12" GS Dob: first light

janoskiss (Steve H) · #1 13-04-2006, 02:21 AM

Just very quickly because it's late and I should be in bed.

- New 12" "Limited" Dob from Andrews (because local Bintel shop would not sell without Crayford and fan so

)
- Came with free Crayford because Andrews did not have any limited models in stock

- White tube

- One bent collimation bolt

So collimation was a struggle, but got it in the end.
- Got the azimuth motion very nice and smooth with one CD-spindle nylon washer and a few milk jug washers. Altitude is very good also.

Big difference after the 8": Amazing to see so much detail on the full Moon. Much easier to see cloud detail on Jupiter, although mirror never cooled properly. Still saw heaps of very nice fine detail. I liked the Pentax XF 8.5mm best on Jupiter in this scope tonight. This is going to be one hell of a planetary scope. But I cannot wait to get it out to a dark site and start going after galaxies.

On the downside:
- it is a large and heavy beast. I have to lug it down a flight of stairs to get to the backyard. It's hard work and even harder to stop the tube getting knocked against something.
- I'll need to invest in a taller stool too, because the eyepiece is normally too low for standing but too high for sitting on a normal chair or stool. Perfect recipe for a sore back.
- My HD orthos don't reach focus, nor the binoviewer. Not enough in-travel.

There is plenty to do.

Fitting the fans is next. Three 80mm 2.5 watt fans. Overkill? Maybe. But who cares. Better more than less.

There is a set of truss tubes waiting too..

acropolite (Phil) · #2 13-04-2006, 03:11 AM

Might as well add a peltier to the list Steve...

astronut (John) · #3 13-04-2006, 06:49 AM

Congratulations Steve,

It's always nice to have a new scope in the house especially a 12"!!!

I've just come up from a very good 4" refractor to a LB12" and even in it's first light last week under a moon filled sky it was a quantum leap forward. I can't wait for new moon.
If your thinking of converting it to a truss system I can thoroughly recommend it. It was the main reason for buying the LB.
I'm thinking of buying new eyepieces, I would like to know your opinion on what works well on your scope. In the mean time have fun with your baby.

[1ponders] (Paul) · #4 13-04-2006, 09:07 AM

congratualtion on your new window to the heavens Steve. I must say I'm getting a bit envious of all the new 12" scopes getting bought these day.

Wonder if I could fit one on the G11

You do know that if you take this scope to a dark site during a new moon we won't hear from you for a week.

Have you thought about putting some carry handles on it until you chop it up? If you're looking for a good chair, drop Astroron a line, he has a great adjustable chair. I don't know what it is called but I do know they are very popular

rmcpb (Rob) · #5 13-04-2006, 09:16 AM

Congrats on the new scope Steve. Did you keep the 8" as a hell of a grab and go? I want to get a 12" sometime and convert it to a truss for those observing sessions over the new moon period.

I'm envious

janoskiss (Steve H) · #6 13-04-2006, 09:26 AM

I hope I won't need Peltiers, Phil. All the hassle with temperature monitoring and regulation seems painful. Maybe a low-tech version: esky full of icepacks to stick behind the fans.

Yes Rob, the 8" is not going anywhere. It is a great grab-and-go scope, which the 12" is not.

davidpretorius · #7 13-04-2006, 10:01 AM

well done steve, i recommend the dob driver, but servo cat works well too. toucam is a must along with a powermate 5x and extension tube.

please sell your eyepieces as you now no longer need to look thru it, just image.

it will be nice to have a 12" in the planetary imaging family!

janoskiss (Steve H) · #8 13-04-2006, 10:15 AM

Stop it Davo!

ving (David) · #9 13-04-2006, 10:25 AM

thats it stave! you are so out of the 8" club!

my eyes turned green just reading your post, congrats

vespine · #10 13-04-2006, 11:15 AM

Update your sig Steve

And congrats!

One thing you could do, which is what I've been thinking about is get a seat belt, or rope, or something similar and make a loop that is long enough to sling around the scope and under its alt bearings and sling over the back of your neck. Does that make sense? So you are still carrying the scope but a lot of the weight is supported by the sling around your neck. I can imagine that being particularly handy when going up and down stairs.

dhumpie · #11 13-04-2006, 11:38 AM

Congrats on your new light bucket Steve! And yes keeping the 8" dobbie is a good move. I have a 6" EQ that I keep as a supposedly grab and go but my 10" GS dob sees more light now due to the sheer convinience...anyway enjoy your new scope....

Darren

spacezebra (Petra) · #12 13-04-2006, 11:51 AM

Congrats Steve

Looking forward to seeing any modifications that you undertake - Im collecting ideas for LB

Cheers Petra

Starkler (Geoff) · #13 13-04-2006, 12:27 PM

Steve i saw somewhere a graph showing cooling curves of mirrors vs cfm of air pushed through the tube.
The conclusion was that a single 80mm fan with typical 25cfm of airflow was sufficient for up to a 12" mirror and any increase over that only yielded very diminished returns.

davidpretorius · #14 13-04-2006, 12:35 PM

Quote:

Originally Posted by Starkler

The conclusion was that a single 80mm fan with typical 25cfm of airflow was sufficient for up to a 12" mirror and any increase over that only yielded very diminished returns.

but bigger is better!!!

quote Tim the toolman

vespine · #15 13-04-2006, 12:41 PM

yeah I'm thinking http://www.airconco.com/scripts/air-...l-cooling-fans

davidpretorius · #16 13-04-2006, 12:56 PM

spot on vespine, no holding back.

Asimov needs these for his parks mirrors. I also suggest a 6" diameter copper pipe and heat sink welded to the base of the scope.

oh yes, and holes for collimating

oh yes, and anti vibration mounts

oh yes, and an aircraft license to operate such a size fan!

janoskiss (Steve H) · #17 13-04-2006, 02:16 PM

I have seen those graphs too, Geoff. But they did not consider airflow around the mirror. I think you need a fair bit more airflow to break the boundary layer. The fan also keeps the dew off my mirror when I bring the scope inside from the cold into the warmer house. It used to dew up all the time before I fitted the fan (90mm 4 watt on the 8" Dob).

You cannot have too much power, only too little.

Andrews Super Ultra Deluxe Dob! Now with free wind tunnel!!

danielsun · #18 13-04-2006, 04:15 PM

Go Jano!!!! Congrats on your new scope!!

I'll forgive you for not buying a Saxon because they dont have the 12" but if you want some saxon stickers just let me know!!

How do you go transporting it?
Does it fit in your car?

janoskiss (Steve H) · #19 13-04-2006, 04:51 PM

Thanks Dan. Donno how if it will squeeze into the Corolla. It looks doubtful. But I really want to convert it to a truss tube anyway.

wavelandscott (Scott) · #20 14-04-2006, 11:08 AM

Quote:

Originally Posted by janoskiss

.
On the downside:
- I'll need to invest in a taller stool too, because the eyepiece is normally too low for standing but too high for sitting on a normal chair or stool. Perfect recipe for a sore back.

I've heard tell of some pretty nice chairs around that might fit your needs...

Hope you enjoy the new scope!!!