Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
Get a Cloudy Nights T-Shirt Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu uh, User

Equipment Discussions >> Mounts

Pages: 1 | 2 | 3 | 4 | 5 | 6 | (show all)
gnowellsct
Postmaster
*****

Reged: 06/24/09

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Ad Astra]
      #4335832 - 01/24/11 12:23 AM

Quote:

Hello Max!

I must admit that I was very surprised (and a bit aghast!) at your description of the 'slap-test' for mount stability! That is SO FAR beyond the level of stability that I have now, it seems literally like science fiction. On the CGEM mount, I can observe (if the wind is low), but no one can come near the mount. I'm used to shouting at people, "Look, don't TOUCH!!!"
Dan




The slap test is a bit idiosyncratic, a better test is a weight hung from the rear of the OTA and swung (to provide a constant level of force for comparison) pendulum style.

A long fl refractor on an AP900 *might* do a lot better vibration wise if one custom machined a LONG dovetail to provide better stability fore and aft.

Someone here posted on the C11--look there's nothing wrong with an AP900 I love mine, but I also have my G11. And a G11 is certainly plenty of mount for a C11.

I have used lots of mounts which always vibrated when you touch the focuser. My various rigs always passed that test.

C14+G11: passes test, also OK in moderate winds, not OK when you add 4" refractor
C11+G11: passes test, very good in moderate winds, room to add a refractor
G11+9.25: maybe be used in hurricanes
G11+10 inch f/6 Newt: Surprised me, pretty stable, seems to be more stable than larger aperture dobs (probably because the support is "right in the middle" in a T shape rather than cantilevered from the base). I have decided that I will be using the 10" Newt on my G11 instead of my AP900QMD which I find surprising to say but it seems to be where I'm headed. Suffice to say that I don't like using mounts that are "delicate" when you touch the focus and which can't stand up to 10mph winds with their OTAs.

Incidentally Super Polaris is great with c8 or 4" refractor.

All my mounts are stepper versions, no go-to.

Greg N


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: gnowellsct]
      #4395068 - 02/18/11 02:22 PM Attachment (160 downloads)

Hi Gale and all,

As per your request.
This is what I can do at the moment: AP900, Titan and AP1200.
Others are being used -- Titan will in a few minutes.
Bottle of red wine for size comparison.
Hope this helps,

-- Max


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Max Lattanzi]
      #4395095 - 02/18/11 02:38 PM Attachment (166 downloads)

Side view...

Post Extras: Print Post   Remind Me!   Notify Moderator  
jmasin
Carpal Tunnel


Reged: 12/22/08

Loc: Murphy, TX (DFW)
Re: Mach1 GTO vs. A-P 900 mounts new [Re: Max Lattanzi]
      #4395102 - 02/18/11 02:45 PM

Wow I didn't realize that the 1200 was so much bigger.

I thought my 900 was hefty... now I have mount envy


Post Extras: Print Post   Remind Me!   Notify Moderator  
nemo129
Post Laureate
*****

Reged: 01/03/10

Loc: WMass
Re: Mach1 GTO vs. A-P 900 mounts new [Re: jmasin]
      #4395256 - 02/18/11 03:59 PM

Wow, I didn't realize I could drool that much...and it's not the wine!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Ad Astra
professor emeritus
*****

Reged: 05/12/10

Loc: Riverside Co., California
Re: Mach1 GTO vs. A-P 900 mounts new [Re: nemo129]
      #4397250 - 02/19/11 03:12 PM

Thanks Max! That photo is a big help. Looks like the Titan and the AP-900 are about the same size - for some reason, I had thought the Titan was a lot larger than that!

Dan


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Ad Astra]
      #4398620 - 02/20/11 04:56 AM

Hi Dan,

Glad it helped.

Mind you: the Titan IS larger and, moreover, although not as precise, is definitely more robust. The AP900 is a light mount in comparison. It weighs almost half and, to set it up is just one trip. You can literally walk with the RA in the right and Dec in the left w/o problems. This is totally out of the question with the Titan, which is about the same mass of the AP1200 and does require that first you carry the RA with both hands and again the same with Dec (the axes weight alike).

If it can be of help, I definitely feel more comfortable in charging heavy scopes on the Titan than on the AP900. It remains that the AP900 can work with a very tight mesh while the worm wheels/gears coupling of the Titan needs to be looser. And you find yourself adjusting it more frequently.

Cheers,

-- Max


Post Extras: Print Post   Remind Me!   Notify Moderator  
skybsd
Post Laureate
*****

Reged: 02/01/08

Re: Mach1 GTO vs. A-P 900 mounts [Re: Max Lattanzi]
      #4398652 - 02/20/11 05:34 AM

Hello Max,

Quote:

Mind you: the Titan IS larger and, moreover, although not as precise, is definitely more robust.




Can you explain a bit more about your describing the Titan as "more robust" (than the AP900GTO), please?

