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Triple-stack 90mm Solarmax PDF Print E-mail
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Sunday, 15 May 2011 19:12

The testing of two 90mm Coronado Solarmax scopes using a separate T-max tuner and aluminium adaptor plate.

Equipment available was two 90mm Solarmax telescopes serial No 900198 and No 900009 [with bespoke double stacked unobstructed front etalon unit] and a spare front etalon unit together with separate T-max tuner and aluminium adaptor ring. I had been trying since May 2010 to get a T-max tuner and adaptor ring. Rikki Hocking at Lunt Solarsystems was eventually suggested to me and she supplied these within just over a week of placing the order – that’s what you call customer service!  I used my EQ6 mount, tested visually with 18mm eyepiece and then photographically using a DMK21 monochrome camera.

Photo 1 the two scopes on a home made cradle plate. The top scope is No 900009 with double-stacked un-obstructed front etalon unit [photo 2] to compare 900198 with two front etalon units fitted [photo 3] to double stack it. The observed image is 40% dimmer but I could still photograph at 1/57 of a second to get good data even under the very milky skies that day.


Photo 1

I started visual testing initially using a 18mm Cemax eyepiece and I then continued photographically using a DMK21 monochrome camera.  The first two videos of 500 frames were shot in the single stacked 900198 @ 1/300 seconds. Next two videos also 500 frames were in the double stacked 900198 [@ 1/57 seconds]. The next runs were captured using 900009 through the double-stacked unobstructed etalon unit at 1/300 second. Final runs were done on triple stacked 900009 at 1/100 second. Seeing conditions were poor – lots of limb boiling under varying milky skies [4 – grade BAA seeing conditions].


Photo 2 this is the bespoke double-stacked unobstructed front etalon unit.


Photo 3 shows double-stacking of 900198 with second etalon unit.Photo 4 shows triple stacking of 900009 using the second restricted etalon unit coupled to the unobstructed double stacked initial unit.


Photo 4 shows triple stacking of 900009 using the second restricted etalon unit coupled to the unobstructed double stacked initial unit.



FIRST TEST PHOTOS – All videos were just 500 frame processed using Registax 5 seeing a poor grade 4


Testing was done on 24 February 2011 at between 15-18UT and 16-09UT.


Photo 1 through single stacked 900198 Estimated to be at about 0.7A.


Photo 2 through double stacked 900198. Estimated to be at about 0.5A


Original double stack 900009 photo. Estimated to be at about 0.5A.


Triple stacking 900009 estimated to be at 0.35A


Preliminary conclusion – seeing conditions really were very poor and did not show just how well even the single stack unit can perform. That said, there is a definite improvement between the single stacked and double stacked unit with the unobstructed version giving shorter exposure rates. The triple stack shows significant promise with much higher contrast to features observed and I cannot wait for good seeing conditions and decent features to have a go!


Further testing on 1 March 2011 Double and triple stacking of 900009 photographing AR1164.

Seeing conditions were again a limiting factor [grade 3], lots of limb boiling observed very milky skies only permitting unobstructed double stacking at 1/183 second max and triple stacking at 1/38 second max capture rates set at 1/30 second on camera. I still used the Cemax 2x Barlow for high magnification as I was wanting to test the contrast levels produced on the surface features. The DMK21 was used using IC capture. Photos processed in registax 5.


Photo double-stacked prior to colouring.


Photo double-stacked after colouring


Photo triple-stacked prior to colouring.


Photo triple-stacked after colouring.


Finally some better seeing 22 April 2011 C3-class flare associated with AR1195.


Coloured version of the same photo – this photo is showing structure that I have never seen before.



Finally after some decent seeing conditions there is a definite improvement with the triple-stack system this for the surface detail only. Further testing will continue and this report will be extended with prominence features.

Here is a still taken at 3.2m focal length in grade 2 seeing and was produced from a set of only 300 frames as part of a movie sequence and not for a hi-resolution still!

6 October 2012

Last Updated on Sunday, 07 October 2012 19:44