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I've been considering a strainwave mount for several months now but there are aspects of the offerings from pegasus, ioptron and zwo that keep me from pulling that trigger. I'm looking at Rainbow rst135 (non encoder) now. My big hesitation is that there is no brake if power is lost. Has anyone had a pier crash because of something like this? With the 3 less expensive companies entering the market, used prices of rst135 are really low, which has some appeal. Additionally, how do people like theirs? |
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Oh, and I'm looking to use this with a refractor. 550mm FL. With all my gear it comes in at 26lbs. I also have an epsilon 160ed. Weight is about the same but it's a much bigger setup with more moment. I would be guiding. |
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| And finally, I'm a pixel peeper. So eccentricity at 0.45 or less is important to me. My seeing is average. |
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Hi Chris, I put some time into this question a while back. (searching for a similar mobile mount that I can use with the smaller refractors) I've owned a few different mounts and the one I've been most happy with is the HEM44EC. The EC for ioptron mounts is fairly modest compared to the likes of SB, AP, or 10micron, but they do seem to allow for better overall guiding. The carbon tripod from them is solid (compared to the NYX-101), but you'll likely need the pier extender for anything decent size.I was tempted by the RST and also looked at the Hobym. I just couldn't find consistently good feedback on them. (can't find much on the ioptrons either) I've mostly run it with a FRA400 or Redcat71 to date. With a 7xEFW, asi6200, and Guidescope, etc it comes in around 20-25 lbs. On good seeing night I can get around .5"-.7" rms. On more average night it's around .8" I haven't tried it on my Epsilon 160 yet though. (i keep that on my larger mount) I think I would have considered the RST more if it didn't seem so overpriced for the payload. I also couldn't verify what sort of guiding to expect (better than other harmonic mounts? or the same?) |
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The lack of a brake is mostly relevant for bigger and/or heavily unbalanced systems. If there is no power, there is still resistance of the gearing inside the mount. Heavier scopes will start to move slowly if it is out of balance. If the scope is very heavy it can go reasonably fast, but I doubt it will be going so fast to do any damage when hitting the tripod. I've just 're-instated' the mount again for a travel setup based around the Takahashi FS-60CB/QHY268c. In that setup the mount never moves with power off, regardless how the scope is pointing. I know many people carry quite heavy scopes on these mounts, and that is how they are advertised. In my personal experience I have found that heavier scopes (let's say 8-10kg and above) are getting quite precarious, especially when using unbalanced. Also strain wave mounts can't deny physics. Even the smallest play in mount, connection, mini pier, tripod legs, etc all adds up and just makes it a wilder beast to tame. The general rule of not going higher than 50-75% of a mounts' payload is probably as true for these strainwave mounts as well as any other one. I've never done a side by side comparison, but the RST-135(E) is extremely compact and light. More so than some of its competitors. If you want to use it for a 550mm setup and your scope/camera etc. is let's say 6-8kg all together, I'm sure you will find the RST-135 a great mount to use. Like I mentioned, for my travel setup I could not be happier with it. |
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Chris White- Overcast Observatory: I've used both the non-encoder and encoder versions. Very similar performance, though the encoder version takes total PE down to a level you can guide with longer focal length scopes. Or go unguided with shorter focal lengths. I've used a 32lb 100mm refractor on both, without issue. I have had the power lost once because I wasn't paying attention but it's more of a slow motion crash, as it slowly ratchets down to bump the pier of the mount tripod. No damage occurred. But the motors are very strong, and if you stick your hand between the pier and scope you can get pinched. So just best to grab the scope and stop it from moving down. I've been using it unattended since these mounts have come out and the only power loss was my fault (turned it off while not in a balanced position (something other than home). Turning power back on immediately stops it. I've used my 135E with the Epsilon 160, two photos: https://www.astrobin.com/vqslr8/ and https://www.astrobin.com/djbwib/ Seeing in the latter one wasn't great. But it did manage to handle the weight just fine. Since these were such low integrations I didn't remove any subs. Guiding on average is around .6 RMS and can go higher like .8 in poor seeing. I think you will find this type of performance is what you can expect out of this kind of mount (strain wave), no matter the brand. They all seem to hover around the same total RMS. The Rainbow mounts are the most compact if that makes a difference to you. I've traveled with mine on an airplane, and the scope and mount fit in a single pelican case. |
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I bought a used RST-135 last November with an Innorel carbon fiber tripod. I was looking for capacity in the 15-20 pound range and light weight. Also needed to be travel friendly. I've been very happy with it. Having to home it after every session is something to get used to, as is the inability to point manually. I have had the scope swing down once when I turned the mount off without thinking. It did move slowly and did not crash before I caught it. I considered two other mounts in the same capacity range that were about $1000 less than I paid. The AM-5 is just a bit too heavy and bulky. The HAE27 was new at the time and I actually had one on order but I realized that both wifi and USB connectivity required the hand controller to be connected. I use an ASIair and like to keep everything as simple as possible. |
