, so it would not be good to put the corrector plate back rotated by 90 degrees, for example.

I am expecting there to be a need to mark up so that everything goes back with the original orientation. I saw a procedure for doing this job somewhere but I can't find it again. It did mention orientation. I'll keep searching.

Terry

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TerryW

TerryW

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I couldn't stand the strain of leaving the inside tainted by water marks so I watched the video below . . .

Spurred on by how easy it looked I waded in. The job was more stressful than difficult. Taking the retaining ring off was a little worrying as you have to squeeze it past the lugs for the large cap.

Once the ring was off and the corrector lens taped up with two marker tapes (duly cut to allow lens removal) the corrector plate just lifted off. Then I was free to clean up the mirror and inside of the corrector. Re-Assembly was a doddle.

The mirror was smeared quite badly and is now glistening with cleaniness as is the inside of the corrector. I look forward to trying her out on the next clear night.

Terry

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brantuk

brantuk

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I allways bring my 925 indoors after a session - but I have left it outside under one of those Greenwich covers at star parties up to ten nights in a row without a problem. Dessicant is a good idea - I also ensure there's plenty of airflow by not wrapping the cover too tight. :icon_salut:

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TerryW

TerryW

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I allways bring my 925 indoors after a session - but I have left it outside under one of those Greenwich covers at star parties up to ten nights in a row without a problem. Dessicant is a good idea - I also ensure there's plenty of airflow by not wrapping the cover too tight. :icon_salut:

Well mine has spent some time out of doors but it was really bad when I looked at it after a single night. Same "green witch" cover. The OTA was pointing up (parked) but the OTA cover was on and an old eyepiece left in. If you look at the attachment on the earlier email you can see the extent of the water. . . .

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x6gas

x6gas

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This doesn't sound right to me...

I've left my scope out imaging and gone to bed even on very humid nights and even though the outside was litterally dripping there was no moisture inside the OTA. Mine is an Edge and so not open at the EP end, but does that make such a difference if the scope was stored pointing up? Hmmmm.

So is everything OK now?

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TerryW

TerryW

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This doesn't sound right to me...

I've left my scope out imaging and gone to bed even on very humid nights and even though the outside was litterally dripping there was no moisture inside the OTA. Mine is an Edge and so not open at the EP end, but does that make such a difference if the scope was stored pointing up? Hmmmm.

So is everything OK now?

Everything is working OK. I just need to check collimation when I can get access to the sky (a bright defocussed star).

Thanks for asking. I'll post when I have checked the collimation.

Terry

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