Astrophotography with 20" dob with synscan?

[Ships and Stars]

Hi all, do you reckon I would be able to do any DSO photography with a 20" dob on a SW synscan tracking mount? As in alt az tracking, but not equitorial (haha, I wish). I don't have an eq plate for this beast and guess I'd have to make one - someday. My camera is a Nikon D810, so it has a pretty good sensor at high ISOs. I was thinking 2-3 sec exposures max, and crank up the ISO for the faint stuff. I realise I'm not going to get fantastic DSO images, but more along the lines of some record shots. Ideas? 

Cheers all.

[CraigT82]

 You mean the SW tracking dob mounts?Not sure a 20" tube would fit into any of the skywatcher tracking dob mounts?? The largest is the 14" (400P) and then you get into the stargate dobs. Maybe an EQ platform instead?

[Ships and Stars]

Just now, CraigT82 said:

 You mean the SW tracking dob mounts?Not sure a 20" tube would fit into any of the skywatcher tracking dob mounts?? The largest is the 14" (400P) and then you get into the stargate dobs. Maybe an EQ platform instead?

Hi Craig, the scope is a Skywatcher Stargate 500p with synscan/goto capability. Based on my limited knowledge of most things astronomy-related (I'm new to this but have been reading up every chance for a few months now), I'm assuming the system will track targets in an alt-az fashion, but not equitorial rotation? If that's the case, I'd be limited to taking very short 2-3 sec exposures, etc. An eq platform would be great, but I'd probably have to make one, so that's something for later on in the year perhaps. I'm hoping the light gathering ability of the large mirror will allow me to make useful short exposures of DSOs... hoping!

[CraigT82]

Oh I see, the actual stargate 500p... yes I've never done it before I'm sure you be able to get some images using a dslr and tracking in alt az.  There is a thread on here  full of images done with relatively short exposures and alt az tracking.  You could search "stargate" or "500p"on Astrobin to see if anyone is already using one for imaging.

 

 

 

[Geoff Lister]

I have Synscan on my 10" Dob. I use it mostly for visual, but on odd occasions have used it with my GPCAM and laptop. As I understand it, field rotation is minimum with objects close to the horizon (Jupiter at the moment), and worst at the zenith. I tend to use Sharpcap on the laptop, and have had some reasonable results using the "live stacking" feature and exposures of up to 10 seconds. This way, given reasonable atmospheric conditions, I get a sharper image, and start to see some colours with the fainter fuzzies.

Geoff

[Ships and Stars]

Ah cool, I'll have a look and see how they're approaching this in more detail. I'm hoping the 500p mirror will make up for short exposures. I don't suppose I'd be able to use the full sensor size of the D810 (36x24mm I believe) through a standard 2" focuser, but that's kind of a side issue... I bought the Stargate to get away from obsessing about photography and just enjoy the views, but a few shots would be ok!

[Ships and Stars]

1 minute ago, Geoff Lister said:

I have Synscan on my 10" Dob. I use it mostly for visual, but on odd occasions have used it with my GPCAM and laptop. As I understand it, field rotation is minimum with objects close to the horizon (Jupiter at the moment), and worst at the zenith. I tend to use Sharpcap on the laptop, and have had some reasonable results using the "live stacking" feature and exposures of up to 10 seconds. This way, given reasonable atmospheric conditions, I get a sharper image, and start to see some colours with the fainter fuzzies.

Geoff

Thanks Geoff! 10 second exposures aren't too shabby for an alt az setup I suppose! That opens things up a bit, great. I'll look at sharpcap, etc. Lots and lots to learn here. Cheers!

[Buzzard75]

 

I did some live stacking with a 12" dob using an ASI178 and a 0.5x reducer. Exposures were limited to about 15 seconds. Problem with a big dob is you require extremely calm winds, like no wind at all, for this to work. They're so big they just act like sails and get bounced all over the place. You can even see some of that in this image. 

 

Edited July 1, 2019 by Buzzard75

[dph1nm]

On 01/07/2019 at 16:57, Ships and Stars said:

If that's the case, I'd be limited to taking very short 2-3 sec exposures

Over most of the sky you can happily do 30 sec exposures in alt-az before rotation becomes an issue. Just don't point straight up! The challenge is going to be the tracking accuracy of the dob mount at 2000mm FL with 4.8um pixels ...

NIgelM

[Ships and Stars]

28 minutes ago, dph1nm said:

Over most of the sky you can happily do 30 sec exposures in alt-az before rotation becomes an issue. Just don't point straight up! The challenge is going to be the tracking accuracy of the dob mount at 2000mm FL with 4.8um pixels ...

NIgelM

Ah thanks, I was wondering about that. Stay away from zenith, makes sense, moving faster from our perspective. I;ll do some standard long exposures next time I can escape. I'll have to abseil down the prison wall with all my gear and leg it before the wife sounds the klaxon and searchlights. Wife.

Edited July 3, 2019 by Ships and Stars

[Ships and Stars]

36 minutes ago, dph1nm said:

Over most of the sky you can happily do 30 sec exposures in alt-az before rotation becomes an issue. Just don't point straight up! The challenge is going to be the tracking accuracy of the dob mount at 2000mm FL with 4.8um pixels ...

NIgelM

If there is anything you want to do in life before you have children, I would heartily recommend you attack it right now. If you are single and childless, we have a three year old demon to stir your motivation. You'll laugh, you'll cry....you'll probably end up dialling 999 a few times as well. Don't worry about the choking fits, I just turn them upside down and knock the spine a few times until the pear or apple falls out. I feel like God when I do that. See how imaging suddenly became easier?

[Ships and Stars]

Sorry, just answered my own question! Hey, if I can get 15 sec exposures, I could do that from inside the prison. Ta!