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There is a very steep price to pay for using a focal reducer with a 2" diagoanl in a C14.

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There is a very steep price to pay for using a focal reducer with a 2" diagoanl in a C14.

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I believe the C14 focal reducer for the Edge uses the 3 1/4" opening, not the 2" opening. Does that change your calculations any?

Patrick

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Are we talking Edge here or the standard C-14? I see Rod commenting:

"Bottom line for me? A c14 compares very favorably to an equivalent dob matter what it's pedigree and is far more versatile. Given current prices for premium dobs, it is a no brainer. Assuming you can handle a c14 and that you might someday want to do more than look."

- Given that the 14 edge OTA alone costs aobut what a Zambuto 14.5 inch Starmaster costs , it looks to me like the pricing comes down on the side of the Dobsonian. But that is neither here nor there.

- I think what is clear from this discussion is that it really comes down to deep personal preferences. My first serious scope was an orange tube C-8 that I purchased used. I enjoyed it and at the time, I considered Dobs to be Crude Cardboard Creations, barely worthy of being called a telescope. Somewhere along the line I picked up a 125mm Newtonian on an alt-az mount. Optically, it was a rather poor scope but it was better suited for doing the things I liked doing so the C-8 just sat in the corner. When I finally met my first Dob, it took a while to settle in but eventually an 8 inch F/6 Pirate Instruments Dob showed up on the local Craigslist, I bought my first Dob. Optically it probably was not the scope the C-8 was but it certainly was a better fit doing the things I liked to do and as they say, the rest is history.

So, while I think there are specific advantages to Newtonians optically and advantages to SCTs too, it really comes down to those very personal parts of observing that are the very things that attracted us to this hobby and keep us going out there when the cold wind is blowing and there is a big day at work tomorrow.

For me, it comes down to the fact that Dobsonians are just much better telescopes for Starhopping and that their simplicity. The telescope and mount are not black boxes filled with magic, Dobs are simple and there is a togetherness and intimacy that allow me to enjoy the observing the night sky just the way I like to. Simple and personal.

Sure it would be hard to convince me that an SCT reaches thermal equilibrium as quickly, that the views of stars are as bright and sharp, that the planets quite jump out at me the way they do in a Newtonian but all that is secondary to the simple fact of my relationship with the telescope...

When one is choosing a scope, it is that relationship that determines whether it is the right scope for you. In my case, I much prefer a manual/telescope mount to one where I am spending my time with hand controllers and dew heaters, gizmos and gadgets...

So, I am not trying to convince anyone that Dobs are better than SCTs. My goal is just the opposite, I am hoping to point out the importance of choosing a telescope that does the things you want to do the way you like to do them.

Jon Isaacs

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Are we talking Edge here or the standard C-14?

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- I think what is clear from this discussion is that it really comes down to deep personal preferences. My first serious scope was an orange tube C-8 that I purchased used. I enjoyed it and at the time, I considered Dobs to be Crude Cardboard Creations, barely worthy of being called a telescope. Somewhere along the line I picked up a 125mm Newtonian on an alt-az mount. Optically, it was a rather poor scope but it was better suited for doing the things I liked doing so the C-8 just sat in the corner. When I finally met my first Dob, it took a while to settle in but eventually an 8 inch F/6 Pirate Instruments Dob showed up on the local Craigslist, I bought my first Dob. Optically it probably was not the scope the C-8 was but it certainly was a better fit doing the things I liked to do and as they say, the rest is history.

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So, I am not trying to convince anyone that Dobs are better than SCTs. My goal is just the opposite, I am hoping to point out the importance of choosing a telescope that does the things you want to do the way you like to do them.

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You'll get no argument from me on that.

Patrick

Edited by Patrick (03/17/12 09:45 PM)

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- Increases Field of View by 43% to Better Capture Wide Field Images

- Threads Directly onto the 3.25" threads of the EdgeHD which Reduces Mechanical Vignetting and
Allows for use with Larger (Full Frame) Sensors and Off-Axis Guiders.

