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Category: DayStar Owners
My T-scanner is showing a blank red disc.
Posted on May 1, 2011, 5:03 pm Author: Jen Winter

Several T-scanner owners often report a simlar frustration.

Tuning the T-scanner is a delicate and sometimes frustrating task.  The product line was added over 20 years ago as an entry level compromise to the more expensive heated models, albeit with certain limitations in performance.

Tuning the DayStar to find H alpha can be somewhat challenging, especially the first time.   We encourage owners to follow these steps in order to locate H alpha: 

  • With the Filter installed, find and center the sun with the telescope, focus to accomplish a sharp edge on the limb of the sun.
  • Be sure to use a recommended Tele Vue Plossl eyepiece, for its su
  • Place one hand on the tuning knob of the t-scanner while viewing visually through the filter.
  • VERY SLOWLY, move the tuning knob from side to side, looking for the following feature changes.
  • The first discernable difference will be a "dark stripe or band" which moves from one side of the sun to the other as the tuning knob is dialed.    It may take some time going back and forth to notice this dark band, take your time.
  • Once the dark band is identified, position that area into the center of the sun's disk or the center of the field of view.  This darkening is actually the most accurately tuned area of Halpha. 
  • With the darkened band centered over the FOV, stop turning the knob and let your eye adjust to the view.  Often, observers need time to dark adapt before the details of Halpha appear.
  • If no dark band appears at any time, note the following information below.

The t-scanner is designed to operate in a temperature range of approximately 20°F.   The filter is then tuned within that range to the correct wavelength of 6562.8 by means of tilting the optical stack via the screw.    While this method of Tuning by Tilt does work and for many can provide a very high quality and reliable view, there are some significant limitations.  

T-scanner transmissions are selected for on-band temperatures BELOW the desired operative temperature range.  Tilt tuning brings the wavelength DOWN in the blue wing for operation in warmer temperatures.   

  • On cooler days, the filter would be on-band in a less tilted position
  • On warmer days, the filter must be tilted in order to shift the wavelength down in blue.

If the ambient temperature is below the labeled on band temperature marked on the filter's serial number label, then the filter will not offer Halpha views regardless of the tuning setting at all.   Some owners of T-scanner filters have reported using dew heaters or some kind of warming device in order to use T-scanner filters in the cold, in winter, or in climates in which they were not sold to match. 

It should also be noted that when a T-scanner filter is tilted, the overall fit and finesse of the transmission curve will suffer and widen.  Therefore, on particularly warm days, a T-scanner who is dialed to tilt more in response to the warmer temperature will suffer FWHM bandpass widening and may not deliver as high of contrast as on cooler days. 

DayStar has since discontinued the T-scanner line, as owners are frustrated by the sensitivity to ambient temperatures.  We are offering upgrades from the older T-scanner filters to be used in temperature controlled ION housings.  The ION housing will fix the optical assembly's temperature such that it will transmit 6562.8Å whenever plugged in.  The ION housing upgrade will allow owners to keep their same etalon, without a trade-in or apertu re reduction.    At this time, ION upgrades cost $900 to move into the new 1.5" aperture housing style.   T-scanner owners may also prefer to upgrade into the 20mm ION housing at a reduced cost (blocker and trimmer age will be prorated and may result in a blocker and trimmer upgrade cost) 

Tagged Keywords: find, knob, Tscanner, ION, upgrade, tuning, temperature, cold, warm, tilt

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