Compliment to C11 - What would you choose?

[Flame Nebula]

This is a variation in my previous topic, but now with a bit more firming up. 

I'm in the planning stages but it looking more like the foundation setup will be an az-eq6 with secondhand C11 (new price just too high for me!) when one comes up. Still saving the pennies(been saving for nearly 3 years) at the moment, and trigger may get pulled later in year(if it looks like my job is safe... another story). 

To give you more info, I already have an ed80 and 127mm mak. 

However, I feel there is a gap between these and what a C11 would give. The latter would be used primarily for AP of planets, and I'd probably give it a go on tight doubles too! I wouldn't be expecting a great deal on visual obs of faint fuzzies with the C11 and AP of dso with it would be a hard place to start, and the ed80 would be a better option for that. 

So, we've had discussions refractors, which were useful, but without the context I am now providing. 

Given this information, what would you choose? It doesn't necessarily need to be a scope to go on the mount, but ideally, I may as well utilise it as much as possible, as it's not cheap! The scope would only be used for visual only, and must offer things the ed80 and 127mm mak can't, and of course the C11. 

Looking forward to your choice, and why. 

Thanks 

Mark 

 

[Elp]

I think with SCTs they quickly get a magnitude larger and heavier from a C8 onward, you'll then be affected more by thermals and seeing conditions. Is there a reason you're looking at a C11 in particular?

[Flame Nebula]

2 minutes ago, Flame Nebula said:

 

 

2 minutes ago, Flame Nebula said:

 

 

14 minutes ago, Elp said:

I think with SCTs they quickly get a magnitude larger and heavier from a C8 onward, you'll then be affected more by thermals and seeing conditions. Is there a reason you're looking at a C11 in particular?

Hi Elp, I'm after the best images of saturn and jupiter that I can afford. C14 out of the question for me. Potentially, I've seen images with 12"f5 Newts that nearly match the C11, but that's a big thing to store and move. 

[Peter Drew]

What gap?, I don't see one between what you already have and your proposed C11.  The 80mm refractor should cover most of what you might need to do visually for very wide field visual and AP DSO, the 127Mak should be fine for physically manageable visual double stars and solar system objects and the C11 for more advanced AP.  There is a numerical gap but not one of performance.  The C11 would trounce anything affordable in the numerical gap on visual DSO's.        🙂 

[Flame Nebula]

Just now, Peter Drew said:

What gap?, I don't see one between what you already have and your proposed C11.  The 80mm refractor should cover most of what you might need to do visually for very wide field visual and AP DSO, the 127Mak should be fine for physically manageable visual double stars and solar system objects and the C11 for more advanced AP.  There is a numerical gap but not one of performance.  The C11 would trounce anything affordable in the numerical gap on visual DSO's.        🙂 

Hi Peter, this thought has crossed my mind. Targets I have failed with those scopes are sirius B and E/F stars in trap. If I was confident the C11 could resolve these, I may be inclined to hold off on filling the gap. Of course, the one scope that might fill the gap is a 8"f5. Wider than the sct and mak, much better light grasp, not to expensive, potentially faster for dso AP than the ed80. 

[Elp]

You can always Hyperstar a Celestron SCT, it's how I use my C6. But a refractor is much sharper. For emission/reflection nebulae the difference doesn't matter so much. Since I've gone down this route I don't use the refractors so much for DSO AP, they're just too slow in comparison, but a lot of that is attributed to the aperture increase.

Edited March 10 by Elp

[Cosmic Geoff]

Depends on how these scopes of yours are mounted.  If the C11 is not permanently mounted on the EQ6, I foresee a certain reluctance to heave these heavy items outdoors, erect and align them for a session interrupted by cloud etc.   If it is permanently available, I do not see any pressing need for yet another scope.  Have you seen and handled a C11?  You might conclude that mounting it up without assistance would be no fun. 

I have retained my  C8 SE + Starsense as a lighter weight and quick to deploy alternative to my CPC800 which is much heavier and has to be assembled before use.

BTW I imaged E & F in the Trapezium with the CPC800 so the C11 should do it too.