- Maintains the Identical Back Focus When Used at F/10 and Provides Generous Back Focus to
Accommodate Additional Accessories and Wide Variety of Cameras

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We average 77 clear days a year here in Ohio. San Diego averages 146 clear days per year, almost double Ohio.

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I think my biggest issue with the large SCTs is that they rarely reach thermal equilibrium.

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For me, it comes down to the fact that Dobsonians are just much better telescopes for Starhopping and that their simplicity. The telescope and mount are not black boxes filled with magic, Dobs are simple and there is a togetherness and intimacy that allow me to enjoy the observing the night sky just the way I like to. Simple and personal.

Jon Isaacs

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That is the conclusion I came to as well, although I resisted for 30 years

Nothing comes closer to the feeling of standing on the deck of a spaceship sailing across the heavens

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Mount Palomar claims 300+ clear nights a year.

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I think my biggest issue with the large SCTs is that they rarely reach thermal equilibrium.

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They can but it depends on what your climate is or whether you are willing to go to active cooling.

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That’s a pretty big “whether you are willing”. Disassembling and drilling holes in a new $2,500 C11 or a $4,500 C14 and invalidating the warranty and impacting resale value is not for the faint of heart and the vast majority will not do this – nor should they have to.

The stopgap methods of removing hot air from the OTA are just that. Removing hot air does little to cool the main mirror and that is where the problem is. The only way to “rapidly” cool these scopes and keep them cool throughout the night is to expose the main mirror to the outside air or blow lots of outside air on the mirror or both. Look at the back of the Tak Mewlon 250 and especially the Astro-Physics 10-inch Mak. Almost all of the back of the AP Mak can be removed - and for good reason.

Bob

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They can but it depends on what your climate is or whether you are willing to go to active cooling.

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That’s a pretty big “whether you are willing”. Disassembling and drilling holes in a new $2,500 C11 or a $4,500 C14 and invalidating the warranty and impacting resale value is not for the faint of heart and the vast majority will not do this – nor should they have to.

The stopgap methods of removing hot air from the OTA are just that. Removing hot air does little to cool the main mirror and that is where the problem is. The only way to “rapidly” cool these scopes and keep them cool throughout the night is to expose the main mirror to the outside air or blow lots of outside air on the mirror or both. Look at the back of the Tak Mewlon 250 and especially the Astro-Physics 10-inch Mak. Almost all of the back of the AP Mak can be removed - and for good reason.

Bob

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Not a problem with the Edge HD that already have vents that can be converted for active cooling. And it works. The OP question was about the Edge HD. Even the big Mewlons are going to active cooling now instead of just relying on opening up the back. It takes more than just exposing the primary. You have to remove the heat while the temperature is dropping since the mirror will lag well behind a relatively fast temperature drop.

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They can but it depends on what your climate is or whether you are willing to go to active cooling.

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That’s a pretty big “whether you are willing”. Disassembling and drilling holes in a new $2,500 C11 or a $4,500 C14 and invalidating the warranty and impacting resale value is not for the faint of heart and the vast majority will not do this – nor should they have to.

The stopgap methods of removing hot air from the OTA are just that. Removing hot air does little to cool the main mirror and that is where the problem is. The only way to “rapidly” cool these scopes and keep them cool throughout the night is to expose the main mirror to the outside air or blow lots of outside air on the mirror or both. Look at the back of the Tak Mewlon 250 and especially the Astro-Physics 10-inch Mak. Almost all of the back of the AP Mak can be removed - and for good reason.

Bob

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Not a problem with the Edge HD that already have vents that can be converted for active cooling. And it works. The OP question was about the Edge HD. Even the big Mewlons are going to active cooling now instead of just relying on opening up the back. It takes more than just exposing the primary. You have to remove the heat while the temperature is dropping since the mirror will lag well behind a relatively fast temperature drop.

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Ed

Do you know the time that it would take to cool a C14HD from say 70 degrees F (inside temperature) to 40 degrees F (outside temperature) by using the existing HD vents and adding fans to those vents? – no drilling.

Bob

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