Lunt selling 6" apo for $2990 (Astromart) and the lens-in-cell for $1600.00

On Tuesday, 7 July 2015 08:09:02 UTC-4, wrote:
On Monday, July 6, 2015 at 8:48:45 PM UTC-4, RichA wrote:
On Monday, 6 July 2015 10:58:28 UTC-4, wrote:
On Sunday, July 5, 2015 at 8:13:23 PM UTC-4, RichA wrote:
But...it is a 2-element six-inch and I don't think they are specifying what glass is being used so "apo" might not be as "apo" as it should be. We'll see.

Is this the scope?

http://www.cloudynights.com/page/art...8-ed-apo-r2889

For the price, it sounds MUCH better than the smaller apo with which it was compared side-by-side. How might it stack up against a good 8-inch Newtonian of similar focal ratio, for visual use at least?

That's it, I believe, but there is some oddness on pricing. The pricing on Astromart Lunt ads was/is different from Lunt's site, where the price is higher.
Despite what refractor nuts tell you, NO six inch will match an eight inch Newtonian on deepsky, not even close. PROVIDED the 8" and the 6" are similar quality. The apo will show "tighter" star images by virtue of its less luminous diffraction rings (focused star) so globular clusters might look nice (depending on the obstruction percentage of the Newtonian, SCT, etc) but an extended object like a galaxy or nebula? Forget it, the 8" wins.
On planets, it's a toss-up. There are too many variables that effect the scope'
s differently to say outright which will win on what night. They will be close.
I compared a 7" AP refractor (to my mind, the best refractor I've ever seen)
and an 8" Ceravolo Mak-Newt and they were so close it was hard to tell them apart on the planets. I'd give the smallest edge (that night) to the AP.

To fan the flames:

http://msfastro.net/articles/gso_tec...c_compare.html

COMA!!! But no, it doesn't surprise me since the Chinese are figuring the mirrors for these things likely on $500,000 machines that are designed to turn-out the same shape one after another. I first noticed this when I tested 32 Meade ETX-90's and found no real difference.

On Tuesday, July 7, 2015 at 9:16:46 PM UTC-4, RichA wrote:
On Tuesday, 7 July 2015 08:09:02 UTC-4, wrote:
On Monday, July 6, 2015 at 8:48:45 PM UTC-4, RichA wrote:
On Monday, 6 July 2015 10:58:28 UTC-4, wrote:
On Sunday, July 5, 2015 at 8:13:23 PM UTC-4, RichA wrote:
But...it is a 2-element six-inch and I don't think they are specifying what glass is being used so "apo" might not be as "apo" as it should be. We'll see.

Is this the scope?

http://www.cloudynights.com/page/art...8-ed-apo-r2889

For the price, it sounds MUCH better than the smaller apo with which it was compared side-by-side. How might it stack up against a good 8-inch Newtonian of similar focal ratio, for visual use at least?

That's it, I believe, but there is some oddness on pricing. The pricing on Astromart Lunt ads was/is different from Lunt's site, where the price is higher.
Despite what refractor nuts tell you, NO six inch will match an eight inch Newtonian on deepsky, not even close. PROVIDED the 8" and the 6" are similar quality. The apo will show "tighter" star images by virtue of its less luminous diffraction rings (focused star) so globular clusters might look nice (depending on the obstruction percentage of the Newtonian, SCT, etc) but an extended object like a galaxy or nebula? Forget it, the 8" wins..
On planets, it's a toss-up. There are too many variables that effect the scope'
s differently to say outright which will win on what night. They will be close.
I compared a 7" AP refractor (to my mind, the best refractor I've ever seen)
and an 8" Ceravolo Mak-Newt and they were so close it was hard to tell them apart on the planets. I'd give the smallest edge (that night) to the AP.

To fan the flames:

http://msfastro.net/articles/gso_tec...c_compare.html

COMA!!! But no, it doesn't surprise me since the Chinese are figuring the mirrors for these things likely on $500,000 machines that are designed to turn-out the same shape one after another. I first noticed this when I tested 32 Meade ETX-90's and found no real difference.

The Newt was equipped with a coma corrector during the test. That's allowed.

On Wednesday, 8 July 2015 05:52:03 UTC-4, wrote:
On Tuesday, July 7, 2015 at 9:16:46 PM UTC-4, RichA wrote:
On Tuesday, 7 July 2015 08:09:02 UTC-4, wrote:
On Monday, July 6, 2015 at 8:48:45 PM UTC-4, RichA wrote:
On Monday, 6 July 2015 10:58:28 UTC-4, wrote:
On Sunday, July 5, 2015 at 8:13:23 PM UTC-4, RichA wrote:
But...it is a 2-element six-inch and I don't think they are specifying what glass is being used so "apo" might not be as "apo" as it should be. We'll see.

Is this the scope?

http://www.cloudynights.com/page/art...8-ed-apo-r2889

For the price, it sounds MUCH better than the smaller apo with which it was compared side-by-side. How might it stack up against a good 8-inch Newtonian of similar focal ratio, for visual use at least?

