Thank you Alex for spending some time on n-star alignment for pointing vs polar alignment for tracking. This was something that took me a while to figure out when I was getting started and was a real ah-hah moment. A real key concept for beginners!
The documentation on the Gemini software website is quite specific about how many stars and where they are located is used by the pointing model. The pointing model also should correct for polar misalignment when tracking. They also have a polar alignment correction routine in the Gemini system. For example flexure of the RA counterweight is with the 5th star. added to the model. In any case, once the model knows the polar error it can correct with dec movement to compensate for polar error. Cold start - No pointing model retained, no location data retained. Warm start - pointing model and location is retained but RA/DEC position is unknown - assumes you are starting in CWD position. Warm Restart - all model and location and data is retained and RA/DEC position is also known (after a Park). Regarding manually moving telescope. - If you have extra encoders installed you can move the telescope and Gemini will track where the telescope is pointed. Otherwise, if you want to manually move the telescope you should put tracking in 'closed loop mode' and it will track whatever object that you point the scope at. You can easily get the scope resynced with the model by doing a warm start and a 1 star align or even just point at a known object and syncronize. The model doesn't get messed up.
This review is very informative, detailed. I'm thinking Losmandy in the future, and this has helped me. I must say, though that some of the add-ons are ridiculously expensive. $100 for 3 glow in the dark tripod feet? I got a roll of luminous tape, and appliance pads for about $18.
"Quick Start" - This selection will take you to menu's to select your "Mount Type", Enter your "Location", then "Time, Time Zone and Date" Then you will go to the "Main Screen" This also does a "Cold Start". "Cold Start" - A cold start wipes out all stored modeling. You need to have your mount positioned at want is called CWD. This is with the counter weights down, and the Declination pointed towards Polaris in the Northern Hemisphere, and the South Celestial Pole in the Southern Hemisphere. The processor in the Gemini-2 uses this approximant position to start it's calculations from. It expects you to do an alignment, or synchronize on a bright star. When you align or synchronize on the bright start, then the processor refines the known position in the sky and also repositions the limits correctly. It also updates the All modeling calculations will start from this point in space. "Warm Start" - This is basically the same as a cold start, but does not wipe out any models built. It also remembers all your setting. You still must start with the mount pointed to CWD position as in a cold start. If you have models built, but have moved your Right Ascension axis or Declination axis, but not the location of the mount itself, then you can use this startup mode. Warm Start uses the CWD position as an approximant starting position, but expects you to do either an alignment, or synchronize on a bright star. When you align or synchronize on the bright start, then the processors re-centers the model, and positions the limits correctly. "Warm Restart" - This mode also remembers your modeling and all setting. You can only use this mode if, and only if you have not moved both the Right Ascension axis or Declination axis and also have not moved the mount in position. All calculations will start from this point.
William Finn when putting the declination in CWD ( counter weight down) position I find it easier to put a level under my losmandy d style mounting bar rather than on the side of the declination like Scott shows in his video. Hard to get a level in the proper position on a round surface. I have a gm811g . The G11 I understand has a bubble level on the declination to make it easier. If you look at the tripod leg and try guessing at CWD then you will have alignment issues. My mounting plate sticks out of saddle a few inches so it's easy to put a level on the bottom side of that.
Hi Alex. I still have a question on the polar alignment, since this is needed for accurate tracking during imaging. Lets say you do a 4 or 5 star alignment and the mount "calculates" that your polar alignment is off. What happens next? Do you need to manually move the latitude and azimuth knobs to correct the polar alignment manually? (those controls are mechanical right? So the software can't move the RA axis). Or do you mean that you don't need to do anything and the software can figure out how to move the mount to track correctly based on the previous calculation of where Polaris should be. This is still not clear to me. Best Regards
Well, maybe someone can convince me for stepping into the Losmandy train?... can anyone tell why I should spend a ridiculous amount of money ( here in Europe Losmandy is very expensive! ) for lets say a G11GT ( round about 6k Euros ) when I get for nearly the same amount for example an IOPTRON CEM120 EC2 ? Is the G11 really so much more accurate - I guess no , does it have buildin encoders on both axes - definitely a no , has it internally cabling including cable management - also a big no. Has it a comparable carrying capacity - also no! So, sorry to say: now atm I am definitely NOT CONVICED to buy one, but now its your turn....
You should buy the ioptron since your mind is made up. I have a GM811 and I'm thrilled with it. If any new advances in the mounts are made Scott will do them so I can add them to my mount if it's something I want. With Ioptron you would have to buy a new mount if you wanted that upgrade.
Well, it's a year later.......so, you should've discovered the SDE problem in that mount you considered.............and the encoder problem(s). If not, you didn't do your research!
Thank you Alex for spending some time on n-star alignment for pointing vs polar alignment for tracking. This was something that took me a while to figure out when I was getting started and was a real ah-hah moment. A real key concept for beginners!
