film on optics

[Shiraz]

Hi

have been trying to chase down an annoying feature of my Newtonian optics - they generate a significant amount of close scatter around bright stars.

1. removed the spiders web from the baffles in the OTA and washed the mirrors. Didn't really help.
2 repainted the interior of the OTA with chalkboard paint. Slight improvement.
3. closer inspection of the mirrors - maybe the surface is giving way. Not too bad, but could see a slight filminess using an off angle bright torch - ahaaah. tried washing with detergent, windex, alcohol, acetone - still there, nothing touched it. In desperation, tried some wax and grease remover from the local hardware - this is light petroleum distillate and it removed the film after a few applications. wash with distilled water and the mirrors looked nice. However, there was still a lot of scatter.
4. this morning, removed the coma corrector - sure enough that had a light film as well, which was gingerly attacked with the wax and grease remover(hoping none of it would wick inside the CC). all went OK and now that looks clean as well.

Don't know what the film was, but suspect that it has something to do with the wood fires that all of the near neighbours use - could be some form of vapourised gum I guess. This is a seaside, rural and mining town, so it could also have come from other sources I guess. anyone got any ideas? Anyway, now have to test it out when the clouds clear and see how much improvement there is - hoping.

thanks for reading. regards Ray

[Atmos]

It's an interesting issue that you've dealt with, something that affects most out in rural territory with more people using wood fire heating than in the city.

[glend]

Ray was it on both Newts? I get airborne gum sap this time of year, from the bush reserve behind my place. Normally Bintel UHC cleaning fluid, or acetone takes it off. I assume you checked the secondary mirror as well. Do you keep the scopes capped when not in use?

[Wavytone]

Ray,

Certainly hazy films on the optics don't help. But... how old is the scope ? It may be simply that your primary needs recoating.. the coatings don't last forever and scattered light is one of the consequences of a mirror in need of a refresh.

[Shiraz]

well I hope it is dealt with Colin :thumbsup:. Obviously, nobody has been using their fires lately, but the performance of the scope has been a bit suss for a while now, so it could have been stuff carried in smoke last winter. Out this way, most people have wood fires for heating - not ideal health wise, but real cheap when they can get free wood.


haven't looked at the other scope Glen, but it spends almost all of it's time indoors these days - worth a look though. Both mirrors needed cleaning and I was surprised that acetone did not work - maybe I didn't leave it on for long enough. The scope is capped when not in use, but it's open to the elements on most nights when the sky is clear - astro imaging gear leads a hard life.

[Shiraz]

thanks, that is the next step if the cleaning does not do the job.

the mirrors are 3 years old. There are a few minor imperfections, but overall, the coatings look pretty sound. However, we regularly get winds blowing in off the sea, so salt corrosion is always a possibility, as the bolts on the EQ8 attest.

[Wavytone]

In which case I'd suspect that most of the hazy film you found on the optics was from salt spray. And yes it will attack a mirror coatings quickly, from personal experience.

If you can take the mirror out of the scope and put it in a sealed box when not in use, do that.

An alternative is to make 2 hole in the OTA large enough to get your hands in there and put a shower cap over the mirror.

Lastly, when storing the scope don't leave it standing vertical with the mirror facing up - this is the worst thing you could do. Either on its side - so airborne crud cant settle on the mirror, or better, vertical with the mirror at the top facing down. I used to have a pair of octopus straps in my storage cage for securing an OTA like this so it won't fall over.

As for the secondary - put a sock over it - literally :)

[strongmanmike]

Ray's Telescope and Optical Cleaning Services :thumbsup:

Luckily (touch wood) I haven't had any cleanliness issue since washing the primary mirror before mounting the scope in the new observatory way back in August 2014 :eyepop:...haven't adjusted the polar alignment or colimation either since then..still spot on after using the NJP Polar scope and a rock solid pier (http://www.pbase.com/strongmanmike2002/image/156695968/original) :D :2thumbs:

Look forward to some even better Rayzor sharp images from you :)

Mike

[brian nordstrom]

:question:if it took a petroleum product to remove it I would think its ' Out - Gassing ' from the origonal paint inside the tube , its a common problem with some scopes/optics .

Glad you had luck getting it off , its scary putting harsh cleaners/solvents on optics .

Brian.

[RickS]

Could be bad seeing condensing on the glass, Ray :lol: It's got to go somewhere :P

[Shiraz]

thanks for the advice. the scope is in an ROR observatory and it is parked pointing at the SCP, so the mirrors are protected from anything settling out of the air. No way to protect on clear nights though - it spends all of the night pointing upwards with no protection at all - regularly have to remove straw/lawn clippings that blow in and found some bird/bat/insect? dropping of some sort one morning. I cannot store the OTA upside down - in this scope, the mirror will fall out against the stops and the coating will take the weight.

My wife told me to put a sock in it recently, but maybe that was nothing to do with the telescope..


thanks for the encouragement Mike. Must be nice to have such a well sorted gear. My biggest problem around here is to keep everything reasonably clean - it is amazing how much barley dust can get airborne during harvest...


that's a good point Brian. There was originally some gooey stuff in the mirror stop threads that I cleaned out with solvent. maybe there is still a bit in there. agreed, it is not a good feeling to be messing with the mirror surfaces. Found a website on some pro-level (ie expensive) paint-on solvent/polymer that peels off and takes dirt with it, but it doesn't seem to be available anywhere local. Might try to import some. EDIT: no I won't - enough for a single clean of an 8 inch mirror costs US$122 - won't cost much more for a high reflectivity recoat.


naaah, pretty sure the seeing is still all up there.:thumbsup: Could it be condensed moonlight or PE residue I wonder??

[strongmanmike]

Yeah!!??? Well then, collect it all and make beer mate!! :eyepop: :lol: :drink:

Mike

[Shiraz]

gluten intolerance - can't drink the stuff :sadeyes: :violin: payback for drinking too much of it in the past??

[Shiraz]

:2thumbs: heeey, success. mirror cleaning etc did the job. the furry balls surrounding the cores of bright stars have pretty much gone - all that is left now is the diffraction from the mirror clips (next job). image shows before and after with stacks of 10 subs from both - under similar sky conditions and with similar linear remapping to show dim bits. I think that the improvement is consistent with the very light film of gunk being the issue - have to keep an eye on optics hygiene from now on, but at least it looks like the coatings are still fine.

thanks for the advice encouragement - and particular thanks Ken for your generous offer.
regards Ray

[Atmos]

Congrats on fixing your issue :)

[Merlin66]

Good news, mate!
All's well that end's well.

[Shiraz]

thanks Folks - has been a pretty good result