I've got a NEQ6 with which I've been shooting unguided with a DSLR through an ED80; I just obtained an old 8" f/5 Newt and it all works beautifully but I'm reluctantly admitting that I'm never going to get great results until I get guiding sorted.
I've got a spare laptop with PHD2 installed. I don't own a guidescope or guiding camera but I've been offered a decent rig for (I think) a decent price; I'd like to know more about how it all works. Mike at Bintel gave me a basic rundown but I've since forgotten most of what he told me...!
So how does it work exactly? From what I remember there are two ways to connect it all. One is that the guide camera goes straight into the mount, and the mount connects to the laptop; the other is that the camera and mount both connect to the laptop. The latter sounds better to me but apparently there are adherents to the former. Curious about advantages either way.
Also wondering how Backyard Nikon would be involved. I don't know anything about it at all, no idea what it does.
You can either have mount guiding corrections sent directly to the mount (via the ST4 port) which means that you do not actually need to be connected to the mount. You can also connect to both and forego the ST4 cable and have guiding corrections sent via the computer to the mount.
If I am using PHD2 I tend to use the ST4 port myself as I find it tends to play nicer personally. May have something to do with several programs wanting to talk to EQMOD at the same time. Whatever works I guess. If I am guiding in MaximDL I'll just have it all go through the mount and not bother about the extra cable. If using TheSkyX I think it much prefers to use the ST4 cable.
Not entirely sure how it all talks to BYNikon, it's on my To Buy list but not too high up there at the moment.
Guiding works best when you have a good set up to begin with.
Make sure the mount is level and pointed to the SCP. Make sure the scope is properly balanced, esp when using the newt. Make sure you do at least two star alignment so the mount can calculate any offsets etc.
Try and be selective when choosing the alignment stars, you want to place your imaging target within the three alignment stars if possible.
Once all these are done. Then do your guiding calibrations. You should also do drift alignment to fine tune your mount, esp when you are imaging at long FL and for longer subs.
Remember guiding is only for fine tuning and can only work if you laid all the solid ground work above.
It may sound complicated but with practice you can do all these in 30 mins.
Good luck!
Bo
A bit more information might be useful.
What is the 'decent rig' you have been offered ?
Different setups have different requirements. Some astro cameras do not work as guiders, no port eg.
Guiding can be a PITA to setup first time hardware dependent and the software can be a bit recalcitrant but once it is going it is amazingly good. PHD2 is a big improvement on the first version, my setup just worked from day 1 without any adjustments at all. But I did have all the 'standard' options required, 80F5 scope, camera with ST4 port and plenty of PC hardware to play with. I'm also in an Observatory ( OK, tin shed with a sliding roof ) which means I can leave it setup and aligned, a big help.
So, a bit more info and we should be able to offer more applicable options or suggest solutions.
The NEQ6 and that newt will be fine together. Just keep it simple to start with, and that means using something like the 60mm ZWO guide scope and a ZWO guide camera ( a cheap one is fine for guiding). It can mount on a rail on top of your scope, or just use the mount hole on top of the newt ring. Use PHD2 or Metaguide, both are simple but i prefer Metaguide because it works better imho with the video cameras like the ASI ones. The cable from the guide camera to the ST4 port on the mount is supplied with all the ASI cameras. The other usb cable plugs in your laptop. You mount alignment does not need to be perfect if your guiding. I usually just do a single star alignment near my imaging target using the hand controller then turn on my wifi Nexus to drive the mount via Sky Safari on my tablet. BYEOS is great and easy to use, but leave dithering settings alone for now until you get familiar with guiding. Don't worry about PEC etc, it is not necessary if guiding. Btw at tuis time of year a dew heater strap will be needed for the guide camera, a 2" one is fine for a little guidescope. Have fun.
Btw, if you go down the path of guiding off the main scope (OAG) you will have different required configurations for both your scopes but with a dedicated guidescope it can easiky be moved between scopes without worrying about spacers, etc.
I recently setup a cheap guiding system using a viewfinder and this is a bullet-point list of how it works. It describes one of the two scenario that you mentioned, I am not sure about connecting the camera to the mount:
The webcam connects to laptop.
The mount connects to laptop as well.
Laptop is running PhD or Metaguide or some other guiding software.
PhD analyses the webcam images and sends guiding corrections to the mount.
You do not need Backyard Nikon for guiding. However, you should be able to use it for dithering. Dithering means that the image is slightly shifted between each exposure. After each exposure the imaging software sends a dithering command to the guiding software which then adjusts the mount.
Dithering improves image quality significantly, especially when a DSLR camera is used. I would say it is a must once you get the guiding going. You just have to enable the option somewhere in the software.
An EQ6 is sufficient for carrying an 8" scope and guiding quite happily. What will matter most is getting very good polar alignment...your mount needs to track well with only minor corrections by the guider. Guiding is not a substitute for sloppy polar alignment.
A "decent rig" may give you better engineering and look prettier, but when it comes to the crunch, if you look across the imaging field at a star party you'll see everyone - regardless of mount - is guiding. There is no perfect mount. All the extra money buys you is a -chance- at better mechanical tracking in the first place.
Hi everyone and thanks for your tips, appreciated as always.
I should clarify - I've been shooting unguided through an ED80 for months and have a pretty good handle on alignment; I actually took the attached shot with the 8" Newtonian unguided with 40 second subs.
I'm just wondering how I physically connect the required parts - guide camera, laptop and mount - and what software I should use besides (or instead of) PHD2. Just curious as to the signal path and how it all works; knowing that will help me understand and remedy the inevitable problems.
If someone could also explain dithering that would be helpful too. Not sure what that is.
