Best and most economical mounts for 8SE and AP, short term vs long term with bigger OTA? Avx vs cem60 vs hdx110 etc?

[theskyisthelimit99]

Im beginning construction on at least an in ground pier with a deck and maybe a nexdome in the near future.

Currently i just have an 8SE on nexstar plus az mount, maybe 19lbs in total payload when using a canon 6d dlsr.  I cant really say what the future might hold aside from maybe wanting to jump up to a 9.25 or 11" edge or some other larger aperture scope one day with hyperstar, or larger aperture and piggy back say an 80 to 130mm refractor for DSO, guessing 45lbs on the 11" option, maybe up to 80 or 90 with a refractor piggy back.

For now all i know is i need to get to a GEM mount and hopefully something that can resume from power off to make remote ability a little easier, but it wont be impossible to walk out and get it going (at least if it could just resume and not need re-polar aligned each time)?

So that said, i'm looking for input on mounts for short term and long term with a shoe string budget in mind.

I've come up with a few options:

Short term just to get to a GEM (and still use the celestron staralign and focuser i have)... AVX $799?

Or

CEM60 $2200 with max payload ability of 60lbs would probably last me forever without upgrading unless i go super heavy 11 one day? (i've seen reports of many doing 50lbs no issues)

Or

HDX110 with 110 lb ability at $3000 (getting too far out of my price bracket, but more of a one shot deal)

Then of course there are the mach1 options but at $5400 not really an option for me, even a used ap900 would probably exceed my limits (trying to be under 2200).

 

Then there is the question of guiding ('m largely unfamiliar with the ins and outs, aside from a camera + refractor + phd software), there are the cem60EC versions or even cem120EC that have encoders built in to avoid the need, but does their extra cost outweigh the cost of a guider system (or even a cheaper $360 one from orion that i've seen mentioned), sounds like probably not worth trying to afford the ecs?

I briefly considered the skywatcher eq6, but it was mentioned somewhere it doesnt really resume well from a power off state, so i threw it on the backburner as even a short term solution.

 

Can anyone provide some input here, are my options about right?

 

Thanks in advance

[cotak]

Avoid the AVX. It's workable but I am firmly in the believe that it is the cause of many a post traumatic mount disorder.  PTMD is when someone get their first eq mount, crashes with it and go off the deep end spending a fortune on a "premium" (don't you just love that love fest of a discussion over on CN?) mount and get the same performance others do on a skywatcher eq6. Typically that ends up with the user also telling everyone how the extra money paid resulted in round stars all the time (but dropping up to 50% of frames in private), and no stress or worries (tell that to people who sold their premium on cause they couldn't get it to work well enough either, these folks do exists).

So lets go over your other options.

I use a CEM60EC and I like it a lot. It took a bit of tuning to work out what guide settings works with it but overall satisfied customer here. The common warning you hear is about the worm, and it is scary at first but don't worry too much as long as you are taking your time during the engagement disengagement part you shouldn't have an accident. The worm mechanism does allow you to perfectly balance you kit if you spend the time at it which pays off I think in better results. Also, you get essentially zero backlash once balanced and worm is floating on the magnets. Otherwise be aware that while iOptron does stand by their products, quality control is not perfect so there is a small risk of a lemon. If you do get a lemon I think you'll find they will work with you to fix up to your satisfaction. The CEM60 is similar from my perspective for why you should or shouldn't buy one. 

HDX110 would be a good mount for the price. It'll be unlikely you'll out grow it. It is older styled and if backlash bugs you it might not be the best choice. I don't know too much about it but you don't see a lot of complaints. 

Mach1, ahh the premium of the lot. It's discontinued due to the up coming mach2. You do realize the base price does not include dovetail plate, counter weights, and hand controller (optional for AP)? While it is supposed to be a great mount and folks worship it, it isn't perfect. For the cost you don't actually end up with more performance for lower payloads, and for SCT it's limits as AP have said before is 11".  Since 11" is also roughly what the CEM60 can do why would you pay more? Or why not throw the cem120 into the mix if you are willing to pay mach1 prices? What's more if backlash bugs you it's been stated by AP that the mach1 and everything else not mach2 (which has belts) can have 0.5 to 1 second of backlash due to the spur gears in the reduction drive. Personally, I find there aren't many reasons to buy AP. Now, if you are keen on talking to someone on the phone for support and wanting the "long term" support maybe this is for you. However, long term doesn't mean forever as older mounts like the 400 appears to be having difficult to find parts for (circa 2000 last copies I think). 

