Mounting 12” DOB Newt OTA on a GEM

[Scooter]

Hi Folks,

Ok I think its about time I upgraded my GSO 12” DOB Newt tube onto a GEM so I thought I would fire off some questions for you fine folks to answer :)

Reason for the upgrade is basically to give me tracking (tired of manually trying to keep high mag stuff in the eyepiece) and goto (tired of going back and forth between my PC inside – although that’s my fault as I have yet to set the lappy up near the scope – and the scope using my dodgy setting circles and altimeter to find stuff). Then once I have tracking I wouldn’t mind having a go at astrophotography.

So now you know the background here are roughly my thoughts (thus questions):-

1.) Is a GEM the best choice? What are the alternatives given I wouldn’t mind using the 12” OTA visually as well as for Astrophotography? I know the GEM can cause issues with where the eyepiece ends up for visual (is it really that bad?). To make it easier did you need special tube rotation rings or if it is just a few targets chosen do you just use normal rings and then loosen and rotate for best orientation (does that effect balance etc.)? Could even consider viewing via a cam and PC if needed (actually I do kind of like idea of controlling the scope from the lappy and seeing the real-time output on the PC so eyepiece orientation wouldn’t be a problem. Thing is the output would need to be at least as good as visual so what are the cam choices. I know that the mallincam was hyper sensitive (i.e. better than visual – who was it that had one in Brissy – would love to see it’s output) but just would be happy with something that was naked eye equivalent. Yeah – I know there are a few questions in that lot…..

2.) Choice of mount – I know wisdom dictates get the best mount possible and whilst I would love a G11 that’s a hard spend to justify whilst an EQ6Pro (@$1500) I won’t need to justify (wish I could work out how to get a G11 back from the states as the Oz prices seem pretty inflated but that’s a discussion that’s already been done yeah ;)). So given an EQ6Pro I assume that would be fine for visual and the 12” OTA but for astrophotography is still OK (planets and DSO)? Is it a reasonable assumption that if the scope is guided (manually or auto – and assuming comparable setup etc.) then essentially the EQ6Pro will perform as well as a G11 guided etc?

3.) On guiding if the scope is interfaced with the lappy and X software can you get away with the one capture and guide camera? I know there are high end cameras with a separate guide CCD and capture CCD on the same chip but it seems everything I read you seem to need two scopes and cameras etc. so what I am asking is their any software that enables you to capture and guide from the same source using the one scope. It just seems that so you had a capture device connected to the scope then couldn’t the software control the mount to keep a guide star in a particular spot whist still capturing frames or exposures?

4.) Assuming going with the EQ6Pro what else did I need (to get the OTA on the mount)? Rings - (special ones if still interested in visual or not?) and what about weights for balance or will it come with sufficient?

5.) Setup (no doubt a lot to learn) but on the actual setup of the tripod (or a pier for that matter) did it need to be 100% level or does the actual set up (star alignment and drift etc.) allow for small inaccuracies it the actual mount position?

6.) Semi remote setup – could I set up the mount in the backyard and then do all the other setup (like alignment etc.) and imaging/control from inside the house? Basically if so what would I need? I am assuming this is possible I just need long cables etc. Like I said above I quite like the idea of control and observing from the PC instead of the eyepiece (and certainly sounds like the lazy way of capturing data whilst watching TV etc.) and doing it from the luxury of the house rather than at the scope sounds like a good idea. Suppose this would be like a quasi observatory just requiring me to setup and packup the scope. Anyone done anything similar (perhaps wirelessly)?

Anything else I should know or consider? Basically I was goning to just get the mount and what was required to put the OTA on the mount as a start and then go from there and these were the initial things I was thinking.

Thanks in advance folks :thumbsup:

[Jazza]

This just came up, have a read of:
http://www.iceinspace.com.au/forum/showthread.php?t=34279

I think basic summary is it works, but not for DSO only planetary, and visual is difficult. I'll lett someone else try and answer your other questions!
Good luck,
Jay

[Scooter]

Thanks Jazza :thumbsup: - Sure I read that thread (I am a lurker) which might even be where I got some of my concerns about DSO's but I thought it was because of the length of exposure required thus I thought if you were guided you were OK - but maybe not as comments in that thread suggest issues with stability.

As I said provided I can see capture output in realtime at the screen with comparable views to naked eye that would negate any issues with where the eyepeice ends up but the view would need to be as good (can it be in realtime - I assume yes as the cameras are made more sensitive than our eyes).

[AlexN]

You could get the 12" on the GEM with a G-star EX camera in the focuser. The G-star series cameras use frame integration, meaning that it automatically stacks the frames on the fly. When you first center your target, the image on the screen will be a little dim, but after a few seconds it will start to gather detail and bring out some more of the darker features...

These cams can effectively give you a MUCH better view of DSO's than your eyes ever could.

