Goto Mounts

Nortilus (Josh) · #1 30-08-2006, 08:55 PM

I was wondering if those goto mounts that come with most new scopes track well enough for astrophotography...

Dennis · #2 30-08-2006, 09:51 PM

Hi Nortilus

For long exposure astrophotography (say greater that 2 or 3 mins) at long focal lengths (say 1000mm +), your mount will need to be polar aligned and capable of auto guiding.

Tracking is where the mount simply tracks the object at a standard rate, usually the sidereal rate, to compensate for the Earth's rotation. This can be achieved in an Alt Az mount as well as an Equatorial Mount for visual observing. For astrophotography, you will require an equatorial mount, accurately polar aligned, that is also capable of auto guiding.

Auto guiding is where the tracking of the mount receives feedback to the drive motors, making (hopefully) small adjustments to compensate for small mechanical errors in the gears, poor polar alignment, atmospheric refraction, etc.

Therefore, a mount need not be GoTo, although that helps find objects easily. But, it needs to be a well engineered mount that has low gear errors (periodic error) otherwise you will get trailed stars.

Generally, such a mount will cost over $1500.

Hope that helps

Cheers

Dennis

rogerg (Roger) · #3 30-08-2006, 11:18 PM

It depends what you mean by "most new scopes". There's a lot of variations out there. But, considering that the first 3 years of my astro photography was done on a wobbly equatorial mount with irregular RA motor only, I would in fact err towards the "yes" end of the spectrum, but add "with lots of patients".

If when considering "most new scopes" you are looking at Vixen, Losmandy, Takahashi, Meade or Celestron then the "yes" is more likely.

And agreeing with what Dennis says, < $1500 will be tough going. > $3000 will be easier going.

Roger.

g__day (Matthew) · #4 31-08-2006, 12:10 AM

You might get a CG5 for just under $1,000 that has both goto and autoguiding.By the time you've added a second scope + autoguide camera + cabling + mounting rings + counterbalance weights + free auto-guide software, you've spent another $1,000 - $ 1,400 easily too (assuming you don't have to buy a PC as well to run everything).

JohnG (John) · #5 31-08-2006, 01:52 PM

I would also add to whats said above, the carrying capacity of the mount, you need to work out the weight you will have on the mount and try and work on the 2/3rds rule for astrophotograhy.

Cheers

JohnG

Geoff45 (Geoff) · #6 01-09-2006, 12:34 PM

You can astroimage with a cg5 mount, especially if you strip and regrease it. However you will almost certainly find it frustrating and I wouldn't put anything bigger than a short lightweight 6" on it. The frustration factor has resulted in me ordering a Losmandy so that I can stop buggerising around with inferior mounts. Remember that the three most important things in astroimaging are the mount, the mount and the mount.

g__day (Matthew) · #7 05-09-2006, 01:45 PM

I'm curious - if you're considering a Losmandy with Gemini - why not save up and go for the Vixen Atlux?

JimmyH155 · #8 05-09-2006, 04:31 PM

I have a Meade LX100 bought 14 years ago. No goto but it has electrical with siderial rate, (equatorial wedge) you can polar align it easily, and of course drift align, but why bother? Because the cheapo Meade imaging camera (DSI) I bought last year comes with this software called Autostar suite., which takes care of out of alignment scopes. Its a breeze to use.
The computer drives the camera, and after focussing etc, all you do is get an image of the object on the monitor and an option comes up to draw a box round a bright star for tracking. Draw the box then hit "GO" and the software will take each image and "stack" each image on top of the last one, and will align the image on the guide star. I have taken some images over 60 mins and when I stopped and reset, because of the imperfect scope alignment, the guide star was the other side of the screen.

. You dont need goto or GPS - just electric drive.

g__day (Matthew) · #9 05-09-2006, 10:14 PM

Jimmy,

I like Autostar too, am trying to get it to work with my CG5 - so far almost there with auto-guiding via guidestar (LX200 emulator) and a virtual serial port.

Geoff45 (Geoff) · #10 06-09-2006, 10:54 AM

Quote:

Originally Posted by g__day

I'm curious - if you're considering a Losmandy with Gemini - why not save up and go for the Vixen Atlux?

Hard to say. (It's too late anyway, I'm picking up the Losmandy tomorrow). I guess it's a combination of price, reputation, favorable reviews, serves the purpose for which I want it.
Geoff