Confessions of an Ignorant Astronomer…Part 2
At one time I had an ST80 telescope and Meade DSI attached to do autoguiding on the 11″ CPC telescope. As described in part 1 it never worked very well due to the practically non-existent tension on the worm gear. So I had switched to the internal chip guided ST-8E camera hoping that it would make the balancing issue much easier to deal with. Obviously, adjusting the drives correctly was the real solution!
The other big issue is polar alignment. This CPC (Temple 28) has a solid, non-adjustable wedge that came with the telescope. The way to adjust it is to physically move the mount side to side and up and down. This just makes doing fine adjustments to polar align a caveman’s chore. To change the altitude you grab the front leg, lift the scope, loosen the leg locking screw, adjust the leg, lock it back and gently lower it to the ground. To change the azimuth you kick, push or bang the mount right or left! Not a procedure for the feeble of body!
Fork mounts, like the one on the CPC are wonderful but very hard to polar align! There is no polar scope or other easy to use method for getting things even roughly lined up. Typically you place the telescope pointing as close to the pole position as you can, with the tube perpendicular to the base and the scope pointing directly towards the pole, spot Polaris in the main scope and you will be close. After that you can drift align to make it more accurate. All of this is relatively easy, if you have an adjustable wedge! There has to be a way to do it easier and maybe get it close in daylight even with a non-adjustable wedge.
Enter the cell phone method! You take a cell phone, strap it to the wedge, turn on your planetarium app on your cell phone and then move the wedge until the pole is positioned inside the Telrad circle and you will be close. It is quite brilliant and seems to work well for the majority of people that use it, and then review it. One caution you have to strap something non-metallic onto the wedge so the close proximity to the metal in the wedge won’t throw off the compass. Since I did not want to take it apart I strapped the phone to an area below the wedge, knowing it was not as good but would work. Wow, this is way easier but I still couldn’t get it to come out right.
So looking to make an adjustment, I lifted the already teetering mount up on one of its back legs. Suddenly the mount started to tip and I reached out to grab it, trying to ease its fall enough that nothing would break. With soft ground and slowing its fall the telescope hit without damage! The term, “heart stopping” flashed through my mind! Since it was already down and I need help to lift up the whole telescope, it seemed prudent to separate the wedge, mount and telescope. Putting the cell phone and books on the wedge and mount itself and not the telescope base it was quickly determined that there was no way to use the included wedge without the telescope falling over!
The wedge was designed for 32 degrees in New Mexico. The angle on the wedge was approximately 25 degrees with the difference being made by raising or lowering the telescope leg. I had used it at 35 degrees in northern New Mexico but when reflecting on it, the mount seemed somewhat unstable even at that time. Adding 3 to 4 degrees to the tilt just made it totally unusable!
Now a Celestron CPC super wedge needs to be purchased. There are other products that even work better than the super wedge but are much more expensive. After years of frustrating use of Temple 28, it will be a joy to finally be able to get everything right, with minimal effort and just do astronomy!