Pegasus Astro Forum

Hi,

I'm trying to get a good star alignment in Altaz mode but am having problems.

I have leveled the mount. The scope is pointed north and level and I have set this as home. I confirmed that the app says "At Home". I select my 3 stars, centering them in the eyepiece and confirming each one. I get the "Success" message at the end. But when I try to slew to an object, even one of my alignment stars, I appear to be several degrees off. Even going back to an alignment star I have the error. I've tried this multiple times and the error always seems to be about the same amount and in the same direction.

I was unsure if I was truly pointed north when at home (before doing the alignment) so I slewed to Polaris and rotated the base of the mount in azimuth to be pointing north. I then slewed home and ran the alignment procedure.

I'm not sure if this matters, but I purchased this mount through a dealer as a customer return. Other than the password being changed (which was more than a little bit annoying/scary) it seems to be "as new".

What am I doing wrong?

Thanks,
Tom

I might be seeing something related to this. If you take off the scope, disable refraction correction and put a dovetail plate in the saddle. If you slew directly E or W using the N/S slew buttons, is the plate horizontal when the readout in Unity is zero degrees? I noticed something strange when I tried to do a TheSkyX sky model. I noticed that the slew was pretty accurate in RA but the plate solved image was just over a degree higher in DEC when I plate solved near the imaging horizon (East and West).

Hence the trick with the dovetail plate. An easy visual check with a digital level and not compounded by heavy scopes or flexure. Something odd going on.

I know this is an old post, but I am struggling with this as well. My mount when in AltAz mode cannot point well at all. It is perfectly leveled (checked multiple ways: bubble level, horizon visual alignment, and 12” spirit level. All of these read true.), I have my home position set properly. Time, date and location are correct.

I do the three star alignment. Not a single star is in the FOV during OR after the alignment. I am always off by 2-4 degrees. I was trying the 2, 3 and 5 star alignment with no success. For example, I chose Polaris, Dubhe, Procyon, Arcturus and Vega. 5 great alignment stars, all spread throughout the sky. I tried slewing back to them AFTER alignment said “success” but nope, it was off by two to four degrees. Not a single star showed up in the eyepiece (panoptic 35, C8 edge). I am both lost and frustrated. This mount should perform way better than this for the price.

I am interested in this issue for alt-az operation. Just had first light with this mount and am using the mobile Unity Apple iOS app. Gotos were quite a bit off. Started with home position pointing horizontal and north (but not at Polaris). Will try with home position pointing at Polaris next time out. Any ideas on sensitivities with respect to mount being precisely horizontal? Any further guidance?

Got substantially better results second night out. Leveled mount using Pegasus mount level, then refined that horizontal measurement (and home position) using fine adjustments with iPhone app level placed on telescope dew shield. The result was that - three aligned calibrations star were well within my 2.7 degree eyepiece true field of view, as was a fourth unaligned deep space object goto. Aside - check on mount alt-az tracking capability, showed it to be spot on for at least 15 minutes. Learning continues… starting with the fact that achieving a fully horizontal scope home position (not just the mount) is important for accurate guide stars calibration.

So third night out. Again leveled both mount and scope, latter with iPhone app level. Calibrated iPhone app level to real physical level. Got more aggressive with scope focal length (150 mm Mak Cass f/12) and use of 22 mm Nagler Type 4 eyepiece that provided a field of view diameter of about 1 degree (vs. 2.7 degrees previous night). Used same alignment stars as previous night - Arcturus, Spica and Big Dipper - Alioth. Return slew to guide stars maintained them in same 1 degree filed of view, but barely. Swinging to acquire new DSO targets on other side of meridian was problematic. Had to calibrate on Vega to find M13 and M92. Again, though Messier objects were within a 1 degree Filed of View, after sync with Vega - it was barely so. One final bit of frustration is after slewing from the North to the South to view Antares, M4, etc. (which are way off), is the fact that software is shutting down azimuth movement back to the North home position (where it came from in the first place - I can only get about 90 degree movement in azimuth from the South. Very frustrating. Will keep at it, of course, but for comparison - accuracy and simplicity of goto experience with alt-mode on very modest SkyWatcher AZ-GTi mount was much better at this point.