User`s guide

10
the S/N ratio will be lowered. Remember, for each 10°C drop in operating temperature a
gain of about one stellar magnitude is achieved in limiting magnitude.
The focus seems to shift significantly throughout the evening.
Focus is a common problem among the Schmidt-Cassegrain type telescopes. With the folded
optical path of the SCT, slight thermal changes have a significant effect on the overall focus
of the system. You should routinely check the focus by using the focus mode of the data
acquisition software. Most of the standard CCD control software packages offer a focus
mode. An even better solution is the Optec TCF temperature compensating focuser. Visit
the Optec website at www.optecinc.com for more details.
The telescope is properly balanced, but in certain directions the tracking seems less
than adequate.
With CCD imaging, proper balance and polar alignment is essential. Any slight movement in
declination or right ascension can result in a blurred image. Remember that each pixel is only
about 10 microns, so even a slight nudge will show up in the final image. Try fastening the
cables of the CCD camera head directly to the telescope fork arms with tape or zip-ties. The
key is to remove as much stress from the photometer head as possible. Another safety tip
for SCT owners is to add a second thumbscrew to the visual back. Drill and tap the hole
such that the two thumbscrews are 90° apart. When installing the CCD photometer tighten
both thumbscrews to avoid a catastrophic fall.
When observing a number of faint variables, glare from the reticle makes it difficult to
center the object.
PFE-1A users have the luxury of simply adjusting the reticle brightness with the large knob
on the bottom of the unit. Standard PFE-1 users will need a small screwdriver to adjust the
pot on the underside of the unit near the reticle power supply jack.