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Old 08-05-2008, 07:34 PM
Ian Robinson
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When is autoguiding overkill ?

Autoguiding is definitely beneficial for prime focus long exposures , and for probably for most long exposures with telephotos longer than 150mm if you plan on blowing up the images significantly.


Just wondering what others think EFFECTIVE region for autoguiding is in the fov vs t(Exposure) plane. Assuming you have good polar alignment , accurate tracking perhaps including PEC.


Anyone have thoughts on this (based on experience in their digital astrophotography) ?
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  #2  
Old 09-05-2008, 10:56 AM
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bojan
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Well, if all that above is true, you do not need autoguiding :-)
Really, it depends on how good is all that you mentioned.
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Old 09-05-2008, 11:28 AM
gbeal
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Even with a wide field camera lens shot, I ALWAYS auto-guide, why not?
Maybe for a 60 second shot, with the likes of a 17-40 zoom, then maybe not, but again, it is all set up, why not guide.
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Old 09-05-2008, 12:11 PM
Zuts
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Quote:
Originally Posted by Ian Robinson View Post
Autoguiding is definitely beneficial for prime focus long exposures , and for probably for most long exposures with telephotos longer than 150mm if you plan on blowing up the images significantly.


Just wondering what others think EFFECTIVE region for autoguiding is in the fov vs t(Exposure) plane. Assuming you have good polar alignment , accurate tracking perhaps including PEC.


Anyone have thoughts on this (based on experience in their digital astrophotography) ?

The answer is quite simple, if you dont get nice round stars then you need to autoguide. Most people would autoguide I think.

Paul
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Old 09-05-2008, 12:28 PM
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dugnsuz (Doug)
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Up to 60 sec shots with short FL lenses perhaps not. But, like Gary said "Why Not?"
Your 40D will be most likely connected to a Laptop running the EOS Utility which controls camera and exposure setup anyway - so utilize PHD or whatever your choice of guiding software is too.
Belt and braces!!!!
I'm trying to push way past the safe guiding area of my mount on every exposure, so for me, autoguiding is permanently on.
Couldn't imagine life without it - perhaps a bad thing...one more thing to go wrong!
Cheers
Doug
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Old 09-05-2008, 02:42 PM
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I often take photographs while I'm polar aligning. During that time there's 5 minute periods where the scope is just tracking with me not moving it (and no autoguider moving it), so I figure I may as well. They often turn out perfect.

I also often do wide field shots later on at night without autoguiding, again, no problem.

All of them using my 17-40mm lens, so somewhere in that range, not all wide open at 17.

Providing your polar alignment is vaguely OK, and RA tracking good, you shouldn't have much of a problem for exposures up to 5 mins I'd think.

I sometimes decide to do this because autoguiding is just too hard... I just put the camera on the back and take the shots. There's no doubt it's simpler. Sometimes the PC isn't behaving or the autoguiding isn't behaving too.

Roger.
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Old 09-05-2008, 05:28 PM
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Bassnut (Fred)
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Sheesh Ian, dont be a woose, always autoguide. Youll have to eventually, so get used to it now, set it up now so its a click away (may be but shoudnt be hard to set up, anyway get it right once and its there), or suffer eggy stars. Not worth not to.
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Old 09-05-2008, 06:19 PM
Ian Robinson
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Autoguiding if you have nice dark backyard (I don't cf the nutty neighbour) and can set up a permanent observing station and don't have to move a stack of gear about is OK.

Long exposures call for it.

But I need to cart my gear to another site to get a dark spot , I don't fancy carting my laptop all over the countryside and getting it wet (even if it would be sitting on the back deck of the trusty Pajero) unless I need to. This is in addition to the cameras , the telephotos lenses , and big bulky 10" newt and Atlux and tripod and maybe a camping chair and folding camp table and portable jumpstarter pack. It's like moving house each time I want to do some photography even now (with my older gear).

There will be times I will need to autoguide , and times it wont be necessary.

Last edited by Ian Robinson; 09-05-2008 at 08:00 PM.
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Old 09-05-2008, 07:20 PM
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rogerg (Roger)
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Ian,

I know exactly what you're saying and agree with simplicity.

If you have a mount that behaves reasonably well, and get it polar aligned, then you can make it simple for yourself and not autoguide.

What I used to do more than I do now, is setup (align, etc) then take shots without autoguiding (this was pre autoguiding), having illuminated crosshairs eyepiece in the telescope, check it every 5-10mins and make necessary corrections, otherwise leave it. It worked fine. occasional trailing perhaps.

But you do need to stick to relatively wide field stuff with that type of activity, say wider than 70mm. Although even that depends on your equipment.

Roger.
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Old 09-05-2008, 07:54 PM
Ian Robinson
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When I purchase my autoguider , I will use it , but only if I plan on doing long lens or prime focus photos , or track a comet say.

The Atlux has pretty good tracking precision with PEC on and when polar aligned properly.

I think it comes down to how much tracking error is acceptable taking into account focal length , the object (fuzzys are more forgiving) , and when I start using the DSLR , the pixcel size (keeping the tracking error within less than a pixcel).

When my Atlux arrives (it's ordered costing me 6682 AUD) , if it proves as good as I hear it is , I should be able get away without autoguiding most the time unless I do the imaging at prime focus (on the 10' f/4.66 newt) , I may even be able to get away without autoguiding with the 70-200mm f/2.8 telezoom (at 200mm) when that shows up with the 40D or with my older 200mm f/3.5 on the XD5 (35mm SLR).

I can see I have some theoretical numbers to crunch to come with my own WHEN TO AUTOGUIDE GUIDELINES CHART.
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