Issue with AA+ and Nexstar 8SE

[Startrailer42]

Hey there,

 

I need some advice on what I might be doing wrong with Asiair+/PHD2 and the Nexstar 8se please.

 

The obvious answer is - the combination of both, I am aware of that. After a long time in visual observing I am gradually moving my equipment towards EAA and maybe some AP again. Though my actual goal is to re-enter into observing minor planets and variable stars. This is how I came into the hobby a lot of years ago, Imaging with an SBIG ST-7 of my local club.

My present rig is:

Celestron Nexstar 8SE at f6.3

AA+
Zwo 220 mini for guiding

ZWO OAG-L

ZWO EAF Focuser

Zwo 678 mc as main cam (actually my planets cam, but it fits nicely into the AA eco-system)

Mount is connected via HC to the AA+

Slew and tracking rate is set to 1.

One or two-stars Alignment for Goto on HC.

Celestron GPS-Module for Time and Coordinates.

Mount is quite levelled.

Focus is sharp.

I use the center of the main camera for fine alignment of the HCs Goto-Alignment.

I sync to mount after each goto, which seems to work. Goto works smoothly, AA+ corrects the gotos mostly once or twice until centered.

Rough alignment and tracking works more or less, given the small FOV with the 678 I can take exposures of 1-3 seconds length over a period of 2-4 before too much of larger objects disappears out of field.

! But what never worked at all is guiding. Not. At all !

I don‘t mean it’s not working nicely, it’s a repeating disaster.

As soon as I switch from tracking to calibration or guiding in AA+ the guide star is being drawn out of field of the guide cam within seconds. No matter what guiding parameters are used.

My best try seemed to be something like

Calibration step around 500

RA/DEC correction around 200

Aggressiveness around 50% each

BIN 2 

Mount 3 secs stable

I am curious what experienced imagers make out of this?

So far I have connected the mount via hand controller, which is proposed in most threads.
I wonder whether I should give ST-4 guiding a chance - most people say it’s a lot worse than the present connection - but I can only guess that either I am using entirely wrong guiding parameters or my connection / HC-AA+ cable is defect or it doesn’t work this way?

Has anybody any clues what else I could do?

[Cosmic Geoff]

Using a SE mount is probably not a good idea. I have a C8 SE, and I used it for planetary imaging and, IIRC, a few shots of planetary nebulae, but the performance of the mount was such that I bought a CPC800 to use for planetary imaging.  It performed far better in that role, and I also used it for some EVAA style imaging of planetary nebulae.  (with f6.3 focal reducer).  Exposures were up to 20 secs, unguided, with the alt-azimuth mount.

My regular EVAA rig is: 102mm f5 Startravel, EQ5 Synscan mount,  ASI224MC camera, software for capture: Sharpcap.  I platesolve with Sharpcap for fine positioning. 

[Elp]

I'll stand to be corrected as a lot of people do this trying to use an Asiair with an altaz mount. It won't work I believe. The air uses the equatorial coordinate system so even guide calibration will fail as it won't calibrate NS and EW as it does with an equatorial mount. This I believe is your problem.