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I have an RST-135e version and I debated selling it for a while as I wasn’t using it much. I’m glad I didn’t, as now it has come in handy with me trying out visual astronomy. So easy to throw a scope on, not worry about balance and get to it. Now on the imaging front. I actually used it for a bit with my AP130GT with 3.5” focuser and a light camera setup and it imaged great for what the seeing allowed. I used a counter weight in that setup, and parked pointing at Polaris (AP park3). No movement if powerless at that position. But in an active imaging position, it’s going to swing down. Though pretty slowly. So that is an issue with scopes on the heavier end. Rokinon lens and camera, no movement. Will experiment with the Stowaway at some point. If you want to chat more about the mounts little quirks and strong points that I have experienced in more detail, I’m more than happy to do a call. Tom |
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I’ve had my RST-135 for a few months now. Purchased used on Cloudy Nights. Not sure if I would have purchased it new at full price. I absolutely love it. I’ve had a few sessions on it and average total RMS was no more then .25 with a Starlight Xpress Ultrastar guide camera. Love that it doesn’t need a counterweight - for most rigs up to 30 lbs. Ed at Deep Space Products swayed me to seek out a Rainbow Astro mount. He had a lot to share. I spoke to him at the time the ZWO AM5 was hitting the market and the Pegasus Astro NYX-101was available for pre-order. Rainbow Astro had proven itself in the strain wave mount market, unlike the new mounts that were coming out. I never considered the ioptron offerings. I’m sure they are good mounts. The RST-135 is such a compact mount, ideal for remote dark site use. I use the mount with a Redcat 71 on a Gitzo carbon tripod and pier extension. I love the mount. It gets 2 thumbs up from me. |
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I have the 135E and it's a great travel mount. I started with the 135 and upgraded to the 135E for easier guiding. I like the RST-135 much more than my NYX-101. I am contemplating selling the NYX but it has the capacity to run my Epsiilon 200 and I think it's a bit much for the RST-135. I took it with me to Moab in early June and it is light and easy to carry. It works well with the ASIAIR and I've had no issues. I have used the 135 with my TEC140 imaging the moon and had no issues. I was somewhat close to balanced and I had an oops with the power. Like others posted, the back driving was slow. I was able to stop the back driving with slight force from my hand and it stopped completely when power was plugged back in. I havent ran my Epsilon 160 on the RST-135 but the TEC140 is roughly the same weight. The moment of inertia is higher for the Epsilon but Ive known people to run one on the 135. If you were using a heavier setup I would be weary of leaving it unattended in case of power loss. Since the back drive is slow I wasnt too concerned about camera or OTA damage but i dont want to leave anything like that to chance. I did have my Stowaway with an ASI2600MM and Filter wheel along with the flattener attached to the RST-135E. I unplug it and leave the whole setup ready to go on my TPod-110 in my garage. It was not heavy enough to cause any back driving when power was turned off. If you do end up with a RST-135, I have several more risers that work with the TPod 110 and 130. I had a local machine shop make them and had them anodized red. I think a riser of some sort is a must when using a longer refractor with the RST-135. I've been very happy with both the 135 and 135E. Now that Ioptron has some new higher capacity strainwave mounts coming out im sure the prices of the RST-135 sill come down. I really wished Rainbow Astro would release a RST-300E. Their 300 mount does have the RA brake but I would prefer the encoders for improved guiding performance. |
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| I did a view showing how the back driving works on the 135 with different payload weights here: https://www.youtube.com/watch?v=cro59ERtwrY |
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Nick Grundy: Thanks Nick. I agree that the Rainbow being so expensive is a tough pill to swallow if buying new. It's not like a premium mount that holds its value either. I'm not saying it isnt better quality than the other options and maybe it is totally worth the extra cost, but since it loses about 35 to 40% of it's value as soon as it's used makes me not want to buy new if I go that route. The used prices on the buyer side make a compelling argument. I think between the Peg/ZWO/iOptron that the ioptron interests me the most. They have a new line the HAE that has strainwave gears on both axis. The main thing holding me back from iOptron is that they seem to have copy variation (which they have always had). If you get a good one you get a good one. I had an awesome CEM60. This is what has made me look towards the Rainbow now. I'm hoping that the higher cost does in this case give you what you paid for. |
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Willem Jan Drijfhout: OK Willem and the others that addressed my concern about a free-fall. I didnt realize that it would be a slow "crash." This makes me MUCH less concerned about this. I thought it would really rip with the potential to cause damage. That does bring me to another consideration. With strainwave mounts being so strong, what happens if you have a pier crash when slewing or tracking? My AP mount just stalls. You can run the scope into the pier and it will never cause any damage. Does the RST135 stall or keep grinding away? And as you mention the size is really appealing. I have a small obsy with a perm pier, but my other mount and all of the accoutrements are well over 100lbs to lug up from the basement. I just dont do it. I'd love to just grab it and toss it into the backyard on a whim, or drive somewhere. |
