iOptron CEM60 vs CEM40 Mounting Holes

[Stratis]

Hi all,

Coming back to astro after a long break, many ups and downs  

I recently hauled my trusty CEM60 out of limbo and realised I'd like to shift to a smaller mount, as I have never come near the incredible weight limits on this mount for imaging or visual. The new CEM40 really looks perfect in most regards, so I am hoping that will serve as my new main imaging mount. I image with apo refractors, from a 7kg 115mm TS triplet down to a little WO Megrez 72 at only 2kg on an AstroTrac, with both DSLR and QSI 583wsg (so about 2kg camera package). My greatest imaging load has never exceeded 12kg.

I already have an amazing Avalon T-110 T-pod underneath the CEM60, with an iOptron adapter atttached, this one in fact: https://www.teleskop-express.de/shop/product_info.php/language/en/info/p10799_Avalon-T-Pod-110-130-Adapter-Kit-for-iOptron-iEQ45-and-CEM60-Mounts.html

This adapter has the central peg for iOptron, plus mounting holes set around the perimeter for the alignment pegs. The adapter has two sets of two threaded holes; the first set is 130mm apart across the centre, and fits the CEM60 perfectly. The second set is 120mm apart across the centre, and I think is meant to fit the smaller iOptron mounts like the iEQ30. 

So the £1400 question; can the adapter accept a CEM40 mount? Can the two threaded holes set 120mm across the centre mate with the CEM40? If anyone has any info on the absolute mounting hole arrangements for the CEM40 alignment pegs it would really help  

[cotak]

Best to email ioptron support with that question as reports suggest that the cem40 has its own mounting setup.

[Jkulin]

Its all in the manual: -

https://www.ioptron.com/v/Manuals/7400_CEM40_Manual.pdf

" STEP 2. Set up tripod The tripod top is 120 mm in diameter with 2x M6 holes 103 mm apart for mounting. Two additional M6 holes are for the Alignment Peg (the one on top of a leg is for high latitude use; the other one between two legs is for low latitudes). Thread the Alignment Peg into the correct M6 hole. Insert the Accessory Tray through the center rod and secure the setup by tightening Locking Knob from underneath."

HTH

[Rainer]

Hi Stratis,

Is this what you want to load on a CEM 40 ?

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p3041_TS-Optics-PHOTOLINE-115-mm-f-6-96-Triplet-APO-with-2-5--RP-focuser-1-11.html

If yes, I do not recommend to go down to a CEM 40.

Weight is not everything. Moment arm is more important then total weight ...

There is a big difference between a cylinder 40cm long weighing 7 kg or a cylinder 100cm weighing 7 kg. Both have the center of gravity in the middle but the moment arm exert totally diferent forces on the mount if 40cm or 100cm at the same weight ...

You can test it your self. Take a 40 cm long stick and move it rotational back and forth and take a 100cm long stick and do the same ...

regards Rainer

Edited May 16, 2019 by Rainer

[jed2i]

I have that telescope and i am also thinking about cem40 and i believe that you are wrong

If you balance it correctly, then only thing that matters is a mass of an object, it is the same if you have an object that is 100cm long or 200cm long if the weight is the same

That optical tube is 6.4 kilos, mount the guidescope, camera, filterwheel..... and you are well beneath the 18 kilos that mount can handle, just balance it carefully

[cotak]

No he's not wrong, but maybe more details would help.

It's why you have the crazy 1/2 and 2/3 rule that's outdated but keeps being repeated. All the rule does is helps beginners avoid being overly ambitious and end up discouraged.

Now I am no fan of Astro-physics for various reasons but even they have admitted their payload rating isn't the simple old dogma of "it's premium so it's imaging payload" by publishing a diagram for the mach2 showing what the limits are based on OTA dimensions. Go check it out if you want but basically longer the tube the less it can hold, and the wider the tube the less it can hold. So even though the mount claims 75lb of payloads it only can achieve it if the diameter of the OTA is around 8 inch. Sobering news actually for anyone considering a so called premium mount. Btw please never use the word premium again here, it's uniquely useless in providing any useful information. All it does is divided people by implying some is more equatorial than others (if you are confused about this joke, go read up on animal farm ).

The reason why dimensions and moment matter is this:

http://web.mit.edu/4.441/1_lectures/1_lecture5/1_lecture5.html

Boil it down and it's basically about leverage, longer arm the more force applied at the other end.

One thing to also note is that longer the OTA the more the ends of the OTA move in an arc for a given rotation at the pivot. It's actually the related physics for moment arm/leverage but it also means that for a given tacking error the impact is greater for a larger OTA. And if you think about it this is spelled out also in image scale calculations, with different implications depending in relation to moment arm forces and the mount ability to resist the force.

Edited May 17, 2019 by cotak

[Rainer]

On 16/05/2019 at 04:26, Stratis said:

Hi all,

Coming back to astro after a long break, many ups and downs  

I recently hauled my trusty CEM60 out of limbo and realised I'd like to shift to a smaller mount, as I have never come near the incredible weight limits on this mount for imaging or visual. The new CEM40 really looks perfect in most regards, so I am hoping that will serve as my new main imaging mount. I image with apo refractors, from a 7kg 115mm TS triplet down to a little WO Megrez 72 at only 2kg on an AstroTrac, with both DSLR and QSI 583wsg (so about 2kg camera package). My greatest imaging load has never exceeded 12kg.

I already have an amazing Avalon T-110 T-pod underneath the CEM60, with an iOptron adapter atttached, this one in fact: https://www.teleskop-express.de/shop/product_info.php/language/en/info/p10799_Avalon-T-Pod-110-130-Adapter-Kit-for-iOptron-iEQ45-and-CEM60-Mounts.html

This adapter has the central peg for iOptron, plus mounting holes set around the perimeter for the alignment pegs. The adapter has two sets of two threaded holes; the first set is 130mm apart across the centre, and fits the CEM60 perfectly. The second set is 120mm apart across the centre, and I think is meant to fit the smaller iOptron mounts like the iEQ30. 