Thanks for the comparative photos, they're fantastic as illustrative reference for curious minds

Regards,

skybsd


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts [Re: skybsd]
      #4399120 - 02/20/11 11:37 AM

Hi there !

Well, it's actually something you "feel".

If you look at the specs on paper -- shafts and wheels -- the two mounts look indeed comparable. In both cases the AP900 has a slightly bigger shaft and wheel in RA (2.2" and 7.2" vs 2" and 6.75"), and slightly smaller in Dec (1.75" and 6" vs again 2" and 6.75"). This is nothing really significant.

OTOH, the masses are significantly different: 54 lbs vs 75 (and this difference is especially significant in Dec, i.e 17 lbs vs 37.5). Again, the AP900 is really a no-brainer portable mount, while both with the Titan and the AP1200 you have to be careful with your back.

In any event, assuming that both mounts have an hypothetical similar recommended payload (AP and Losmandy give different figures, 70 vs 100 lbs, but we all know how conservative Roland is...), I feel it more appropriate putting a 150lbs 2mt-long refractor (including cws and accs.) on a mount whose mass is 45% bigger than the other. Consider that in the Titan case the mass is just half -- and in the 900 only *one-third* -- the *moving long-arm* weight being supported.

Further, during one single evening, going to different objects, shifting observer, going straight through or using a diagonal, I find myself flipping scope easily five, six, seven, many times. This is usually done not using slewing but literally pushing the instrument to the other side of the meridian and flipping it. It's a very swift exercise and usually in 5 secs people can exchange their place at the eyepiece. This kind of flipping is dynamically demanding on the mount with a long instrument and really gives you the wrist of it. You do feel that, even if the pier is the same, the heavier mount reacts much better. In the same way dampens better any vibration...

Trivially, get two guys, one heavier than the other. Both of them lift the same when on the gym board. You would still call the heavier "more robust", btw. Now if they both have to lift something steady, no pbl. But if they have to hold it, spin it around and then stop, even though their strength on the gym board is similar, the heavier guy -- the more robust -- will stand the momentum drag much better than the other. And imagine that here the weight being considered is twice or three times their own weight...!

In any event, roughly, on similar pier, I find the AP900 dampens a 180 f/9 as efficiently as the Titan dampens a 200 f/9. If you do the maths you'll see that the ratio between the two OTAs is about 1:1.45. And that happens to be exactly the ratio between the two masses of the mounts.

Hope it makes sense

-- Max


Post Extras: Print Post   Remind Me!   Notify Moderator  
skybsd
Post Laureate
*****

Reged: 02/01/08

Re: Mach1 GTO vs. A-P 900 mounts [Re: Max Lattanzi]
      #4399258 - 02/20/11 12:34 PM

Hi Max,
Good to hear from you..,

Yes - I think I see where you're coming from..,

But tell me something - do you believe that an uninformed person (that is, someone completely unaware of the specification sheets for both mounts) would discern (note that explicitly did not use the word "detect") a difference?

See I'm wondering if it might the case that one's own knowing the build and performance specifications combined with having prior experience of both mounts would have a bearing on one's assessment of this sense of robustness..,

I'm just curious..,

Thanks, Max!

Regards,

skybsd


Post Extras: Print Post   Remind Me!   Notify Moderator  
Larry Geary
Carpal Tunnel
*****

Reged: 09/24/06

Re: Mach1 GTO vs. A-P 900 mounts [Re: Max Lattanzi]
      #4400727 - 02/21/11 01:01 AM

Max,

The NJP, and its successor the EM-400, I believe are rated slightly higher in load capacity than the AP900. Would you say the NJP is better at handling a long refractor than the 900? Also, do you know the size of the worm wheel used in the NJP?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Larry Geary
Carpal Tunnel
*****

Reged: 09/24/06

Re: Mach1 GTO vs. A-P 900 mounts [Re: Larry Geary]
      #4401775 - 02/21/11 02:51 PM

BTW, there is a used Losmandy Titan on AMart for $5000.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts [Re: skybsd]
      #4402227 - 02/21/11 06:27 PM

Quote:

do you believe that an uninformed person (that is, someone completely unaware of the specification sheets for both mounts) would discern (note that explicitly did not use the word "detect") a difference?

See I'm wondering if it might the case that one's own knowing the build and performance specifications combined with having prior experience of both mounts would have a bearing on one's assessment of this sense of robustness.




Well, you know, I think a while ago on this same thread I did talk of my own feeling facing the possibility of putting the 8" on the 900. That was a matter of pudding. I did not consider the sheets to make a decision. I had both mounts before me and was holding the 8" while the 7" was still inside. I had just set the two mounts. 900 is a breeze. Titan you have to move carefully. I really did not feel like the heavy ota I was holding was going to be properly managed by the 900. Again, maybe I am too careful and possibly the 900 would do. But I really don't think just as well. I had the same damping time with the 7" on the 900 and the 8" on the Titan. The 7" is a breeze vis--vis the 8". The only possible test to confirm is to mount them crossed. But that will have to wait a couple of weeks. Still, again, lifting the 7" is nothing in comparison with the 8" which requires attention while taking it out of its case and breathing out when you lift it up. Not to mention when you put it into the rings. Mounting the 7" you do it while whistling. It's really difficult to believe that the 900 would dampen with the same effectiveness... but shall let you know in due time.

