#1  
Old 27-02-2008, 04:08 AM
žAB
Its only a column of dust

žAB is offline
 
Join Date: Aug 2007
Location: New Iceland
Posts: 761
12 inch dob first light

Ok I found a great deal on a used 12" Abell muncher so I bought it. The scope is truss and has a hand figured mirror. The mirror is 304mm and focal length is 1415mm making it F4.65. The finder is actually a 50mm binocular objective fitted with a 1.25" diagnal with interchangable eyepiece capability, how cool you can change the finder's mag! Now I've got a use for my 25mm Kellner The finder has an old 30mm Celestron plossl in it, and its views are pretty good I must say! Physically, the scope is beast! Although its mirror is only 2" larger than my 10", the thing is basically twice the size!!! The collimation springs are about as big as your 4WD suspensions

This is my first experience with a truss scope so its all a learning process. Ofcourse, being the first time out I did a few clumsy things, which I learned from. After 5-10 uses, I'll feel right at home.

I messed with the collimation in the dark, so I'm not sure if I got it right, but with the views I got I'm assuming I did something right! When I dropped the 22mm LVW in, I was shocked that it would not come to focus. I tried my other EPs, no focus. I then moved the primary as far forward on its collimation screws as possible, then voila! The 22mm JUST reaches focus while the remaining EP / Barlows are comfortably within focus range. I also tried shifting the secondary closer to the focuser (might've been too far off, dunno) to move the focal point further out and get comfortably within focus range. I'll have to experiment with collimation later and get a feel for it. Unfortunately, I discovered that the collimation shifts slightly when the scope is moved towards the zenith. For instance, the primary center ring moves away from the cheshire dot once you get above around 60-70║ altitude. That;s something I'll have to follow up.

First views, very encouraging. Especially considering my collimation attempt!

M42
I suspected that the nebula actually appeared more textured than with the 10". This was at 108x, and all 6 trap stars were easy. One thing that struck me was 3 faint stars at the limit of visibility in the 10" were quite bright in this 12".

Eta Carinae
Moon was just rising, but I do believe the star count in this region has increased somewhat over what is visible in the 10". The nebula appeared similar, but the keyhole was slightly more obvious. Actually I was surprised by how well the nebula was visible in moonlight.

Homunculus Nebula
Damn, its a different object in this thing! Using powers of 217 to 272x, The structure was crazy....I could see a tiny star right next to Eta Carina which I've never seen before. There were two spikes shooting out from Eta Carinae perpendicular to the main lobes. Haven't ever seen these either. The difference between the 10 and 12 here is pretty big

Saturn
Very nice views at 217x, sharp but seeing wasn't fantastic. Cassini division easy, extending beyond the ring tips. Crepe ring easy aswell, some banding visible on the globe. IMO, the view in the 12" was virtually the same as in the 10".

Physically, the scope is more demanding than the 10" solid tube GSO. The size means I have to dismantle it with each trip in n out which takes a bit of effort, but the views are so worth it This puppy will be saved for those moonless all nighters, rather than casual observing. Frankly, my 10" dob is MUCH more easily deployed and packed away and hence will definately continue to see good use
Reply With Quote
  #2  
Old 27-02-2008, 06:18 AM
GrahamL's Avatar
GrahamL
pro lumen

GrahamL is offline
 
Join Date: Jun 2006
Location: ballina
Posts: 3,056
that was a nicely priced scope you got your hands on
they do get big pretty quick when you build a box around something round
I was surprised how big my 12" finished up..If set up bothers you to much you could grab a set of moonlite connecters for the top and bottom(pricey) but they are good and would top mount on your mirror box by the looks without to much trouble..The best thing about them is collimation becomes repeatable every time you set up..I recently didn't have a adapter for my cheshire for a few weeks and trimed my poles when I got round to checking it was still perfect .. set up takes about 2 minutes (probably less)now i have the hang of them.

great report lots of fun times coming your way
Reply With Quote
  #3  
Old 27-02-2008, 09:41 AM
goober's Avatar
goober (Doug)
No obs, raising Harrison

goober is offline
 
Join Date: Nov 2007
Location: Melbourne, Australia
Posts: 792
Wow, was that the "Hartung" truss scope that was advertised in Melbourne a week or so ago? Great pickup. Were you out last night? I got home from work too late ... it was about midnight by the time I was ready to head out. A quick 30 minutes with binoculars ... looked nice seeing. I'll get home earlier and get "sirius" tonight
Reply With Quote
  #4  
Old 27-02-2008, 10:11 AM
Dave47tuc's Avatar
Dave47tuc (David)
IIS member 65

Dave47tuc is offline
 
Join Date: Dec 2004
Location: Mornington peninsula. Victoria.
Posts: 1,658
One scope not enough Eh!

