Coronado PST VS Coronado SolarMax 40
Copyright (c) 2004 Cloudy Nights Telescope Reviews
By Don Wyman click to email author Ive owned and observed through a number of Hydrogen Alpha systems over the past 10 years or so. Previously I owned a Daystar ATM.7Angstrom system and now possess two systems from Coronado, a SolarMax 40 and the newest addition to their lineup, the P.S.T. (Personal Solar Telescope). A few years back a friend loaned me his Lumicon 1.5A Prominence filter for a few months so Im also familiar with that as well. Without getting into great detail, the Daystar and the Lumicon/Thousand Oaks systems have one big shortcoming. They require an f/30 or higher system in order to get the best results. This limits the amount of the solar disk that you can see at one time and also makes it a bit difficult to find and center the sun. These systems work best on 8 and larger SCTs that are stopped down to a smaller aperture which give the longer f/ratio. Refractors can be used as well but usually require a special multiplier lense similar to a barlow but give a parallel light path. I always found it was a great hassle to set up my big old SCT just to take a look at the sun. It was pretty disappointing when there wasnt anything to see. Lets look at the Coronado system. By putting the etalon (main filter element) on the front of the scope instead of the rear as the Daystar/Lumicon/Thousand Oaks systems do, a shorter f/ratio scope can be used. In fact, with short focus scopes you can see the entire disk of the sun in the eyepiece. These filters are also relatively cheaper to make. Coronado now offers several size/ price range filters of this design, the 40mm, 60mm and 90mm. The cost of the 40mm is $1265 and youll need a filter holder for your scope that can run $150 or more bringing the starting system to around $1500. The 60mm is around $2650 and the 90mm starts around $5K. In the HAlpha filter world, the 40mm is a pretty good bargain. When considering an H-Alpha filter, you need to decide what bandpass you need. Very simply, the lower the rating the more surface features youll see. The higher the rating the more prominences youll see. The Lumicon/Thousand Oaks 1.5Angstrom filters will show prominences very well, but hardly any surface features are visible. The Coronado filters strike a happy medium with a <.7A rating which is a good balance between surface features and prominences. This summer, Coronado premiered their newest offering, the P.S.T, or Personal Solar Telescope. This instrument is advertised as an all-in-one H-Alpha viewing system allowing the user to have very good views of prominences and decent views of surface features too. Its rating of <1.0Angstroms should theoretically fulfill that promise. The P.S.T. has an aperture of 40mm and is also threaded to accept a SolarMax 40 filter with T-Max tuner to bring the rating of the system to <.6Angstrom for better surface detail. Add to all this the incredible portability and the variety
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of possible mounting options, this scope holds a lot of promise. All this for a measly $499. Add a $65 case and voila, a portable H-Alpha system. Coronado also offers a small table top tripod, but I havent heard of anyone getting it yet.
Lets move on to the main course, how does the P.S.T. perform against its older sibling the SolarMax 40?
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I had previously obtained a Meade ETX-70 base/fork assembly and had modified it so it would accept the P.S.T. or other small scope. I set this up next to my Televue 76/Solarmax 40 system for a comparison.
P.S.T. on Meade ETX-70 base
Solarmax 40 on Televue 76. Modified Celestron 80GT mount.
I had heard some reports that the PST actually showed prominences better than the SM40. If this
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were true, it would make the PST an incredible bargain and have the effect that potential buyers of the SM40 would opt for the PST instead. In fact, when I first got the PST and set it up in June, I thought it was edging out the SM40. At that time I only had less than an hour to make any comparisons so it was not a fair test. On August 21, 2004, I had the whole day to take my time and run both scopes through their paces. I tried various eyepieces in both scopes, often taking an eyepiece from one and going directly to the other. I also tried to set up the same magnifications in each scope and comparing. I used the stock 12.5mm Kellner that came with the PST. This eyepiece has gotten mixed reviews. I find it to be a good performer in the PST giving just the right magnification (32X) and FOV. The other eyepieces I tried were Plossls from the Celestron kit, 6mm, 9mm, 15mm and a several Meade Research Grade Orthoscopic and Wide Angles from 7mm to 16.8mm. Although the Meades gave excellent images, they lacked the eyepiece cup that the Plossls had. That made it necessary to shade the eyepiece with my hand to get the best view. I tried very hard to make the PST perform better than the SM40, but I was unsuccessful. The views of both surface features and prominences were superior in the SM40. The image was brighter and more detailed. Although both systems had a 40mm aperture, the SM40 felt like it was bigger. Contrast was better in the SM40 and it was easier to keep the sun centered in the field. Others have reported a narrow FOV in the PST and I would agree with them. After several hours making the above comparisons I then decided to check out the other noted feature of the PST, doublestacking the SM40 on the end of it. This drops the bandpass down to <.6A which should show better surface detail. My first look though this setup surprised me. The surface detail was definitely better than either bare system alone. There were some bright plages and several sunspots that showed up better in the stacked PST. It was a nice view. Prominences were still there, but definitely harder to see. The whole view was dimmed somewhat which is to be expected with two filters in the lightpath.

