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New mount guiding calibration

 

I received a new G11G about 3 weeks ago. ?I¡¯ve only had a few clear nights since receiving it so I haven¡¯t done any guide calibration yet, I¡¯ve just used it as it came and it¡¯s done pretty good stock. ?Tonight I have a clear night shaping up and want to go ahead and do the calibration and baseline. ?I intend on using the method Brian V has posted several times, but I have a problem. ?I can¡¯t see the intersection of the meridian and celestial equator. ?So, I was wondering if I could be off of that a bit and still get an acceptable baseline and calibration? ?I have several ¡®windows¡¯ of sky I can use that are in that direction but not where it should be. ?Those closest window I have is about 45min past the meridian at about +5 dec. ?the closest window I have before the meridian is about an hour and a half before the meridian at zero dec. ?I can get right on the meridian if I go +20 dec. Are any of these acceptable or should I just continue using it stock until I can get my rig into a clear view of where I should be?
 

Hi Bill

That should be fine - i would try to get close to DEC 0 as long as you aren't low in the sky

the recommendation is generally two parts:

1. aiming close to that intersection is where star movement is the greatest, so you will get more accurate calibrations, If you are in that area, you should be fine

2. it also avoids areas of calibration that often cause issues: calibration close to the horizon?or calibrating near the poles






On Wed, Jul 21, 2021 at 2:53 PM Bill Grogan <bgrogan267@...> wrote:
I received a new G11G about 3 weeks ago.? I¡¯ve only had a few clear nights since receiving it so I haven¡¯t done any guide calibration yet, I¡¯ve just used it as it came and it¡¯s done pretty good stock.? Tonight I have a clear night shaping up and want to go ahead and do the calibration and baseline.? I intend on using the method Brian V has posted several times, but I have a problem.? I can¡¯t see the intersection of the meridian and celestial equator.? So, I was wondering if I could be off of that a bit and still get an acceptable baseline and calibration?? I have several ¡®windows¡¯ of sky I can use that are in that direction but not where it should be.? Those closest window I have is about 45min past the meridian at about +5 dec. ?the closest window I have before the meridian is about an hour and a half before the meridian at zero dec.? I can get right on the meridian if I go +20 dec. Are any of these acceptable or should I just continue using it stock until I can get my rig into a clear view of where I should be?



--
Brian?



Brian Valente
portfolio

 

Hi Bill,

I'd get as close as I can to that intersection point.? The question is ...where is it best?

If you think about possible errors in polar alignment effects: when you are on the meridian, only errors in AZ affect the star tracking.? That's why you only adjust AZ in a drift alignment procedure when you are on the meridian.? So that suggests you should stay close to the Meridian line, and just be (as you said about 20 deg) off in DEC off the equator.?

Anyways...some thoughts for you ...

Michael



On Wed, Jul 21, 2021, 2:53 PM Bill Grogan <bgrogan267@...> wrote:
I received a new G11G about 3 weeks ago.? I¡¯ve only had a few clear nights since receiving it so I haven¡¯t done any guide calibration yet, I¡¯ve just used it as it came and it¡¯s done pretty good stock.? Tonight I have a clear night shaping up and want to go ahead and do the calibration and baseline.? I intend on using the method Brian V has posted several times, but I have a problem.? I can¡¯t see the intersection of the meridian and celestial equator.? So, I was wondering if I could be off of that a bit and still get an acceptable baseline and calibration?? I have several ¡®windows¡¯ of sky I can use that are in that direction but not where it should be.? Those closest window I have is about 45min past the meridian at about +5 dec. ?the closest window I have before the meridian is about an hour and a half before the meridian at zero dec.? I can get right on the meridian if I go +20 dec. Are any of these acceptable or should I just continue using it stock until I can get my rig into a clear view of where I should be?

 

So my first try at calibrating didn't go so well, but it wasn't a mount issue.? I couldn't for the life of me get a good focus with the guide setup that was good enough for guide assistant to be happy.? It's my own fault.? I'm using a WO 50mm guide scope with the Rotolock.? I took the rotolock off and tried to get the camera hard attached with the correct spacers for back focus, while trying to error on the side of leaving a little room on the focus mechanism (dew shield) to fine tune.? I errored in the wrong direction and couldn't get to focus.? It doesn't get? dark enough here to use the equipment until about 10:15 this time of year and I have a real job so I called it quits and went to bed rather than try to play with the adapters on the camera/scope.

I did get an unexpected bonus yesterday.? ?The neighbors had their monster 100' oak tree removed that blocks my southern view.? I can now see the correct part of the sky from my patio.? I like trees, but I'm glad that one is gone!?

I was thinking about purchasing PEMPro.? Is it worth it just to go ahead and buy it and be done with it or do some of the other tools do just as well when I get to that stage of the setup?? $150 seems a bit steep but I've already dropped the money on the G11, plus about $600 in the addons so what's another 150 I guess.
 

Hi Bill,

The WO 50mm is what I used for awhile before I moved to a larger guide scope. I had to insert one 1.25" eyepiece extension to gain proper backfocus. Even with the threads full out there was not enough distance. Plus if you are too far unthreaded, you may start to jiggle and create flexure between guide scope and main scope.?

PEMPro is worth it in my opinion since you can do tracking analysis and upload a PEC correction curve right to the Gemini unit. With a good curve in place your guiding software should not have to work as hard and should be more accurate. PEMPro also uses your main imaging camera for more detailed star tracking than with your guide scope. You have a 60 day trial period, so really you can do the proper analysis and curve upload without have to buy immediately. Then you can try guiding with and without PEC turned on to see if it makes a difference in total error.?

Regards,

John

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