For photography with a 12" on a GEM, the mount would have to be pretty substantial. A losmandy G11 would be a good choice, but I would only go up from there.. anything less just wont have the stability required.

If you went with an EQ6 pro, you can forget about dso photography except of the stillest of still nights... Autoguiding with a camera would help, but the accuracy of the mounts tracking will fall as the payload rate rises, and now you're talking about a 12" OTA, a guidescope, guide cam, imaging cam, 2 sets of rings, 3 dovetail bars... pushing all kinds of weight limits for the EQ6..

I've had my mount going remote from the comfort of my lounge room...
The setup.

Mount -> Laptop -> wireless network -> desktop pc inside.

set it all up manually, aligned... then went inside. Using RDP (remote desktop protocol) I took control of the laptop from inside, fired up the sky, and established a connection to the mount. used the sky to acquire a target. Then, using MaximDL I fired off a 30second test shot to check focus/comosition of the image. (the focuser driven with a FCUSB from shoestring astronomy) I used ASCOM drivers to alter the mounts position in order to get the composition I wanted, after getting that all sorted I set up an imaging run, fired it off and watched the images as they started coming out of the camera... It was nice, but I think I prefer being out there with the setup.. (especially considering with my LONG refractor, I like to keep an eye on it, as the focuser/camera reaches to the legs of the mount at certain angles and would do serious damage to the mounts motors if it were to hit it...

You're entire plan would be fine, if you were able to get the extra $$ together for the G11 instead of an EQ6... Maybe save for a bit longer (if you can handle the weight)

Alternatively, a 10" OTA would be fine on the EQ6, would not require expensive custom made rings, wouldnt require so much counter weight in order to balance...

No matter which way you look at it, there are sacrifices to be made... Its up to you.

You would need extra counter weights (dumbell weights would be better) and custom made rings to mount the tube.

[Scooter]

Thanks for the detailed response Alex (even if it's not quite what I want to hear :sadeyes:). "No matter which way you look at it, there are sacrifices to be made... Its up to you" probably sums it up pretty well :)

[coldspace]

If you want to see images in real time then a Astro video like the Mallincam or G-star is the go. You won't need to use an EQ mount as these camera's don't go over 1minute of intergrated exposure. Thus no field rotation. You will neen at least ALT/AZ tracking though to keep the object centred. The G-star is B/w and does not have cooling but is a very capable camera for real time viewing at around $700 bucks and can be sourced locally. The Mallincam is a very highly modified unit and is colour with cooling and hyper circuitry to increase the gain with very little noise and intergrated exposures upto 1 minute but has to be ordered from Canada via the US at around $1600 landed here. Both these cameras will show you far more detail in light pollution than what you could see in the 12 inch under dark skies. So you can imagine what they can do under dark skies.

I use the colour mallincam and a 12 inch Meade and the views are unreal to say the least. Looking at M16 the other night the pillars of creation stood out in full colour and the dust lanes were clearly visable all done in 28 second intergrations in suburban Brissy last Saturday night. Lagoon, trifid were also a sight to behold. Looked at numerous globs, some that are almost impossible to resolve clearly under dark skies were easy targets at 14 second intergrations. The bug and box panetaries also were great. M83 , silver coin and M104 Galaxies were also nice targets. All these,unless you have reasonbly dark skies are fairly boring targets at the eyepiece in suburbia.

If you want to only use a video system you could put your Dob onto a round-table dob tracker like they use alot overseas and this would be excellent for holding an object for higher power viewing as well as been adequate for use with an Astro video system. You could then use an Argo Navis for finding things.

My mount is Alt/Az and I only get a slight field rotation showing when I have the scope pointed near Zenith and the mallincam set to 56 second intergration. But this does not cause any trouble for real time viewing, Most of the time the camera points alot lower and I only use 7,14 or 28 second intergrations.

This won't be a problem using a G-star camera as well.

Just some more thoughts for you to consider. To find out more join the Yahoo Mallincam or G-star user groups on the Yahoo site. You will find out alot more on these systems there.

Regards Matt.

[Scooter]

Hey coldspace it was yerself I was refering to in my initial post :) I know ages ago I looked at the mallincam and it does indeed look like a great bit of kit (and I did a bit of reading and looking at the results at the time) but the only thing that put me off was that the output wasn't digital. But aside from that as you said it looks like it deliver great results in light poluted Brisvegas far and beyond what the humble naked eye could resolve (I know my attempts at Galaxies on the soutside have so far been in vain).

Been looking and reading about alternative mount types - e.g http://home.earthlink.net/~indig/DesignMusings/text/Design_Mountings.html (and awhile ago had toyed with a DIY job - but got heaps of other "projects" to keep me busy) and just thought for $1500 the EQ6Pro looked a cheap way to go. Pity it's not an ideal solution for the price :sadeyes: