First steps in autoguiding

[old_eyes]

Last night I tries autoguiding for the first time. For a wonder it all worked so I'm dead chuffed. Seeing was not great, lots of hazy cloud high up, but what the hell - getting out with the scope has been so rare in the last 6 weeks, I'll take anything!

My rig is characterised, by what someone called 'submariner' engineering - you make do with waht you have lying around.

Imaging scope - Equinox 80ED mounted on CG5-GT

Imaging camera - Atik 16ic

Guidescope - Helios ST80

Guide camera - Imaging Source DFK21

Image acquisition software - Artemis CCD Capture

Guiding software - PHD Guiding

First problem was mounting the two scopes. I had a set of WO CNC rings and a set of skywatcher rings, but no dovetails. So I screwed the skywatcher rings to the WO rings, clamped the two scopes in place and then mounted the package on the CG5 with the Equinox foot. No adjustable guidescope rings, I just hoped I would be able to find a star in the field of view.

I used a USB to serial converter and then the Celestron programming cable plugged into the bottom of the handset to control the mount. I checked that I could control the mount using the Nexstar Observers List free software. Once I was sure I could communicate I downloaded the ASCOM Celestron drivers and connected everything together with PHD Guiding in the house to make sure all communication worked.

Once outside, I polar aligned using the mount's polarscope and the polar align routine in the Celestron software, then aligned the GoTo. Then fitted the cameras, took a deep breath and slewed to M13.

M13 was on the imaging chip first off - good 'cos the chip is small. I centered it up and started PHD Guiding.

Disaster - I could connect the camera straight away, but could not get the porgramme to talk to thetelescope mount. Closed all the software and started it again, plugged and unplugged cameras and mount control, tried different sequences. Finally the penny dropped and I checked the COM port for the telescope control. Yes I had closed down and restarted the laptop and the stupid operating system had changed the COM port number! Aaaargh!

OK - now everything is talking to the computer. Checked the guide camera - yes I can see a star at 1 sec exposure. Select it and hit the guide button. PHD guiding sets off on its calibration run. I watch the star move right and back again, then up and back again. PHD Guiding is clearly in control.

Once it locked on and started guiding, it seemed absolutely solid. I was able to easily take 5 min subs, whereas previously 1 min was about the limit with my skill in polar aligning, and there was no drift frame to frame when it came to stacking. Looking at the graph that PHD Guiding produces, I think it was deviating by about a pixel on both axes.

The guiding stayed locked through some hazy cloud drifting across the field of view (although the guiding was not so tight), and a taxi coming up the drive with full headlights on delivering my son back home from a trip.

I managed to get 12 x 5 min subs on M13 with the colour Atik, before the clouds got too thick.

For a first trial I account that a major success. All the gear except the Imaging Source camera and the usb to serial converter was second-hand - all bought from people on this forum. So thanks to everyone who helped out a newbie by sharing both their experience and their used gear. PHD Guiding is an amazing programme. I just used the default values. Once I had sorted out the COM port fiasco, it was simply connect to camera and scope, focus the guidescope until I could see stars, select one, hit the guide button, wait for the calibration run, and sit back to collect data. So thanks to Greg Stark for producing such a robust and easy to use programme.

After processing with Astroart and PS, my 60 mins of data gave me this. Now I have to get focusing and image processing right!

old_eyes

[Uranium235]

Congrats on getting it to work old boy First time is always a challenge, especially with all the faffing around with ascom drivers and calibration.

Now your subs are getting longer, you might want to start thinking about getting a good filter so you can go even further (10-15min) and see how far you can push it. But be mindful that you cannot guide across the meridian with a CG5, so if youre setting up for a long(ish) session just check to see if your target has at least 90 min on it before crossing the meridian.

[blinky]

It is a great feeling, once PHD is calibrated and the first long subs start to roll in with no trailing.

Nice first guided image as well, lets hope there are many more this winter.

[old_eyes]

Congrats on getting it to work old boy First time is always a challenge, especially with all the faffing around with ascom drivers and calibration.

Now your subs are getting longer, you might want to start thinking about getting a good filter so you can go even further (10-15min) and see how far you can push it. But be mindful that you cannot guide across the meridian with a CG5, so if youre setting up for a long(ish) session just check to see if your target has at least 90 min on it before crossing the meridian.