In the end I'd suggest the CEM60 as that's what I know the best. It does pretty much what most people want of it. It can recover from power lost on it's own. And generally works out of the box without any work by the end user (some of us are picky and would end up adjusting something anyhow). The downside is a small risk of a lemon and living with some idiosyncratic software design choices made in Nanjing (btw their local staff is great, but getting response from Nanjing can be challenging if you want to ask a serious question). If you are OK to pay more consider the CEM120, it's got better worm switches and better cable management. 

 

[theskyisthelimit99]

11 hours ago, cotak said:

Avoid the AVX. It's workable but I am firmly in the believe that it is the cause of many a post traumatic mount disorder.  PTMD is when someone get their first eq mount, crashes with it and go off the deep end spending a fortune on a "premium" (don't you just love that love fest of a discussion over on CN?) mount and get the same performance others do on a skywatcher eq6. Typically that ends up with the user also telling everyone how the extra money paid resulted in round stars all the time (but dropping up to 50% of frames in private), and no stress or worries (tell that to people who sold their premium on cause they couldn't get it to work well enough either, these folks do exists).

So lets go over your other options.

I use a CEM60EC and I like it a lot. It took a bit of tuning to work out what guide settings works with it but overall satisfied customer here. The common warning you hear is about the worm, and it is scary at first but don't worry too much as long as you are taking your time during the engagement disengagement part you shouldn't have an accident. The worm mechanism does allow you to perfectly balance you kit if you spend the time at it which pays off I think in better results. Also, you get essentially zero backlash once balanced and worm is floating on the magnets. Otherwise be aware that while iOptron does stand by their products, quality control is not perfect so there is a small risk of a lemon. If you do get a lemon I think you'll find they will work with you to fix up to your satisfaction. The CEM60 is similar from my perspective for why you should or shouldn't buy one. 

HDX110 would be a good mount for the price. It'll be unlikely you'll out grow it. It is older styled and if backlash bugs you it might not be the best choice. I don't know too much about it but you don't see a lot of complaints. 

Mach1, ahh the premium of the lot. It's discontinued due to the up coming mach2. You do realize the base price does not include dovetail plate, counter weights, and hand controller (optional for AP)? While it is supposed to be a great mount and folks worship it, it isn't perfect. For the cost you don't actually end up with more performance for lower payloads, and for SCT it's limits as AP have said before is 11".  Since 11" is also roughly what the CEM60 can do why would you pay more? Or why not throw the cem120 into the mix if you are willing to pay mach1 prices? What's more if backlash bugs you it's been stated by AP that the mach1 and everything else not mach2 (which has belts) can have 0.5 to 1 second of backlash due to the spur gears in the reduction drive. Personally, I find there aren't many reasons to buy AP. Now, if you are keen on talking to someone on the phone for support and wanting the "long term" support maybe this is for you. However, long term doesn't mean forever as older mounts like the 400 appears to be having difficult to find parts for (circa 2000 last copies I think). 

In the end I'd suggest the CEM60 as that's what I know the best. It does pretty much what most people want of it. It can recover from power lost on it's own. And generally works out of the box without any work by the end user (some of us are picky and would end up adjusting something anyhow). The downside is a small risk of a lemon and living with some idiosyncratic software design choices made in Nanjing (btw their local staff is great, but getting response from Nanjing can be challenging if you want to ask a serious question). If you are OK to pay more consider the CEM120, it's got better worm switches and better cable management. 

 

Thanks for that detailed reply, it all makes good sense.  Yeah it seems like the cem60 (non ec one) might be my best choice, downside, if i end up like one or two people i've seen putting 90lbs of piggy backed equipment on an 11" then ill have to sell/upgrade later, wasting probably $1000 anyway, however thats neither here nor then for the time being and all conjecture though the cem120 makes the most sense but not economic sense, as i'm putting a lot into a dome just to get a permanent base outside (automation etc too).

There doesnt seem to be stock of a cem60 right now which adds to the issue perhaps.  The hdx would also make sense but it too is $3400 (if that includes everything).   I originally considered used but i'd rather not get someone elses issues (that they may not even know about)

On the backlash, i guess at this point i dont quite understand the term or implications, i mean right now i have the 8se alt/az there will be a huge learning curve im sure, but i have a host of issues with the existing mount.  IE: planetary imaging the planet moves on its own over 30-60 seconds (i think this is backlash?) maybe due to too much weight already.  

