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AP 900 saddle plate choice

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#1 mgwhittle

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Posted 27 October 2012 - 11:20 AM

I have an AP 175mm on the way and have narrowed down my mount choice to a 900 GTO due to my need of portability. I would like to hear any ideas for the saddle mount plate, specifically between using a dovetail saddle plate versus a flat mounting plate. The 900 will only be used for the 175, so using a flat mounting plate seems like the most sturdy connection since I won't be changing out scopes.

If someone could give me the pros/cons comparing either method, I would appreciate hearing about it.

#2 m2k

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Posted 27 October 2012 - 12:25 PM

If your not changing out scopes, I see no advantage in using a saddle and dovetail plate. However, it does make the DEC section of the mount bigger and a little harder to handle with the flat plate and rings attached...
You can attach the scope/rings assy using the keyhole(s) in the flat plate keeping the rings on the scope. Or leave the rings on the flat plate and just open them to admit the tube.

Mike

#3 blueman

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Posted 27 October 2012 - 12:33 PM

I like the tilt in dovetail type. It is easy to put it up and you do not have to line up any holes. Then you can slide it forward and aft to get balance without slipping the scope in the rings.
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#4 woodworkt

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Posted 27 October 2012 - 01:25 PM

So, pros and cons:

As long as you go with a good quality saddle and dovetail, like an AP, or even better, a Robin Cassady saddle, there shouldn't be a difference in the strength of the connection.

The flat plate itself is thinner than having a saddle and dovetail, and you'll save some weight which might be useful with the 175. The AP plates look reinforced enough you really shouldn't have to worry about the plate itself flexing, but here I'd bet a saddle/dovetail combo could be even more solid in preventing any possibility of flexure than a flat plate, as long as the saddle is close in length to the dovetail (I use a 14" Cassady saddle and a 17" Losmandy dovetail plate with my TMB-152).

If you're talking about using the AP900 for portability, then I would say that neither the option of leaving the rings connected to the mount nor the option of having to tighten and loosen four bolts each time you set up and take down (as you'd have to do with the flat plate) sounds particularly appealing.

Will you ever need to piggyback anything on top, say a guidescope for imaging? If so, consider that you might want to mount a dovetail on the other side of the rings from the mount to help with this. So you might end up wanting to keep both the main plate, rings, and top dovetail attached to the DEC axis part of the mount, which might make the assembly a bit unwieldy.

That's all I can think of...

--Ken T.

#5 mgwhittle

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Posted 27 October 2012 - 01:32 PM

Ken, I'm not too familiar with the Casady saddle. What made you decide on that one versus the AP version?

#6 jmiele

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Posted 27 October 2012 - 02:03 PM

I like the DOVELM162 from AP. Has 3 clamping holds. At 16" it has plenty of room for making adjustments for different weight instruments, or when adding equp to the rear of that 175.....

Best, Joe

#7 mgwhittle

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Posted 27 October 2012 - 02:18 PM

Joe, that's the one in the mix between it and a flat plate. Still not sure which way to go.

#8 Tom and Beth

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Posted 27 October 2012 - 05:53 PM

IMO, as your main use is as a PORTABLE mount, a tip in saddle would be my choice. I don't have the newer 16 inch, but do have smaller AP and Robin Cassady saddles. Each company goes about the manufacture of the saddle a little differently, but both are well made and easy to use with gloves on.

#9 woodworkt

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Posted 27 October 2012 - 07:19 PM

Ken, I'm not too familiar with the Casady saddle. What made you decide on that one versus the AP version?


Mark, when I bought mine (I forget how long ago, but I think it may have been 8 or 10 years) there were a couple of factors involved. At the time, I don't think AP even offered a tip-in saddle that took Losmandy dovetail plates, they were geared to a different AP dovetail bar standard. Also I'd known that Cassady's machining and build quality was first rate, having bought a counterweight of theirs before. But I seem to recall there was some other deciding factor I can't quite remember, which was probably specific to my setup, in comparison to other options that were available back then. Might have had to do with the specific saddle lengths Cassady offered or something; I can't say for certain now.

