Massa, Italy, April 30, 2008
First of all, let me tell in a short the history of this telescope as I have records with any.
The Gladius CF315 telescope serial number 071001 was personally delivered by Lazzarotti Optics company through his own official distributor Unitron Italia to the reseller (and not to the final user directly) on October 22, 2007. The reseller has then delivered the telescope to the final user.
Lazzarotti Optics received a problem notification by the reseller on November 21, then any appropriate direction was suggested to the reseller to fix the problem. Given the persisting problem, in the Christmas period the telescope was returned from the user back to the reseller for an inspection. On January 29, 2008 Lazzarotti Optics received a report from the reseller notifying the telescope was properly aligned by them and the image delivered was great. From that date on, Lazzarotti Optics heard no longer both from the user and to the reseller until March 26 when appeared mr. Rohr test here.
According to the reseller, Lazzarotti Optics has returned back this Gladius telescope on April 15, 2008 through the official distributor Unitron Italia because of a persisting optical aberration (astigmatism) was noticed by the user and then verified by mr. Wolfgang Rohr (see mr. Rohr test) throughout this forum.
On April 16, Lazzarotti Optics found the problem which caused a primary mirror misalignment. Carbon fiber rods used with this telescope had an abnormal ovalization (up to 0.7-0.8mm with the 14mm internal diameter, twice the admitted value here) causing a loosening link between the 2 main parts of the telescope. The aluminum link mechanism couldn’t thus keep safely in place the 2 mirrors from time to time in a random way despite all secondary mirror collimation efforts: the primary mirror misalignment was a not fixable issue by the user.
The random appearance of this subtle problem explains why it could have escaped both to the Lazzarotti Optics original test and the reseller tests as well.
Over the following 2 days, rods’ tips were finely rectified and the problem has definitively disappeared over a wide amount of tests performed. The primary mirror holder and other parts involved with mirrors were checked in depth as well and no further problem was found.
Given the very long Gladius effective focal length (hereafter called as EFL), no artificial star can be successfully used to evaluate such an optical set. A light source placed to close to the Gladius telescope is adding there spherical aberration because the 2 mirrors should work at a different enough distance respect the one established by factory specs. Such a source should be placed at 1/4 a kilometer or so to avoid any aberration adding.
On April 26, the sky cleared for the first time since the telescope repairing and the stability was good enough to have a decent star test of the repaired Gladius.
Find it here:
Some additional note:
1. Any extraneous stuff added in by mr. Rohr was removed before of the star test.
2. Images there are a stack of 120 (focus) and 350 (intra and extra focal) raw frames grabbed through a red filter to smooth down as more as possible the atmospheric turbulence. The CCD camera was placed at the Gladius primefocus (EFL=7875mm, image scale=0.18 arcsec/px). More datas are enclosed to the test image itself. A moderate sharpening was applied to put on evidence eventual subtle irregularities otherwise unnoticed in the blurred raw sum image.
3. The odd diffraction pattern superimposed both to the intra and extra focal images is caused by the circular secondary support and doesn’t introduce any image degradation at all.
4. Please, take into account this star test was recorded at 8 meters focal length, a 2-4 times bigger EFL than other scopes have. That means a natural amplification of optical aberrations if any is there.
5. No astigmatism was detected, the 4X enlarged version of the focus image (EFL=31,5 meters!) shows a star as close to the ideal PSF as it could be according to the local seeing conditions. The ideal PSF image was made by Iris software (http://www.astrosurf.com/buil/us/iris/iris.htm) specifying any Gladius parameter (aperture, EFL, image scale, central obstruction and wavelength) involved with the Airy disc drawing process.
A detailed interferometrical test will follow soon in the part II report.
Any way, these will just add numbers matching the star test itself introduced here which I personally consider as the key for the true quality estimation. In fact, the star test is made with the telescope working under the real sky looking exactly at the same real objects will be then observed by the users. If a telescope delivers a star image reasonably close to the ideal PSF given for a determined telescope up to an huge focal length (in this case, an amazing 31,5 meters EFL), there is no reason not to be happy with such a telescope, both with the optical set and mechanical parts.
Lazzarotti Optics sends his deepest apologies to the user who suffered with this problem and it’s promising to have an in-depth inspection from now on also with incoming rods and any else third parts used to assembly a Gladius telescope for the time being.
Lazzarotti Optics always welcomes any constructive suggestion, comment and feedback to improve his own solutions for You, The very new primary mirror shield (to be released later on next May) just proves that. I don’t like the idea of such a shield (although nicely realized) but I just followed nonetheless what Gladius users wanted.
Thank you for your attention.
Paolo Lazzarotti, head of Lazzarotti Optics