AP1200 versus Paramount MX

[Moon (James)]

Not sure if you plan to use the mount in an observatory or in the field, but this is relevant (from the PME manual, but applies to any EQ mount):

The accuracy of the leveling required depends on the long-term use of the mount. If the mount is attached to a permanent pier, without the intent of portable use, leveling is less important. When used in a portable sense, a level mount helps speed the polar alignment process.

James

[pmrid (Peter)]

Originally Posted by Moon

Not sure if you plan to use the mount in an observatory or in the field, but this is relevant (from the PME manual, but applies to any EQ mount):

James

I wrote to OPT about this and got a reply that said essentially the same thing. I found that a bit curious.
I'm planning on having a new pier made and am about to "put pen to paper" to get that started but am held up with the design of the top plate. I think I'll have to go for a separate adjustment plate - adds to the cost but I just can't go ahed without being able to get a proper level.
What heights were you guys thinking about for this rig. My present thoughts are that keeping it down to about 600mm above floor level (for the top plate) will be about right. Any thoughts?
What sort of height does the tripod offer?
Peter

[pmrid (Peter)]

It occurs to me that my last post was diverting this thread a bit away from the original AP vs PMX direction so I was going to suggest that a new and perhaps sticky thread entirely for the PMA/PMX mounts might be worth considering since all of us who are waiting on a PMX will want to be pooling ideas and experiences. A semi-permanent thread in the Equipment section might be useful - even if it is only for a finite period - 12 onths or so.
Mods? Any thoughts?
Peter

[gregbradley]

Pier height is a good question. I got a pier made in Qld by I think it was Sirius or was it Pegasus Piers. They did a super job and it is superbly well made.

I would answer about height it depends on a few factors.

What mount, what scope, height of your observatory wall. Then you've got wind protection versus sky coverage.

Generally I prefer to only image between 30 degrees up or down and in between. Less than that and it generally isn't worth it.

My pier is 1 metre tall. When I installed the PME (by the way the mount is called PME not PMA) on top and then the CDK17 I thought it was too high. But it has worked out well with good wind protection (never lost a night due to wind) and good coverage.

Wind protection also comes from planning the observatory position and orientation. You need to know the prevailing wind directions.

My obs wall is 2.3 metres tall and it is located in a fairly windless part of the property.

Greg.

[pmrid (Peter)]

Originally Posted by gregbradley

I got a pier made in Qld by I think it was Sirius or was it Pegasus Piers. They did a super job and it is superbly well made.

I also have a Pegasus pier courtesy of Sirius Optics. I agree they're well made. I just had a look at it for both height and also placement of mounting holes for the PMX.
Height: My gut reaction was that it was a bit high but I've decided to run with it for now rather than lose money selling it and have another one built. I'm encouraged by what youy say about finding the height of yours worked well for you. I'm undecided which scope to put on this at the moment. I have a choice between an EdheHD 14", a plain C14 or a 10" F3.8 astrograph newt. I've also just bough an 11002-size chip camera and matching that to focal length etc is my next mission.

Top Plate: the existing holes in my Pegasus are 4 x 13mm unthreaded at 148mm centers whereas the base of the PMX seems to have it's bolts at 7.45" centres (189.23mm). So I am deciding whether to try to tap new holes in the top plate of the pier (not the adjustment plate) and do away with the adjustment plate altogether (levelling by smimming the base instead) or to have a new adjustment plate made with holes at 189.23mm for the mount but also using the existing 148mm holes in the top of the pier. What are you planning on doing Greg?
Peter

[Moon (James)]

I think I'll have to go for a separate adjustment plate - adds to the cost but I just can't go ahed without being able to get a proper level.

Why? What are you trying to achieve? It will add cost and might make it less stable. If the mount can be secured by passing bolts down into a captive nut, this is the best way to go. Keep it simple. It won't help your polar alignment at all.
If you want to make life easy for a portable setup, then yes it makes sense. Also you might need a top plate if the mount requires a bolt to go up into the base of the mount, like the EQ6 does. Otherwise, forget it.
James

[gregbradley]

Hi Pete,

The PMX I ordered is for my dark site observatory that I travel down to and setup when I get there. It has an 8 inch steel tube buried 800mm in a hole and concreted in.

I will need to get an adapter plate with the PMX and attach it to this pole.

I may need a 2 plate system like the Pegasus Pier as it will be very hard for me to get a single plate level. The Pegasus one is very strong with quite a few large stainless steel bolts locking the top plate in place.

So I intend to get an adapter plate. I assume SB sell one or perhap Rob Miller does or could make a custom one.

As far as 11002 chip. It has 9 micron pixels and seems to work well with long focal length scopes. So the HD14 or C14 would be good. The F3.8 10 inch maybe not as well but experience will show it make great images. F3.8 and 10 inch Mak Newt - is that the Intes?