You could always get a Synguider, which is a stand alone device that plugs into the mount. You just need a small scope that its 1.25" nosepiece will slide into.
raymo
You could always get a Synguider, which is a stand alone device that plugs into the mount. You just need a small scope that its 1.25" nosepiece will slide into.
raymo
Like his ED80 Then all you'd need is to be able to mount the ED80 on the 8" Newt.
Chris, your guide scope needs to be rigidly fixed to the imaging scope so that it sees the same movement as the main scope.
Basically, you need to wire up:
1) the mount to the computer
2) the guide cam to the computer
3) (optionally) the camera to the computer
As described above, PHD will lock onto a star that the guide cam sees. The guide cam takes an image regularly. If the star moves in the crosshairs, PHD will tell the mount to move to counter it until it's back in the centre. Rinse and repeat.
You don't have to use software to control the imaging camera, with a DSLR you can get away with an intervalometer. But it's nice to see the images roll in one by one.
With an EQ6, you'll want to use EQMOD and ASCOM to be able to control the mount and present a controllable interface to other software. PHD will connect to ASCOM to send it push commands. Image capture software often includes functions to slew the mount, plate solve, dither, etc.
Dithering is a process where after every x amount of frames, the mount is moved a few pixels in a random direction. This shifts the object in the image slightly, but since the hot pixels are in fixed positions on the sensor and not with respect to the FOV, they get eliminated during stacking since only "real" signal is retained.
The OSSAG has 2 ports on it. The first plug is USB and it plugs into the laptop. The second port is an RJ-12 plug and it connects directly to my mount via an autoguide cable (and communicates via ST-4 interface). I then open PHD2 on the laptop, activate the OSSAG camera, and then activate the mount (using the on-camera option). Once I calibrate the star movement in PHD2 I start guiding. It then locks onto a star and uses the USB cable to transfer the image in real time so I can watch what's happening (PHD2 also has a graph etc). Once a guiding correction needs to be made, PHD2 automatically sends this to the camera (via the USB cable), the camera then uses its internal software to pass it through the ST-4 interface, into the autoguide cable and down into the mount. This command then moves the mount the necessary distance to counteract the movement of the star. Obviously the less wind & better your polar alignment the less movement that theoretically should occur. In a perfect world I think it's usually just teeth slippage etc. on the gears that causes movement. Things like Periodic Error Correction also help with this.
Interestingly Hubble also uses a similar concept. It has a large Guide Star catalog and uses a guide camera (or three?) to lock onto a guide star(s) and then uses reaction wheels to orientate itself accordingly so it can expose for long periods of time. Pretty neat!
RE: Dithering - This essentially works by randomly moving the FOV ever so slightly between exposures (for example, imagine a few pixel widths or star widths). It helps to reduce noise in the image by moving the object across different pixels, sometimes with varying sensitivity levels and also helps pick out dead pixels etc. To use dither effectively you may need to use some type of capture software.
Perfect, thank you both, that's exactly what I was after - a decent understanding of how a guiding system works, how it gets hooked up and what software does what.
Dithering sounds like a step too far at this point. Probably won't bother until I move away from DSLRs.
I think the rig that was offered to me is a simple 50mm scope with either a ZWO 120MC or a QHY5L-II. Nothing flash but should do the job.
There's one major thing I don't understand, however.
How can a low-powered guidescope and lower resolution camera send correction info for higher magnifications & resolutions? By the time the guiding system notices the guide star has moved even slightly, wouldn't the much more magnified, higher-res image from the main camera be all streaked to hell? I mean obviously it's not, but I don't understand why.
Ah! Pixel & frame size. That's the answer, of course. Thanks, all makes sense now.
So just to recap:
I currently have an 8" f/5 Newt on a NEQ6, shooting with DSLR. I also have a spare laptop with PHD2 installed, and a cable that goes from the mount's serial port to USB. I need a guidescope & camera and a way of attaching them securely to the imaging OTA.
Once everything is acquired and solidly in place & properly balanced, I do a normal drift alignment and 2- or 3-star align. Then I connect the camera's ST4 port to the mount, and its USB port to the laptop. Then I connect the laptop (USB) to the mount (serial). Then I run PHD2 at which point magical wizardry magically happens with magic and I can take 5 min subs forever.
... Right? Or am I missing a few steps? Something about EQMOD (which I'm completely unaware of)? And where do programs like Stellarium come into play, ie how do I locate targets?
Sorry for all the questions,thanks for all your patience!
If you have both the camera and mount connected to the laptop (both being controlled by the laptop) then you do not need the ST4 cable as the commands can be sent to the mount via the USB/Serial.
If you wanted to continue controlling the mount via the Hand Controller (as you're already doing this if you doing the 2-3 star alignment routine) then you will need the ST4 cable as the mount is not connected to the laptop.
EQMOD is what you need to run the mount on your computer. If you connect your NEQ6 to your computer via the Serial-USB you need EQMOD to actually be able to talk to the mount. It is a very easy to use ASCOM plugin. Programs like Stellarium use EQMOD to control your mount, basically turning your computer into the hand controller.
At first I would suggest you just continue to use the hand controller, don't worry about connecting your mount to your laptop and guide using the ST4 cable. Saves any other headaches until you're happy with that
I agree with what Colin said, keep it simple to start with.
Use Backyard Nikon for your focusing, flats, darks, lights and planning etc.
Use PHD2 to control your guide cam and the ST4 cable for the mount.
Use your hand controller for GoTo to find objects, the Synscan controller has quite a comprehensive database so you won't be caught short.
Then all you'd need is to be able to mount the ED80 on the 8" Newt.