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P.S.T. doublestacked with SM40
So after spending half the morning and most of the afternoon with these two systems here are my findings. The P.S.T. is not a SolarMax 40. It does show prominences and surface features very nicely. Its compact and easy to set up. Focus range is not very huge but I was able to bring all the eyepieces I tried into focus. It can seem a bit mushy at times, but you get used to it. Build quality is excellent. It really feels solid and well made. Just before the P.S.T. went into production, Coronado added a tuner ring just in front of the main block that forms the units body. It was a smart move. It allows the user to fine tune the unit for best views of H-Alpha objects. It also is needed to fine tune the system when you doublestack an SM40. Doublestacking the SM40 on the P.S.T. is a nice feature, but only if you already have an SM40. I had hoped to include some images taken through all configurations, but I had some problems with my Coolpix 995. If I can resolve them, Ill try to include them in an addendum to this article. If you are looking for a relatively inexpensive way of observing the sun in H-alpha, the P.S.T. is a great bargain. Its not a SolarMax 40 but at roughly 1/3 the price, it cannot be beat. It combines portability and performance in a small package. Im amazed that Coronado can produce it so inexpensively. I just hope they can keep up with the orders. Click to discuss this article in the forums
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2008 CORONADO SOLARMAX 90 SM90155
Review by Stephen W. Ramsden (spike@solarastrophotography.com) Sunday, November 23, 2008
This is the Astronomics ad information. Coronado Instruments SolarMax 90 3.5" f/8.9 solar telescope with dual etalon <0.5 ngstrom H-Alpha filter and 15mm blocking filter

$7,199.00

Our Product #:

