Jerry Hubbell - Explore Scientific VP Engineering
On Mon, May 27, 2019 at 01:41 AM, George wrote:
I've done the polar alignment, it should be good. I spent several frustrating hours tonight thinking this would be the time, it was going to come together tonight. 3 star alignment, first star a few degrees off, second star still....a few degrees off, third star.....still...a .... few.... degrees.... off! So, I sucked it up, I would redo polar alignment and do it all over again. Nope.... first alignment star wad Regulus.... the score barely leaves the area of Polaris.
I am sorry you have had such a frustrating time with your mount. We will help as much as we can to get this working for you although I think you are not up to spending a lot of time with it. Please indulge me George as I describe the steps needed for a beginner, as this is for those that are new to the PMC-Eight system and be starting out. I am sure you have done this multiple times, but you may see something in this process that might give us a clue what may be going wrong in your case.
There are a few things to understand and also get right before you attempt a 2 or 3 star polar alignment. It's best when first starting out and learning this mount to verify a few things first.
1) First, during the day, make sure your tablet is setup and you can communicate reliably with the mount using ExploreStars. The ExploreStars application is available in Windows, Android, and iOS, there are small differences in the user interface so make sure you understand the basic functions and test them out. Don't worry too much about learning the steps to do the alignment just yet, just make sure you can bring up catalog objects and slew to them. Also make sure you can set the manual slew rate values (0-9) and manually move the mount using the Up, Down, Left, Right buttons. Sometimes you will see these referred to as UDLR. If you have issues with the communications dropping out, use the WiFi dongle to change the WiFi channel on your PMC-Eight to find a better channel.
2) When you set up the mount outside, first use a level to level your tripod, or the bubble level on the mount and use a compass to get the mount's RA axis close to TRUE NORTH as you can. The compass indicates MAGNETIC NORTH and you will need to correct the alignment for MAGNETIC DECLINATION. You can find out about that here: https://en.wikipedia.org/wiki/Magnetic_declination You can find the value for you location here: http://www.magnetic-declination.com/ You can use the indicator on the side of the mount to set your RA axis close to the correct altitude. which will be the same as your location's Latitude.
3) After putting your telescope and your finder scope on your mount, manually loosen the clutches and point your scope to a far off target that you can use to align your finder scope to your telescope. Start out using an eyepiece in the 25 mm range and align your finder scope so that when you point your finder at an object in the distance, you will see it close to the center of your eyepiece. If you want to make your finder more accurate, move to a shorter focal length eyepiece such as a 12-16 mm eyepiece. After aligning your finder scope, make sure all the adjustments are tight and verify that the alignment is still accurate.
4) When it gets dark outside and you are ready to do a polar alignment, i would suggest doing it first using your finder scope to get pretty close. In this exercise, you will be aligning on Polaris at first and not the North Celestial Pole (NCP). This will get you to within a degree of the NCP. You will be doing a fine adjustment of the Azimuth and Elevation (Altitude) axes of your mount. First, make sure that your RA and DEC axes are set to the home position where the little arrows are lined up on the side of the mount on each axis. Then using the Azimuth and Elevation adjustments, move the mount so that you center Polaris in your finder. There are a couple of ways to make this more accurate and should be done for the best physical alignment using your finder scope, first, you can use an app on your phone or on your PC to determine the current location of the NCP in relation to Polaris and align your mount to that location. You need to understand the field of view of your finder to do this correctly. Also, you need to correct for another error where your telescope is mated to your mount called Cone Angle. This is a condition where the telescope is not in optical alignment with the mount's RA axis. You can find more about that here: https://www.youtube.com/watch?v=WatdQlPp22Y . You can get a fairly good polar alignment (within a couple of degrees) without doing a cone angle adjustment, but it will throw things off a small amount.
5) Once you are satisfied that you have a good (not excellent) polar alignment, it is time to verify that there are no other mechanical issues with your PMC-Eight by slewing to a bright object in the sky. Don't worry about doing the 2 or 3 star "virtual" alignment procedure in ExploreStars. This test is used to make sure your mount is mechanically sound. Pick a planet or the moon, or if not available, pick one of the alignment stars that you can see in the sky such as Arcturus, or Sirius, or some other star that you "know" is the one you are looking at. There cannot be a case of mistaken identity here. Go ahead and slew to this object and once it is finished slewing, see how close to the center of your finder scope it is. It may be a couple of degrees off. Once you have determined how far off it is, use your Azimuth and Elevation adjustments to center the star in your finder scope and then in your telescope with a higher power eyepiece. Lock your mount adjustment down. The goal here is to refine your polar alignment. If you haven't done a Cone Error adjustment, then there will always be small amount of residual error that may amount up to a degree or so. It could be worse if the adjustment on your telescope is way off.
6) Slew to another object in the sky and see how it is in your finder. Slew to a few other objects to gauge how close in general the mount is pointing via your finder scope. Hopefully, with no mechanical issues you should be pointing to objects all over the sky fairly well.
It is important to do this procedure first to get a good feel for the mechanical condition of your mount in terms of pointing and then report any issues if you are still "several degrees off". If you can manage it, you should attempt to measure and correct the Cone Angle and then retest using this procedure to see if you are still several degrees off in pointing.
I hope this will help George getting your mount to perform.
Vice President of Engineering
Explore Scientific, LLC.
jrh at explorescientific.com
1010 S. 48th Street
Springdale, AR 72762
Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home
Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Mounts: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras: QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating
Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!