mikee
professor emeritus
Reged: 01/10/05
Posts: 740
Loc: Maine
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Hi all -
I'm going to be trying my hand at auto guiding for the first time and am wondering which if either of the 2 scopes I currently have would be better for guiding (or neither if they aren't recommend).
My main scope is an SV90T. My guide scope options that I currently have are an SV66 f/6 or an Orion 70mm f/10 (Observer OTA). The Orion is a tiny bit lighter and my thought was f/10 would go deeper?? The SV66 optically and mechanically is a better scope but I'm not sure that makes so much difference in a guide scope.
I also need to figure out how to mount either one of those onto my SV90T. I'll probably call Vic to find out unless anyone has any tips.
Thanks!
Mike
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kcgolden
super member
Reged: 04/01/07
Posts: 181
Loc: Austin, TX
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What is your main camera and guiding camera?
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Kelsey
Eyegloo Observatory Homepage
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HendyPhoto
Sith Lord
Reged: 08/09/06
Posts: 1502
Loc: Bountiful, Utah
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Mike what mount are you using? WELCOME to the world of autoguiding!! If you dont have grey hair yet, plan on buying some "Just For Men"!! lol
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~jon
SparkCast
CGE1400XLT w/HyperStar
90FD 66SD C6-R SN-8
CPC1100XLT Hutech 20D
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Mallincam MCHP
SPC900NC
CG-5 GT
"Two things are infinite: the universe and human stupidity;
and I'm not sure about the universe." --Albert Einstein
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FoxK
Carpal Tunnel
Reged: 11/07/07
Posts: 2765
Loc: Cape Cod, MA
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As we speak....i'm guiding for +10 minutes on M109 with the 70mm AZ-A from walmart at $19...worth considering if your just looking for a guider
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Orion 80mm ED Apo Refractor
8" Classic Dob (used as Newtonian on CG5 mount)
Meade 70-AZ-A 70mm Guider using PHD
LS60TCaK/B600/C
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Philips SPC900NC(1/4"ccd)& Quickcam 9000(1/3"CMOS)
Imaging Source DMK 21AU04.AS
- click for cloud prediction for Plymouth, MA. area
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Patrick
Postmaster
Reged: 05/16/03
Posts: 8190
Loc: Franklin, Ohio
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Quote:
I currently have are an SV66 f/6 or an Orion 70mm f/10
I think I'd try out the SV66 first, mainly because it will be easier to find quide stars with the wider field of view in the 66. With today's autoguiders (what are you using?) and guiding software, using long focal lengths is not necessary.
Patrick
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Celestron CPC 1100 XLT
10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
The heavens declare the glory of God; the skies proclaim the work of his hands.
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groz
Pooh-Bah
Reged: 03/14/07
Posts: 1288
Loc: Duncan, BC
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You dont say what the camera is you are using on the guider, that'll make a big difference.
As far as figuring out what is appropriate in terms of how accurate it can guide with reference to the imager, that's trivial to figure out. Download ccd calc. Plug in the numbers for your imaging train, and make a note of the 'arc seconds per pixel' on that side. Now plug in the numbers (scope and camera etc) for the guiding train, note the 'arc seconds per pixel' on that side.
From there its basic arithmetic. If your guider is running at 10 as/p and your imager at 1 as/p, assuming the guide software reacts to 1/2 pixel of guide star movement, then that translates to 5 pixels on the imaging side. The other thing to consider, as you run the FL up on the guide side, the field of view goes down correspondingly, making it harder to get suitable stars into the FOV. What comprises a suitable star is wholly dependant on your guide camera. Mag 9+ is a walk in the park for something like a DSI, but it's a tuff nut to work with for a webcam.
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s58y
Postmaster
Reged: 12/12/04
Posts: 5629
Loc: Eastern NY
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I use the SV66 as a guidescope with the SV80S as an imaging scope. My (older) SV80S came with two mounting rings with threaded holes on the top and bottom flat serfaces. I attached a camera mounting bar from Really Right Stuff to the mounting holes in the top of the rings, and attached the SV80S mounting foot to the camera bar.
Does your SV90T come with two mounting rings, or the newer clamshell?
