Ultimate planetary scope for a HEM15

[Ags]

I finally made up my mind about my mount upgrade from my current AZ-GTi, and have gone for a HEM15. The stated capacity is 8 kg without counterweight and 12 kg with counterweight, and I can believe the capacity having seen a video of the little mount throwing an 8 kg RC around like an anodised toilet roll. Admittedly it was just the RC OTA and no accessories.

The question I am asking myself is what planetary telescope to aspire to put on this mount? I am assuming it would be something with a folded light path and would take a year of saving, so what should it be? The objective is something with a bit more imaging and observing oomph than my worthy C6. I want to get a lot closer to the Moon for example.

The obvious option is a C8, which the mount would carry very comfortably indeed. 

A cheaper option more skewed to visual enjoyment would be the 8" Classical Cassegrain - the main downside being it is more of a 7" Classical Cassegrain?

Instead of the C8, I could save a few months more and get a C8 Edge? Worth it for visual? Am I right in thinking there would be no benefit from a planetary imaging viewpoint?

For the same money as the C8 Edge, I could get a C9.25 non-edge. At over 9 kilos a counterweight would be needed but I wouldn't be using heavy accessories.  My main concern is not that the scope would be too big for the mount, but rather that the scope would be too big for me!

For the same money I could also get a Mewlon 180 - possibly the best visual option?

Edited January 14 by Ags

[bosun21]

The 180 Maksutov is a great scope for lunar and planetary. Sharp as a tack.

[Elp]

The main thing about the weight consideration for this application is the setup not falling over, this is down to your tripod.

I bought mine with the intention of eventually getting a C8 Edge HD, Rasa 8 or a 120 APO for imaging, whether it can track stably for imaging for these weights and FLs I don't know yet, I intend not to have to use a CW if I do go down this route.

Edited January 14 by Elp

[Ags]

1 hour ago, bosun21 said:

The 180 Maksutov is a great scope for lunar and planetary. Sharp as a tack.

I do like Maks! But I think the 180 has a bit too much focal length for me

[michael.h.f.wilkinson]

Apparently the C8edgeHD is also better corrected in the centre, and that could mean quite  bit for planetary. I have been considering a C9.25 for better planetary views as well, but then the weight of that scope is not that much lower than a C11, so I am tempted to go for that one (I also have an AM5 which could handle that). I will have a go with my HEM15 to see how well it carries the C8, should the weather clear at some point.

[Ags]

I think it comes down to aperture vs quality, so I think it will be either the C9.25 or the Mewlon 180. Decisions!

[M40]

It might help you make up your mind. Including the losmandy plate underneath the thing its 11kg. It sits on an heq5 which has no challenges with it albeit I would guess its on the mounts limits.

[Ags]

Yes, but what is it?

[M40]

It's a skymax180 🤦‍♂️ would have been an idea to say that 😁

I have added the second focuser and eaf as it completely removes the shakey hand syndrome on high power.

Edited January 16 by M40

[dweller25]

Hello @Ags

I have also had this question and have tried a lot of Maks and SCT’s  before settling down to my final folded type planetary scope.

It is a Mewlon 180 and the reasons I settled on it are :-

No corrector so it does not dew up

1/20th wave optics.

Superb contrast - only an Intes 715 Mak was this good but it dewed up !

Excellent build quality

Fairly light weight - I use mine on a Vixen GP

Hope that helps.

 

 

Edited January 16 by dweller25

[Ags]

@dweller25 those do not appear to be favorable observing conditions! I think I will save up for a Mewlon 180. A C9.25 would be nice but I believe rather too big for me whilst being too small for the Jupiter pictures I want to take.

But if I do successfully save up for the M180, will I be able to resist the temptation to push on to the M210?

[JeremyS]

19 minutes ago, Ags said:

@dweller25 those do not appear to be favorable observing conditions! I think I will save up for a Mewlon 180. A C9.25 would be nice but I believe rather too big for me whilst being too small for the Jupiter pictures I want to take.

But if I do successfully save up for the M180, will I be able to resist the temptation to push on to the M210?

The M210 is lovely too 😊
Mewlons are the only scopes that would deflect me from refractors, visually 

[Ags]

I wonder how the Mewlon 180 compares to the 8" Classical Cassegrain? They have the same effective aperture and the CC design has theoretical advantages over the DK design off axis. 

[JeremyS]

4 minutes ago, Ags said:

I wonder how the Mewlon 180 compares to the 8" Classical Cassegrain? They have the same effective aperture and the CC design has theoretical advantages over the DK design off axis. 