What sort of filter would you suggest with a OSC camera?

Hmmm! I haven't really got my mind around this meridian crossing lark. More study need to work out what 90 mins looks like!

old_eyes

[rawhead]

Glad to see someone getting 5 min subs on a CG5-GT

After recent reading I was beginning to think the mount wasn't up to it. Have you done anything special with the mount? Strip regrease rebuild etc?

Lovely pic. Well done

Cheers

[old_eyes]

Glad to see someone getting 5 min subs on a CG5-GT

After recent reading I was beginning to think the mount wasn't up to it. Have you done anything special with the mount? Strip regrease rebuild etc?

Lovely pic. Well done

Cheers

No, It is exactly as I received it from the previous owner. I don't think they did any specific maintenance. Don't forget that I am operating at a short focal length (500mm), and the mount should be operating well within its capacity with only the Equinox, a light ST80 and a couple of light cameras. People on this forum and the dedicated CG5 forum on Yahoo get very good results, both out of the box and extensively tweaked. Seems a pretty good mount for what I want.

So far I am very pleased with it. I have not reached it's limits (my limits are still the operative ones ).

old_eyes

[Uranium235]

Glad to see someone getting 5 min subs on a CG5-GT

After recent reading I was beginning to think the mount wasn't up to it. Have you done anything special with the mount? Strip regrease rebuild etc?

Lovely pic. Well done

Cheers

Ive managed to get 20min out of my cg5 so far, and 10min is the norm for me now (with appropriate filter). The only reason i havent gone further is because 25 or 30 min would be a lot of time to waste if the tracking went wrong.

Ive just stripped mine and greased it with superlube and its running well smooth now (no stress in the motors), whether it improves guiding even further or not, we will see (waiting for clear sky).

Old eyes, you asked about filters? Did you use a UV/IR blocker with the Atik? Because im pretty sure its a must if youre imaging with a fraccy. My understanding is that UV and IR isnt focused properly with a frac, no matter how good the glass is. The Astronomik CCD CLS 1.25" filter will do the job and its a mighty fine LP filter too.... riff-raff photons begone!

PS: Oh, about the meridian. When youre out on the next session just load up Stellaruim and hit ";" that will show you the meridian from your location, if your target is on the eastern side (eg: IC1396) you can easily work out how long you've got before it crosses. If your target crosses the meridian, you need to stop guiding, then do another goto where the telescope now approaches from the other side - the downside to all this being that your next images will be upside down and back to front from the ones youve just taken. It can be sorted out with software, but its easier to just avoid the hassle (or wait till it crosses before you start imaging).

[old_eyes]

Ive managed to get 20min out of my cg5 so far, and 10min is the norm for me now (with appropriate filter). The only reason i havent gone further is because 25 or 30 min would be a lot of time to waste if the tracking went wrong.

Ive just stripped mine and greased it with superlube and its running well smooth now (no stress in the motors), whether it improves guiding even further or not, we will see (waiting for clear sky).

Old eyes, you asked about filters? Did you use a UV/IR blocker with the Atik? Because im pretty sure its a must if youre imaging with a fraccy. My understanding is that UV and IR isnt focused properly with a frac, no matter how good the glass is. The Astronomik CCD CLS 1.25" filter will do the job and its a mighty fine LP filter too.... riff-raff photons begone!

OK so 20mins is something to aim for. I think I will aproach it stealthily. With sky time severely limited at the moment, the longer the exposure, the more the frustration if something goes wrong.

I am using a Baader UV/IR cut neodymium filter - labelled "Moon and Skyglow". I assume that is similar to the Astronomik. I don't know how much it helped, but the moon was up at 3/4 whilst I was imaging

old_eyes

[Uranium235]

Ahh, I see you have the newer Baader filter then. I have the 2", but its the older version so its not UV/IR blocking. I think that can safely take you to 10min, even 15. But 20 would be pushing the limit - it depends on your level of LP I guess.

With the weather we're having right now (unless its a clear night nailed-on), im playing it safe and sticking with 10min in case of passing cloud. But build it up slowly, try going 3,5,8,10,15 & 20. Luckily, you dont have to think about darks with your cam so you can mix and match sub times as you please.

