Need help - CEM40, CEM60, or EQ6-R Pro?

[cfrommen]

I am undecided what mount to buy right now. iOptron CEM40, CEM60 or Skywatcher EQ6-R Pro.

I will either use a lightweight refractor for widefield imaging (around 2.5 kg) or a 130 mm F6 APO (8.5 kg incl. tube rings and dovetail bar) plus CCD (0.5kg), 60m  guidescope with rings and guidecam (1.5kg).

The total weight for the larger imaging setup will be less than 12 kg incl all accessories.

 

Question: will the CEM40 be sufficient for this job or should I consider the CEM60 instead? I also looked at the EQ6-R Pro as an alternative, but the additional 5 kg of weight compared to the CEM60 mount head is putting me off. I know the EQ6-R is an excellent and affordable mount but I am really concerned about the added weight  😞

Any suggestions?

 

-Christoph

[Rainer]

5 hours ago, cfrommen said:

130 mm F6 APO (8.5 kg incl. tube rings and dovetail bar) plus CCD (0.5kg),

I am iOptron biased 🤓

With that beast only a CEM 60. Moment arm not weight is here important. CEM 40 is too small for that even if it could carry it 40 lbs ~ 18kg ...

And if the budget allows it a CEM 60EC 🥰

Rainer

[Icesheet]

I have exactly the same dilemma and I have a similar set up to you.

If you believe the EQ6-R will get the job done then the CEM40 will too. Your maximum payload of ~12kg is 2/3 of the rated payload of the EQ6-R and CEM40 which likely puts you towards the upper end of the mount capabilities for imaging. So if you are considering the CEM40 in my opinion given the price difference just now the CEM60 is a no brainer especially if you already have a pier. It will future proof you in the event you want to get something bigger (which let's face it will happen!).

For me the choice is really between the EQ6-R and CEM60 which is primarily a price over performance decision. Secondary to that is future proofing and portability. Since the CEM60 is going to work out double the price of the EQ6-R once I factor in a tripod  then the question is will I get the extra performance from the CEM60 with my 550mm focal length refractor to justify double the cost?I'm not sure there. Hopefully someone can answer that!

When it comes to weight I would rather carry a heavier mount out and have an extra £1000 in my pocket if I get say 80% of the performance in the focal range I'm imaging at. If I decide to get a longer FL instrument then it gets more difficult. My pockets are only so deep though!

 

P.S where in Norway are you and where do you usually buy from? It's almost always cheaper to import than buy from Norwegian dealers!

Edited June 29, 2019 by Icesheet

[Icesheet]

15 minutes ago, Rainer said:

I am iOptron biased 🤓

With that beast only a CEM 60. Moment arm not weight is here important. CEM 40 is too small for that even if it could carry it 40 lbs ~ 18kg ...

And if the budget allows it a CEM 60EC 🥰

Rainer

I didn't consider moment arm. So do you think the EQ6-R being physically bigger could handle his set up even although it takes the same payload?

[jjosefsen]

31 minutes ago, Rainer said:

I am iOptron biased 🤓

With that beast only a CEM 60. Moment arm not weight is here important. CEM 40 is too small for that even if it could carry it 40 lbs ~ 18kg ...

And if the budget allows it a CEM 60EC 🥰

Rainer

Aren't the encoders only really useful if he intends to image unguided?

I think those £900 could be put to better use..

 

Edit: I would add that I would trade my EQ6 Pro for a CEM60 any day of the week..

Edited June 29, 2019 by jjosefsen

[Icesheet]

6 minutes ago, jjosefsen said:

Edit: I would add that I would trade my EQ6 Pro for a CEM60 any day of the week..

Would you pay double the price to do so though? Do you think that would justify the extra performance?

[jjosefsen]

42 minutes ago, Icesheet said:

Would you pay double the price to do so though? Do you think that would justify the extra performance?

It depends what your needs are I guess.. And how much you like to fiddle with your mount.

I've had my EQ6 for a year and already had to adjust RA/DEC backlash once to get good guiding again.  Now i get 0.5 - 0.8 RMS routinely and I am quite happy.

From what I read the iOptrons use springloaded worms, which should reduce backlash significantly.

 

I image at 520mm FL with around 5-6 minute subs being the absolute maximum, so I don't need perfect guiding, right now.. If I wan't to get something with a longer focal length, I might find it difficult to get good enough guiding.

Sometimes it really does make sense to buy once feel the sting once, instead of maybe getting the cheaper option, only to have to upgrade a year or two later.

 

Edit: I forgot to mention that my EQ6 has pretty bad pointing accuracy due to a significant amount of dec backlash.

It is not a problem for me as i use platesolving and software that will make sure that it automatically gets the scope pointing where it needs to be, even if it takes a couple of tries..

Edited June 29, 2019 by jjosefsen

[cfrommen]

4 hours ago, Icesheet said:

 

P.S where in Norway are you and where do you usually buy from? It's almost always cheaper to import than buy from Norwegian dealers!

I am located just 20 km east of Oslo. I usually buy from Teleskop-Express in Germany or from whatever country with the best exchange rate compared to Norwegian kroner 🙂

After paying 25% import duties it doesn't make a huge difference though compared to buying from a Norwegian dealer. The problem is more that you cannot get certain things in Norway. Astrosweden and Teleskop-Express have the best deals on EQ6-R Pro (12.500 NOK) currently. The CEM60 w/o tripod is available for 15.600 NOK from Teleskop-Express right now. There is a waiting time of 4 weeks, however.

