One-arm Nexstar alt-az in Equatorial mode

This is a question about the inexpensive one-arm Nexstar goto mounts sold by Celestron. These mounts have an option on the hand controller to operate in equatorial mode, and I'd like to try and use one as a tracking mount for a DSLR for wide-field AP. But before I invest a bunch of time building a base wedge and brackets, here are a few questions some others might know answers to:

1) I've read that the controller in the cheap Nexstar alt-az mounts only approximates the sidereal rates, IOW the mount is still operating both axes and just interpolates the RA position every few seconds. Does this cause trailing on images?

2) If I ignore the equatorial mode and instead tilt the mount to the correct angle for my latitude (point the azimuth axis at the pole), can I do a 2-star alignment and track in alt-az mode without field rotation?

thanks in advance!

Jim McSheehy said:

This is a question about the inexpensive one-arm Nexstar goto mounts sold by Celestron. These mounts have an option on the hand controller to operate in equatorial mode, and I'd like to try and use one as a tracking mount for a DSLR for wide-field AP. But before I invest a bunch of time building a base wedge and brackets, here are a few questions some others might know answers to:

1) I've read that the controller in the cheap Nexstar alt-az mounts only approximates the sidereal rates, IOW the mount is still operating both axes and just interpolates the RA position every few seconds. Does this cause trailing on images?

2) If I ignore the equatorial mode and instead tilt the mount to the correct angle for my latitude (point the azimuth axis at the pole), can I do a 2-star alignment and track in alt-az mode without field rotation?

thanks in advance!

Hi Jim

Maybe I'm all wrong and someone will correct me, but I have the nexstar SLT (stripped down Nexstar) and also a CPC 2 arm fork. Both of those guys seem pretty sensitive to the proper leveling of the mount before they want to report a proper 2 star or 3 star alt-az alignment.

But have heard others report that their identical rigs are not very sensitive to exact level.

Have had several nights where I'd have several failed alignments till taking the trouble to properly level the mount, but maybe something else caused the failed alignments. Nowadays I just always use a bubble level to make sure it is nearly perfectly level before even trying to align.

My sky isn't very big because of trees on all sides. I can't pick wide-separated stars for 2 or 3 star alignment. So often I'll do a 1-point alignment on polaris or the moon. Then point to some random point of the sky and tell it to find a binary. It slews to where it thinks the binary should be, and then I center the binary and add it as a second alignment point. Then possibly repeat the procedure for a third alignment point. It is a bass-ackwards procedure that seems to point near-perfect at everything else the rest of the night.