Hopefully you will have any backlash in dec under control with such a light payload (thats been the killer of many a session!), which is my only gripe with the cg5 - I wish it could take a bit more weight without going all sloppy. Which is exactly what happens if you mount a 6" Newt, an ED80 and all the other gubbins.... things tend to get a bit wobbly

[Euan]

Nice to see you have it cracked quite quickly, I spent months of frustration trying to autoguide for the first time, a lot of mistakes were made but it's how you learn I suppose

There is a reason why some people call it a black art, there is so much that can go wrong. It's great when you see it doing it's thing and you can start really pushing the subs

[old_eyes]

Nice to see you have it cracked quite quickly, I spent months of frustration trying to autoguide for the first time, a lot of mistakes were made but it's how you learn I suppose

There is a reason why some people call it a black art, there is so much that can go wrong. It's great when you see it doing it's thing and you can start really pushing the subs

Bearing in mind Uranium235's comments - what sort of subs to you normally work on?

old_eyes

[Euan]

Bearing in mind Uranium235's comments - what sort of subs to you normally work on?

old_eyes

I go between 15 and 30 mins. I have really good polar alignment and guiding, so I'm quite confident about longer subs, but there are two problems to consider with longer subs:

If you have a night with the occasional bit of cloud, it only takes one small one to reflect loads of LP for a few seconds and waste a single sub, if this a 30 min one it can be a right pain

The noise level in your images is directly related the number of exposures you have, the more the better. So with longer subs it gets harder and harder to get enough subs to keep the noise down to a reasonable level

I prefer 15 mins just now, but now I'm doing narrowband I will step this up to 20 mins

[old_eyes]

...Hopefully you will have any backlash in dec under control with such a light payload (thats been the killer of many a session!), which is my only gripe with the cg5 - I wish it could take a bit more weight without going all sloppy. Which is exactly what happens if you mount a 6" Newt, an ED80 and all the other gubbins.... things tend to get a bit wobbly

Flushed with my initial success, I'm thinking of trying another configuration. I have a side-by-side dual mounting bar, and I'm thinking of putting the Equinox and the ST-80 on that. Why? I am also interested in using a DSLR with camera lenses for wide-field shots, and I have an f10 C6 SCT. It would be nice to have a setup where I can swap imaging scopes fairly quickly. I m guessing that the dual mounting bar, ST80 and Equinox still weighs less than your 6" Newt plus guidescope and cameras. Do you think I would be OK or hit the Dec problem you mention?

I also wondered what your experience with the strip, clean and relube job was? How long did it take you and was it fairly straighforward or heart in mouth stuff?

old_eyes

[old_eyes]

I go between 15 and 30 mins. I have really good polar alignment and guiding, so I'm quite confident about longer subs, but there are two problems to consider with longer subs:

If you have a night with the occasional bit of cloud, it only takes one small one to reflect loads of LP for a few seconds and waste a single sub, if this a 30 min one it can be a right pain

The noise level in your images is directly related the number of exposures you have, the more the better. So with longer subs it gets harder and harder to get enough subs to keep the noise down to a reasonable level

I prefer 15 mins just now, but now I'm doing narrowband I will step this up to 20 mins

Thanks. Good advice. Now I need more clear nights with longer gaps between the clouds .

old_eyes

[Uranium235]

You will be fine with mounting the ST80 on top of (or at the side of) your equinox, with plenty of room to spare for cameras etc - as thats almost exactly what I use. In fact, you might find yourself having to use nose weights to keep it in balance (leg weights are great for this).

If at some point you can bodge together a 50mm finderguider (you should have got one with the equinox), you could even use your C6! With the advatage that you would never need to move your ST80 and wreck its alignment with the main scope.

The CG5 can hold 15kg max, and as long as you stay within 50% of that (7.5kg) you can use whatever scope you like without fear of dec backlash. Ive heard of people using a C8 with a finderguider on the cg5.... mmmmmm

But hold back on the dual mounting bar for the mo, theyre quite expensive. It would be much cheaper to get (or make) another dovetail bar, some adjustable guidescope rings and a couple of bolts. Mine are set up now so ive got the choice, will attach a couple of pics to illustrate... lol... along with homemade dovetail bar for a finder on the newt

1) ED80 + ST80: With cam and extras = about 6-7kg

2) 150p + Finderguider: With cam and extras about 6kg, but definitely lighter than the ED80/ST80.