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Andrew Burwell: Thanks Andrew. I'll keep the encoder version in mind as well then. I will be guiding either way, and with my frac thats no big deal. A little more challenging with epsi, although I think I can slip a pegasus OAG into the image train. I made a gemini flange so I could mount that focuser on it. I have too much stuff to test though and no clear nights. |
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Chris White- Overcast Observatory:Andrew Burwell: I've used both the 135 and 135E. The added convenience of the encoders especially for guiding is worth the cost in my opinion. If the mount happens to crash when slewing I think you could have some serious issues. The strainwave gear is very strong and has a ton of torque. If a collision occurs during slewing I would be worried about something breaking. |
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| @Chris White- Overcast Observatory If it a a grab and go mount then it is much easier to baby sit and make sure collisions don't occur. I never leave mine unattended for very long and I can usually monitor mine with the camera I have in my back yard once i have a session started. |
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I have used an RST135 extensively as a travel rig with my FSQ106 and FSQ85. There are numerous results in my gallery. I find it to be a great little mount overall. I choose to use a counterweight to roughly balance it and prevent the low speed crash on power loss. To me, it is worth the extra bit of luggage weight. It is not going to damage anything when it contacts the pier, but it could apply pressure on your image train and cause some flex/tilt or if you OAG, knock your guide camera out of focus. Other than the annoying lack of a brake, I wish the power cord had a locking connector on it. I find it the male end of the power cord easily pops out of the mount which has interrupted more than a few sessions. Other than that, it is flawless. It will never perform like a premium mount. But at under 1000mm focal length, it does just fine. BTW I recommend using the half pier which helps get you more clearance. JD |
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Daniel Carter: What sort of guiding did you get from the encoder version? I was tempted by that one before I bought the HEM44EC. |
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Nick Grundy:Daniel Carter: When I have decent seeing I get 0.3 to 0.5" guiding. Even with bad seeing I normally still get 0.75 to 1.25" guiding. This was using an OAG with a Stowaway with the field flattener. I can normally use 3 to 5 second exposures and get good guiding. How do you like the iOptron mount? I was interested on the HAE69EC if Rainbow doesn't release a 300E. |
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I like the HEM44EC. It differs a bit in that it had a standard worm/belt on the dec axis though. With good seeing I can usually get just under .5" rms. With poorer seeing, it's closer to .8". Never usually above 1' though. Generally it's a great for my mobile rig or anything under 25-30lbs payload. Anything bigger and I stick with my CEM70. I've heard quite a few people interested in the HAE69EC, which should have a lot of promise. I just like to wait until a see them out in the field and hear feedback. |
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Chris White- Overcast Observatory:Willem Jan Drijfhout: A pier crash or cable snag when slewing can result in serious damage, the motors are very strong. So it is important to make sure that the scope can move freely around and cables are properly guided. I believe it switches off if it encounters heavy resistance during tracking, but not sure. Better is to define limits in software. Very important is to home the mount on each startup. Also check the location each time. There have been reports that the mount can default back to its original GPS location, which is S. Korea. That will make any slew command do very strange things. So I made it a habit of checking each time. |
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I use the RST-135 with an Epsilon 130D and find that a counterweight is necessary. I’ve gone without it a few times and a slew has failed in a way I can only attribute to severe RA imbalance. Some degree of DEC balancing is also helpful, although maybe not mandatory. The mount parks facing west, so when the power is off the northern end of the axis can slew on its own if too heavy. This is more just an annoyance and I haven’t found it to have any potential to cause harm. I also don’t get consistently good guiding with the 130D, but others do, even with the 160ED. I’ve had the most success with high aggression settings in PHD. Next I’ll try increasing the voltage to 15v, which is supposed to improve performance with this mount. If I had to redo my purchase I would have just spent a little more on the 135E. |
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Daniel Carter: Daniel Carter:Nick Grundy:Daniel Carter: Sounds like you are getting pretty much seeing limited guiding performance. Are stars coming out nice and round as well? The idea of a pier crash is a concern. I will most definitely not be babysitting it. I sleep through much of my imaging night otherwise I'm a zombie the next day. It seems that it would be an easy feature to have protection against a pier crash. Just something that senses a power draw and stops the motors. I emailed Rainbow a few days ago (Maybe wed or thurs) but have not had a reply yet. I'll ask them for a little more details about what the mount does if there is a crash. |
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Nick Grundy: Thats pretty good performance especially for short focal lengths and if it's consistent like that across the night as the load center shifts around. |
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Chris White- Overcast Observatory: i'm not sure if it makes a difference, but i'm slightly obsessive with balancing the dec and z axis. |
