A white layer

lsy_98 · Post by **lsy_98** » Thu Mar 18, 2004 2:53 pm

Hi,
Is there anyone knows the problems when the scope gives a white layer on an image? It is like when we set the TV colour mode to low contrast. This problem happens to my scope when I magnified the image to about X180 using my 10mm eyepiece. However, it is clear at the low magnification. I have posted a picture which taken from my WebCam (http://www.singastro.org/album_pic.php?pic_id=100). I noticed this problem when I made a land viewing to a construction site is about 1Km away from my flat. It is all right during the night sky viewing (may be planets were bright enough). Hope someone cans give me an advise. My scope is an 80mm diameter with 700mm focal length refractor homemade telescope.

Questions:
1) It is due to my primary lens has not multi-coated?
2) It is 180X is the maximum magnification for my scope.
3) Will the multi-coated eyepiece alone will help to improve the cleanliness/sharpness of the image?

(I must clarify here that I use the construction site as a far object to testing/adjusting/repairing my scope. It is not to spy the site. )

blurblock · Post by **blurblock** » Thu Mar 18, 2004 3:05 pm

Your 10mm eyepiece is starting to fog? Try another eyepiece, if the eyepiece still produce the same problem.

lsy_98 · Post by **lsy_98** » Thu Mar 18, 2004 3:18 pm

Thanks for you suggestion. I've checked all lens. All are clear.

Post by **weixing** » Thu Mar 18, 2004 3:50 pm

Hi,
The magnification is 70x with a scope of 700mm focal length and 10mm eyepiece. How do you get 180x??? with barlow??

Your maximum practical magnification for astro observation should be around 160x (base on 2x per mm in Aperture), but due to the fact that your primary len is not multi-coated, the actual maximum practical magnification may be a lot lower. But for terrestrial viewing, magnification normally are not an issue, because there are plenty of light.

Anyway, I think the main cause of your problem is both the background lightning of your object is too bright and your primary len is not multi-coated. Try looking at the ground on the construction site, does the image quality improve??

By the way, the quality of the image will depend on both the eyepiece and the scope optics and will be limited by the scope optics or the eyepiece depend on which has the lowest quality. For example: If you use a TeleVue best eyepiece on a department store scope, you will get the best image a department store scope can offer, but it is still a department store scope quality. If you use a department store eyepiece on the best takahashi APO scope, you still get the best image a department store scope can offer, because your department store eyepiece is unable to bring out the best of the takahashi APO scope. Below is a simple expression:

Image Quality = Scope Optics Quality x Eyepiece Quality

Have a nice day.

ChaosKnight · Post by **ChaosKnight** » Thu Mar 18, 2004 3:53 pm

I don't think there's anything wrong with your scope. Sometimes during daytime, when i look through my 4" refractor at faraway things, the contrast is so low i almost couldn't see any colour.

lsy_98 · Post by **lsy_98** » Thu Mar 18, 2004 4:22 pm

I see....will it help if i put a filter before the primary lens ?

Is anyone tried do multi-coated lens before ?

My primary len has 2 lens joined togeter. May I know how big is the gap should the 2 lens joined?

Thanks you guys

Post by **Airconvent** » Fri Mar 19, 2004 12:02 am

Looks to me like its normal haze.
I would not be abit surprised from the recent weather we've been having...

shoelevy · Post by **shoelevy** » Tue Apr 27, 2004 12:56 pm

hey guys...hm...i also have this problem of hazy images but mine is not like his...his is high magnification then got this problem...but mine is at all magnifications got this problem...meaning as long as i use the same eyepiece i'll get a foggy hazy image. after i did some checking i realised some white substance has grown and coated the eyepiece...do u guys think it is fungus?....and how can i store my eyepieces to prevent such things again?....i am really desperate for a solutoin

Post by **weixing** » Tue Apr 27, 2004 1:02 pm

Hi,
Get a small dry cabinet with dehumidifier to store all your optics...

By the way, normally you won't have fungus problem if you use your optics often.

Have a nice day.

shoelevy · Post by **shoelevy** » Tue Apr 27, 2004 4:58 pm

no wonder i got fungus....i never use my optics often..ok thanks