How well does the Infinity work with motorized Dobs?

[scpanish]

Hi All,

Has anyone tried the Infinity with something like my Dob - a 10" SkyWatcher Goto model, f4.9, 1200mm FL?  The drive is the Synta SynScan, also used by Orion on comparable models.  Given the f number, and the quality of the Alt-AZ drives, I'm wondering if the exposures required (whatever they are) will allow sharp images.  Does the software provide auto-alignment?   Is the field size such that a flattener or CC is required?  Etc.....  Sounds like a great product for enhancing visual observing but I'd really like to not have to buy a new scope to use it effectively.

thanks,

Steve

[Howie]

Hi Steve,

The problem with your dob is the 1200mm focal length. There's no prob being AltAz - you can do 20-30sec exposures (sometimes less sometimes more!) with AltAz without problems. But the camera sensor may give big magnification on your Dob. That maybe fine for what you want to go look at (planets maybe?) - in which case go for it! But it might not suit the objects you want to go look at if they are bigger.

If you havent already, download Stellarium (free) and turn on the occular plugin (only available for pc & mac but not for phone apps). Put in your scopes details and then look up the sensor details of the camera and put them into the Occulars plugin too. Then search for objects in Stellarium. It will show you what they will look like with your scope.

Definitely take a look at the link in one of mega256 previous posts ... or google it on youtube .... his vid shows his setup ... AltAz Evolution mount with a short focal length refractor on it. Hmmmm ... If you put a StarBlast 4.5" f/5 on your dob you'd be away!

cheers
Howie

[scpanish]

Thanks Howie.  I'm mostly interested in DSOs, so magnification is OK.   Particularly DSOs that are too dim for visual observing, greater than mag 11 I don't see much, or anything.  And to see color too would be great.   The 1200mm should be outside of the aliasing range.  I'll check out Stellarium and anyway need to calculate FOV.  Mainly I was concerned with the tracking smoothness of the drive.  It is very accurate for finding stuff but at 200X I can see the image woggling about a bit.  I don't know how that compares to an Evolution in granularity of tracking.

best,

STeve

[mega256]

Hi Steve
When doing real time viewing....The scope size isn't as  important as the F ratio..
Being under F5 is a big help,,and under F3 is better...
The scope size will make a difference of the object size...At the same F#
The Infinity is a very capable camera, I can reach very deep even with my 80mm F4.8.
Using my C14@F1.9  does amazing things....
So you will be fine,,but try to go as fast as you can with the 825 ccd  @11mm diag.
And use wide camera to scope adapters...I use "T" s  and have had good success..
Under F5 and it things start to pop...lol

Enjoy the setup,and have fun...The software is a pleasure to use.

Bob-mega

[scpanish]

Thanks Bob.  I'm mainly worried about the very short-term tracking error in the AZ drives.  They keep the scope on target fantastically well over hours, but the granularity is suspect- I can see many very quick, small, image movements as the drives track.  The hand controller could be the culprit, it may be clocked slowly so the scope is moved in larger increments than the drives are actually capable of, which is fine for purely visual observing.  I'm going to experiment with a friends DSLR and see what kind of star trails I get over various exposure times.   

The adapters will be interesting, I'll likely use this with my GSO CC, which has a 2" adapter and is an infocus nightmare on this scope.

Thanks for the inputs....

Steve

[scpanish]

Here are results from testing the tracking accuracy of the SkyWatcher 10" collapsible Goto Dob, 1200mm FL, f4.9.  Hmm, I can only post one attachment...so here is a 25 sec exposure captured with a Nikon DSLR using a 2" adapter stuck into the focuser.  No lens, flattener or corrector.  The scope was partially collapsed to get the needed infocus, so collimation is certainly off. The target is Procyon and surround.  There doesn't seem to be too much trailing.  A 5 sec exposure is a bit sharper, maybe because it is darker and has less bloom.  I don't know why the pictures aren't sharper, maybe focus, which was done through the viewfinder.  Visually, this scope gives very sharp images.  It isn't mirror bounce, the exposures were done manually by passing the scope cover in front of the scope, removing it after the mirror went up and replacing before it went down.  Maybe the blobs are tracking inaccuracy.  However, a very short exposure (1/400 sec) of the moon was similarly unsharp.   Do any of you more knowledgeable folks have any idea why these images aren't sharper?

So, this test is suggestive that tracking is OK, but not definitive that images will be sharp.  I am still not sure how well suited the scope is to the Infinity.   I'd sure like to try it.   I just hate $1K experiments.

Steve