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Equipment Discussions >> Mounts

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Raginar
Postmaster
*****

Reged: 10/19/10

Loc: Rapid CIty, SD
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5790622 - 04/10/13 04:06 PM

Travis,

What he's trying to tell you is that it is very difficult for very experienced people to do what you're asking. Your mount doesn't have the mechanical fortitude to perform in a manner you think it can. If it did, why would most of us APers spend several thousand dollars on our MI250s, G11s, and AP mounts?

The real problem is your mount is overloaded. I had trouble with my AT8IN on my CGEM. I imagine you will run into similar issues with your CG5.

I know, it sucks. You could try hypertuning, but you're shining a *BLEEP*. A *BLEEP* that works with light weights (which your AT8IN isn't) and widefield refractors. But a *BLEEP* nonetheless.

Good luck!

Chris


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: What method do you Polar Align with? new [Re: Raginar]
      #5790666 - 04/10/13 04:30 PM

Quote:

Why would most of us APers spend several thousand dollars on our MI250s, G11s, and AP mounts?





That is a great question. So what did make you choose one of those mounts over a less expensive model? Was it because someone told you it couldn't be done with anything less or because you tried other mounts and no matter what you did they wouldn't meet your expectations.

Sure we would all love to have those mounts that you listed. However, some of us simply do not have the means to purchase them. Instead we make compromises and purchase lesser mounts and then spend extra effort on optimizing them to get the results we are after.

In the end we both are happy with our equipment. What gets me is when people say "It can't be done" and what they really mean is that "It is really hard to do".


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Footbag
Postmaster
*****

Reged: 04/13/09

Loc: Scranton, PA
Re: What method do you Polar Align with? new [Re: mpgxsvcd]
      #5790745 - 04/10/13 05:10 PM

Quote:


However, I would like to be able to accurately track from 1-3 minutes without guiding. I have found that I can achieve that with the Polar Finder Scope and I thought I would share that with anyone else who would like to do the same.




If you are happy with your results, then nobody can tell you otherwise. I suspect that as you improve, you will look back at the images you took and not be as impressed as you were previously. This hobby is a moving target. As you improve your images, you realize there are other aspects to improve.

I switched to the Mach 1 because my last mount couldn't do what I wanted. Track 30m guided for narrowband @ 2032FL. At that point, I knew my equipment very well. It wasn't somebody telling me it couldn't be done, it was me trying it over and over. The new mount makes it easy.

As far as the "it cannot be done". In this hobby, one can do anything. That's not to say everyone would be happy with their results. Keep in mind, most imagers throw away their images that show drift, but not all.


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psu_13
sage


Reged: 05/30/10

Re: What method do you Polar Align with? new [Re: Footbag]
      #5791146 - 04/10/13 07:51 PM

Here is my experience with mounts.

I started out trying to use a Mallincam on my 8SE alt/az mount. Here is maybe a 20-30 second frame from that

http://www.flickr.com/photos/79904144@N00/5738121295/in/set-72157629128096583

Notice how the stars are already trailing.

Here is a shot I look later on after I moved the telescope (an 8inch SCT) to a CG5

http://www.flickr.com/photos/79904144@N00/5793350900/in/set-72157629128096583/

This is at around a minute. I found that with the scope at F5 (1000mm focal length) I could get 60 to 90 seconds out of the CG-5 without a lot of jumpiness. I always used the all-star polar align scheme.

As a comparison here is a shot at 300mm focal length (a refractor) at almost 2min

http://www.flickr.com/photos/79904144@N00/6788830992/

After using the CG-5 for a while I decided that I was serious enough about taking pictures and had the money to get a "serious' mount. More on what I think "serious" means later. But I bought a Mach-1. Here is a stack of 2min exposures with the Mach-1 at 1200mm focal length:

http://www.flickr.com/photos/79904144@N00/6835654848/

They register well enough that stacking worked. And there is less trailing than in the short focal length shot above. This is why people buy expensive mounts. They are mechanically more accurate, smoother, and more reliable than the cheaper stuff. This is not to say that you can't make the cheaper stuff work, of course you can. It is just to say that the expensive stuff does have value and it makes everything easier.

I'll also say that even having spent thousands of dollars on the Mach-1, I never managed to do better than about 3min unguided without the stars trailing too much. Here is such a frame, also at 1200mm

http://www.flickr.com/photos/79904144@N00/7213284504/in/set-72157629550839360/

There is enough jitter in even the best gear train to require that you do some kind of guiding or other computer-enhanced tracking (modeling, encoders, whatever). For the Mach-1 I have used the same meridian flip based scheme at Peter from Reno, and more recently PEMPro. My experience with the mount pretty much matches his.

Later on I finally decided I had to investigate guiding, so I bought an SBIG camera with a guider in it. Here's 4 minutes guided without even thinking too hard. Note how everything is rock solid:

http://www.flickr.com/photos/79904144@N00/7828074704/in/set-72157631169684214/

I sympathize with the desire to keep things simple, but we are talking about holding a camera and telescope exactly in sync with the earth's rotation for hundreds of seconds. You can't buy that with just polar alignment and a relatively cheap mount IMHO.

My longer thoughts about mounts:

http://atelescopeinthecity.blogspot.com/2011/05/mount.html

and the Mach-1

http://atelescopeinthecity.blogspot.com/2012/03/value-for-money.html

Oh, and, FWIW, the control box of the Mach-1 does not move, so you can hook wires up to it without worrying about it.

Cheers and good luck


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jsines
sage
*****

Reged: 09/06/11

Loc: Berkley. Michigan
Re: What method do you Polar Align with? new [Re: Dwight J]
      #5792210 - 04/11/13 11:58 AM

Quote:

Hi Travis: try using your camera to assist you in getting a better polar alignment once you have used your polar scope. It is a modified drift alignment which is best explained by this link: http://www.observatory.digital-sf.com/Polar_Alignment_CCDv1-1.pdf
A camera such as yours is just as capable to do this method.





Question on this method - I've been trying it for a few weeks with good results, but I'm not sure I'm doing it right. Should I polar align, then find a star, then turn on sidereal tracking, then image and move the scope east/west at the lowest speed? Or, should I keep sidereal tracking off?

I'm doing it with tracking on right now, and I'm getting spot-on solid lines every time the first time, with up to 2 minute exposures. I'm wondering if I'm doing something wrong, or if I'm doing something right. :P


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psu_13
sage


Reged: 05/30/10

Re: What method do you Polar Align with? [Re: jsines]
      #5792418 - 04/11/13 01:48 PM

Since you are moving the mount by hand it doesn't really matter if it's tracking or not. The sidereal tracking only tracks in RA anyway, and you are using the scheme to look for drift in DEC.

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