[Flame Nebula]

1 hour ago, Cosmic Geoff said:

Depends on how these scopes of yours are mounted.  If the C11 is not permanently mounted on the EQ6, I foresee a certain reluctance to heave these heavy items outdoors, erect and align them for a session interrupted by cloud etc.   If it is permanently available, I do not see any pressing need for yet another scope.  Have you seen and handled a C11?  You might conclude that mounting it up without assistance would be no fun. 

I have retained my  C8 SE + Starsense as a lighter weight and quick to deploy alternative to my CPC800 which is much heavier and has to be assembled before use.

BTW I imaged E & F in the Trapezium with the CPC800 so the C11 should do it too.

Thanks Geoff. I've seen some very good images of saturn taken with the edge version of sct8, appearing to my surprise to show the encke division (gap). How does your scope do with that target? 

[Cosmic Geoff]

1 hour ago, Flame Nebula said:

Thanks Geoff. I've seen some very good images of saturn taken with the edge version of sct8, appearing to my surprise to show the encke division (gap). How does your scope do with that target? 

I can't say I have managed to capture the Encke division.  It's extremely narrow (about 325 miles) compared with the overall size of the ring system.  (The diameter of Saturn is about 74,000 miles, and the diameter of the ring system about 170,000 miles.) The Edge versions are allegedly finished to a higher standard.

[Flame Nebula]

1 minute ago, Cosmic Geoff said:

I can't say I have managed to capture the Encke division.  It's extremely narrow (about 325 miles) compared with the overall size of the ring system.  (The diameter of Saturn is about 74,000 miles, and the diameter of the ring system about 170,000 miles.) The Edge versions are allegedly finished to a higher standard.

I think theoretically a scope would need to resolve to <0.1 arc seconds, but I wonder if it is the contrast that allows scopes with resolutions under 1 arc second, to sometimes show a thin dark line. 

[Deadlake]

4 hours ago, Flame Nebula said:

I think theoretically a scope would need to resolve to <0.1 arc seconds, but I wonder if it is the contrast that allows scopes with resolutions under 1 arc second, to sometimes show a thin dark line. 

Yes, you can find more detail here

https://telescope-optics.dish-cable.com/eye_intensity_response.htm

on a separate note if you’d re looking at planets then a 5” APO would fill a gap, none of your scope would have a MTF to match.

A C11 on planets gives a mush view compared to a APO.
Just a better light bucket for DSO…

[Flame Nebula]

1 hour ago, Deadlake said:

Yes, you can find more detail here

https://telescope-optics.dish-cable.com/eye_intensity_response.htm

on a separate note if you’d re looking at planets then a 5” APO would fill a gap, none of your scope would have a MTF to match.

A C11 on planets gives a mush view compared to a APO.
Just a better light bucket for DSO…

Thanks Deadlake, 

Interesting point on the mtf. When you say Apo, do you include SW 120ed, which I understand is not a full Apo? The C11 and C9.25 are primarily AP scopes, where lower apertures can't compete, as I understand (and supported by astrobin) 

Mark 

[John]

32 minutes ago, Flame Nebula said:

Thanks Deadlake, 

Interesting point on the mtf. When you say Apo, do you include SW 120ed, which I understand is not a full Apo? The C11 and C9.25 are primarily AP scopes, where lower apertures can't compete, as I understand (and supported by astrobin) 

Mark 

Can any doublet be a "full apo" ?

Thats the subject of many long threads on another forum I can think of !

 

[Flame Nebula]

1 minute ago, John said:

Can any doublet be a "full apo" ?

Thats the subject of many long threads on another forum I can think of !

 

How about 'APO - like' or 'APO-light' I'd go for that. 🤪

[John]

1 hour ago, Flame Nebula said:

How about 'APO - like' or 'APO-light' I'd go for that. 🤪

For what I think you are interested in, the levels of accuracy of optical figure, polishing and coating are just as important as control of CA, IMHO, maybe even more so 🙂

[Deadlake]

8 hours ago, John said:

Thats the subject of many long threads on another forum I can think of !

I'd agree 😀

Also older threads on this subject do not take into account advances made.

A takahashi DZ or Agema Optics are for effective purposes are giving the performance of a triplet with the cool down properties of a doublet.

125 mm seems to be where most of the action is, also consider this scope which has a Strehl measured in the green of at least 0.95

https://astrograph.net/epages/www_astrograph_net.sf/en_GB/?ObjectPath=/Shops/www_astrograph_net/Products/AGTEC125F78