That's it, I believe, but there is some oddness on pricing. The pricing on Astromart Lunt ads was/is different from Lunt's site, where the price is higher.
Despite what refractor nuts tell you, NO six inch will match an eight inch Newtonian on deepsky, not even close. PROVIDED the 8" and the 6" are similar quality. The apo will show "tighter" star images by virtue of its less luminous diffraction rings (focused star) so globular clusters might look nice (depending on the obstruction percentage of the Newtonian, SCT, etc) but an extended object like a galaxy or nebula? Forget it, the 8" wins.
On planets, it's a toss-up. There are too many variables that effect the scope'
s differently to say outright which will win on what night. They will be close.
I compared a 7" AP refractor (to my mind, the best refractor I've ever seen)
and an 8" Ceravolo Mak-Newt and they were so close it was hard to tell them apart on the planets. I'd give the smallest edge (that night) to the AP.

To fan the flames:

http://msfastro.net/articles/gso_tec...c_compare.html

COMA!!! But no, it doesn't surprise me since the Chinese are figuring the mirrors for these things likely on $500,000 machines that are designed to turn-out the same shape one after another. I first noticed this when I tested 32 Meade ETX-90's and found no real difference.

The Newt was equipped with a coma corrector during the test. That's allowed.

The two were close, but I'd still give the edge to the refractor, at least based on the images. Plus, no collimation issues and no diffraction spikes.. I'm sure they could design a Newtonian with permanent collimation, but no one has done it effectively yet that I've seen.

On Thursday, July 9, 2015 at 12:46:29 AM UTC-4, RichA wrote:

The two were close, but I'd still give the edge to the refractor, at least based on the images. Plus, no collimation issues and no diffraction spikes. I'm sure they could design a Newtonian with permanent collimation, but no one has done it effectively yet that I've seen.

====
Was the refractor "$5000" better? That much loot pays for a lot of collimation!

On Thursday, 9 July 2015 08:45:50 UTC-4, wrote:
On Thursday, July 9, 2015 at 12:46:29 AM UTC-4, RichA wrote:

The two were close, but I'd still give the edge to the refractor, at least based on the images. Plus, no collimation issues and no diffraction spikes. I'm sure they could design a Newtonian with permanent collimation, but no one has done it effectively yet that I've seen.

====
Was the refractor "$5000" better? That much loot pays for a lot of collimation!

Better is always more expensive and every gain costs exponentially more. If the Newtonian's performance was duplicated by a refractor, it might be a six-inch Takahashi FS-152. Which would cost around $4200. So, the TEC is priced in-line with its class of telescope. But images taken with a camera don't really let you see what the refractor might be capable of. Same thing might have been seen between a Celestron 9.25" SCT and the old Tak 9" SCT. The Celestron cost $1500 for the OTA, while the Tak was around $3000.00 from what I remember. The minor improvement in image and build quality with the Tak cost double. Whether it makes more sense to spend many times the price of a Newtonian for an apo refractor depends on how picky you are and if other characteristics of Newtonians versus refractors matters. But like I said before, with computers doing a far better job on these mass-produced scopes than before, the gap has closed considerably. For anyone who remembers the horrors of the 1980's-era SCT optical variability, this is welcome.

On 10/07/2015 05:54, RichA wrote:
On Thursday, 9 July 2015 08:45:50 UTC-4, wrote:
On Thursday, July 9, 2015 at 12:46:29 AM UTC-4, RichA wrote:

The two were close, but I'd still give the edge to the refractor, at least based on the images.
Plus, no collimation issues and no diffraction spikes. I'm sure
they could design a Newtonian
with permanent collimation, but no one has done it effectively yet
that I've seen.

Not worth the effort.

====
Was the refractor "$5000" better? That much loot pays for a lot of collimation!

Better is always more expensive and every gain costs exponentially more.

It is the 80:20 rule as applied to optics. It applies in many fields.

Obtaining perfection costs a lot more than getting 80% of the way there.

If the Newtonian's performance was duplicated by a refractor, it
might be a six-inch Takahashi FS-152.
Which would cost around $4200. So, the TEC is priced in-line with
its class of telescope.
But images taken with a camera don't really let you see what the
refractor might be capable of.
Same thing might have been seen between a Celestron 9.25" SCT and the
old Tak 9" SCT.

I don't know why you don't think that cameras cannot show the
diffraction limited optical capabilities of telescopes. The availability
of cheap video webcams and Registax has put lucky seeing diffraction
limited imaging within reach of every amateur. The learning curve is
steep but plenty of people have mastered it with stunning results.
Planetary images taken by amateurs today are amazing.

The Celestron cost $1500 for the OTA, while the Tak was around $3000.00 from what I remember.
The minor improvement in image and build quality with the Tak cost
double. Whether it makes
more sense to spend many times the price of a Newtonian for an apo
refractor depends on how
picky you are and if other characteristics of Newtonians versus
refractors matters.

There is always a big hit in refining the quality of optical surfaces
and assembling them to be just right independent of temperature.

But like I said before, with computers doing a far better job on these mass-produced scopes
than before, the gap has closed considerably. For anyone who
remembers the
horrors of the 1980's-era SCT optical variability, this is welcome.

The Halley's Comet effect where they were churning them out the door
with the clear expectation that they would be used only once.

--
Regards,
Martin Brown