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Gemini 2: Polar alignment

Rahul
 
Edited

I have a G11G and G2 GoTo. I have never fussed about getting perfect polar alignment as till now it was all about visual observing. However decided to try imaging for a change.
So far what I have been doing:
1) Polar align mount using polar scope.
2) Cold start every time as I don't have a permanent setup. However lately what I have started to do is plunk down the tripod at same spot so maybe I could do away with cold start & rely on warm start instead.
3) Park mount in CWD position.
4) Then align using 1 or two bright stars. This usually gets me close the star though never centered in eye piece (wide field) which for me was OK for visual observing.

I do this from my backyard & like any other suburban location don't have unhindered views of sky in any direction.

For imaging I still plan on doing above steps however wondering what else do I need to do to get #3 right every time so that star(s) is centered in eye piece ?
 

Rahul,

If you are shooting with a wide field scope (80mm f/6 refractor, or f/4 reflector maybe) your polar scope with? alignment and autoguiding might be ok. Certainly to start getting experience it's ok.? A long FL scope will require very good polar alignment by drift usually.

But to get the best image sharpness, you'd be better off doing a "drift" alignment.? You can read about that elsewhere.? The same free PHD2 program used for autoguiding has a nice drift alignment tool.? Try that method and you will get to perfect polar alignment for imaging.

Just take it a bit at a time.? ?There are many facets to master in deep sky long exposure imaging.? Each skill must be mastered.??

Michael

On Wed, Feb 24, 2021, 3:50 PM Rahul <trwway@...> wrote:

[Edited Message Follows]

I have a G11G and G2 GoTo. I have never fussed about getting perfect polar alignment as till now it was all about visual observing. However decided to try imaging for a change.
So far what I have been doing:
1) Polar align mount using polar scope.
2) Cold start every time as I don't have a permanent setup. However lately what I have started to do is plunk down the tripod at same spot so maybe I could do away with cold start & rely on warm start instead.
3) Park mount in CWD position.
4) Then align using 1 or two bright stars. This usually gets me close the star though never centered in eye piece (wide field) which for me was OK for visual observing.

I do this from my backyard & like any other suburban location don't have unhindered views of sky in any direction.

For imaging I still plan on doing above steps however wondering what else do I need to do to get #3 right every time so that star(s) is centered in eye piece ?

Rahul
 

Thank you Michael.

For a moment, if I take imaging out of the equation.? I don't understand even after polar aligning the mount , mount in CWD postion why two star alignment won't work 100%? I want to fix this first before I jump to other tools/methods and imaging.

One thing I noticed tonight is that even when I query GPS hand controller was showing time 1 hour ahead of actual time. I was under the impression G2 using GPS figures out the local time as well. Do I need to set time manually?
 

Rahul,

The difficulty I find is with "daylight savings time" and the 1 hour uncertainty it creates.? It is far preferred to set the UTC time, and then your longitude and latitude work properly.??

On the Gemini-1 you set the UTC time directly.? The special entry code format is given below.

But in the Gemini-2 you enter local time, with your hour offset to UTC.? I can see how this could be a cause of trouble.? There is an easy solution.? A nice member of our group explained recently that on the Gemini-2, you enter the UTC time this way:
Set the Time Offset hour = 0.??
Enter the UTC time as the "local" time.

Your 1 hour error ought to be fixed by entering only the UTC time.?
Try it and?let us know if that?works.

Best,
Michael

------

Gemini1 time and date UTC format, from the Gemini1 manual.?

UTC Date/Time
The "UTC Date/Time" menu item is where you set Gemini's real time clock (RTC).
Upon executing "UTC Date/Time" the UTC date and time display freezes but the RTC continues to keep time.
The display of date and time from left to right reads as follows:?

"yymm.dd hh:mm:ss"
(yy = year, mm = month, dd = day, hh = hour, mm = minutes, ss = seconds).

So would be for 2021, Feb 23, at 06:15:25 am you'd enter. You take the 21 is the last 2 digits from 2021, the 02 is February, ...:

2002.06 06:15:25

For time after noon like 14:00 = 2pm enter like
2002.06 14:15:25

Link here works:
Click here to get the UTC data/time in?Gemini style.

Or full link:







On Wed, Feb 24, 2021, 10:54 PM Rahul <trwway@...> wrote:
Thank you Michael.

For a moment, if I take imaging out of the equation.? I don't understand even after polar aligning the mount , mount in CWD postion why two star alignment won't work 100%? I want to fix this first before I jump to other tools/methods and imaging.

One thing I noticed tonight is that even when I query GPS hand controller was showing time 1 hour ahead of actual time. I was under the impression G2 using GPS figures out the local time as well. Do I need to set time manually?

 

Hi Rahul

>>> I was under the impression G2 using GPS figures out the local time as well. Do I need to set time manually?

it does, but it does not determine?timezone. you need to set that manually


Brian

On Wed, Feb 24, 2021 at 10:54 PM Rahul <trwway@...> wrote:
Thank you Michael.