I'd like to be able to image without constant pressing of the arrows to recenter, i assumed the gem will help.  Same deal with dso if i get the hyperstar or even now as is with the canon 6d, i'd like to be able to do exposures without trailing issues/drift.  I'd imagine a time where i could do minutes at least over a series of exposures letting it run all night through say SGP or similar in the dome, ideally.  (living in the suburbs class 5, the longer the better i suppose, to cut through the light pollution issues)

 

[cotak]

Yes the CEM60 appears to be in short supply. FLO reports it is due to some component shortage but no one knows anymore about it. I think is is likely a combination of the launch of CEM120 + CEM40, and the popularity of the CEM60 itself. 

I wouldn't worry too much about ultimate payload for now. There are example of CEM60 carrying 50lb of kit without too much trouble, and for a lot of people lifting 50lb regularly and in the dark is not consider a favorite activity. For a lot of people 8" of aperture is all they'll ever need so you need to ask yourself how likely you'll go above 8 from a weight and cost view. Since you are just starting you might end up deciding that for you APO refactors are the way to go, and in that case you might be hard pressed in the wallet sector to reach the theoretical payload limits.

Backlash in general is in relation to declination only. It's is caused by gaps between metal gears. In older designs the reduction drive from motor to worm often use spur gears which cannot be 100% tight, so those tends to have more backlash where the space needs to be taken up before the worm turns. In the worm/wheel interface you could also have gaps which causes similar issues. In spring loaded worm system the gap is very small, just the space for the oil film from the grease. On fixed worm system the gap can only be set once and needs to allow for some variation due to temperature changes so tends to be larger than spring loaded systems. The end result of all this is that with a mount that has backlash your DEC guiding would show traces where a lot of guide inputs need to be given before there's a response, which can result in poorer guiding. In RA the worm and wheel gap means something else where the scope can end up bouncing between the two faces of the worm gear. To combat this people create a weight bias to force the scope into "east heavy" configuration. You need to be east heavy as that makes the worm/wheel loaded where the motor is driving against the bias. If the bias goes with the motor there are usually catch-slip events where the scope doesn't move for a bit until enough force causes the gearing to slip. As a result you need to either change the position of the counter weight after meridian flip or use some other method to always induce east heavy configuration (some hang a weight on the RA that gets wound up). 

I think what you mean about pressing button is that your target drifts with your current unguided setup? That requires guiding. To really do imaging you need to bite the bullet and just get on the guiding train, or really spend money to buy a system that can go unguided, but the latter often can be a bit of a pain as you also need to work to eliminate all sources of shift in the optical train as well which can be a nightmare for some.

[ollypenrice]

Reading your post makes me suspect that you are, maybe, concentrating on the wrong numbers. Mounts do have to carry the payload you put on them, certainly, but they also have to deliver a tracking accuracy under guiding which is at least twice as good in arcseconds as your imaging scale in arcseconds per pixel. A C8 and 6D are working at 0.66" per pixel at native FL or 1.07"PP with O.62 reducer. 0.66"PP would require you to achieve a guide RMS of about 0.3 arcseconds, which is just about possible on a premium mount and with good seeing.  1.07"PP is more reasonable and can even be supported by a good EQ6 (they vary a lot) or by a CEM from what I read. It is also worth noting that, even when the mount can deliver these accuracies in principle, the seeing may not allow you to capture real details at anything like this resolution. (I image at 0.9"PP on a Mesu 200 mount but it is common for the seeing to make imaging in Luminance pointless. By using a mono CCD I can shoot colour when the seeing is unstable and wait for a steady night for the luminance.)

This brings us to the possibility of moving to an even longer FL SCT. Unless you could considierably increase your pixel size there would be no point in doing so because the resolutions in question will never be supported by the atmosphere in anything resembling a normal location and without a seriously premium mount. If using a mono CCD camera you could usefully make effectively bigger pixels by binning 2x2 or even 3x3. A mono CMOS could do likewise but the gain in efficiency would not be so great.