These are planetary/ high res scopes so on axis is what really matters. That and the legendary 1/20 wave Tak optics + baffling

[Elp]

From my experience viewing sharpness, contrast and quality go in this order: apo refractor, reflector/Newtonian, acro refractor (can also perform like an apo visually), SCT.

[Ags]

I wasn't aware the Skymax 180 was only 7kgs, not too bad. It is one I will consider while saving for the Mewlon, and I might make a detour into Mak territory if one comes up second-hand for a nice price in the interim. If the insulation approach really works, the Skymax could even be up and running before the Mewlon...

Did I mention I like Maks?

I would need 2" eyepieces for these monsters, at these slow focal ratios I am tempted by the Speers WALER 31.5mm 90 degree eyepiece, which is both very light and same true field as a 56mm Plossl. Even in the Skymax, it would give a degree field and a pleasant 2mm exit pupil. 

[alex_stars]

Hi @Ags

when it comes to planetary visual observation, which is what I do mostly, I so far tried:

• 5" Skymax (too small)
• 180 Skymax (a nightmare to cool, seriously) and with bad focus behaviour (as the mechanism in the skymax 180 can be of poor quality, at least compared to better quality scopes) in my unit
• 5" APO f/7.8 (the TS one), really nice views but too big too handle for me, else really great
• OMC 140 Mak, which is a beast it itself (cooling) and can be of poor build quality, however great if it works

Currently I'm stuck with the OMC140, which I spent quite some time optimizing (see here) and testing/collimating (see here). This is a great scope, at least my unit, others might be different, however I dream of a Mewlon 180.

If I would redo my journey with planetary scopes with the knowledge I have now, I would straight go for the Mewlon 180. You can skip the Skymax 180 (which is actually a 172 mm AP scope with a 34% CO, see here) in my opinion, but hey just my thoughts on the matter. And BTW, I really like Maks too, not joking.

Looking forward to see what you end up with! All the best.

[Ags]

Saving for the Mewlon would be a long-term endeavor so my reasoning is I might as well shift some of the savings into a stopgap and secondhand CC8/C8/Mak180 rather than have no upgrade at all for a long time. I can then sell the stopgap for what I paid for it later on.

I think the CC8 is probably the best stopgap choice but I'll see what comes up. If I did get a Skymax, I would try insulating it.

[alex_stars]

That's a very reasonable plan, no question and I fully hear you on the "long term endeavour" of saving up to a Mewlon. I bought my OMC140 used for about 1/3 of the price of a new Mewlon 180, so there you go. I kind of got stuck on my stopgap scope and I do enjoy it. Towards the Mewlon it might be cool to try the CC8 first, especially used. It shares some features with the Mewlon, like an open design (similar cooling?) and the spider vanes (and diffraction) holding the secondary mirror. So you might get a feel of how a Mewlon might be.

[Ags]

I think it would not be bad to be "stuck" on the CC8, they seem to be rated really highly by their owners, at least those that can forgive the slightly dodgy aperture. It's heavy for its size though.

[Ags]

I must say I am a bit disappointed with my C6. It's collimated, but star images are just a bit soft, so the extra aperture over my other scopes doesn't give any more sparkle in star clusters.

[JeremyS]

2 minutes ago, Ags said:

I must say I am a bit disappointed with my C6. It's collimated, but star images are just a bit soft, so the extra aperture over my other scopes doesn't give any more sparkle in star clusters.

Sparkle in star clusters is the realm of refractors, not SCTs (or CC for that matter)

[Ags]

Well, I have convinced myself the CC8 would be somewhat sharper. Maybe I am wrong...

[JeremyS]

4 minutes ago, Ags said:

Well, I have convinced myself the CC8 would be somewhat sharper. Maybe I am wrong...

Watch out for the diffraction spikes on bright stars and planets. I’ve still not got used to them with my Mewlon. I find them distracting 

[globular]

18 minutes ago, JeremyS said:

Sparkle in star clusters is the realm of refractors, not SCTs

My SCT provides me with lots of sparkle in star clusters.
It's an 8" Edge HD and I use it at fl 2125 (by ensuring back focus is 133mm). Deviating only marginally from that and things soften - but parfocalising all my EPs makes keeping everything sharp no problem. And that includes with binoviewers too.
I suspect most SCT users don't consider their back focus position and regularly push or pull their primary mirror far too far from it's optimal position - hence softening their views and leading to the bad reputation SCTs have.