Bintel now have it listed for $999 and Andrews have since dropped the price to $899.
Still a lot of basic information is missing: size of secondary, design of primary mirror cell, amount of backfocus available...
Bintel now have it listed for $999 and Andrews have since dropped the price to $899.
Still a lot of basic information is missing: size of secondary, design of primary mirror cell, amount of backfocus available...
They're not going to list that on a site like Bintel...you'd have to ask the guys if they knew the full specs, which they may or may not.
I've been seriously considering getting the 12 f4 OTA from andrews.
will have to call them for the weight and secondary size.
but wouldnt a 2" coma corrector suffice as if you're using a dslr, the coma corrector would be only an inch or so from the ccd chip of the dslr or the focal plane, and at that point, the light cone wouldn't be over 2". just guessing.
I wonder if it would be possible to cut out sections of the OTA tube to make it lighter, but still retain stiffness. anyone done anything like this?
other option is to buy just the mirror and build the rest.
is it possible to get a decent mirror cell for a 12"? any recommendations?
Bintel list it at 18.4kg without rings or mounting plates- so I guess you can bank on 25kg by the time it is all kitted up to take exposures ( with guidescope and rings , camera etc)
I noticed that they will have their own branded coma corrector available for it soon too.
The Eagle has landed.
To give you can idea of the size, it just fits on the back seat of my car.
For the record, Andrews website currently has it listed at $799 and Bintel at $999.
That's about all I can say at this stage.
James
The Eagle has landed.
To give you can idea of the size, it just fits on the back seat of my car.
For the record, Andrews website currently has it listed at $799 and Bintel at $999.
That's about all I can say at this stage.
James
Now this is going to be interesting! Please keep us posted.
First impressions posted here: http://deepspaceplace.com/at12in.php
I'll update this page as I progress. The first step will be to stabilise the OTA under the focuser.
James
Great to hear about this James, watching with interest.
A shame to see that the issues that were exposed with the AT8" (of which I see you have as well) haven't been addressed. The collimation system on the primary is farcical, one set pushing, and one set pulling OK, but not when they are "apart", as all it means is the cell twists or alignment is altered. I simply removed the "push" knobs on my AT8".
Again, the AT8" focuser base area is pathetic, I made a stiff metal reinforcing section that helped the stiffness of the tube. And that is with the AT8" with a 2" (Feather Touch in my case) focuser.
Baffles or flocking on the agenda soon?
Regards,
Gary
It needs some flocking. I like the plastic baffles in the AT8IN, too bad they are missing here.
Quote:
I simply removed the "push" knobs on my AT8".
I did the same to mine, and I added some bigger springs I got from Cost Less Bolts. The difference was amazing. Will do the same again this time.
Quote:
I made a stiff metal reinforcing section that helped the stiffness of the tube.
Can you share a picture how you did it? I'm open to ideas. I also had to do this to my AT8IN and I plan to do it the same way this time : put a big sheet of Aluminium inside the OTA, curve it around, cut a hole for the focuser and secure with lots of stainless steel bolts, and paint black. It worked a treat last time, but this is a bigger tube and it moves a lot more - but only in the direction at right angles to the tube. Length wise it's ok. It's made worse by the grub screws on sides of the base of the focuser - it rocks on those too. But the base is also moving. Added together it moves a lot. The focuser itself is fine - for example the focus lock does not impact the collimation at all.
Its a shame about the weight. Given that the cost of CF tube in China / Taiwan is much less than in the US or Europe, you'd think it would be at least an option.
it could be deliberate..
I have a 12" skywatcher with steel tube and about 70% of it is on the focuser side of the center of the dovebar attachment point.
so much weight is in the mirror and assy.. only about 10% of the scope actually sticks out the back from the rings. if it were CF maybe there would be too little tube to attach to the rings... maybe
Can you share a picture how you did it? I'm open to ideas. I also had to do this to my AT8IN and I plan to do it the same way this time : put a big sheet of Aluminium inside the OTA, curve it around, cut a hole for the focuser and secure with lots of stainless steel bolts, and paint black. It worked a treat last time, but this is a bigger tube and it moves a lot more - but only in the direction at right angles to the tube. Length wise it's ok. It's made worse by the grub screws on sides of the base of the focuser - it rocks on those too. But the base is also moving. Added together it moves a lot. The focuser itself is fine - for example the focus lock does not impact the collimation at all.
James
Elegant it is not, but it does work. If the weight is significant, and the flex objectionable, maybe a complete circle of stiffener, sized to be a tight fit within the tube? Mine I simply secured with the Feather Touch attachment bolts.
Gary
Thanks Gary.
I tried a large thin sheet of Aluminium. I tested it last night with the Catseye XLK installed, but it didn't work. Still lots of movement in the tube. I'll see if I can find a thicker sheet like yours.
James
Have a look at Mike Sidonios 12", it has a brace around the outside near the focuser. You could get another set of tube rings and do the same, then drill and screw or rivet the the tube to the tube ring.
I really like that part of Mike's scope - for me new rings will be plan "C". Before I added the Al sheet, I moved the rings really close to the focuser as a test and tightened them up as much as possible (but no screws / rivets) - it made no difference at all.
I've just got back from Bunnings, this time I have 3mm instead of 1 mm Aluminium. Hopefully this will be enough.
My 3c worth, large tubed newtonians are just plain difficult to work with. The flex in the tube. Lack of strength in the area surrounding the focuser.
For 1000 all up throw the focuser away and buy a decent one.
Wind effect on the tube whilst imaging.
It just goes on and on.... Been there done that.
If you must use one of these creations then do yourself a favor and get an SBIG with built in guide chip, or perhaps a large off axis guider.
In reality someone needs to rip out the mirror and cell, start again with a custom made truss setup.
Edit.... Mikes scope cost a lot more than these so you'd expect it to be a better unit ( my critique for unit doesn't apply)
Clive
Last edited by Alchemy; 11-05-2011 at 03:41 PM.
Reason: Added comment about better quality newts