Cheers,

-- Max


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts [Re: Larry Geary]
      #4402237 - 02/21/11 06:29 PM

Quote:

The NJP, and its successor the EM-400, I believe are rated slightly higher in load capacity than the AP900. Would you say the NJP is better at handling a long refractor than the 900? Also, do you know the size of the worm wheel used in the NJP?




Hi Larry,

I am not sure the NJP is rated higher than the 900 actually, nor I think it would be a better mount at handling a long refractor. Rather, I think they're quite similar with maybe an edge going to the 900.

But this edge is very slight, more than what a superficial analysis of the wheels dia. would suggest. If you don't mind, I may address this tomorrow morning. It's late at night here and I am returning from a trip...

Cheers,

-- Max


PS/ NJP 160 wheels were 146 and 86 mm. The specs of the last version (JP-Z) report 6" and 4". I have not opened them so cannot tell for sure. In any event, this is only part of the story. Devil's in the details. Tomorrow...


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts [Re: Max Lattanzi]
      #4405965 - 02/23/11 12:44 PM

Hi Larry,

So, as said, my best data are those of the original NJP-160. For the JP-Z are mentioned RA-6" and DEC-4" but I don't know whether this is marketing or what. Right now I can't but I may end up opening the JP-Z and tell you for sure. But, since motors are interchangeable, I suspect that the wheels are the very same.

In any case, the JP-Z does carry heavy loads with accuracy despite its relatively small wheels.

When I had a bit less white in my hair, I used to get all excited by looking at specs of wheels showing high number of teeth, but one day I ran into a guy who was into mount building and who taught me a bit more and showed me where to look for sturdiness and precision. Proper materials, proper number of teeth (read, for heavy loads, better bronze wheel with fewer larger well-executed teeth, than alu wheel with thinner teeth...), and then precision, precision, precision. He showed me how he could make, for instance, a mount with a smaller bronze wheel behaving better than a bigger alu wheel having an improper number of teeth, and even more if the mechanical coupling with the worm gear was not accurate.

The NJP is perfectly engineered and has a dia/teeth ratio similar to those of the AP900 and Titan. Already 30 years ago, when finely tuned, was able to deliver about 2" of periodic error relying solely on the accuracy of the mechanics... something that very many modern mounts cannot achieve today even using PEC.

Again, I would give a slight edge to the AP900, still there is someone in this community who uses a NJP with on top a 7" f/9 refractor and another smaller refractor piggy-packed... so, you see, it's not made of jelly either...

What makes the NJP special is its ageless beauty, and its conception with all the mechanics being visible and accessible. You can fine-tune any small mechanical coupling if needed. Move the mount manually if you wish. Add a Crouzet, a stepper, a servo, a computerized GoTo system... even a weight-driven clock... the mount will always respond. This is a unique feature that makes it to my eye a perfect modern match to a classic long focus...

I could go on but I guess you see my point.

Cheers,

-- Max


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Max Lattanzi]
      #4481820 - 03/29/11 10:41 AM Attachment (98 downloads)

Hi All,

Returning after a couple of days at the obs after a few weeks away.
OF COURSE it was fine when I arrived and left, but pouring rain for almost 48h while I was there... SGRUNT...!

Anyhow, since I was there and blocked for anything else, I did some cleaning and tuning. And this thread came to my mind. I seem to recall that there was a request for further side by side of mounts. So here you go with two of them on my working table. Sorry for the bad lights and for the messy background. It was not intended as a photo set. The Titan, which is deep black, suffers a bit for one cannot fully grasp its size. But I guess it's better than nothing...

So, first the JP-Z with the AP900. Classic elegance vis--vis perfect function !

-- Max


Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Max Lattanzi]
      #4481830 - 03/29/11 10:43 AM Attachment (95 downloads)

Side view... one can tell that JP-Z is taller...!

Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Max Lattanzi]
      #4481833 - 03/29/11 10:44 AM Attachment (77 downloads)

Facing each other...

Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Max Lattanzi]
      #4481842 - 03/29/11 10:47 AM Attachment (87 downloads)

And now the B-side: it looks like Robocop having a walk hand in hand with a Supermodel...

Post Extras: Print Post   Remind Me!   Notify Moderator  
Max Lattanzi
professor emeritus


Reged: 06/27/07

Re: Mach1 GTO vs. A-P 900 mounts new [Re: Max Lattanzi]
      #4481851 - 03/29/11 10:50 AM Attachment (92 downloads)

And now the Supermodel and the Sumo Wrestler...

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | (show all)


Extra information
22 registered and 42 anonymous users are browsing this forum.

Moderator:  Dave M, richard7, bilgebay, iceblaze 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 13112

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics