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Hi All,
I'm a recent joiner here. I was fortunate to purchase a well taken care of G8 with an extension between the tripod and head. It’s has the 492(?) drive system.?
I have been using a 4.25” Orion Newtonian and a GoTo Celestron 8se with the computerized single arm mount.?
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I’d love to fit the 8se onto the Losmandy. But the dovetail bar on the ota is about an inch narrower then the mount accepts.?
I also received a dovetail plate with the mount that I’m hoping to find specs for. Maybe I could attach the Celestron bar to this unknown one which fits perfectly on the G8 mount. But who knows just yet.
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Thank you for any suggestions anyone may have.?
pete
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On Tue, Oct 15, 2024 at 05:35 PM, PeteL wrote:
Hi All,
I'm a recent joiner here. I was fortunate to purchase a well taken care of G8 with an extension between the tripod and head. It’s has the 492(?) drive system.?
I have been using a 4.25” Orion Newtonian and a GoTo Celestron 8se with the computerized single arm mount.?
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I’d love to fit the 8se onto the Losmandy. But the dovetail bar on the ota is about an inch narrower then the mount accepts.?
I also received a dovetail plate with the mount that I’m hoping to find specs for. Maybe I could attach the Celestron bar to this unknown one which fits perfectly on the G8 mount. But who knows just yet.
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Thank you for any suggestions anyone may have.?
pete
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That is an old GM8s!? ?I bought one just like it a few years ago!? ?That is the original as in proprietary "Small" Losmandy dovetail.? To allow your GM8s to use the now standardized dovetails you need to replace the saddle on the GM8s mount.? I recommend buying a , also known as the 4" dual D/V saddle mount, this is what I am using.?
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Hi Pete, welcome to the group.
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I’m not sure what vintage your mount is but, it very likely accepts Losmandy style dovetail plates only. The one on your scope seems to be Vixen style and will not work on the mount as is. The best way to use your C8 on the GM8 is to get a C8 specific dovetail plate with its associated radius blocks. Losmandy sells those on their ?website.
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Like Chip mentions, you could also upgrade the base on your mount to the newer version which accepts both Losmandy and Vixen plates but, imo Losmandy’s bigger sized plates offer better stability and stiffness. However, if you have other, smaller scopes with the Vixen plates, this option may be more versatile. That base is also sold on Losmandy’s website ;)
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Jonathan,
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There was a middle sized Losmandy dovetail, wider than the narrow Vixen which became the small standard but narrower than the Losmandy D which became the wider standard.? I have one of these original GM8s mounts which came with the wider small saddle clamp.? Trust me nothing fits it except for the Losmandy middle size dovetails.? ??
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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oh, I had no idea such a “mini losmandy” standard existed, good to know. My older GM8, from ca 1997 came with the “large” losmandy clamp and that’s the extent of my knowledge :)
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thanks for the info
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This is what your looking for. This mount was originally DDS492 and had a 3" saddle. I had Losmangy send me the dual saddle and converted the drive system to OnStep. Fooling with the motor cabling here. It has the ESP32S based MaxESP3 controller mounted in the aluminum enclosure.
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Jon, after Celestron and Losmandy developed the G11 introduced in April 1992 (just in case any one wondered where the "492" came from) they announced the G9 model, a C9.25 on a modified GM-8. The mods were using a G11 saddle and an inadequate copy of a Vixen AL110 tripod that first served as the CG-5 tripod. The Tripod was complete with the CG-5 hub that had been drilled for a Lomandy made adapter. I noticed that there were some extra threaded holes in the adapter which lead to this discovery.
As far I can determine the HD Field Tripod was never offered as an?option with the G9.
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Apologies for not replying with my thanks earlier - my email was filtering lots of my groups.io to junk for a bit. So thank yo all for the help and suggestions. I have been mulling over which path to pursue as I like the computerized mount for my learning the sky or if time is short, as well as my kids know how to operate it on their own. I had quickly seen the dedicated bar and blocks to change the OTA over to losmandy - but with the potential option of changing the saddle to allow me to move between the two, that might make more sense for me currently.
Thanks again,
PeteL
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Celestron sells a 3" wide bar it calls the for the C8, 9.25, 11 and 14. The C8 bar is quite a bit lighter and certainly?stiff enough. About $50.
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On Fri, Nov 15, 2024 at 06:16 AM, PeteL wrote:
Apologies for not replying with my thanks earlier - my email was filtering lots of my groups.io to junk for a bit. So thank yo all for the help and suggestions. I have been mulling over which path to pursue as I like the computerized mount for my learning the sky or if time is short, as well as my kids know how to operate it on their own. I had quickly seen the dedicated bar and blocks to change the OTA over to losmandy - but with the potential option of changing the saddle to allow me to move between the two, that might make more sense for me currently.
Thanks again,
PeteL
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Pete,
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See my previous post dated Oct. 16th.? The best possible option is to purchase the current Losmandy GM8G saddle that accepts both the smaller Vixen and larger Losmandy "D" style dovetails which have become the two most popular dovetail styles and the de facto standards.? Here is a link to the right part from Losmandy:? they are in stock and if you are local you can pick one up on Monday at the shop.? If you tell them you have an old GM8s and if you ask Tanya they can provide the fasteners. Tell her Chip sent you.??
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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On Sat, Nov 16, 2024 at 07:25 AM, George Cushing wrote:
Celestron sells a 3" wide bar it calls the for the C8, 9.25, 11 and 14. The C8 bar is quite a bit lighter and certainly?stiff enough. About $50.
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The stock Celestron CGE dovetails are cheap crap.? They are inexpensive under engineered extrusions that tend to crack where the dovetail top meets the part that is clamped by the saddle. I have seen several others as well as my own, purchased used, C14 and C11 factory CGE dovetails crack or were cracked when I bought them.? I had no idea you had to look for this issue before it happened to me, TWICE!?
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The problem is the clamped part has no mechanical support against the compression forces of the saddle clamp.? This causes the flange to act as a spring and because in general aluminum is not a good spring material that joint flexs, fatigues, cracks and then the crack migrates up and down the extrusion.? If you don't see it in time and replace the dovetail the SCT will end up on the ground.?
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Buy once cry once.? You can buy a Losmandy or ADM dovetail and use it on your SCT and when you sell the SCT continue to use the basic dovetail plate with your next scope sans the radius blocks which are popular as used items.??
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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I am new to this stuff. I got an ADM Losmandy dovetail for my 10" deforked Meade for use on my EQ6R Pro. I find getting on my mount a little harder than the Vixen dovetail. The section it clamps onto is shallow compared to the Vixen and it takes me a while to line up with my heavy telescope. The vixens are narrower and deeper and they seem very solid. If I could go back, I think Vixen or another brand of Losmandy next time, something that has more to grab onto.
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Allan Der
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I find the Celestron bar to be fine for the C8, while the Losmandy and ADM are heavy and clumsy. I was a bit surprised that they offered one for the C14.
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On Mon, Nov 18, 2024 at 09:54 AM, George Cushing wrote:
Celestron bar
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The discussion prompted me to examine the terminology, as I had not previously equated the two items.? The curved extrusions are tube-rails that connect to OTA tubes, creating a box-like structure. This structure utilizes the tube's rigidity to form a truss-like unit with a dovetail.? Losmandy's dovetail plates are versatile, featuring holes for bolting various items, thus the plate alone must provide rigidity. Tube-rails serve a more singular purpose, requiring attachment to the tube—here, with prestressed connecting bolts—to ensure rigidity.
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These two choices present their own sets of pros and cons. For me, portability, weight, inertia, and simplicity are important, and I prefer stock option. I'm comfortable with the lighter weight and relying on the OTA for rigidity since I don't need to support heavy accessories with my C11HD usage.
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Doug
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On Sun, Nov 17, 2024 at 12:07 PM, Allan Der wrote:
I am new to this stuff. I got an ADM Losmandy dovetail for my 10" deforked Meade for use on my EQ6R Pro. I find getting on my mount a little harder than the Vixen dovetail. The section it clamps onto is shallow compared to the Vixen and it takes me a while to line up with my heavy telescope. The vixens are narrower and deeper and they seem very solid. If I could go back, I think Vixen or another brand of Losmandy next time, something that has more to grab onto.
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Allan Der
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HI Allan,
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You should use the best part for the job to stay happy in the long run.? The Vixen dovetails were developed back when Vixen sold lightweight tiny refractors and these days they are just too small which is why most SCTs larger than 8" and many higher quality refractors usually come with the larger Losmandy D dovetail.??
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Maybe this will help you, do you know the trick where you open up the saddle enough to just drop the dovetail into the saddle sideways without having to slide the dovetail down the full length of the dovetail?? You should test your saddles first to see if there are enough extra threads to allow opening the saddle jaws without the coming apart.??I do this with all of my newer dual D/V Losmandy saddles as well as older dual D/V ADM saddles.?
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Years ago I also installed longer threaded bits to my older Orion Sirius and Atlas saddles to allow this same trick.? But many better, newer mounts have dual D/V saddles with tapered or beveled entry to the saddle to make it easier to load the larger dovetails.? If not the side-loading trick is one to try but be aware that not all saddles designs can accommodate this without adding longer threaded parts to them.? If you do modify your saddle be sure to use only stainless steel threaded bits to avoid rust which will happen.? ? ? ??
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HTH
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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On Mon, Nov 18, 2024 at 07:40 AM, WayBack wrote:
On Mon, Nov 18, 2024 at 09:54 AM, George Cushing wrote:
Celestron bar
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The discussion prompted me to examine the terminology, as I had not previously equated the two items.? The curved extrusions are tube-rails that connect to OTA tubes, creating a box-like structure. This structure utilizes the tube's rigidity to form a truss-like unit with a dovetail.? Losmandy's dovetail plates are versatile, featuring holes for bolting various items, thus the plate alone must provide rigidity. Tube-rails serve a more singular purpose, requiring attachment to the tube—here, with prestressed connecting bolts—to ensure rigidity.
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These two choices present their own sets of pros and cons. For me, portability, weight, inertia, and simplicity are important, and I prefer stock option. I'm comfortable with the lighter weight and relying on the OTA for rigidity since I don't need to support heavy accessories with my C11HD usage.
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Doug
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The only redeeming factors about the stock Celestron dovetails are that they are already on the OTA and they are a cool Halloween color.?
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I don't know where you got your ideas or if you have ever used and setup a Losmandy or ADM SCT dovetail on a larger SCT but you are wrong about the Losmandy SCT dovetails.? The Losmandy and ADM dovetails are more rigid than the relatively flat Celestron extrusions even if you include the OTA in your cross section dimension.? The reasons that Losmandy and ADM use the radius block design is to add depth to the box shape to take full advantage of the existing OTA structure and to introduce the loads into the tube and cells more evenly reducing stress on the OTA across multiple fasteners and area. I think you know that the larger the box cross section the stiffer it can be.?
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I have seen too many cracked and failed CGE dovetails to recommend that people use them even just for visual use.? ??
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Pretty sure the first use of the 1.75" wide bar by Vixen was for the C8-SP. The female saddle was mounted on the rear cell of the C8 using its two rear weight system mounting?holes. The dovetail bar was bolted to? the Super Polaris's saddle. The?bar had a strip of steel to protect the bar from the clamping screw. When the bar was copied by others the clamping guard was omitted resulting in a?narrower bar. This arrangement replaced two rings on the C8 that bolted to the SP's saddle.
The problem with this design was that the female saddle was fastened by two #8-32 screws and the entire load of the OTA was cantilevered. The screws loosened under the load and the weight was borne by the thin aluminum of the OTA. Most of these C8s will have dimples where the tube rested. This also caused the OTA to be out of collimation with the mount's RA axis. The problem was resolved by moving the female saddle to the mount when the Great Pacific was designed. A new dovetail bar was designed that mounted at both ends of the tube. It had side flanges similar to the orange bars but was a bit heavier.
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The simple answer here is to replace the saddle on the mount with the dual D /V saddle.?
You can move your C8 back and forth as it has a V style rail.? Any other scope will have one or the other.?
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The slightly narrower plate that came with the G8 and its original saddle are relics of the past.
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On Thu, Nov 21, 2024 at 02:54 AM, Michael Ben-Yehuda wrote:
The simple answer here is to replace the saddle on the mount with the dual D /V saddle.?
You can move your C8 back and forth as it has a V style rail.? Any other scope will have one or the other.?
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The slightly narrower plate that came with the G8 and its original saddle are relics of the past.
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This is what I said in the second post of this thread, the rest is commentary.?
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Well, at least the bar has enough meat on it to be milled to the Vixen profile.
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Chip Louie