CORONADO SOLARMAX II 90mm

Review by Stephen W. Ramsden

(info@solarastronomy.org)

Sunday, October 24, 2010

MANUFACTURERS INFORMATION:

Coronado SolarMax II

90 Solar Telescope with

RichView Tuning

Our Price: $3,599.00 to $4,399.00

Price varies based on options selected.

All new redesigned SolarMax II

Features precision RichView Tuning System

<.7A Bandwidth

Choice of 15mm or 30mm Blocking Filter

800mm Focal Length, 90mm f/8.8 Refractor

Includes Cemax Eyepieces, Travel Case, Sol Ranger Finder

Clamshell mounting ring

REVIEW:

The Coronado (Meade) corporation has released its long awaited new line of redesigned narrowband H-Alpha dedicated

solar telescopes under the name SolarMax II. In a previous review we looked at the 60mm SolarMax II and now it is my

privilege to take the 90mm version out for a spin.

I must confess up front that I always dreamed of having a 90mm double stacked Coronado Scope years ago and when I

finally was able to purchase one in 2007 I was absolutely elated and blown away with the quality of this product. Of

course, in those days Coronado was almost the only game in town and the scope went for over $14,000. I have been

extremely pleased with my American made previous version of this scope in its double etalon configuration and hoped

that the new Mexican made version starting at a very competitively priced $3599 was nothing less. I did not purchase

this scope as in most of my reviews. It was loaned to me for the review only. Since I have years of experience using a

Coronado 90mm scope I felt that I could do an adequate laymen’s review without purchasing it. I may go back and buy

it though as it was an incredible view.

First things first… The scope came in the expected mangled box as it had arrived via UPS. The box looked like it had

ridden from California inside the landing gear well and then been dragged to the store under the truck.

When the box was opened the inner case was packaged perfectly and hadn’t sustained even a scratch. Way to go

Meade shipping department!

The case was the standard “scratch and tear attractant” Coronado black leatherette and pressed wood design as used in

the past. I don’t even want to show a picture of my 3 year old case as all of the leatherette has been ripped to shreds

and the black shiny case is now a beat up and tattered mess. The inside is still perfect though so I guess it is durable. A

stainless steel case or a molded plastic type enclosure would be a really good idea for such an expensive telescope.

The case contained an instruction manual, the telescope with attached sol ranger, a full set of CEMAX eyepieces with 2X

Barlow (12mm, 18mm, 26mm) and a locking key. It was a very impressive site. The foam was very tightly fit around the

scope and there was a removable piece for the 2nd etalon to remain on the scope in the case when purchased. One of

the nylon screws on the focuser was bent but it was quickly corrected. It was very difficult to get the telescope in and

out of the case because of the tight fit. The BF15 diagonal blocking filter arrived in a 2nd box about a week later.

The telescope has a metal screw on lens cap protecting a 90mm objective on an F 8.8 doublet refractor. There is a black

objective ring, a long gold anodized tube, a black 2 piece clamshell secured by 3? Chrome plated metal bolts, a sol

ranger solar finder scope, a rich view tuning arm, black etalon housing and then there are 2 drawtubes with a helical

focuser attached ending up in a 1.25 inch eyepiece holder with retaining screw.

The first drawtube is held in place by a hard plastic screw and extends around 8 inches. The helical focuser has a black

rubber grip and travels in and out around 2 inches. The 4 inch extendable eyepiece holder is attached to the main

drawtube with 2 plastic screws and the eyepiece is held in with one large chrome bolt.

The objective end of the scope has an ERF coating and if you look inside you can see the Rich View etalon assembly.

The rich view arm is attached to a rotating collar that turns a bolt inside the 60mm etalon assembly. Coronado is not

forthcoming with what is going on in there but from what I can see, it is a rotating etalon that changes the bandpass of

the filter. Whether this is a sloped etalon, a turning filter of some sort, a compression system or whatever has yet to be

explained by the manufacturer. It looks pretty heavy duty in there and whatever it is blocks about 10mm in the center

of the etalon. It resembles a bolt and a washer and like I said, the whole thing turns when you move the tuning arm.

The central obstruction created by this system is about the same size as the previous central obstruction in the former

model 90 mm scopes.

I placed the telescope on a Celestron CGEM mount and aligned and balanced using the standard daytime procedure

(mainly guessing). I used the 18mm CEMAX eyepiece.

As you can see I had to remove the clamshell and place it on the other side of the Rich View tuning arm to balance the

scope. It wouldn’t quite balance on either side of the arm so I settled for the closer balance. It became clear that this

sort of solid clamshell was not the best design. If it had a 2 ring mounting system it would be a lot easier to balance.