--Ken T.

#10 jmiele

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Posted 28 October 2012 - 12:01 AM

Joe, that's the one in the mix between it and a flat plate. Still not sure which way to go.


The flat plate is the most ridged configuration. If you don't need portable and can remove via the rings. I real plus if imaging. That said, the DOVELM162 is still one of the nicest around.

Best, Joe

#11 M13 Observer

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Posted 28 October 2012 - 10:28 AM

I have an AP 175mm on the way and have narrowed down my mount choice to a 900 GTO due to my need of portability. I would like to hear any ideas for the saddle mount plate, specifically between using a dovetail saddle plate versus a flat mounting plate. The 900 will only be used for the 175, so using a flat mounting plate seems like the most sturdy connection since I won't be changing out scopes.

If someone could give me the pros/cons comparing either method, I would appreciate hearing about it.


I have both and have settled on the AP16" dovetail/saddle for one major reason with my 180 scope. I can with some effort, slide the OTA with rings attached back and forth along the dovetail to balance with differing load weights. In other words, my 3 or so pound visual load on the focuser requires that the entire OTA with rings be moved to counterbalance a change to the 15 or so pound load of the CCCD cam, filterwheel, field flattener, Atlas focuser or M-MOAG, adapters, etc. Sliding the OTA in the rings on a fixed plate would not be able to accomplish this. If however, you are not planning on such drastic changes in the loading of the focuser, then you can use the fixed flat plate with the slotted through-hole ring bolts mountings. The 15" fixed flat plate is significantly lighter than the dovetail/saddle combination. They are a wash for mounting as neither the 16" dovetail saddle nor the fixed 15" plate will readily fit in a case affixed to the RA axis so each will have to be bolted on when used. The 15" fixed plate actually is easier to mount as it is machined to be fitted to the top mounting surface of the AP900 and will either stay there on its own or can be held with light finger pressure while the bolts are installed and torqued down. The dovetail saddle slides all over the place until at least 2 bolts are partially to fully installed. The same is true at disassembly.

#12 Paul G

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Posted 28 October 2012 - 11:50 AM

I have an AP 175mm on the way and have narrowed down my mount choice to a 900 GTO due to my need of portability. I would like to hear any ideas for the saddle mount plate, specifically between using a dovetail saddle plate versus a flat mounting plate. The 900 will only be used for the 175, so using a flat mounting plate seems like the most sturdy connection since I won't be changing out scopes.

If someone could give me the pros/cons comparing either method, I would appreciate hearing about it.


I have to transport to observe, use a 900GTO. After a discussion with AP I upgraded my previous dovetail to the DOVELM162 and I put an SBD16 on top and bottom of the 8" rings. I have found it very stable and secure. Sadly it no longer fits my custom mount case.

#13 mgwhittle

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Posted 28 October 2012 - 12:46 PM

So there are no cases made for the 900 that allows the 16 inch dovetail saddle or fixed plate to remain attached? I'm not liking the idea of having to bolt either on or off each time I transport, but if I have to, it sounds like the fixed plate is the way to go. Easier to attach and more secure mounting in the end result.

#14 Paul G

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Posted 28 October 2012 - 01:54 PM

So there are no cases made for the 900 that allows the 16 inch dovetail saddle or fixed plate to remain attached? I'm not liking the idea of having to bolt either on or off each time I transport, but if I have to, it sounds like the fixed plate is the way to go. Easier to attach and more secure mounting in the end result.


No, there are Pelican and Storm cases that will hold the dec axis with that dovetail. Mine was custom made for the mount, it was the prototype for the one at the bottom of this page:

Company 7 mount case

The DOVELM162 is longer than my case from front to back; my case was made for the longest dovetail available at that time (just after the 900 GTO was introduced). A new case could be made to accommodate it but I'll probably put that axis in a Pelican rather than spend the bucks for another ATA case.






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