Dew marks on primary mirror on skywatcher 130pds

[jason32]

Hi guys,

it was clear the other night and I was trying to capture bodes nebula and the scope and camera was set and I left it out for 2 hrs for imaging but when I went out to check... Everything was wet with dew. now the primary has dew marks and can't shoot anymore in this condition. Can I take the mirror out and clean it? Is there any guide on how to do it? 

Thanks

[spaceman_spiff]

Do you have an image of the mirror?

If the dew marks are obvious then I don't think its a big problem. You can remove the mirror and run distilled water over it to dissolve the dew marks. Tilt the mirror to one side and dab off the droplets of water with a paper towel as they run to the edge of the mirror. Do not touch the mirror with the paper towel.

However, some marks on the mirror are not likely to affect its performance noticeably. 

HTH 

 

[Alkaid]

How bad are they, got a pic?

 

[Astrobits]

I would suggest that before you remove the mirror for cleaning you take a pic of an area that you recently shot and compare the result ( allowing for other variable interference such as the Moon ). You could paste the two shots here to get other's comments. If it really is as bad as you seem to think then go ahead and clean the mirror.

Nigel

[brantuk]

You're gonna do it any way Jason, despite advice here - I did - and so does everyone I ever met lol. So "just in case" you do - I followed this advice for cleaning telescope mirrors:

 

[simmo39]

I find that not looking at the mirror works for me. As long as the images look ok leave it. My 12" dob has some marks on the primary, cant tell when looking through eyepiece.

[jason32]

Here is a photo of the mirror...I think its not gathering the same amount of light as before.

 

[jason32]

4 hours ago, Alkaid said:

How bad are they, got a pic?

 

Uploaded a pic please check

[Alkaid]

Looks like dust rather than dew marks?? Hard to tell...I would remove the mirror cell and use a bulb blower (apply from the side). Don't touch the mirror, no matter how tempted. See how it looks then...

 

Generally speaking, dew spots do not effect light reflection off a mirror, or refraction through a lens. I have an older refractor which would give anyone some concern but its performance is unchanged...there is no telescope that will pass the "flashlight test" I am afraid...