[Icesheet]

7 minutes ago, cfrommen said:

I am located just 20 km east of Oslo. I usually buy from Teleskop-Express in Germany or from whatever country with the best exchange rate compared to Norwegian kroner 🙂

After paying 25% import duties it doesn't make a huge difference though compared to buying from a Norwegian dealer. The problem is more that you cannot get certain things in Norway. Astrosweden and Teleskop-Express have the best deals on EQ6-R Pro (12.500 NOK) currently. The CEM60 w/o tripod is available for 15.600 NOK from Teleskop-Express right now. There is a waiting time of 4 weeks, however.

They're actually both cheaper at FLO, particularly the EQ6-R, it comes in at 10.600Kr on current exchange rates. I think the difference might be that FLO don't automatically display ex VAT prices until you get to the checkout whereas Teleskop Express do. After duties the EQ6-R comes in at ~14.000Kr. That's a saving of 3.500kr buying new here. Well worth it in opinion especially since it seems the dealers here seem to drop ship and don't hold stock.

 

Yeah, I was close to pulling the trigger on the CEM60 last month but was put off by the delays and now the price has increased £100  . I think I'm swaying towards the EQ6-R at the moment since it has the tripod and most people seem to guide <0.8"RMS. If money wasn't the object the CEM60 would be ordered already! This isn't helped by the fact I've added highend binoculars to my list of optics!

 

Good luck with it!

[Rainer]

5 hours ago, jjosefsen said:

Aren't the encoders only really useful if he intends to image unguided?

Hi,

No, that is an Urban myth. Honestly I do not know from where this comes that people think encoders are for unguided imaging.

Question: Without Feedback how does an encoder know if it is pointing and maintaining the desired object in the center ¿? It does not ... Only by having a guide camera and fixing the whole Shishkebab with it then it will stay in the center ot whichever position you want to ahve your object.

Encoders just kill the Periodic Error but do not help you with a bad Polar Alignment nor Atmospheric refraction.

Mechanically we have reached a limit in tolerances and a worm and worm gear will always have a periodic error.

I have two CEM 120EC2 and before that I never reached the performance I have now and yes I do guide but I do guide with a cadence of 15 seconds and not 1 or 2 maybe 3 seconds.

I correct for bad Polar Alignment and perhaps Atmospheric refraction. iOptron says they have implemented in the algorythm a atmospheric refraction compensation.

IMHO = In My Humble Opinion

and yes it was worth to spend US $ 3,000.00 more for each mount. Instead of US $ 3.998.00 I paid US $ 6.998,00 for each mount and got a carrying capacity of 52 kg (without counterweights)

Rainer

 

Edited June 30, 2019 by Rainer

[Rainer]

4 hours ago, jjosefsen said:

I image at 520mm

Hi,

I image at 2424 mm or sometimes up to 3203 mm focal length and make exposures of up to 1800 seconds as my main targets are the Arp Galaxies.

Rainer

[Rainer]

5 hours ago, Icesheet said:

So do you think the EQ6-R being physically bigger could handle his set up even although it takes the same payload?

Maybe but I see a design problem in the way the whole head is attached to the base. The CEM 60 has a broader foot ... and therefore is more stable

IMHO = In My Humble Opinion

 

Rainer

[cotak]

In some places like Toronto the temps are 30-40 in the summer, and -25 in the winter. Self adjusting worm like what iOptron has make sense in my use case. 

And once I got my balancing right and the guiding smoothed out we do see this on my EC.

 

Edited June 30, 2019 by cotak

[jjosefsen]

6 hours ago, Rainer said:

Hi,

No, that is an Urban myth. Honestly I do not know from where this comes that people think encoders are for unguided imaging.

Question: Without Feedback how does an encoder know if it is pointing and maintaining the desired object in the center ¿? It does not ... Only by having a guide camera and fixing the whole Shishkebab with it then it will stay in the center ot whichever position you want to ahve your object.

Encoders just kill the Periodic Error but do not help you with a bad Polar Alignment nor Atmospheric refraction.

Mechanically we have reached a limit in tolerances and a worm and worm gear will always have a periodic error.

I have two CEM 120EC2 and before that I never reached the performance I have now and yes I do guide but I do guide with a cadence of 15 seconds and not 1 or 2 maybe 3 seconds.

I correct for bad Polar Alignment and perhaps Atmospheric refraction. iOptron says they have implemented in the algorythm a atmospheric refraction compensation.

IMHO = In My Humble Opinion

and yes it was worth to spend US $ 3,000.00 more for each mount. Instead of US $ 3.998.00 I paid US $ 6.998,00 for each mount and got a carrying capacity of 52 kg (without counterweights)

Rainer

I've just seen this claimed on this forum before, but was never quite sure as I don't have any hands-on experience, hence the question.

But i suppose what you say makes sense, particularly as you are imaging at such great focal lengths.

[jjosefsen]

6 hours ago, Rainer said:

Hi,

I image at 2424 mm or sometimes up to 3203 mm focal length and make exposures of up to 1800 seconds as my main targets are the Arp Galaxies.

Rainer

Aaah Arp Galaxies make for some very interresting targets.

I have the book: "The Arp Atlas of Peculiar Galaxies" - quite interresting.

[Rainer]

8 hours ago, jjosefsen said:

I've just seen this claimed on this forum before,

Hi,

Well yes I think I have written this here in SGL a few times 🤓 but as it looks like as I am the only one with that theory it is not taken serious 🤣

The mount builders now incorporating encoders in their mounts have stirred up the Amateur Astronomy community and a lot do not know how to handle that 🤔 and many assumptions and guesses were made but also due to marketing in one or the other mount producer website ...

Well, the future will tell ...

Rainer

[Icesheet]

I have looked into this is in a bit more detail. I didn't want to hijack @cfrommen's post with my input but if you would like to have a look and comment please do here.