If you're doing longer focal length imaging, and want pinpoint stars, then, the answer is yes.
If you're shooting with a camera lens, then, you could probably get away without one, provided your polar alignment is good and your mount performs well. It's better just to have one. They're not that expensive (for about $200 you can get an ST80) and it will assist greatly.
I have to admit with the 12" meade, anything greater than say about 1min and everything goes up the duff.
Just like everything it depends on what you are looking for, some people just do fix ups or make something up bob the bodger style, others make sure everything is perfect.
Like octane said, if you want to get nice tight stars, then go with all you can get your hands on. and to boot, if you have a nice wide field scope you can swap it over and image with the guide scope, and guide with the main scope. its upto you mate
At prime focus with that GEM and OTA , necessary .... no escaping the need.
You might get away without a guidescope for widefield stuff with that GEM for shorter fl lenses (to 200mm say ??) .
The PE of that GEM is not so flash from what I have read, depends on the pixcel scale on the image , if it is less than your GEM's PE and guiding errors for a given lens your are fine ,. otherwize .... you must guide.
ie at prime focus , my 10" f4.66 has an image scale of 1.0 arcsec/pixcel for a chip with 5,6x5,6µm pixcels.
a 200mm lens has an image scale of 5.8 arcsec / pixcel , if the periodic error and drift is less than about 2x the calc pixcel resolution you wont need to guide.
Last edited by Ian Robinson; 30-12-2008 at 09:26 PM.
How much photography have you done, Ian, at prime focus or widefield?
Guiding is absolutely necessary for any decent astrophotography - whether it's widefield or longer FL. At shorter FL's your tracking or alignment errors aren't as noticeable but when you do long exposures it's essential.
You can certainly start without guiding but ultimately you'll need it if you want to take the best images your setup and skill will allow.
How much photography have you done, Ian, at prime focus or widefield?
Guiding is absolutely necessary for any decent astrophotography - whether it's widefield or longer FL. At shorter FL's your tracking or alignment errors aren't as noticeable but when you do long exposures it's essential.
You can certainly start without guiding but ultimately you'll need it if you want to take the best images your setup and skill will allow.
Read what I typed again ....
I have been doing astrophotography off and on since the early 1970s.
I've always guided , except where I was using wide angle lenses (50mm f1.2 or 35mm f2.8) or doing LONG exposures (I've manually guided for uninterrupted exposures up to 60 minutes on some occasions).
It is easy to calculate the equivalent pixcel scale for a 50mm lens = 24 arcsecs, you can double that as a tracking error before the stars get eggy, that's pretty forgiving.
Don't take my word for it , the maths are in the last link , do the calculations yourself , they are easy enough.
It comes down to how much of a perfectionist you are in your imaging and how much time , money and effort you are prepared to put into producing perfect images.
BTW a guidescope is not the best solution , if you've the money a self guiding camera is the bee's knees as already mentioned, the next best is to use an off axis guider (just too bad Lumicon's coma corrector lenses are no longer available as they work a charm with their 2" Newtonian Easyguider and other coma correctors (Paracorr and MFCC) will not readily adapt for use with this device - I own both a Lumicon Coma Corrector Lens and a 2" Newtonian Easyguider , so I don't need a guidescope for prime focus imaging).
There are other off axis guiders about , most of which require a fair bit of extra back focus.
I also hold to KISS as a good philosophy, especially for someone starting out, little point making it all seem all to complicated and hard. He may be perfectly happy with less than picture perfect images, at least in the beginning of his imaging career.
Last edited by Ian Robinson; 31-12-2008 at 01:57 AM.
Ian, do you have any examples of your work at all?
I did a search in the images area on this forum and found nothing.
I have never posted my images on any forum. Nor have done any imaging lately (since joining IIS) except of Comet McNaught (last year after a break from imaging and much observing - that comet was too nice an object and too bright to pass up the chance of imaging it , been many years since we had such a spectacular comet visible at our latitude.
Never really felt the desire to publish my images or to share them with anyone but my family , this simply is not what motivates me.
A long time ago - I used to share my images at meetings of the Astronomical Society of the Hunter many many many moons ago. I guess then I was looking for encouragement and compliments on my images. That doesn't interest me now.
My main aims in my imaging was nova hunting , comet seeking and other scientific reasons (variable stars etc) , not so much to produce pretty pictures. So most my negatives have never been printed - you can see more in the negative under magnification than you'll ever see in a positive image.
And I've only recently converted over from 35mm and medium format film photography to digital and not yet turned my new 40D on the sky. No rush there, the sky will always be there and I'll get around to it sooner or later again.
Last edited by Ian Robinson; 31-12-2008 at 02:44 AM.
Tell me about it. I've scanned 2 gig worth already and have 10 packs of 32 images left plus a pile of 110 film which doesn't fit in the scanner but can be scanned in a pinch if you fiddle with it. I've found my old negatives are failing and quite a few are stuffed completely, lost forever. I was lucky to grab them while I'm able too or they'd all be gone forever.
Benno, get a cheap 80mm Guidescope and get out there imaging. It will at least teach you heaps. Most "oldies" at astroimaging have been through the guidescope phase for the film days. I still use one frequently.
You will learn terms like "flexure" and "missalignment" and learn how to overcome them. All building towards better and better images.
When you have finished with the guidescope you can flog it off to somebody else just beginning.
Im no expert nor do i claim to be, but from my understanding a guide scope set up with a eq6 is not a complicated or hard thing to get the hang of. You line it up like a finder scope plug your camera in then to your pc for the guiding program, select a bright enough star then..?? your away.
Sure there is going to be better setups but for the beginner i belive this to be a easy option.
Well I have been up all night...and although a nice little guide scope sits where it should the auto guide wont work and the batteries in the illuminated reticle went flat so again last night everything was unguided tracking..... sometimes you get that.
But you can do stuff.... this happens to me a bit..but the mount gets real attention because it has to track without guiding it gets a lots of mechanical attention.
Anyways just see what you can get unguided...it will make you keen to get polar right and correct balance etc...but everyones comments about guiding is best and get a small scope is the final solution.
I think the longest run I got last night was 3 minutes thru 150 x 750 sn (reflector with corrector) but it was a great night I had to get something.
good luck
alex
cheers for all the advice and information that you guys have given, tonight looks like it might be a nice night, so i will go out and see what i can get, then go from there. once i get a bit more coin and more experience ill get me a nice little guide scope and autoguider and go from there.
again much appreciated
and learn how to overcome them. All building towards better and better images.
