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Astro Physics 900 help needed

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#1 JWalk

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Posted 03 February 2011 - 01:20 PM

Looking at taking the plunge on this mount and was wondering what all you guys and gals would get and put on this mount for some good AP. I've got and 8in Astrograph with big losmandy plate on bottom for mounting, its currently on a CGEM. Also have an 80mm scope for guiding. Would you do a dual saddle or piggyback? What portable pier would you get? Precision Rotating Pier Adapter? This is tall order and was just wanting some feeback as to what I should get and do it right. I figured I would talk to you all and get ideas before calling it in and asking these types of questions. Thanks in advance.

Jimmy

#2 LLEEGE

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Posted 03 February 2011 - 01:32 PM

I would piggyback for guiding. (My preference)
Pier height will depend on your preference. I think 42" is about the average. If you are setting up permanent, I'd get the standard pier plate. The rotating plate is better for setup and tear down applications.

#3 gillmj24

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Posted 03 February 2011 - 01:55 PM

I just learned that the pier height will be 6-8" higher off the ground than the labeled height, which is the length of the center post only.

8" astrograph sounds like it is a reflector not a refractor so perhaps a shorter pier is in order.

#4 DeanS

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Posted 03 February 2011 - 03:19 PM

12" losmandy saddle is what I use on both 900 and 1200.

Side by side is hard to balance perfectly, but if you like to have your camera on the top of your newt. then that is about your only choice. Otherwise piggyback is easiest.

Rotating pier cap is nice but not a must have if you have a good compass and know your magnetic deviation. Or you can kick the leg of the pier as needed :smirk:

I don't like tall for imaging. Shorter is more stable, and sure makes it easier to set up, take down, or cover if you leave it set up overnight. My piers are 36 and 40" which is almost too high for me. I have to use a step stool to get a cover over the end of the refractor when in park1.

Recommend the polar scope. There was a good thread about that on the AP users group the last couple of days.

And if you look at this Mount section you can find a recent discussion on different piers.

Enjoy your new mount, they really are what everyone says.

Dean

#5 jmasin

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Posted 03 February 2011 - 03:25 PM

Wait! Careful on the pier height - call AP to be sure.

I recently took delivery. I ordered the 32" pier from the site. When I pulled the pier piece out it was 24" and I though there as a mistake. TOTAL height was 32" (as ordered). I am pretty sure AP advertises total height. Call to confirm.

AP commented that was a short pier (32") but it is perfect for my Newt. It results in a being a few inches higher than it was on the stock Atlas.

AP has a really nice Excel dimension calculator on their website which will give you an idea of mount dimensions for your latitude. This will tell you where your c/w shaft and mounting surface will be with respect to pier/ground. It's a nice tool.

Posted Image

Go piggyback, so much easier to balance than side by side, and with your 8" there will be no problem balancing with piggyback. You can see the position of the 18lb and 10lb weight in my image. Lots of room to spare.

I got the rotating pier adapter. It is a nice piece and AZ adjustments are very smooth and do not require loosening the mount. For the little extra money, I'd recommend it. After all, you are spending ~$9,000, I'd go the extra $100.

Get two weights, 18lb and 10lb. That should be good for your 8", guide and camera. I recently rotated my camera to be down on the mount side and that made a surprisingly big difference in weight positioning.

I also splurged for their 16" mounting plate. I have a 15" ADM Losmandy plate on my OTA. The 16" plate has a lot of flexibility in mounting position.

I just took delivery last week and the skies have been cloudy, so I don't have any in-action advice, but I'd be happy to answer any additional questions about ordering etc.

I eventually plan to put a 10 or 12" reflector up there, but I'm a little broke right now :)

#6 mariobmd

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Posted 04 February 2011 - 09:00 AM

Hi,

I would advice piggyback if you are going to use the 80mm refractor as a guider.Higher chances of flexure when guiding by side-by side set up. At least this was my experience.

#7 gnowellsct

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Posted 04 February 2011 - 09:30 AM

The problem with an AP pier is that the cables interfere with the bottom of the newt. Interesting thread for me since I've just listed a sturdy Optical Craftsmen pier with AP adapter on Astromart. I'm not allowed to post a link though. I've got a picture of it in reflectors/dob hole thread as a "solution" to the dob hole, and I think one can see from the pic that the design is better from the clearance point of view. It's on an AP900.

regards
Greg N

#8 jmasin

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Posted 04 February 2011 - 11:36 AM

The problem with an AP pier is that the cables interfere with the bottom of the newt.


Not true for my setup. I've had it through all angles in the kitchen there to learn where the limits are. As long as the DEC is such that it doesn't hit the pier itself, it didn't come close to the cables.

I'm sure mileage varies though based on DEC balance point and tube length.

My 8" would hit the Atlas tripod legs at certain DEC settings.

#9 gnowellsct

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Posted 04 February 2011 - 03:08 PM

The problem with an AP pier is that the cables interfere with the bottom of the newt.


Not true for my setup. I've had it through all angles in the kitchen there to learn where the limits are. As long as the DEC is such that it doesn't hit the pier itself, it didn't come close to the cables.

I'm sure mileage varies though based on DEC balance point and tube length.

My 8" would hit the Atlas tripod legs at certain DEC settings.


Yeah I was thinking of the 10 or 12" Newt to which you referred. I have used my f/6 10" on the AP900 and on an AP pier the cables would be a problem.

Greg N

#10 jmasin

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Posted 04 February 2011 - 04:54 PM

Greg,

Sorry - gotcha now! I misunderstood.

Cheers.






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