Mount accuracy

[psbenoit2007 (Paul)]

Hello all,
I want to get myself into astrophotography. Before spending a fortune on equipment, I want to confirm this new hobby using my existing photo equipment (my longest lens is 600 4, which I can push to 1200mm) and am planning to buy a second hand Canon 60d I could have modified to let the H alpha through.
Now comes the question of the mount. Provided the fairly short focal lengths I am planning on using (for now), I was wondering about the type of mount I should consider acquiring for clean pinpoint stars on up to 15min PEC corrected and-or guided mount shot exposures. I can see a group of mounts (EQ6, CGEM DX, iEQ45, G11, Vixen SXD) in the 1500-2500$ price range that I would be happy to invest in if they are providing good enough tracking accuracy. Now should I consider going one step up and look at more accurate models such as an EQ8, AP Mac1GTO, 10Micron 1000HGS, Bisque Paramount MX, ASA DMM60 or the like, but then we are really not talking about the same budget.
Advise from forum experts much appreciated. Thank you. Paul.

[Hans Tucker (Hans)]

Since you are starting out in astrophotography I would suggest you limit your choice to the budget mounts (EQ6, CGEM DX, iEQ45, G11, Vixen SXD) which are more than capable of delivering a stable platform with good tracking. If you find that astrophotography is for you and you upgrade to a scope you could move up to the larger more expensive mounts Paramount MX/ME, AP1100/1600, Takahashi EM400/500. The setting up of the mount is the critical element for good results in astrophotography e.g. balancing, polar alignment etc. Many IIS members can give you tips in this area or look over the Projects & Articles section of IIS.

[alistairsam]

I think the G11 has a very low PE and you can upgrade the worms for better accuracy. they're usually below 10arcsecs.
EQ6 has a higher PE but at that short focal length, it shouldn't matter.
Ideal if you can add autoguiding. that will save a lot of hassle and a lot of us use the EQ6 with OAG's and guidescopes and get long exposures at FL's of over 1M.
an ideal setup would be a short focal length 70 or 80mm APO, with an OAG on a G11 or EQ6. I'm not familiar with the other mounts.
have a look at this image taken with a Tak-FS60 from a light polluted site.
http://www.pbase.com/djrlx90/image/152648635/original
That's got 12x60min subs on a G11 with a lodestar guide cam, SX OAG and the Ovision G11 worms.

But with all of this, the most important is good polar alignment. that will allow you to go unguided.
There is a yahoo group dedicated for people taking upto 60min unguided subs with pinpoint stars.

Cheers
Alistair

[Allan]

I can't believe you can get an image of M31 like that with a 60mm scope!

[alistairsam]

Originally Posted by Allan

I can't believe you can get an image of M31 like that with a 60mm scope!

yep, its very impressive, but it was taken with an SX Trius H694 which is a very sensitive camera with a high QE. Other bit is that its got over 12 hours of data.

moreover, his processing speaks for itself cause a 1 hour sub from a light polluted site would normally look washed out with light pollution.
it can be removed effectively in ST and PI but is not trivial.
doesn't look like an LP filter was used for luminance but regardless, that's quite an image.

Cheers
Alistair

[Poita (Peter)]

The G11 is only worthwhile if you fit a worm like the Ovision or the newer worm that gets rid of the 76s problem with the G11.
The EQ6 is okay with a decent autoguider or short focal lengths.

For serious work down the track, the Mach1 is hard to beat if you can get it for a good price, and you can resell it for pretty much what you buy it for if you end up not enjoying astrophotography. If money wasn't a problem I'd start with a Mach1 out of that list, and you are unlikely to ever outgrow it. It is a better investment in the long run if you can afford it. If money is tight, get a 'proven' 2nd hand EQ6 or HEQ5Pro and an autoguider.

Your existing lenses will probably have a very small aperture, you may be better off getting an ED80 scope, you can get a decent one 2nd hand for about $400 or less.

[Jon (Jonathan)]

Rolf Olsen (SkyViking on IIS) uses a G11 for his extraordinary astroimaging. See http://www.rolfolsenastrophotography.com. I ink the newer worms now come standard on a new mount and the 76s error is a thing of the past.

I'm certainly getting round stars with longer subs. There's a lot wrong with the attached image, but I think the mount is the least of them - this was 8 minute subs at 1600mm focal length.

[Logieberra (Logan)]

Great advice. A Mach1 would be a wise investment, assuming that you stick with the hobby and if the passion is still there in years to come. If not, they sell used in a flash.

Originally Posted by Poita

The G11 is only worthwhile if you fit a worm like the Ovision or the newer worm that gets rid of the 76s problem with the G11.
The EQ6 is okay with a decent autoguider or short focal lengths.

For serious work down the track, the Mach1 is hard to beat if you can get it for a good price, and you can resell it for pretty much what you buy it for if you end up not enjoying astrophotography. If money wasn't a problem I'd start with a Mach1 out of that list, and you are unlikely to ever outgrow it. It is a better investment in the long run if you can afford it. If money is tight, get a 'proven' 2nd hand EQ6 or HEQ5Pro and an autoguider.

Your existing lenses will probably have a very small aperture, you may be better off getting an ED80 scope, you can get a decent one 2nd hand for about $400 or less.