Big problems with a new 12" dob

[edwardsdj (Doug)]

Hi Terran,

I've found light pollution (in Brisbane) to be a huge issue with my 12" Lightbridge dob. I likewise cannot see much nebulosity at all except for the central regions of the brightest nebula (like the Orion Nebula). Many open and globular clusters are quite pretty though.

You have to get these instruments out to a dark site to really see nebulosity. When I get it out under a dark sky the extent and amount of detail I can see in the Orion and Tarantula nebulas can keep me busy for hours. The Tarantula is a particularly spectacular sight!

My 12" dob is vastly better for nebulas than my 8" Celestron SCT under a dark sky but in the light polluted suburbs of Brisbane the view through the 8" is better (probably due to the baffling).

I have read people commenting on the internet saying that "apeture cuts through light pollution". I cannot see how this can be true: if the sky is brighter than the object you are attempting to observe, no amount of apeture is going to improve the situation. Maybe they have upgraded to an expensive SCT with good baffling and can see more due to the increased contrast.

Portability is such a HUGE issue with telescopes when you don't have a dark sky in your backyard. I drive a small 2-door Celica and got a 12" Lightbridge soon after they become available as I had wanted more apeture for years but would have no hope of fitting a solid 12" Newtonian tube in my car. Sounds like you are in a similar position.

You can certainly see a lot from a light polluted site with a 12" dob. It will be nowhere near the true capabilities of your instrument though.

Personally I enjoy viewing planets from the suburbs the most. The 8" Celestron SCT is extremely comact, equatorially mounted (with simple clock drive) and most importantly provides awesome planetary views (on those nights when the seeing is good). I find this setup vastly preferable for planetary viewing to the dob.

Hope this helps.

Have fun,
Doug

[edwardsdj (Doug)]

Hi Terran,

Sorry to add even more but many people recommend flocking the tube (making it blacker on the inside). I'm sure this would improve contrast dramatically, particularly when you have strong local lighting.

The worst light pollution is that coming from nearby spotlights. If I use my 12" Lightbridge dob without the shroud, it is virtually useless from my backyard. The shroud makes a HUGE difference as I would expect flocking to do for you.

Have fun,
Doug

[PCH (Paul)]

Originally Posted by edwardsdj

Hi Terran,

Sorry to add even more but many people recommend flocking the tube (making it blacker on the inside). I'm sure this would improve contrast dramatically, particularly when you have strong local lighting.

The worst light pollution is that coming from nearby spotlights. If I use my 12" Lightbridge dob without the shroud, it is virtually useless from my backyard. The shroud makes a HUGE difference as I would expect flocking to do for you.

Have fun,
Doug

Doug,

that's really interesting. I have the same 12" LB and the same polluted backyard. I've got the missus to include a shroud in my unending list of Chrissie presents, but I must say my expectations of what difference it might make have now been multiplied 10-fold I can hardly wait to try it out

Cheers,

[edwardsdj (Doug)]

Hi Paul,

The shroud has little effect (except in relation to dewing) under a dark sky. In my backyard (where there are many neighboring lights often shining directly on the scope) the difference is dramatic.

I'm even considering flocking the inside of the primary and secondary Lightbridge tubes as I have such bad problems with local lighting.

Have fun,
Doug

[§AB]

Also get/make a dewshield that extends past the front of the tube, which prevents any stray light from reaching the area around the secondary and focuser.

From my suburban backyard, the Orion Neb is insane, the nebulosity just fans right out from the detailed and mottled core. The nearby reflection nebulosity NGC 1977 is an easy catch aswell.

[rmcpb (Rob)]

If we are getting into ways of beating light pollution the flocking and tube extension will help dramatically.

Another, often overlooked, consequence of light pollution is that you never really dark adapt. How to fix this is quite simple, use an eyepatch over your observing eye when not looking through the scope and fit an observing hood to your scope and only take your eyepatch off when under the hood. This will let your observing eye fully dark adapt and take advantage of what light you have available.

Cheers

[saturn c (Leo)]

sounds like you need a refractor.

[PCH (Paul)]

Originally Posted by §AB

Also get/make a dewshield that extends past the front of the tube, which prevents any stray light from reaching the area around the secondary and focuser.

From my suburban backyard, the Orion Neb is insane, the nebulosity just fans right out from the detailed and mottled core. The nearby reflection nebulosity NGC 1977 is an easy catch aswell.

Hi SAB,

what is your dew shield made from? And what have you flocked it with?

Cheers,

[§AB]

Dewshield is a black plastic and the flocking is black velvet material. This scope was formally Dave's so he'd know better.