Celestron Compustar Bedienerhandbuch

How To Autoguide The Compustar: The Complete Guide By Rod Pommier, M.D.

10 during the actual imaging sessions. Planetarium software often has provisions for making such overlays for use with that program. Lastly, the imag

11 Guiding Camera The guiding camera is not to be confused with the actual imaging camera at the prime focus of the telescope. Rather, it will be ins

12 Autoguiding Software Obviously, you can‟t just connect an imaging camera to a computer and expect it to begin interpreting the images and put out

13 Figure 5. Two examples of RJ-11 autoguiding cables, a flat ribbon cable on the left and a coiled cable on the right. An RJ-1

14 Figure 6A (left). A GPINT connector, available from Shoestring Astronomy. Note the male plug to be connected to the parallel port on the autoguid

15 Figure 7. The GPINT connector attached to the parallel port of the autoguiding computer and a coiled RJ-11 cable inserted into its female m

16 The Compustar Can Be Autoguided Fortunately, the answer is “Yes, the Compustar does have some other type of guide port”, and that almost seems lik

17 Figure 9. The front edge of the Compustar computer module showing its three female DB-9 ports. Each port receives 9 pins. The right port is for a

18 Many older telescopes, likes the Compustar, require electrical isolation between the electronics of the autoguiding computer and those of the tele

19 modular jacks on the opposite ends of the cable. There are two ways the modular jacks can be connected if the ribbon of cable is out laid out flat

2 Astrophotography Astrophotography is more popular today than it has ever been. Electronic imaging has revolutionized the field and high quality dig

20 Figure 12. The color coding and pin numbering of an RJ-11 autoguiding modular cable jack. With the cable to the left and the copper wire pins of

21 receptacle for the retaining clip on the bottom, then pin 1 for the white wire will be on the left, and so on, with pin 6 for the blue wire on the

22 In ST-4 language, the pin out for an RJ-11 cable (repeat, cable) is as follows: Pin # Wire Color Direction 1 White Not used 2 Bla

23 Figure 14A (left). The pin out of a female RJ-11 modular jack connector, suc

24 Group (http://tech.groups.yahoo.com/group/CelestronCompustar-User/). Mr. Borgman published this in response to a request for autoguiding wiring po

25 Figure 15. The modified wiring diagram for the relay interface between the RJ-11 cable from the autoguiding computer to the DB-9 connector for th

26 unless they are autoguiding directly from one of those devices instead of using an RJ-11 cable from an autoguiding computer. If the reader will be

27 autoguider relay box would not operate unless pin 9 on the DB-9 connector plug was grounded. Subsequent tests by Tom Sorbel confirmed that pin 9

28 When the input stops, the electromagnetic field will decay, the spring will flip the relay switch back to its “nc” position and restore electrical

29 Figure 16. The assembled autoguider relay box. The coiled RJ-11 input cable with its modular jack at bottom center is not connected to the autogu

3 able to automatically slew to any one of thousands of objects in their database. They were produced as 8, 11, and 14-inch versions of their popular

30 There is a fourth speed, and that is “AUTO”. As the name implies, “AUTO” is for autoguiding. The computer module beeps four times when “AUTO” spe

31 through the autoguiding software. Set the exposure time for the guiding camera so that the star is imaged well, but not saturated. Typical exposur

32 relay box click as they flip from their “nc” to their “no” positions when the autoguiding computer commands the mount to move in any direction. Yo

33 guide camera chip and is lost. This takes some trial and error, but is best accomplished by placing the calibration star in the center of the guid

34 framed on the imaging chip, just as you set it up before. With the software properly calibrated for that orientation of the guide camera, it will

35 By the same token, if you set the autoguider aggressiveness to the maximum, you are likely to get rapid fire jerky movements of the mount as the g

36 direction, then there may be some slack that has to be taken up whenever the next correction is in –Dec before the drive engages the gear teeth in

37 Fork mounted telescopes should be balanced first with the optical tube assembly aimed in the vertical direction, then in the horizontal direction.

38 generate. All these problems result in guiding errors. The goal of rebalancing the telescope is to put the telescope‟s center of gravity back at t

39 have counterweights in the left fork arm to counterbalance the declination drive box on the right fork arm. Most locations where equipment can be

4 With all their features, it is no wonder that Compustar owners lovingly care for and maintain these telescopes rather than buy some of the newer Go

40 away from the Milky Way. Odds approach essentially 100% as one images subjects progressively closer to the Milky Way. Another wonderful feature a

41 Figure 19A (left) The author’s SBIG STL 11000M CCD camera with the adapter plug (labeled RC-7) plugged into the camera’s autoguider output port.

42 fatigued. The author has manually guided astrophotographs for long periods of time with no errors, only to make a single error pushing the wrong b

43 shot color) by taking many, many 30 second sub-exposures. This was because 30 seconds was the longest period that the Compustar could ever track a

44 Figure 21. M57, the Ring Nebula in Lyra. This is one of the author’s first autoguided images obtained with his Compustar 14 and the autoguider de

45 Figure 22. M57, the Ring Nebula in Lyra, enlarged and cropped from the image in Figure 21. Note the fine structure detail in the upper right port

46 Figure 23. The author’s “first light” image of M51, the Whirlpool galaxy and NGC 5195, obtained with the SBIG STL 11000M and the Compustar C14 an

47 Figure 24. M63, the Sunflower galaxy a self-guided image taken using the autoguider on the Celestron Compustar 14 with a 0.75x focal reducer (f/8

48 mass produced. It is estimated there are only 500 Compustar 14 telescopes, a number smaller than any other commercial model. Fortunately, this is

5 What Is Guiding? Because of these tracking errors, virtually all astrophotographs must be guided. That is, the tracking of the drive and mount are

6 Figure 1. An illuminated red cross hair reticle. This reticle has a double cross hair. The gu

7 crosses the meridian, but this will not occur in the guide scope. Thus, even if the guide star is tracked perfectly in the guide scope, differentia

8 Figure 2A (left). An off-axis guider is a T-shaped connector that connects to the threads of the rear cell

9 not a problem with separate guide scopes in which the subject can always be framed as desired and a reasonably bright guide star can be selected qu