Put some wheels on the 12" then you can just wheel it in and out of the house.

Have a look at Geoff's SDM the wheel design is the best I have seen.

Another great report.
Reply With Quote
  #5  
Old 27-02-2008, 10:21 AM
PhilW's Avatar
PhilW
Registered User

PhilW is offline
 
Join Date: Mar 2007
Location: Melbourne
Posts: 283
It did look like a great buy. You could always take kilos off the weight of the structure & turn it into an ultralight if you had a mind, eg:
- use a single upper ring design
- shrink the mirror box down by using bigger bearings
- shrink the rocker box.

As for Doug's pun: You owe me another look through your scope at Snake Valley for that one, Doug!
Reply With Quote
  #6  
Old 27-02-2008, 11:23 AM
goober's Avatar
goober (Doug)
No obs, raising Harrison

goober is offline
 
Join Date: Nov 2007
Location: Melbourne, Australia
Posts: 792
Quote:
Originally Posted by PhilW View Post
You owe me another look through your scope at Snake Valley for that one, Doug!
Will the binoscope be there? Scope swapping!

Siriusly, I'll warn my observing chair you'll be dropping by.
Reply With Quote
  #7  
Old 27-02-2008, 11:41 AM
PhilW's Avatar
PhilW
Registered User

PhilW is offline
 
Join Date: Mar 2007
Location: Melbourne
Posts: 283
I'm tossing up between bino & cyclops for Snake Valley. I see more stuff with the cyclops , but it all looks better in the bino.

I am very wary of your carnivorous observing chair now. I am sure it leapt out at me that last time, like a hungry panther in the dark. Or maybe it was just after the Ethos?
Reply With Quote
  #8  
Old 27-02-2008, 01:33 PM
žAB
Its only a column of dust

žAB is offline
 
Join Date: Aug 2007
Location: New Iceland
Posts: 761
Quote:
Originally Posted by goober View Post
Wow, was that the "Hartung" truss scope that was advertised in Melbourne a week or so ago? Great pickup. Were you out last night? I got home from work too late ... it was about midnight by the time I was ready to head out. A quick 30 minutes with binoculars ... looked nice seeing. I'll get home earlier and get "sirius" tonight
Yep! Seeing was pretty good, but Saturn was blurring in n out of focus at 217x.

Quote:
Originally Posted by Dave47tuc
One scope not enough Eh!
It's like eating KFC - "I want MORE!!"

Quote:
Originally Posted by Dave47tuc
Put some wheels on the 12" then you can just wheel it in and out of the house.
no can do - the trip from my house to the backyard involves a narrow corridor, dog infested deck, 4 stairs and pomeranian crap covering the back courtyard

Quote:
Originally Posted by PhilW
It did look like a great buy. You could always take kilos off the weight of the structure & turn it into an ultralight if you had a mind, eg:
- use a single upper ring design
- shrink the mirror box down by using bigger bearings
- shrink the rocker box.
It sure was! 12" custom built dob with hand figured mirror, a complement of accessories, 600 bucks, the trap was set!

Optical performance does look great with my rough collimation, even at 400x I got nice tight stars but seeing was getting mushy. Omega Centauri was a plethora of pinpoints at 272x and Saturn very sharp in moments of good seeing. Comparing to views in my 10" from memory, I can say that the 10" is virtually just as sharp!

This saturday, forecast is for clear skies so I'm going to fiddle with the 12" collimation and have a showdown between both scopes
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 09:31 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Lunatico Astronomical
Advertisement
Meade Australia
Advertisement
Bintel
Advertisement
OzScopes Authorised Dealer
Advertisement
NexDome Observatories
Advertisement
Celestron Australia
Advertisement
SkyWatcher Australia
Advertisement
Astronomy and Electronics Centre
Advertisement