So the £1400 question; can the adapter accept a CEM40 mount? Can the two threaded holes set 120mm across the centre mate with the CEM40? If anyone has any info on the absolute mounting hole arrangements for the CEM40 alignment pegs it would really help  

Hi Stratis,

Any news about your project about downgrading from CEM 60 to CEM 40 ? 😲

Rainer

[Chris Tardif]

Nothing like being late to a thread, but in my quest for a new mount (still undecided (CEM40, CEM60, EQ6R-Pro)) I found a graphic that shows how the capacity of a mount falls off as the diameter of the OTA increases.  It lives here: https://astro-physics.com/mach2gto 

I would think that all mounts would behave in a similar manner.

[Rainer]

3 hours ago, Chris Tardif said:

Nothing like being late to a thread, but in my quest for a new mount (still undecided (CEM40, CEM60, EQ6R-Pro)) I found a graphic that shows how the capacity of a mount falls off as the diameter of the OTA increases.  It lives here: https://astro-physics.com/mach2gto 

I would think that all mounts would behave in a similar manner.

 

Hi,

That is a nice example of how to specify the real carrying capacity of a mount 👍

What are you going to mount on the new mount you intend to buy ?

Rainer

 

[Chris Tardif]

I am expecting delivery of an Explore Scientific 102mm FCD-100...should be arriving tomorrow by 5pm if I believe FedEx....and yes I completely realize I am putting the cart before the horse.  I just started tinkering with this hobby in February when I bought an Explore Scientific iEXOS-100 mount.  It was $500 CDN and I got it as a "proof of concept".   My plan was to use cameras and lenses I already had to see if I enjoyed this.   What I learned so far is that this is an immensely satisfying and frustrating pursuit.  

I ramble....

All of these mounts will hold my new refractor.   My questions are do I buy the forever mount (CEM60), the cheapest mount (EQ6R) or the newest mount (CEM40).  All of which will meet my short term needs and all of which have drawbacks.  The CEM60 is expensive, the EQ6R is heavy and the CEM40's minimum operating temperature is -10c.  Living in Canada it can be -10 from December to March.  The CEM40 is the front-runner...maybe I just wrap a dew-heater around it.  

My two month plan is to put the ES-102 on the little iESOX-100 mount and watch it cry while I figure out what to do.  I hope to have the new mount by end of summer.

Thanks!

[cotak]

The min temps are based on the commerical electronic components ratings, but those are nothing more than suggestions in reality when you talk lower end of temperature.

I have used the ieq45 pro and cem25 at -25C many times without issues. Even when the ieq45 been cold soaked for a few days outside in the observatory.

So don't worry too much about that. Since we have such wide temperature ranges here in Canada, the eq6 would likely require different worm mesh adjustments to achieve best possible performance based on temperature. And if you are hauling it in and out that might be an issue if you want to do the adjustments in doors. My ioptron mounts work the same without adjustments whether it was approaching 40C out or -25. 

As for forever. Never say never. Although for most people who aren't very wealthy or just spending all their money on this hobby, going to a point of exceeding the payload limits of the cem60 would be prohibitive in cost.

Edited June 25, 2019 by cotak

[Chris Tardif]

Alas...FedEx let me down.  Overnight.....ugh.

[Rainer]

On 24/06/2019 at 20:06, Chris Tardif said:

My questions are do I buy the forever mount (CEM60), the cheapest mount (EQ6R) or the newest mount (CEM40).

Hi Chris,

I am strongly biased but I would go for the CEM 60 and if the money does allow go for the EC version.

Rainer

[Stratis]

Well it's been a bit of a rollercoaster since I started this thread, thank you to those offering advice  

My CEM60 has to have a full service as it turns out the previous owner (since learned he is a convicted criminal....) did some 'DIY' inside the mount and badly screwed it up. It's entirely correctable, but I want a proper repair warranty on it for the next owner so they can be assured it'll work as advertised. Til I get a new mount I am confined to my AstroTrac and baby refractors.

I've reviewed the payload specs for the CEM40 and it really should work fine with my largest imaging scopes, the C8 and the 115mm triplet. My biggest and most irritating scope to mount is a 152 f/5 achromat which is both long and heavy so that may be out of its comfort zone for imaging, but for visual should be ok. I recently sidegraded my imaging camera to a much lighter setup which should help a lot with its payload moment too.

I've confirmed I cannot use my beloved Avalon T-pod 110 with the CEM40 so if I go that route I will have to abandon it. Anyone in the market for a near-mint black Avalon T110 T-pod with free CEM60 adapter plate?  

[x6gas]

My CEM40 finally arrived last week (long story) and it's due to be clear tomorrow.  I want to run it with my baby Q first but I hope to test my TS130 frac on it; not that I really plan to use this scope / mount combo but I am curious as to how it will perform.  Will post the results...

[Sreesha74]

Can CEM40 handle a RASA 8"?

[Chris Tardif]

Yes.  RASA 8 weighs 17 pounds the CEM 40 can handle 40.  Check out Ben's Astrophography on YouTube.  He's got a 22lb Newtonian on his.  

Looking back on this thread, I commented when I was about to receive my CEM-40.  Ten months later I am very happy with it.  I have the usual photography kit including me ED-102.  I took it out once when it was below -15c.  The mount performed significantly better than I did.  It turns out that I didn't need a mount that could perform at lower temperatures because that's just too cold to be imaging.  My limit is -10c.