The sky conditions were crystal clear and 74 degF in Atlanta during the review. The scope showed a very bright and

highly detailed view of prominences and a moderate amount of surface detail. It was brighter than the older model and

a little harder for me to see surface detail because of this. The prominences were breathtaking and clear. It was an

outstanding visual presentation. There was significant glare around the image from the brightness. It was certainly

beautiful regardless of the brightness. Probably better for first time viewers as the prominences were plainly visible.

The Rich View turning arm only rotates about 1/5 of a turn around the etalon assembly but seems to cover all of the

available features. Tuning it made a significant change in details from one end to the other. This arm is removable and

there are several tapped holes to place it in possibly to compensate for air temperature or pressure. Coronado isn’t

talking.

I like to have passersby in the city come up and take a look to give me their opinions on the scopes I review so I set up in

a conspicuous place and wait for people. My new friend Ron Bradley dropped by and took a look.

Ron had never looked through a solar telescope and does not own a telescope of any kind. I adjusted it for proms and

had him look through the 18mm CEMAX. Ron said that the prominences were clearly visible and asked what that black

spot was. When I explained that it was a sunspot he also noticed within a couple of minutes all of the moderate surface

details including the magnetic lines of flux and the grey area around the small twin spot. One filament was also evident

to him. This is important because I have had several people in their 40’s or 50’s like Ron and I not be able to see

anything except a red circle in a few of the scopes I review. The SolarMax II’s brightness allows for even first time users

to see immediate prominences. He also commented on the glare from the very bright image. I don’t consider this bad

as it just means that I can add a 4X or 5X Barlow lens and still have enough light to focus.

Ron also examined the camera live view and was of course fascinated at the structure and form of the solar surface and

proms. I always get the biggest kick out of people’s first impressions of the Sun through these scopes….even a Canadian

like Ron couldn’t hold back on the “wows”!

So far, so good.

On to the imaging…

I attached an Imaging Source DMK41 monochrome camera to the eyepiece tube and used IC capture to get several 1000

frame movies of different features. I used an ancient Dell Inspiron 9300 laptop running Win XP and an external 500GB

hard drive to capture images.

I overexposed drastically for the proms and underexposed for the surface detail. The scope provided for easy focusing

and etalon adjustment as the RichView arm was much closer to the business end of the scope than the Coronado 90mm

that I own which has the 2nd etalon adjustment on the far end of the objective and no internal etalon adjustment.

The images were beautiful and detailed in the live view. It was easily focusable with lots of extra focus room for binos or

other type cameras.

I noticed a little uneven illumination or sweet spot, about the same as my current Coronado scope, but easily compensated

for it using the cameras settings and the etalon adjustment arm.

(See the next page for imaging results)

This is the surface detail shot after stacking but before wavelets:

This is the same image after applying the pictured wavelet settings:

And finally this is the same surface image after the “Cloudy Nights treatment” as I call it… (For those of you unfamiliar

with the Cloudy Nights Solar Forum it is a web forum where the world’s absolute best solar imagers and sketchers

gather to show off their images. If you want to know anything about solar imaging this is the place to go…

http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/solar you will have to register for a free account

before entering—it is WELL worth it)

I have to comment here that the spicule ring was clearly visible in the picture. It may not show as well in these images

but it was beautifully visible. To me that is the dividing line between the real scopes and the cheapies. The slightly

greyer ring around the edge of the Sun that shows the grass-like spicules that cover the disk is my favorite part of the

Sun.

I then upped the gamma significantly (91) and brought the exposure up to around 1/23 sec to get the incredible

prominences in to view..

The scope was able to provide a suitable image for prominences at a much faster exposure time than smaller apertures

which makes it much easier to get a clear, crisp overexposed prominence avi. This is great for creating animated movies

of the prominence motion also.

Here is the pre wavelet image for the prominences

And the post wavelet image:

Here is the B/W prominence only image with the disk blackened out.

One thing that struck me right off the bat with the prominences was the excellent focus and the variations in the

brightness internal to the prominences. This is surely the mark of an excellent etalon and scope. Here is a close up of

the towering prominence:

…See what I mean? It’s awesome!!

another processed view:

Here is the final Cloudy Nights version of the proms and surface detail on the first try with the SolarMax II scope…

(that always makes me just stare and stare….)

THE BOTTOM LINE

This scope is beautiful, functional and provides an excellent image both visually and through the camera.

The intense competition in this market has been a big winner for the consumer as these single etalon scopes are now

blowing away the double stacked systems of just a few years ago for less than half the price. This scope is no exception.

It lacks a little in the case quality, the cheesy helical focuser and the cheap nylon screws holding things in place but it

makes up for it in function and form. The etalon design is far from revolutionary when compared to other innovations in

the market but it certainly works and works very well. Excellent job Meade! And at $3599 it is an absolute steal for

anyone wanting to do serious solar imaging.

Thank you for reading,

Stephen W. Ramsden

www.solarastronomy.org