11 replies to this topic

[chrisjgreenfield]

Good evening,

 

I'm hoping that this might be the correct forum to ask about the Meade ACF 16 inch OTA.

 

My local astro society are planning to replace our ageing 14inch Meade, the electrics in the fork mount died and after numerous replacement parts were fitted and tried, we gave up and replaced the Meade fork mount with a Skywatcher EQ8 Heavy duty mount. All has been well, but the OTA is now showing signs of many years use and we are almost at the point of having raised enough funds to replace it with the 16" tube.

 

According to the specs, the Skywatcher Mount should be more than sufficient for the 35kgs (it's rated at 50kgs) but I believe that Skywatcher maybe be "optimistic" with their ratings. 

 

Does anyone here have a 16"inch Meade mounted on a Skywatcher EQ8, and able to share their experiences?

 

Many thanks,

 

Chris

[Skywatchr]

Good evening,

 

I'm hoping that this might be the correct forum to ask about the Meade ACF 16 inch OTA.

 

My local astro society are planning to replace our ageing 14inch Meade, the electrics in the fork mount died and after numerous replacement parts were fitted and tried, we gave up and replaced the Meade fork mount with a Skywatcher EQ8 Heavy duty mount. All has been well, but the OTA is now showing signs of many years use and we are almost at the point of having raised enough funds to replace it with the 16" tube.

 

According to the specs, the Skywatcher Mount should be more than sufficient for the 35kgs (it's rated at 50kgs) but I believe that Skywatcher maybe be "optimistic" with their ratings. 

 

Does anyone here have a 16"inch Meade mounted on a Skywatcher EQ8, and able to share their experiences?

 

Many thanks,

 

Chris

I would find a better mount. Add the scope weight and counterweights weight to get your actual payload. The weight of the OTA, plus counterweights will strain the EQ8 to it's limits and beyond.

[aneeg]

And that sum is for visual only!

 

Arne

[Bill Barlow]

Maybe a new 14” Meade might work better with that mount?

 

Bill

[akulapanam]

I would find a better mount. Add the scope weight and counterweights weight to get your actual payload. The weight of the OTA, plus counterweights will strain the EQ8 to it's limits and beyond.

The payload rating is for the scope only

 

And that sum is for visual only!

 

Arne

It doesn't look like they are trying to do deep sky imaging with this anyways.  For planetary (which is really the only thing any one can recommend on a Meade 16") this mount would be fine.

 

Having played with the EQ-8 in person I would have no hesitation that it can handle a Meade 16" ACF for visual or planetary imaging.  Teleskop Express suggests that it is the minimum sized mount that can handle their heavier and longer GSO 16" RC for Deep Sky (minimum sized mount).   https://www.teleskop...op-von-GSO.html

[Skywatchr]

The payload rating is for the scope only

 

It doesn't look like they are trying to do deep sky imaging with this anyways.  For planetary (which is really the only thing any one can recommend on a Meade 16") this mount would be fine.

 

Having played with the EQ-8 in person I would have no hesitation that it can handle a Meade 16" ACF for visual or planetary imaging.  Teleskop Express suggests that it is the minimum sized mount that can handle their heavier and longer GSO 16" RC for Deep Sky (minimum sized mount).   https://www.teleskop...op-von-GSO.html

I did deep sky with an 8" SCT so a 16" will gather plenty of light for DSOs. Minimum mounting is never the way to go with any heavy instrument and be able to actually enjoy using it. Though on a solid pier it may work alright and not get the shakes too bad.

[Skywatchr]

The payload rating is for the scope only

 

Exactly. When you start adding anything, like finders, cameras, dew shield, heavy eyepieces, diagonals, etc you quickly use up the "margin" and get to the limit.

[akulapanam]

I did deep sky with an 8" SCT so a 16" will gather plenty of light for DSOs. Minimum mounting is never the way to go with any heavy instrument and be able to actually enjoy using it. Though on a solid pier it may work alright and not get the shakes too bad.

