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astropaz
2011-Feb-24, 04:01 PM
Hi all,
I have a Skywatcher EQ 3-2 mount and I often hear that this mount is not really best suited for taking long exposure astrophotos due to stability and tracking issues with the telescope(Explorer 150PL) weight and size.
What I was wondering is if I took the scope off all together and just used my DSLR with a ballhead and dovetail piece would the less weight make it better suited for use that way for widefield shots?

RickJ
2011-Feb-25, 06:25 AM
It doesn't have any guider inputs, this makes it unsuited for through the scope deep sky imaging unless you want to do the the old fashioned way with manual guiding. I did it for years. Still this drive isn't very smooth so even manual guiding would be a major chore.

But that isn't what you are asking. For just a DSLR with a basic lens or low power telephoto lens (no more than 135mm equivalent) it should do. You will need the scope however for accurate polar alignment (drift method). You don't say what the scope is. If it doesn't present much wind load you can just leave it on and mount the camera atop it. Balancing, either with or without the scope could be an issue. System may be too light with just a camera and no counterweight Additional weight with the camera might be needed.

With decent polar alignment up to 5 minute images with a 135mm and 10 minute exposures with 50mm equivalent lenses should be possible. Camera noise may limit exposure times.

A good low light DSLR really needs no drive at all. A simple tripod can work. With a 50mm lens equivalent 20 second exposures can be made. Align and stack 10 minute worth would give a nice image. Some of the Canon's can get by with one 30 second image. Many can be combined into a movie showing the skies rotation. Many such examples are seen on the net. No drive needed. Other cameras aren't so low light sensitive and a driven camera might be needed.

For many years I used a simple home built barn door platform. At first I turned the screw manually. Later I rigged the mechanism of a 30's era wind up alarm clock to do the turning. This was in the late 50's and early 60's so I had to use film which was a pain compared to today's digital world. I'd not know how my polar alignment was until the next day when I developed the film. Once I found I'd aligned the mount perfectly -- due south! All shots were ruined. A mistake easily avoided today as after the first image you'd know something was very wrong.

I'd recommend finding a local club. It will have astro imagers that can give you hands on help greatly speeding up the time it takes to get decent images and diagnose those that failed. They've made all the mistakes, we all have.

Also a book like Covington's Astrophotography for the Amateur can help get you started but is no substitute for hands on help from a local club.

Rick

astropaz
2011-Feb-25, 09:42 AM
Thanks for the reply.

I do have dual axis motors for the mount which seems to be good enough with the scope and webcam for planetary stuff, but I haven't tried anything else with the tracking yet.

But yeah, I was specifically talking about removing the telescope all together. It is a Explorer 150PL and seems like it is right on the limits of the mount at the best of times but wanted to try with the camera so the mount will still get used if and when I upgrade to a sturdier one. It just would seem to be an easier option as long as it is possible than as you say, stacking together a heap of shorter exposures to create a longer one.
I guess the best option is to try it out and see what I can get.

ebutts
2011-Feb-26, 03:50 PM
Hi there,

I don't know much about astro imaging, but I just recalled a thread on a danish message board, where a guy used an EQ3. Here's the LINK (http://translate.google.com/translate?hl=en&sl=da&tl=en&u=http%3A%2F%2Fwww.astro-forum.dk%2Fforum_posts.asp%3FTID%3D3609).

Cheers

astroclu
2011-Jun-30, 02:16 PM
Hi,
I have a very similar equipment (EQ3-1 and DSLR) and piggyback astrophotography is totally possible at low focal length. I have done up to 2-3 minutes exposures at 35mm giving me good wide field shots the size of a constellation. Align and Stack tens of these exposures and with a little play on PhotoShop you should get good pics.
Greetings