Make sure the focuser is OK, mirror shift etc. F3.8 is going to be pretty intolerant of mechanical issues but Mak Newt is probably an excellent format. It would be good for widefield images and a bright image fast. Depends on what type of image you want. An AP 67 reducer works on these HD scopes so that could make it F7 or so. HD14 would be great for galaxies and closeups. The reducer would be handy and it may just work with an 11002 chip. Not sure now. I had one once. I don't think I used the AP reducer with an STL11 I had though.

Greg.

[frolinmod]

Originally Posted by pmrid

I have a choice between an EdheHD 14", a plain C14 or a 10" F3.8 astrograph newt. I've also just bough an 11002-size chip camera and matching that to focal length etc is my next mission.

Are you joking? If deep space astrophotography is your passion, go for the 10" F3.8 astrograph newt! It's a no-brainer decision, is it not? I say that as a current C14HD owner/user and former C-14 owner/user. My C14HD is on a Paramount ME, so I'm referring only to the OTA, not the mount.

[gregbradley]

There's also this:

http://astrotroniks.com/store/index....products_id=27

Greg.

[pmrid (Peter)]

Originally Posted by gregbradley

.

So I intend to get an adapter plate. I assume SB sell one or perhap Rob Miller does or could make a custom one.
.

The pier-top and adjustment plate on my Pegasus are separated by 4 lengths of 1/2 SS rod at 148mm centre-to-centre. I imagine yours is the same Greg.
As the PMX bolts are at 189mm centre-to-centre, an adjustment plate will need to have both threaded holes to receive the 1/2 rod coming up from the pier top and also 3/8 24 TPI threaded holes to receive the bolts coming down from the mount wedge and base.
There is a 74x25mm section of the base that is the base for the azimuth adjustment mechanism on the wedge/base assy and this sits outside the basic square of the mount base/wedge assembly.
The easiest design for a top plate would be a circle of 360mm diameter compared with the existing circle of 250mm for the standard Pegasus adjustment plate.
There is a minor problem then with sections of that circular plate protruding outside the basic square shape of the base/wedge assembly because of the risk that the mount and dec weight shaft may foul it in some configurations. So it would be better if the adjustment plate was actually shaped to fit the square (plus azimuth block) base/wedge assy. That would probably mean starting with a circle of say 1/2 steel and cutting it back after the mounting holes have been drilled and tapped.
I'm going to take this basic design to a local machine shop next week and have one knocked up. It doesn't sound too complex or expensive.
Have I missed anything?
Peter

[Bassnut (Fred)]

Originally Posted by frolinmod

Are you joking? If deep space astrophotography is your passion, go for the 10" F3.8 astrograph newt! It's a no-brainer decision, is it not? .

Well geez, is it?. Depends what yr after doesnt it?.

Not to say a 10"f3.8 isnt great, if you like that kind of FOV thing.
But.

A 10" f3.8 950mmFL with an ST11k at bin 1 gives a 1.95 arc/secs image scale.

A 14" C14HD at f11 3850mm FL with an ST11k at bin 3 gives a 1.44 arc/sec image scale.

A nice large 14" (over 10") with a very tasty close up FL and low noise, big signal bin3 sub might strike some as somewhat preferable perhaps ? .

[frolinmod]

You guys who already have an ME and who are getting an MX to go with it, please do us a favor and once you've settled in, give us your impression of the MKS-5000 electronics. Software Bisque may offer an MKS-5000 electronics upgrade for us ME owners at some point and so it would be good to know if it'll be worth doing.

[PRejto (Peter)]

Originally Posted by gregbradley

I wonder if you can buy those microlevellers as an accessory.
Otherwise 2 pier plates with adjusting height bolts would do similar as long as they are strong.
Greg.

I started a thread about this at SB MX site, having not seen the discussion here about the micro levelers. Here is a reply from Dan Bisque:

PRejto:
I'm in the process of building a concrete base

The top surface of a properly mixed and proprely floated concrete pier will be level. Make sure your concrete person clearly understands this goal before the job is started.

PRejto:
. My question concerns the amount of error (hopefully none, but I know that's impossible) that is workable at the pier/mount interface.

A Software Bisque pier mounted to the top of a horizontal pier surface should be sufficiently level so that no adjustments or modifications are necessary for optimal performance.

PRejto:
Does the MX mount have the same sort of micro-levelers as the ME (and same tolerances of 3 mm)?

No. We've had to repair too many micro levelers on Paramount MEs caused by misuse and minunderstanding of how this system works that microlevelers were intentionally left out of the MX design.

Note that an "absolute horizontal orientation" of the mount's base is not critical to the Paramount ME or Paramount MX's performance. In the case of level, "close enough" is generally good enough.

Daniel R. Bisque Software Bisque

[gregbradley]

Thanks Peter. Most informative.

Greg.