The problem with the 16” for deep sky is the focal length. Even with a full frame, large pixel, sensor your FOV is limited and your resolution is high which requires mechanical stability the 16” just doesn’t have. Then you have to consider the ACF does not have a flat field unlike the EdgeHD and will show poor results with a full frame camera as a result. Even if I was using the 14” EdgeHD with a reducer I wouldn’t want to be switching to visual configuration all the time. If you want a large telescope for visual, especially planets, buy the 16” or a big dob. If you want a nice deep sky imaging scope get a Planewave.

Edited by akulapanam, 20 October 2019 - 06:10 PM.

[carolinaskies]

OK, people who haven't owned a 16" SCT need to get some experience.... 

The new 16" F/10 tubes weight with included dovetail is 67lbs with the smaller dovetail. 
The new 16" F/8 tube weight with included dovetail is 70lbs... this has the beefier dovetail I would recommend using with the 16".  

An EQ8 payload (this means what it can carry for an OTA/acc package)  is 110lbs.  Net payload does not have to address counterweight weight therefore the 16" will reside quite comfortable.  Depending on dressed out accessories you'll likely be adding 10-15lbs pushing the weight to about 85lbs.  Still not an issue for the EQ8. 

  

[carolinaskies]

The problem with the 16” for deep sky is the focal length. Even with a full frame, large pixel, sensor your FOV is limited and your resolution is high which requires mechanical stability the 16” just doesn’t have. Then you have to consider the ACF does not have a flat field unlike the EdgeHD and will show poor results with a full frame camera as a result. Even if I was using the 14” EdgeHD with a reducer I wouldn’t want to be switching to visual configuration all the time. If you want a large telescope for visual, especially planets, buy the 16” or a big dob. If you want a nice deep sky imaging scope get a Planewave.

Not a problem... you dont' buy a 16" SCT for widefield... please refrain from false flag arguments.

As for stability in either F/10 or F/8...  mirror locks on the F/10 are more than sufficient and the internal crayford focuser on the F/8 is quite stable.  Pity you like making false arguments about flat fields when a 16" is used quite a bit with larger than full frame instruments where some vignetting is an issue more than flatness. Thousands of images taken by professionals with 16" don't lie. I guess they all suddenly sold their 16s for 14 Edges?  Nope.... rofl.    

But that does bring up an option of 14" XLT Celestron with Hyperstar which will give the wide field IF desired while also delivering widely accepted performance in visual mode without the expense of an overpriced Edge which is optimized for the wide-angle 82-110 degree eyepieces which were initially designed for fast optics found on large Dobsonians not on F/10 SCTs.  One could buy the 14" Edge if they felt like they needed it for imaging at F/10 with a full frame camera or paying another $300+ for the F/7 reducer.  Of course if the camera is a 4/3rds or APS-C the Edge advantage disappears, also when imaging the planets as a flat field at the outer 10% is never seen since the imaging chip is only shooting the inner 20-30% of the field. 

Going back to the OP question therefore.... no problem going to the 16" on the EQ8.    

 

[carolinaskies]

I would find a better mount. Add the scope weight and counterweights weight to get your actual payload. The weight of the OTA, plus counterweights will strain the EQ8 to it's limits and beyond.

Never seen an EQ8 eh?  The NET payload is 50KG. 

That means it is rated to handle a payload AND counterweight of 100KG. 

The key is understanding CAN the motor/worm/gear when BALANCED track successfully.  Many machines which handle tons of equipment require simple 1/2 horse motors to drive them because they are balanced... simple laws of physics.   

Many issues seen with GEM setups for AP is not because of bad drive systems but poor balancing.  You'll see a ton of people hanging weight way down a counterweight shaft because they think that's where balance occurs, instead of investing in better weights to place closer to the center of rotation.  This reduces wear and tear and tracking issues.  

[chrisjgreenfield]

Thank you everyone for your comments and advice.

The Scope will not be used for imaging, it will sit in a dome, the mount is on a very solid pier, and be used to show visitors to our observatory the night sky, be used by members for their own use.

It is possible, that someone (we have one member) will want to attach their dslr to the scope, but 99% of the time it will be visual only.

Many thanks,

 

Chris

Edited by chrisjgreenfield, 21 October 2019 - 10:00 AM.