[Euan]

I would tend to agree with the above, I mount my guide scope like this

I have a cracking side-by-side bar, but it added loads of weight and I have a feeling it adds to differential flexure with the two scopes being further apart. At least my movement between subs dropped when I took it off

[Uranium235]

I also wondered what your experience with the strip, clean and relube job was? How long did it take you and was it fairly straighforward or heart in mouth stuff?

old_eyes

Ah, I forgot about this. It was a case of having to do it properly because i didnt do it right the first time When people say "use superlube", its exactly what i should have used and nothing else (as i found out to my cost). But on a difficulty scale of 1-10, its a 3.

Im sure theres an online guide somewhere which takes you through a stripdown step by step... ah, here it is:

Astronomy Boy: CG-5 Mount Improvements

But, if it aint broke... dont fix it.

[old_eyes]

Thanks Uranium235 and euan for advice on side-by-side. I have one I acquired second hand to play with, so no additional cost.

I think I will set it up and see what it weighs. If reasonable, I'll give it a go and see what happens.

The differential flexure issue had occurred to me, but I guess the only way to find out is to suck it and see.

I like the idea of a 50mm finderscope on the C6 giving two permanent imaging rigs. That would then leave me only the widefield DSLR (say 200mm lens) to worry about, and I expect I could get subs long enough for a DSLR without guiding.

Damn me, one halfway decent picture and the man has gone mad!

That's the trouble with ths game; you have so much time to think comapred to time doing that you inevitable create wizzo (but possibly deeply impractical) schemes.

old_eyes

[simon84]

Excellent first image, really glad the Equinox is finally taking some pictures. Looks like you've got things working nicely. Well done matey. Cant wait to see some more images.

[Uranium235]

That would then leave me only the widefield DSLR (say 200mm lens) to worry about

If you use a 50mm finderguider, you should still have room to mount your widefield dslr on top of your tube rings, theres usually a mounting bolt on the rear ring. Then you can shoot both at the same time

[old_eyes]

Excellent first image, really glad the Equinox is finally taking some pictures. Looks like you've got things working nicely. Well done matey. Cant wait to see some more images.

I'll try and do it proud! Many thanks for the help.

old_eyes

[Glider]

I've used Uranium235's arrangements above ^^^^ plus finderguider on 200P with no problems.

[MikeWilson]

You will be fine with mounting the ST80 on top of (or at the side of) your equinox, with plenty of room to spare for cameras etc - as thats almost exactly what I use. In fact, you might find yourself having to use nose weights to keep it in balance (leg weights are great for this).

If at some point you can bodge together a 50mm finderguider (you should have got one with the equinox), you could even use your C6! With the advatage that you would never need to move your ST80 and wreck its alignment with the main scope.

The CG5 can hold 15kg max, and as long as you stay within 50% of that (7.5kg) you can use whatever scope you like without fear of dec backlash. Ive heard of people using a C8 with a finderguider on the cg5.... mmmmmm

But hold back on the dual mounting bar for the mo, theyre quite expensive. It would be much cheaper to get (or make) another dovetail bar, some adjustable guidescope rings and a couple of bolts. Mine are set up now so ive got the choice, will attach a couple of pics to illustrate... lol... along with homemade dovetail bar for a finder on the newt

1) ED80 + ST80: With cam and extras = about 6-7kg

2) 150p + Finderguider: With cam and extras about 6kg, but definitely lighter than the ED80/ST80.

Oh wow!

Sorry, I've just come across this thread and I too have a 150P and am looking to guide with a finderguider.

Please - if you have the time - could you elaborate on what finder you used and how you customised it for guiding?

I'm also looking at getting either the Skywatcher Synguider or the Baader/LVI standalone auto guider - but I assume that as long as the finderguider takes 1.25" eyepieces and can be focussed adequately, there's no issue with finding and tracking a guide star with a homebrew guider?