SM90155 0.5SM90T15

Manufacturer #: Click image for close-up

Supplied Accessories

90mm f/8.9 optical tube; <0.5 ngstrom dual etalon SolarMax 90 filter (90mm external etalon and 60mm internal etalon); TMax 90 tilt-tuning unit; combined 15mm aperture BF15 blocking filter and 1.25 star diagonal; 25mm, 18mm, and 12mm 1.25 CEMAX eyepieces; 1.25" CEBAR Barlow; lens cover; clamshell mounting ring; Sol Ranger Sun finder; hard case.
REVIEW: Ever since I first looked through and then bought a Halpha PST, I had dreamed of owning the flagship Coronado telescope the double stacked 90. Of course, the $15000 price tag was a little bit of a hurdle to this acquisition so I just lived with the double stacked PST. I can remember seeing the pictures taken with the DS 90 and wishing that I could afford one. When Lunt Solar Systems came out and announced their new product line in 2008 apparently Meade decided to reinvigorate the neglected Coronado family of products by offering the Solarmax 90 series of telescopes at DRASTICALLY reduced prices. I jumped on it and boy, am I glad. I ordered the.5SM90T15. This is a SolarMax 90mm scope with the standard external 90mm.7A etalon with an included internal 60mm.7A etalon. The combination when matched properly yields a breathtaking view of the solar disk and limb at <.55A. I have now been using it for 4 months and decided to write a review of it
after heavy consistent use. The scope has been used at numerous outreach events and for extended sessions of photography using a DMK31USB monochrome camera and a Nikon Coolpix 5100 via a scopetronix adaptor. The scope arrived via UPS at my local dealer Camera Bug in Atlanta about 4 weeks after ordering it. It came packaged in a single ply cardboard box. Inside the box was a black leatherette case with three latches. The case was somewhat flimsy and made just like the PST case, only longer. Inside the case was a standard precut foam insert which housed the gorgeous SM90 snugly. Another box containing the included full CEMAX eyepiece kit came separately. The first thing I noticed about the scope was its weight. It is heavy. I removed it from the case and examined it. There was a metal screw in cover for the external etalon and an orange 1.25 inch eyepiece cup in the blocking filter. The visual train of the scope consisted of an external 90mm etalon, a 90mm clear objective, an internal 60mm etalon, a long 2 inch drawtube, a shorter 1.25 inch drawtube and a B15 15mm blocking filter contained in a star diagonal. The scope also had an included SolRanger solar finder that was attached to a clamshell that had three large bolts attaching it to the scope. I attached a 4 inch Losmandy dovetail plate to it and set it up on my Celestron CGE mount for some visual and imaging use.
The scope is absolutely beautiful and there is no mistake that you mean business when you set this bad boy up at a star party. I just sat and looked at it for a few minutes having finally realized one of my dreams in solar observing. In order to focus with any of the supplied CEMAX eyepieces you have to extend both drawtubes out fully and work your way in with the helical focuser. I used a 25mm CEMAX and aligned it on the sun with the CGE. Let me just say that I was absolutely amazed at the clarity of the image with any of the supplied eyepieces and it was a delight to look through. Surface features felt 3 dimensional and the edge proms just came alive with this scope. I could not stop looking that first day and kept it going until sunset. It was amazing!!
One of my favorite shots with this setup is shown below. It clearly shows a circular ripple coming out of the center of this AR taken in November of 2008 using the DMK and two CEMAX Barlows double stacked. I dont know what strikes me about this photo but I just like it. Notice the small filaments in the center. The telescope has really provided me with some awesome pictures.
The telescope has no internal etalon adjustment mechanism and relies on the external etalon for tilting via a brass wheel. The etalon tilt adjustment goes from ghost image at one extreme to an almost completely off band image at the other. It certainly shows the full range of the bandwidth available from the etalons.
The entire etalon assembly tilts with this wheel as shown in the picture to the left.
With the external etalon removed the SM90 becomes a prominence machine. The image is so bright you can focus easily with a 5x Barlow and a DMK camera. The little 60mm internal etalon is fantastic as a.7A prominence viewer.

The telescopes focuser is of helical design. The focuser is pretty good except that it is attached to a cheaply made set of 2 drawtubes. The main tube is held in place by a single small screw. It has a smaller drawtube inserted into it that is held in place by two even cheaper nylon screws. The blocking filter is attached to the end of the smaller tube by one very large chrome screw that gets in the way of tightening the other two screws. It is a silly design that leaves a lot to be desired.
For the life of me I cant fathom how Coronado would put such an inferior focusing setup on the end of their most expensive and sought after Halpha scope.
It is a constant nuisance to try and adjust the three different coarse and fine focusers while imaging.
I understand that JMI corp offers some sort of replacement focuser that is actually usable but wouldnt this scope have the best focuser possible at its astronomical price? Maybe the BFinch straight
through setup is better, I dont know. It is a $1600 upgrade to a previously $12,000 scope and I feel like I invested enough to get a decent focuser. The case is a disappointment also. Look at this wreck after only 4 months of use:
Anytime you even moderately scrap the case against something or put it on a less than friendly surface, it leaves a tear or mark on the cheap leatherette skin. I have no confidence that this case would withstand any sort of travel god forbid an angry baggage handler.
It also has no locking mechanism. It still holds the scope well inside though. Just dont drop the case friends.
The included SolRanger sunfinder is a big plus. It is very sturdy and is aligned perfectly with the scope by use of predrilled holes in the clamshell. It is awesome.
In general I would say that this scope absolutely rocks and is the cream of the crop of Coronados product line. It has provided me with countless hours of amazing views through the CEMAX eyepieces. The focuser and the case are a joke but the scope more than makes up for these ill thought out accessories.
I would strongly recommend this scope to anyone who wants to go to the next step up from amateur in Halpha observing. If you would like to see some of the amazing photos that have come from this scope please see go to my site www.solarastrophotography.com and look around. Thanks for reading, Stephen W. Ramsden