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FORUMS Photography Talk by Genre Astronomy & Celestial Talk 
Thread started 04 Jan 2010 (Monday) 08:06
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Set up Routine

 
chris.bailey
Goldmember
2,061 posts
Joined Jul 2003
Location: Norwich, Norfolk, UK
     
Jan 04, 2010 08:06 |  #1

I'm sure we all have different setup routines and we may well have something to learn from sharing those. This is mine

I don’t have 360 degree horizons due to the position of the house and several large trees. All my imaging needs a degree of advance planning as to what position in the garden to image from so as to avoid these obstructions. I would dearly love an observatory as cantbebotheredness stops me from going through the following hassle on anything but a perfect evening.

My favourite imaging setup is a William Optics Zenithstar 70 as guidescope and Takahashi FSQ85Ed as imaging scope. Both are fairly short, portable and easy to balance up. I mount these side by side on a Geoptics saddle plate which is really rigid. My mount is an EQ6Pro.

I tend to start my setup routine about an hour before darkness by moving the mount and tripod to where I will be imaging from. I then level up and align it roughly north using a compass. I find that even visually with a compass standing behind the mount I can get Polaris into the polar scope once it is dark. I will then set each scope on the mount and set the finder scope/red-dot finder to align accurately with the scope using a cross hair eyepiece. I have a couple of distant radio masts that are handy for this purpose as both have red navigation lights on them that tend to come on as it gets dusk. I then fix the scopes into position and carry out a balance.

Balancing up the scopes is, to my mind one of the most important steps to good images. With the mount clutches off you SHOULD be able manually put the scopes (with cameras attached) in any position in the sky and let go. I have made marks on all the mounting plates I use so I can put everything together very quickly. Balancing a side by side setup is also a lot easier than over and under as there is less counterweight involved though taking side by side balance into account does take a bit of practice. Having got perfect balance I then shift my imaging scope forwards by about half an inch and saddle plate to the left by about the same (to the right when I cross the zenith). This gives a little out of balance to the front and left meaning that the motors are both pulling up. Not enough to put a great deal of strain on the gearing but enough to take up any slack. Without this bias, guide instructions can cause the mount to rock over the balance point leading to very wayward guiding. How much out of balance your mount will need, if any, is a matter of trial and error, my Meade fork mount needs a shed load of forward bias.

Next, the electrical side of things. I use a Panasonic Toughbook laptop for scope control (via The Sky) and guiding and imaging (via Maxim DL). I guide using a Starlight Express Lodestar camera that plugs into a USB port on the laptop (that also provides power) and into the ST4 port on the mount. My imaging CCD, a Starlight Express SXVM25C, has a power block and USB connection. A final cable goes from the Com port on the laptop to the comms port on the bottom of the EQ6 handset. This is used to control the scope from the laptop. TheSky does this directly without the need for Ascom, which I have never got to work properly. I power the mount off a further power brick and then Dew Heaters for both scopes are powered off a car jump starter of which I have two. Less cables than many setups but still enough to trip over when it’s dark.

http://www.pbase.com/c​hris_bailey/image/1075​90011 (external link)

I have since loomed many of them together with cable ties and fixed the dew heater controller to the one of the tripod legs. I am also in the process of making a weather proof power strip that fixes to the underside of my portable table. Be careful to ensure the wires don’t snag as the mount moves through its imaging arc.

My next step is to crank down hard all knobs starting on the scope and saddle plate and then the scope clutches.

By now it should be dark enough to Polar Align. I must admit to a degree of laziness here and use Polar Finder software to give me a polar angle and then estimate the position of this on the reticule of the Polar Scope. I have found that the Alt Az adjustment of the EQ6 to be pretty coarse and I have never managed or had the patience to drift align it. Maybe when and if I get an obsy!
I recheck everything is tight, recheck the polar alignment, make sure the dew heaters are warm to the touch and then fire up the laptop.

I tend to do a three star alignment setup for the EQ6 calibration and get very good GOTO’s from it. If I am only imaging one object I will tend to leave it at that but if I am doing two or three I will also do a synchronisation with TheSky software to get total GOTO scope control from the laptop. It does work very well indeed and once setup I don’t need to touch the scope at all. The laptop is on my wireless network so I can use remote desktop to do a level of control from indoors.

Maxim DL is a great piece of software (though to my mind expensive) but not particularly intuitive. If you try it I strongly recommend working through the Video tutorials and then making sure that going through the setup routine is second nature using the simulator before trying it in the dark. It’s very easy to forget to check a tickbox and it’s quite hard to spot later. One big advantage of Maxim is that it allows you to set up an imaging sequence beforehand. I often do a mixture of exposures and Maxim makes it easy to do say 10 x 3min followed by 20 x 5 min. It will also control a motorised filter for Mono CCD’s. PHD guiding software is also very good and I tend to use it with Nebulosity when imaging with a DSLR but the advantage of Maxim is having all your imaging tools under one roof.

I will now slew to the first target. My CCD screws into the back of the scope so I rarely take it off to put an eyepiece in (too much risk involved). I know that my CCD focus point is around 55 on the focus scale on the Tak so I will dial that in and use a red dot finder to check my object has been correctly found by the GOTO or slew command in TheSky. I will then do a quick test sub in Maxim to make sure it is framed as I want it. The beauty of an 85mm scope with large CCD is that I have a fairly large field of view. Finally I will fine adjust focus using Maxims focus tools. These allow a partial capture of a single star and gives FWHM and a graphical view of focus as that star is continually imaged. I spend a fair bit of time getting the best possible focus on the imaging camera.

When happy I will then setup guiding. The single camera control interface in Maxim handles both guide and imaging camera so I will first focus, pick a guide star, calibrate and then hit Start for the guide camera. Maxim’s calibration routine will check what magnitude of movement and in which direction guide pulses move the mount and is very quick. I will then open the guide graph and give things a couple of minutes to settle down. I have had no problems with the default settings for guiding in Maxim and tend to guide on 2 second exposures.

With guiding running I finally swap to the imaging camera in the Maxim Interface, disable any crop box used for fine focus and load up my previously defined imaging sequence and hit start.
I am a great fan of Deep Sky Stacker software and will tend to use DSS Live on the laptop to stack images as they are captured. The advantage of doing some shorter subs to start with is that you soon get a view of what you are capturing. I have saved a lot of failed imaging time this way when an object has not been framed quite right. M31 is a very large object even for my imaging rig and needs to be well centred. DSS Live gives a good impression of how things will look after even a couple of subs allowing reframing if needs be.

And that is pretty much it. The rest is pretty automatic and I can keep an eye on things from the warm using remote desktop.




  
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Set up Routine
FORUMS Photography Talk by Genre Astronomy & Celestial Talk 
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