The documentation on the Gemini software website is quite specific about how many stars and where they are located is used by the pointing model.
The pointing model also should correct for polar misalignment when tracking. They also have a polar alignment correction routine in the Gemini system. For example flexure of the RA counterweight is with the 5th star. added to the model. In any case, once the model knows the polar error it can correct with dec movement to compensate for polar error.
Cold start - No pointing model retained, no location data retained.
Warm start - pointing model and location is retained but RA/DEC position is unknown - assumes you are starting in CWD position.
Warm Restart - all model and location and data is retained and RA/DEC position is also known (after a Park).
Regarding manually moving telescope. - If you have extra encoders installed you can move the telescope and Gemini will track where the telescope is pointed. Otherwise, if you want to manually move the telescope you should put tracking in 'closed loop mode' and it will track whatever object that you point the scope at. You can easily get the scope resynced with the model by doing a warm start and a 1 star align or even just point at a known object and syncronize. The model doesn't get messed up.
CJ, excellent presentation. I own a G11 and I learned some new things today through your presentation. Well done.
This review is very informative, detailed. I'm thinking Losmandy in the future, and this has helped me. I must say, though that some of the add-ons are ridiculously expensive. $100 for 3 glow in the dark tripod feet? I got a roll of luminous tape, and appliance pads for about $18.
"Quick Start" - This selection will take you to menu's to select your "Mount Type", Enter your "Location", then "Time, Time Zone and Date" Then you will go to the "Main Screen" This also does a "Cold Start".
"Cold Start" - A cold start wipes out all stored modeling. You need to have your mount positioned at want is called CWD. This is with the counter weights down, and the Declination pointed towards Polaris in the Northern Hemisphere, and the South Celestial Pole in the Southern Hemisphere. The processor in the Gemini-2 uses this approximant position to start it's calculations from. It expects you to do an alignment, or synchronize on a bright star. When you align or synchronize on the bright start, then the processor refines the known position in the sky and also repositions the limits correctly. It also updates the All modeling calculations will start from this point in space.
"Warm Start" - This is basically the same as a cold start, but does not wipe out any models built. It also remembers all your setting. You still must start with the mount pointed to CWD position as in a cold start. If you have models built, but have moved your Right Ascension axis or Declination axis, but not the location of the mount itself, then you can use this startup mode. Warm Start uses the CWD position as an approximant starting position, but expects you to do either an alignment, or synchronize on a bright star. When you align or synchronize on the bright start, then the processors re-centers the model, and positions the limits correctly.
"Warm Restart" - This mode also remembers your modeling and all setting. You can only use this mode if, and only if you have not moved both the Right Ascension axis or Declination axis and also have not moved the mount in position. All calculations will start from this point.
I realize I am quite off topic but do anybody know a good website to watch newly released movies online ?
@Clay Jesiah try flixzone. Just search on google for it :)
William Finn when putting the declination in CWD ( counter weight down) position I find it easier to put a level under my losmandy d style mounting bar rather than on the side of the declination like Scott shows in his video. Hard to get a level in the proper position on a round surface. I have a gm811g . The G11 I understand has a bubble level on the declination to make it easier. If you look at the tripod leg and try guessing at CWD then you will have alignment issues. My mounting plate sticks out of saddle a few inches so it's easy to put a level on the bottom side of that.
Hi Alex. I still have a question on the polar alignment, since this is needed for accurate tracking during imaging. Lets say you do a 4 or 5 star alignment and the mount "calculates" that your polar alignment is off. What happens next? Do you need to manually move the latitude and azimuth knobs to correct the polar alignment manually? (those controls are mechanical right? So the software can't move the RA axis). Or do you mean that you don't need to do anything and the software can figure out how to move the mount to track correctly based on the previous calculation of where Polaris should be. This is still not clear to me. Best Regards
Polar alignment is your datum.if your datum is off, everything will be off.
Well, maybe someone can convince me for stepping into the Losmandy train?... can anyone tell why I should spend a ridiculous amount of money ( here in Europe Losmandy is very expensive! ) for lets say a G11GT ( round about 6k Euros ) when I get for nearly the same amount for example an IOPTRON CEM120 EC2 ?
Is the G11 really so much more accurate - I guess no , does it have buildin encoders on both axes - definitely a no , has it internally cabling including cable management - also a big no. Has it a comparable carrying capacity - also no!
So, sorry to say: now atm I am definitely NOT CONVICED to buy one, but now its your turn....
You should buy the ioptron since your mind is made up. I have a GM811 and I'm thrilled with it. If any new advances in the mounts are made Scott will do them so I can add them to my mount if it's something I want. With Ioptron you would have to buy a new mount if you wanted that upgrade.
Try a half hour shot with an Ioptron.
What tripod mount comes with the ioptron? Oh... It doesn't? Well how much does that cost?
Well, it's a year later.......so, you should've discovered the SDE problem in that mount you considered.............and the encoder problem(s). If not, you didn't do your research!