Re: Slewing accuracy question (Mach 1.0)

Chris Spratt

Where do you get the program "Alignmaster" you mention?

Chris. Spratt
Victoria, BC

--- In ap-gto@..., "peteram2003" <phorstink@...> wrote:

Hi Chris,

I am assuming you are using the Pasill polar scope that comes with the mount. One of the problems with it is that it is not possible to check its alignment with the mount as it does not rotate when you rotate the RA axis. Even though you have all the stars lined up in your scope does not mean your mount is pointing the same way. I can tell you mine is off quite a bit and only gives me a very rough alignment. I have taken it out of the RA axis and placed it in a finder bracket attached to the back of the mount. That way I am able to make it orthogonal with the mount. Much better accuracy now! Also I have use a very simple program the last couple of times now to align to the pole. It is called "alignmaster" Very simple procedure and I have gone for 5 minutes unguided now with no significant drift at 500mm focal length. My goto's are deadaccurate as well now after the alignment procedure. By the way Roland's method is very good as well. After you done it once or twice its very ease to do, but I believe alignmaster gives me even better alignment in less time.
Ofcourse all the remarks about orthogonality are correct if you point at both sides of the meridian. When you need accurate pointing it helps a lot to align your mount on the same side so orthogonality does not play a role.

Good luck,


--- In ap-gto@..., cford81@ wrote:

I have a question about the slewing/aiming accuracy of my new Mach 1.0.

Last night I set up my telescope to a high focal ratio equivalent of F/32 (via Powermate) and to focus (with a Bahtinov mask) I slewed to Vega - all worked well. I then slewed to Jupiter and the planet did not fall within the FOV. After exploring the neighborhood with the hand-controller (a "spiral out from the initial slew landing point" would be really useful) without much luck I was able to eventually correct my aim by eyeballing on Jupiter through the telescope tube visually, (with camera dismounted) and I then did a RCAL assuming my model was slightly off. I then slewed back to Vega and the same problem - this time the star was not visible within the FOV.

The slew from Vega to Jupiter and back required the telescope to switch sides from west to east and back. I checked that there was no meridian delay or anything confusing things. The mount drive motors appear firm and secure. (The mount is only a few months fresh out of the box from AP)

OK, I know this immediately sounds like a case of polar (mis) alignment, and I readily admit that is most likely the cause. I believe I was accurate at least to the precision of the polar alignment scope. I checked all 3 reference stars and they were lined up perfectly. However, perhaps this combination is just not accurate enough for these high focal ratios and I need to use Pempro or other alignment method? (I have yet to try the new Roland method) I can work this out by eliminating the variables one by one...

Before I do so however, my question here is really one of expectations for the combination of Mach 1.0, polar scope, and very high focal ratios - what I should reasonably expect as I become familiar with the mount. Does anyone have experience of this?

Chris Ford

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