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
http://www.flickr.com/photos/s58y/
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mikee
professor emeritus
Reged: 01/10/05
Posts: 740
Loc: Maine
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Sorry everyone - I must have "untyped" the camera info.
Guide camera will be a Meade DSI Pro using PHD on my Macbook Pro.
My main camera will be a Canon 350D.
My mount is a Orion Sirius EQ-G.
I realize I'm pushing the mount a bit weight wise but I'm hoping I can get some decent shots out of it.
My SV90T has the clamshell deal so I think I'm probably going to need to get rings??
THanks again for all the info
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Patrick
Postmaster
Reged: 05/16/03
Posts: 8190
Loc: Franklin, Ohio
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Quote:
I realize I'm pushing the mount a bit weight wise but I'm hoping I can get some decent shots out of it.
I can't imagine how you would be pushing the mount weight wise with an SV90T and an SV66. As far as mounting the two, I think you should consider mounting them side by side rather the putting one on top of the other.
Patrick
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Celestron CPC 1100 XLT
10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
The heavens declare the glory of God; the skies proclaim the work of his hands.
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mikee
professor emeritus
Reged: 01/10/05
Posts: 740
Loc: Maine
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Thanks Patrick -
I haven't weighed my SV90T but it feels like it weighs a lot more then SV site claims of 9-10 pounds. Feels more like 15 to me. But maybe I'm a whimp 
I was looking at side by side but doesn't that cause balance problems because the center of gravity is off to the side?
Mike
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s58y
Postmaster
Reged: 12/12/04
Posts: 5629
Loc: Eastern NY
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Quote:
I was looking at side by side but doesn't that cause balance problems because the center of gravity is off to the side?
I used to shoot side-by-side when I used camera lenses for imaging and guiding on a G-11. You need a side-by-side (or dual) mounting plate, like the ones sold by Losmandy or RobinCasady. Unfortunately, these add more weight, and require an extra step when you balance the scopes on the mount before imaging. With the two SV scops I now use, I just mount one on top of the other, so there are balancing problems in one direction only.
As far as the SV clamshell goes, does it have threaded holes on the top? If so, perhaps you could attach the guidescope somehow. It's not clear if there'd be problems with flexure, though.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
http://www.flickr.com/photos/s58y/
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jrcrilly
Refractor wienie no more
Reged: 04/30/03
Posts: 25878
Loc: NE Ohio
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Quote:
I was looking at side by side but doesn't that cause balance problems because the center of gravity is off to the side?
Mike
If the center of gravity is off to one side then the system is indeed out of balance (that's what out of balance means) - but there's no reason to make it out of balance.
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John C
Urban Observatory
A&M/Astreya 76mm F/6 APO
Meade 80mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Meade 152ED, 178ED F/9 "APO"
Meade 12" SCT
Teeter 20" F/3.8 truss Newt w/ServoCat
NJP, LXD700, CGE, GPDX/SS2KPC
ST-10XME, DSI Pro
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mikee
professor emeritus
Reged: 01/10/05
Posts: 740
Loc: Maine
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Quote:
As far as the SV clamshell goes, does it have threaded holes on the top? If so, perhaps you could attach the guidescope somehow. It's not clear if there'd be problems with flexure, though.
Yeah I was concerned about flexure too but I'm not sure how you tell if you have a flexure problem? Is it obvious in the photos that you take or does it masquerade as some other AP issue.
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s58y
Postmaster
Reged: 12/12/04
Posts: 5629
Loc: Eastern NY
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Quote:
Yeah I was concerned about flexure too but I'm not sure how you tell if you have a flexure problem? Is it obvious in the photos that you take or does it masquerade as some other AP issue.
One way to tell is to look carefully at your images. If the stars are small and round, then you have no flexure problems. If they're egg shaped (or worse), you might be dealing with flexure, or something else.
Since you already have the clamshell, you might as well start out by using it. If you have problems, then consider getting the dual rings and a more rigid guidescope attachment, to eliminate any reasonable possibility of flexure. Normally, at these focal lengths, flexure shouldn't be too hard to eliminate.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
http://www.flickr.com/photos/s58y/
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mikee
professor emeritus
Reged: 01/10/05
Posts: 740
Loc: Maine
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Thanks s58y. I'll give it a shot.
Mike
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