For a moment, if I take imaging out of the equation.? I don't understand even after polar aligning the mount , mount in CWD postion why two star alignment won't work 100%? I want to fix this first before I jump to other tools/methods and imaging.

One thing I noticed tonight is that even when I query GPS hand controller was showing time 1 hour ahead of actual time. I was under the impression G2 using GPS figures out the local time as well. Do I need to set time manually?



--
Brian?



Brian Valente
portfolio

Rahul
 

Thank you Brian , Michael.

I am going to re-watch Gemini-2 videos for now. Will post back here if I can't get accurate PA.
 

¿ªÔÆÌåÓý

For a moment, if I take imaging out of the equation.? I don't understand even after polar aligning the mount , mount in CWD postion why two star alignment won't work 100%? I want to fix this first before I jump to other tools/methods and imaging.

***

I found a way ¨C that works for me ¨C to brute force my way into making this work. For me this was mandatory so I would be able to slew to a planet in daylight.. for me, the scope is in the front yard.. Semi Permanent.. If you set up / tear down nightly, you would need to mark the position of the tripod legs so they could be put back exactly ¨C within the tolerance of your eyepiece / camera FOV.. No idea how well that would work, but it certainly should work if you use a widefield eyepiece..

?

Setup.. Polar Align.. Park @ CWD power off.. Verify CWD with the torpedo level method.. Assuming it is your first time, where you would do a cold start / you have no model, start as you wish.. Goto your first Target.. Center it with the Hand Controller and a high power eyepiece or a small region of interest with a camera ¨C whatever you can do for some exactness.. Menu / Align /SYNCH.. Park @ CWD and power off.. Reset CWD with torpedo level..

?

Power on and do a WARM RESTART.. Goto your first target and it will be close to centered.. You can then continue on with building a model or what have you.. Always park at CWD.. Always verify CWD with a level.. And Always do a ¡°WARM RESTART¡±.. Any other start mode ¨C FOR ME ¨C will have the initial target ¡°off¡± just like it was ¡°off¡± before so you end up redoing the above every time..

?

Works for me.. Might work for you..

?

Derek
Sonny Edmonds
 

Hi Rahul!
OK, everybody has slightly different methods, And why not, we all have slightly different equipment. ;^)
Here's mine, not to confuse, but to give you another idea that may work easily for you.

I started using Sharpcap at Brian's recommendation. At first I had difficulty because I didn't understand the relationship of my Camera to Sharpcap. It is not Plug and Play.
It's more like fiddle, fiddle, fiddle, and come back another day. Fiddle, fiddle, Fiddle, come back another day.
But finally, with a 4 second exposure, after checking my focus beforehand, I began to get results like most folks get right out of the gate.
And because Sharpcap gives me the option of carefully adjusting and trying to get 00-00-00 to 0x adjustment, I like to take my time and see what I can do.
The atmosphere often messes with that and the figures can bounce a bit. But the more I did it, and the more I got use to doing it repeatedly the same way, the better my results got. 8^))).

Then I got into a discussion with a young guy here, and he brought up using the guide scope and camera to do my PA. So he convinced me to at least to try it.
I have a HD guide camera, ASI290 MM mini, so I gave it a try and it worked great. So I've been using my Guide Scope and Camera for a couple of weeks or so.
I don't have any of the difficulties I had using my Atik Infinity Main Imaging Camera. And it is easier to bring it into great adjustment. My best so far was 00.00.00 X 00.00.02. I considered that fenominmoninal for me.

OK, once Polar Alignment is good, and I consider anything single digit as great, I shut down Sharpcap.
Then I turn on my GM811GHD, open Gemini II and connect, and my Camera, PHD2, my focuser, and Stellarium.
Using my Main Telescope Camera as my Aligning view, and my Guide camera as my finder view, I use the Gemini II hand control to do a mount alignment.
Were I differ from most, is I do a lot of alignment stars in the Western and Eastern skies. What is "a lot"? 10-12 and even 15 just to fool with it.
Rene, who wrote the program suggests 10 stars. I was doing many before Rene` mentioned a number. So his recommendation solidified my "overachiever" method.
(With my old mount I could only do 2+4 star alignments. But I always wanted more to "fine tune" the alignment. Now... I can do as many stars as I feel like doing.)
It appeals to my sense of giving the Gemini II as many reference points as I can.

OK, so there is my methods of PA, and of Modeling (alignment).
Now then, I have to bring in my mount when I'm done with it, which means I have to set up every night as well.
But I convinced her I could leave the tripod set up, aligned on Polaris, and assemble my Mount and Telescope on the preset tripod. That really helps to speed up the PA and Model building afterwards.
But I always do a Polar Alignment first. Then build a model from a cold start, because I'm always disturbing the mount by dismantling and carrying it in and out.

I did try a warm start once, and it fooled me into thinking I was going to get away with it.
But I wound up going back and doing it the right way. In my opinion, warm starts are for guys with piers in observatories that can park and nothing moves until they come back another night.

Anyway, good luck and keep working with it. And don't expect a two star alignment to be great for imaging. It's good for visual, but not fine enough for imaging.
Have fun!

--
SonnyE


(I suggest viewed in full screen)

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