Well we finally have our new 18" dob up here in Gove.
First light was this Sat night & after a bit of a struggle to fit the secondary cage to the trusses & a collumation we were off looking at some of our Favorite DSO's
First thing that was apparent was the need for accurate Collumation of an F4.5 scope !
Jupiter was not as good as I would have expected ?
We stuck with a a 40mm Konig eyepice for most of the evening as this gave the easiest viewing.
The most noticable improvement was the magnitude of stars visable.
It reminded me of looking at a detailed star Atlas, everywhere I looked !
The DSO that stuck in my mind was strangley enough M4, through the 18" it revealed so much more structure !
Omega Cent, the Lagoon Neb, Eta Carina were of course all brilliant !
M27 was a bright ball of light compared to the usual hazy glow & hunting Globs was a snap where ever we looked !
A few necessary additions to the scope:
*A finder scope! we fitted a laser pointer on a mount, which was good for the well known objects, but not so good for hunting the unknown !
*An Eyepiece holder (does anyone sell these ?)
*A good set of charts down to Mag 16
Observing with a group of people with a scope of this size is a bit more of a challenge (especially if kids are involved)
Try climbing a ladder holding a 5 or 6 YO so they can see throught the eyepiece !
I look forward to a clear dark night with no clouds & just a few people so we can really get the best from the scope.
Yes it is Geoff
Do you thing it is a good Idea to enclose the OTA ?
I was thinking that myself, stray red lights are easily picked up & the risk of dropping something
What is the best material to use ? Black Lycra ?
Well we finally have our new 18" dob up here in Gove.
We stuck with a a 40mm Konig eyepice for most of the evening as this gave the easiest viewing.
Gai-Ian
Congrats on first light with your new scope.
Do keep in mind issues with exit pupil on fast scopes. A 40mm EP has an 8.88mm exit pupil with an F4.5 and at best a young eye will have 7mm so accounting for the eye pupil stopping down the aperture at the eyepiece , you would only be seeing 14" of the mirror aperture . The situation with older eyes would be worse of course. A 28mm focal length if your eye opens to 7mm is the longest FL eypeice you can use with a F4.5 and without effectively throwing light away. People are sometimes impressed at how good the star images look at the edge of these big low power eyepeices. This is becasue with for exapmple the 40mm EP, your pupil is stopping the scope down to F7 or so which allows the eyepiece to works much better at the edge definition: less astigmatism and apparent coma.
Thanks Mike, I figured out the UTA assembly when i looked back on the post later
I figure I might use some of that stiff plastic sheet like U get in the bottom of the "Green" shopping bags, as a light shield for the UTA.
Mark, that is a big help, my next trip out will be like having a whole new scope , I guess i will just have to get a 27mm TV Panoptic, as our wide field eyepiece
That is one fine scope.
I found that covering a truss model will make the views much better. I am in a dark spot and used a 235mm with truss ota regularly (it is out of service now) and found once noticing the improved contrast when covered used it covered from then on. I think the "saffety" aspect is a good one also and if nothing else must restrict dust getting to the mirror.
I hope these clouds go so you get a decent go its nice and dark
alex
Ian, If you can get it, Kydex is a good UTA light shield. If you cannot get that look for some sort of Black stiff plasic, like that you find on plastic folders polypropylene is a good type.. Not the big folders but the small ones. It is still enough to be flexed into the circular shape of your UTA. Put it on the inside of the UTA. You can find these folders at any supermarket in the stationary section
Ian, If you can get it, Kydex is a good UTA light shield. If you cannot get that look for some sort of Black stiff plasic, like that you find on plastic folders polypropylene is a good type.. Not the big folders but the small ones. It is still enough to be flexed into the circular shape of your UTA. Put it on the inside of the UTA. You can find these folders at any supermarket in the stationary section
Where can you source Kydex (or other similar materials)?
Or you can try Formica the same stuff they use on the Alt and Az axis of telescopes with teflon. Works just as well I hear and doesnt have the same thermal issues as kydex. (kydex expands and shinks with Temp variations) But Formica is heavier.
Another suggestion from a recent discussion is neoprene rubber (a bit like wetsuit material. You can get it in different colours and thicknesses and it's nice and lightweight too.
Thanks Blueskies
I will give that a go ... I was going to use black lykra
But noeprene sounds more robust, especially for the UTA.
Hope you are getting good skies !
I know someone with a 22inch scope where the upper assembly is just a metal ring with spider etc attached to it. His shroud covers the entire upper part of the scope and attaches to that ring.
Maybe you could do the same and kill two birds with one shroud
Thanks Geoff
Thats a good idea !
We had our 2nd night out last night, it was superb
Looking at the Eta Carina Nebula, it was like looking at it for the 1st time again Using a UHC filter there was so much Neulosity around the star Eta Carina, that it took sweeps around with a 28mm possol to take it all in.
I am VERY impressed with this scope.
Still have to get the collumation spot on, time to re-read some of those collumating threads I think.
Could not bring the humunculus nebula to a sharp focus, at high Magnification
I guess it does not matter the size of the scope, if seeing does not allow 285x Mag, that is that
Would be nice to have a few of the old hands here along to one of our observing nights to show us the way (hint-hint, ever thought of an Arnhem land holiday )
We have tried laser collumators, but when the laser shows the optics as aligned, they are very obviously out with a visual columation.
Ian. FWIW, keep the primary covered while fitting the 2ndary assy., just in case yas drop something... 
L.