If you are planning ahead and starting from scratch I would first set out to match local seeing, a realisitic estimate of mount tracking error under guiding, focal length and pixel size. In astrophotography these work together.  If any one of these numbers is significantly out of step with the others it will, if it is 'better' than the rest, be wasted and, if it is 'worse' than the rest, totally negate the advantages of all the others. This is a handy pixel scale calculator: http://www.12dstring.me.uk/fovcalc.php  It will give you the imaging scale of any system you choose to model.

You mention Hyperstar. Beware! There is a lot they don't tell you and a lot of what they do tell you is, in my view, deceptive at best and downright false at worse. One thing is certain: F2 will never, ever, be 'easy.'

Olly

[Datalord]

Great advice from the other two gents. And especially the point Olly is making about focal length, which leads me to ask you which targets you want to shoot? Deep galaxies, widefield nebulae or planetary? 

If deep galaxy, long FL, heavy reflectors, ccd and from very personal experience, you need crazy expensive mounts. (I upgraded to a £11000 ASA for this very purpose). 

If widefield (<1000mm), you can relax your mount requirements a bit. I now run my RASA on a celestron CGX, which is a decent match. But you need filters for narrowband and ideally a ccd camera. 

If you want to do both of the above by piggybacking, you need to have an even better mount. 

Planetary doesn't really strain the mount, but you need a fast camera, most likely cmos, which is luckily also cheaper than the ccd. 

As someone with personal experience with celestron, I would advice you to stay far away from them. PTMD is real. 

[theskyisthelimit99]

On 03/07/2019 at 08:22, Datalord said:

Great advice from the other two gents. And especially the point Olly is making about focal length, which leads me to ask you which targets you want to shoot? Deep galaxies, widefield nebulae or planetary? 

If deep galaxy, long FL, heavy reflectors, ccd and from very personal experience, you need crazy expensive mounts. (I upgraded to a £11000 ASA for this very purpose). 

If widefield (<1000mm), you can relax your mount requirements a bit. I now run my RASA on a celestron CGX, which is a decent match. But you need filters for narrowband and ideally a ccd camera. 

If you want to do both of the above by piggybacking, you need to have an even better mount. 

Planetary doesn't really strain the mount, but you need a fast camera, most likely cmos, which is luckily also cheaper than the ccd. 

As someone with personal experience with celestron, I would advice you to stay far away from them. PTMD is real. 

Yes thanks for the posts, good stuff i'm still digesting haha.

In my case, i want it all haha, i want to do everything.  Issue is, i'd rather do it all via one mount rather than swapping in and out and buying duplicate guide equipment for each "set".  But, i guess this isnt how most do things?  

I was planning the nexdome/permanent pier, so the initial thought was cem60, but something like the hdx110 is tantalizing and i know one person that uses 90lbs on it (guided) with multiple options (at least one long 130mm refractor for dso's and ccds and moonlite focusers)

So if this isnt realistic then i guess i need to start envisioning swapping once i get there with multiple options.  I realize i'm ahead of myself, but in creating this dome I dont want to under mount and have to change it all later.

The other question, if i'm swapping, can the GEM mounts be Polar Aligned and then simply swap in and out if the spot where they were is marked (how effective is this)

And yeah i thought maybe hyperstar would eliminate the swap and combine say an 80mm and 127+mm refractor in one shot (I think i could see having an 80, 127 etc for different targets?).

I was about to pick up an ES ED80 thats on sale now and figure out how to add it to my 8se (i think i need a top mounted long dove tail), but in doing so i really should be at the new mount, so not quite there yet.

 

I guess too that the faster the refractor or even a hyperstar, would be better suited for light polluted locations like mine tends to be (bortle 5) resulting in less integration times needed.

 

[Datalord]

23 hours ago, theskyisthelimit99 said:

i want it all haha

Well then, welcome to an extremely expensive hobby. It means you need a very good mount, capable of heavy load.

I have no first hand knowledge of the hdx110, but from what I read it's not impressive. It focuses on load capacity instead of stability in guiding. If you have a friend with first hand knowledge and is having success, then you should rely on his advice. Ask him about his guide RMS with his setup and how hard it was to achieve. 

23 hours ago, theskyisthelimit99 said:

, if i'm swapping, can the GEM mounts be Polar Aligned and then simply swap in and out if the spot where they were is marked (how effective is this)

Nope, expect to do PA every time you touch mount stuff. 

[theskyisthelimit99]

Payload aside, anyone have any thoughts on the quality of the hdx110 vs the cem60 overall?