Problems with focussing
As long as you have not focussed your scopes there is no result whatsoever. Period.
I can only describe my own equipment of course.
Programs to guide your system may handle it in a variety of ways. THIS IS A WARNING:
As focussing is moving parts in your telescope be aware how the focussing is processed by your software! When the software does not process the signals of the autofocusmotor in the correct way the process may damage either your motor or your telescope!
I was used to my Stellarmate Pro which handled this proces very correctly. Once the motor had reached the end of the actuator screw it send a signal to the Stellarmate Pro to reverse the movement or it did that itself and let the Stellarmate Pro know. Either way: the process reversed itself instead of pushing on and damage things. When I switched from the Stellarmate Pro to the ASI Air Plus (which by the way is of the same brand ZWO as the focus motor) this went wrong. I suddenly heard a loud 'bang' inside my telescope and the motor stopped.
On the picture you see the actuator screw sticking out far from the brass screwing cilinder. It got stuck tight and I had to use a wrench to get it going again. I now just hope that nothing else on the inside is damaged. However a quick control showed me that I could still focus so keeping my fingers crossed.
The resulting question is why the focus process ended up at the end of its travel path... When you use different methods of watching the stars, visual, deep sky or planetary you have different optical trains (sets of cameras, reducers, barlows, eyepieces etc). They all need a different focal plane so in order to switch more easily it comes in handy to make a note of the motors positions. Then something strange happened when I first did this with the ASI Air Plus. Moving back and forth to position the main mirror for finding the right focal plane the counter kept going down whichever way it was moving. So I did what I was used to do on the Stellarmate: let it run and reverse in order to reset the counter so it knew where its position is. And there it all went wrong...
Back to the explanation about focussing in general.
So in my case this is about the Askar Guide scope and the main Celestron. But this last ones focussing depends on the used camera or better: the actually used optical train.
The guide scope is the easy one: it takes a small guide camera. At the end of the scope the camera can slide in. Point it in daytime at a distant object, set the focus ring in its center position, slide the camera in while you observe its image on your computer. When as sharp as you can get it fasten the screws secure. Now fine tune the focus ring. The guide scope is now focussed and ready.
The main scope is different. Focussing depends on the optical train. In this case I use the ZWO ASI2600 MC Pro which needs about 133mm of back focus. First… that back focus distance is arbitrary. Up to 2mm difference is no problem.
On my Celestron Edge HD*” I have the EAF controlling the focussing mirror. So first thing to do is get a crude focus but make it as good as you can and this has a very important reason: like the Newtonian the SCT scopes produce donut shaped stars when enough out of focus. The StellarMate uses Ekos routines to focus and it seems to hate donuts. However… there is the donut buster. So activating the donut buster is one thing but also try to stay within the focus range in which the stars don’t get to form the donuts. So the better your crude focussing the less change the software goes focus hunting. It also causes the focus time to speed up significantly. I have set the parameters to low values specifically the amount of steps per focus action and the maximum travel length of the EAF.
Crude focussing or better, read this as manual focussing.
Because that is what you do for a crude focus. Also: this is how you do manual focussing with the EAF attached:
1. Loosen the screws that tie the focus tube to the EAF.
2. Turn the focus tube manually until a fairly good focus is achieved.
3. Fasten the screws to tie the focus tube back to the EAF.
Stellarmate Pro screendumps:
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