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Optimizing Your Celestron Celestar 8
Deluxe Telescope for Photography
By Daniel Del Proposto,
Director, Willow Creek Astronomical Observatory
Celestron's Celestar 8 Deluxe Telescope is a low cost, quality mass
produced Schmidt Cassegrain. I am amazed at the optical quality and the accomplishments of
amateurs over the years utilizing this high performer. But since the telescope is mass
produced there are varying degrees of quality between product lines, individual units and
some reported issues regarding quality control. Fortunately most of the reported problems
are easy fixed by the owner and do not require Celestrons intervention. Many problems
involve simple incomplete assembly issues like loose forks.
We have experimented with light modifications to our own telescope
based on recommendations from other owners and our own ideas. The modifications were
performed on our Celestar 8 Deluxe with varying degrees of success. While the
modifications all yielded improvements caution must be exercised when any modifications
are performed on a telescope especially when it is still under warranty. Any modifications
performed using the suggestions provided are the owners responsibility and discretion
One of the key issues
reported by few owners is a problem with drive vibration. Celestrons vibration pads
greatly improve the situation but the telescopes drive systems utilizes a DC stepper motor
to control RA operation. This motor produces a large amount of vibration that can transmit
into the optical tube and forks with varying degrees of impact depending on balance. If
the drive systems is improperly adjusted and/or if the telescope is improperly balanced
this vibration can reduce visual and photographic quality substantially and seriously
introduce erratic error, playing havoc with autoguiders like SBIG's ST-7. Our
experience with this problem is very extensive and we have
eliminated the problem with proper adjustment of the drive system
including the re-lubrication of worm gear as directed by Celestron technical support.
An additional issue to
check for is worm gear alignment. Improper gear alignment may not have any effect on using
your telescope visually but will likely seriously effect photography especially when using
an autoguider. Our telescopes worm and worm gear (really a spur gear) was not properly
centered on the worm at the factory resulting in the worm gears teeth hitting the end of
the worm tooth. This generated a large and quick periodic error that my ST-7 could not
correct. The way you can detect this error is by simply removing the motor and rotating
the worm shaft by hand. If there is any binding, this will likely effect the mounts
ability to track effectively for photography. This problem can be fixed by the owner by
adjusting the placement of the worm in the worm cage, I however recommend having Celestron
make the repair.
Additional RA adjustments involve the replacement of the worm cage stop screw with a
hex screw and tightened it just enough to prevent the cage from completely disengaging the
worm gear from the worm, but not tight enough to prevent the worm cage from moving. You
should be able to pull back the worm cage against the stop screw, but not far enough to
let teeth of gear slip past the tooth of worm. In regards to worm cage tension screw and
spring, a good starting point is to tighten it just enough to where you can feel the
increased resistance by rotating the worm gear by hand. Then pull back the worm cage
against the stop screw and release. The spring should fully engage the worm to the gear
without need to apply additional pressure with your fingers to fully seat the gear. If
worm does not fully seat when released then tighten hex screw with spring 1/4 turn at a
time and try again. Remember that you do not want the spring too tight and you should be
able to turn the worm by hand and also be able to pull back the worm cage, partially
disengaging the worm from the gear. If it is too tight the gear could bind causing damage
to the motor or premature failure.
Other suggestions include...
- Using a 1/8, male to female, phono plug extension cable (from
Radio Shack) you can extend the focus motor hand-paddle. Attaching
the cable to the side of the telescope and pier prevents tangling, cable strain and
jarring of telescope by accidental pulling of cable.
- Managing wires utilizing adhesive wire clips
can be purchased at most hardware stores and are an excellent option for managing and
routing wires.
- Protect your telescope from the telescope tube accidentally hitting the bottom of fork
base by installing rubber bumpers with Velcro. The rubber
bumpers can be purchased from most hardware stores.
- Use a business card magnet for hanging
hand-paddles on metallic piers, mounts etc. Attach sticky side of business card magnet to
back of hand-paddle. Trim any excess magnet material with a pair of scissors. I have found
this to be very effective.
- To mount your Celestron Standard Wedge on a Pier base plat and get
an accurate bolt pattern transferred, I drilled the pier base plate for just the center
bolt and mounted the wedge/telescope to the pier. Then I obtained
(minimum) rough polar alignment. (See your telescopes documentation). When polar alignment
was complete, I marked the centers of the remaining holes in wedge, removed the telescope
and wedge then completed drilling of remaining holes into the pier base plate.
In conclusion we would like to re-iterate that the Celestron Celestar 8 Deluxe is an
excellent scope for visual work and a good performer for photography. With additional
modifications and some experimentation your Telescope can become an above average
performer. |
