Focusing | Parfocal | Autoguiding camera | |
Focusing can be done in daylight on | ring |
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a distant object, or at night under the |
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stars. For best results we recommend |
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doing final, fine focusing at night at |
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the beginning of your imaging session, |
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following the focusing procedures in |
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the imaging software you use for astro- | 1.25" |
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Nosepiece |
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photography, such as MaxIm DL, PHD |
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Guiding, or Images Plus. |
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1. Slide the 1.25" parfocal ring onto |
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the nosepiece of your autoguiding |
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camera (Figure 2). If it doesn’t | Figure 2. Slide the parfocal ring onto | ||
slip on easily, make sure the three | the 1.25" nosepiece of the Orion StarShoot | ||
setscrews in the ring are backed | AutoGuider or other autoguiding camera. | ||
off enough to provide clearance | Do not tighten the setscrews yet. | ||
for the nosepiece. A 1.5mm Allen |
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Once you’ve achieved the best focus you can get, lightly
Of course, if you turn the objective lens cell until it can rotate inward no further, or you rotate it outward so far that it unthreads completely and comes off, you should reset it to about the mid- point of its thread travel and
Setting the Parfocal Ring
Objective rotate to lens cell focus
Lock ring
Figure 4. After setting the coarse focus with the camera in the guide scope holder, fine focusing can be done by rotating the scope’s objective lens cell. First, you’ll need to loosen the lock ring by rotating it counterclockwise a couple of turns.
wrench is provided for adjusting the | 1.25" Holder Camera nosepiece | ||||
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setscrews. Leave the ring loose on |
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the nosepiece; do not tighten the |
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setscrews yet. |
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2. Next, insert the nosepiece of your |
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guide camera about halfway into |
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the 1.25" holder of the guide scope, |
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then lightly tighten the three thumb- | Holder thumbscrew (x3) | ||||
screws on the holder to temporarily |
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Figure 3. Insert the autoguider | |||||
secure the autoguiding camera in | |||||
place (Figure 3). | nosepiece about halfway into the 1.25" | ||||
3. Make sure your autoguider camera | holder of the Mini Guide Scope, then lightly | ||||
tighten the three thumbscrews on the | |||||
is powered on and connected to | holder to secure the camera in place for the |
Once the guiding camera’s nosepiece has been set at the optimal focus position following the above procedure, you can lock the parfocal ring on the camera’s nosepiece. This will enable you to return the camera to the same position in the guide scope’s holder on subsequent imaging sessions (assuming you remove the camera from the guide scope after each session), obviating the need to go through the coarse focusing procedure (steps 2 and 3 above) again. You should still, of course check the guide scope’s focus at each imaging session. But if any adjustment is needed, it will probably be minor and can be done using the fine focus of the objective lens cell (step 4 above).
To set the parfocal ring, which you inserted on the guide camera’s nosepiece in step 1 above, simply slide it forward until it lies flush against the guide scope’s 1.25" holder (Figure 5). Then carefully tighten each of the three setscrews in the ring.
your laptop computer, and that the | moment. |
software you will use for autoguid- |
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ing is up and running. With the
imaging software set to take continuous exposures, slightly loosen just one of the thumbscrews holding the autoguider nosepiece – just enough to be able to move it very gradually forward or back, while you watch the stars or refer- ence numbers (e.g., FWHM) on your laptop screen. When the stars are pretty sharp, or you’ve reached approximately the lowest FWHM, tighten the loose thumbscrew so that the camera is secure in the guide scope.
4.Final, fine focusing can be done by rotating the objective lens cell on the front of the guide scope. First, back off the objective cell lock ring a couple of turns by rotating it counterclockwise (Figure 4). This frees up the objective cell to be turned either clockwise or counterclockwise. Turn it one way or the other by a quarter turn or so and see what effect that has on the star focus.
1.5mm Allen wrench
1.25" Holder
Parfocal |
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ring | Setscrew (x3) |
Figure 5. Once focus is achieved, set the parfocal ring by first sliding it up against the 1.25" holder. Then, using the provided Allen wrench, secure the ring to the camera nosepiece with the three setscrews.
4 | 5 |