newbie question on tracking mount/dslr

[mattwo1232]

Hi guys, new to the forums here, but always been a fan of astrophotography since as a kid.

I have a question regarding using a tracking mount (I'm thinking a cg-5 but open to other possibilities) and using my canon 60d/70-200mm f/2.8 lense camera.

First question is will this tracking mount be sufficient in doing at max 2 min exposure shots (with good polar alignment) or my other question is if I need to even take such a long exposure shot with my lense.

Another question is would I be able to get sufficient shots of dsos (not super stellar awesome shots but at least something of ok-good quality)

And the general question will I be ok using the ccg5 with my dslr and are there any better alternatives?? Prices to be at least around the same as the cg-5 or upwards to max of 500 dollars more.

Thanks guys for hearing me out. I really appreciate it.

[mattwo1232]

Sorry last paragraph cg-5* not ccg5

[mattwo1232]

Also would I need any accessories to go with the tracking mount (ex: autoguider, polar alignment scope...etc)??

[jambouk]

I would call that type of imaging "dslr widefield astrophotography" - a term which may also be used for other types of imaging using some telescopes. Have a search on google for that term and see if there are any tutorial / help.

The longer your focal length, the less forgiving the set up will be to a poorly tracking mount. At 70mm you may find 120 seconds is ok and there is minimal star trailing; but at 200mm there may be very obvious star trailing.

I don't know that mount well enough, so search for it on SGL and see what sort of tracking accuracy it can achieve (remembering many people "pimp" their mounts by taking them apart and re-greasing, tightening up and clean the motor mechanisms to reduce back lash and minimise periodic errors).

There are lots of other issues you'll need to address such as dew, and stepping down the f/stop on the lens to reduce the coma. If you live anywhere near light pollution your sensor may get swamped with light pollution so you may need to look at light pollution filters; do you have a way of keeping the battery away from the camera to limit it heating up the camera body (such as a battery grip, or a mains/12v power supply)?

There was a good book which i have and which is available free online as a pdf; it talks mostly about film cameras, but lots of the technical set up issues are similar, let me try and find it.

You will need a polar scope in the mount unless you plan to "drift align" the mount (which will be even more tedious if using just a dslr).

What about one of these dedicated dslr tracking devices, "astrotrac" (i might have made this name up, but it's similar i'm sure)?

Jd

[jambouk]

I can't instantly see that book so when i get up imll try and post the title of it.

Just having a look on google, there is loads of information and tutorials and stuff. Plenty to give you more ideas and information.

Good luck

Jd

[jambouk]

Here is the book, and another book i've found useful:

[jgs001]

I don't know that mount, but on both by heq5 and astrotrac I'm able to hit 5 minute exposures at 50mm without any problems at all without guiding. Is therefore expect you to be able to hit your target without too many issues. In yet to try longer focal lengths on the AT but I'm expecting good things. Of your primarily looking at camera and lens only AP then consider the astrotrac, vixen polarie or ioptron skytracker. They are similar prices to an eq mount like the cg5 i think but are much smaller and more portable. You will need a decent tripod to mount then on though.

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[mattwo1232]

Im assuming this is the one you have

http://www.astrotrac.com/Default.aspx?p=tt320x-ag

In this case as you said I have to mount it on a good tripod as well as needing a polar scope for this??

[GarethA]

With decent polar alignment you'll have no problem getting trail-free 2min subs with a 200mm lens on a CG-5, even without guiding.

[jgs001]

Yes and yes matt. Looking at the kit you listed the f 2.8 lens is a costly bit of kit and I figured you'd have a decent tripod already.

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