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  #21  
Old 01-01-2014, 04:46 PM
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Originally Posted by gregbradley View Post
That's great Paul. It sounds like you have great conditions. I know you are an expert in seeing from your planetary experience where its everything.

Of course guide errors are much smaller when using a short focal length. Longer focal length shows up errors much better. You see smaller guide errors with shorter focal length scopes.

I am not sure about this seeing measurement myself. FWHM seem to be a guide only. Good seeing is easily seen in the image given good focusing. I think that is one of the main criteria for measuring. FWHM values vary significantly in the same image on different stars. At least using CCDstack. So I don't know how anyone can come up with a FWHM number that is meaningful as it is more a variable than a fixed item.

Greg.
Hi Greg,

You can always tell the nights of good seeing. The auto guider image doesn't jump about all over the place. I usually sit at the computer watching the guide errors to estimate the seeing. If they rarely go above 0.5, it's the best seeing I can remember, probably only happened once or twice, sometimes the maximum guide errors are about 1, but usually they go out to 1.5, which means I have about 3" p-p, what I expect from suburban Melbourne.

Cheers
Stuart
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  #22  
Old 01-01-2014, 05:03 PM
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I do the same Stuart - I enjoy watching MaxIM the most, since you can zoom right in on the guide star. Nights where the star does not even move make me smile. I have had a few like that. Other nights, even in MaxIM's STRONG guiding, I can see the star dance and jiggle - and a 10 minute sub can take 12 to 13 as it pauses the exposure while the guider settles again (I LOVE MaIM BTW)

PHD is good, but it doesn't do what MaxIM does - but considering the price differential, it's a no brainer
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  #23  
Old 01-01-2014, 08:47 PM
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Originally Posted by strongmanmike View Post
You really get sub arc sec seeing??? You sure? Do you mean sub arc sec seeing for moments or for extended periods? Sub arc sec seeing for extended periods is the stuff of places like La Palma/Cerre Tololo etc...? Even Siding Spring rarely gets sub arc sec seeing

The tracking looks good though

Mike
That's a good question. 5 years ago when I bought the property the society's instrument officer tested the seeing conditions at Clayton with a DIMM. The readings showed that seeing peaked around 0.7 and mean values were around 0.9-1.0 arc. That night from my own experience was about average for Clayton. The seeing comes and goes but we get long sessions when the seeing is good. Anyone who has been there and either images or done viewing there can attest to the still conditions on many nights. I urge you all to buy property there as many blocks are for sale. And; having a bunch of observatories there will help to maintain the dark sky lighting limits.

The down side of course is the amount of cloud we get there due to the proximity to the southern ocean.

There are other sites around Australia such as Exmouth where seeing values are the same ir better. Damien Peach lives in Selsey which also has exceptional seeing. So good seeing at sea level is not out of the ordinary.
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  #24  
Old 02-01-2014, 09:59 AM
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Originally Posted by rat156 View Post
Hi Greg,

You can always tell the nights of good seeing. The auto guider image doesn't jump about all over the place. I usually sit at the computer watching the guide errors to estimate the seeing. If they rarely go above 0.5, it's the best seeing I can remember, probably only happened once or twice, sometimes the maximum guide errors are about 1, but usually they go out to 1.5, which means I have about 3" p-p, what I expect from suburban Melbourne.

Cheers
Stuart
Yes I do the same. I like to see the guide errors before I walk away and let the scope do its thing. It varies with setups but at about 1260mm focal length at my dark site I would see errors of about .1 to .9 with about .3 being the average. Sometimes it is lower and that would be seeing. You see it in the images though quite easily at long focal length. On bad seeing nights I can't even focus my CDK17 as one image can seem in focus the next with no change is out of focus.

1.5 errors would be too high on my setups and locations. When it starts averaging 1 its getting a bit rough and .4 to .5 is usual for the CDK at 3 metres on a PME (which seems a bit better than the PMX - not much but about 25% better) and .3 average for the TEC180. AP140 widerfield is usually around .25 average guide error on a PMX.

Paul, that is a very valuable location you've got there. What sort of percentage of nights are clouded out?

My dark site has a fairly high percentage of clear nights but occassionally plagued with wind of around 20kts. That's ok for a small refractor but not anything else.

Greg.
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  #25  
Old 02-01-2014, 03:30 PM
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Originally Posted by gregbradley View Post
Paul, that is a very valuable location you've got there. What sort of percentage of nights are clouded out?

My dark site has a fairly high percentage of clear nights but occassionally plagued with wind of around 20kts. That's ok for a small refractor but not anything else.

Greg.
Rarely have wind there. Lots of nights of the year you can hear the ocean crashing into the beach and that is 6kms away. It gets that still there. Rarely is there any scintillation of the stars, sometimes near the horizon but almost never at the zenith.

Cloud cover is around 40% of nights on average. The high pressures come in and sit in the bight and can sometimes bring clouds in a constant stream, but as you can see this last year I have achieved quite a few images (nearly 12) and most of those are mega data. So there is still plenty of nights to capture data.
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Old 02-01-2014, 03:51 PM
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Originally Posted by LewisM View Post
I do the same Stuart - I enjoy watching MaxIM the most, since you can zoom right in on the guide star. Nights where the star does not even move make me smile. I have had a few like that. Other nights, even in MaxIM's STRONG guiding, I can see the star dance and jiggle - and a 10 minute sub can take 12 to 13 as it pauses the exposure while the guider settles again (I LOVE MaIM BTW)

PHD is good, but it doesn't do what MaxIM does - but considering the price differential, it's a no brainer

Hi Lewis,

"pausing the exposure"

I didn't know cameras could do that.
Can my QHY9 pause an exposure & then continue the rest of the sub frame when the guiding has settled?

cheers
Allan
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  #27  
Old 02-01-2014, 04:26 PM
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Lewis is talking about the ability to set guider settle criteria in Maxim. It doesn't really pause the exposure. It just doesn't start it until the guide corrections get below a configured limit.

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Originally Posted by alpal View Post
Hi Lewis,

"pausing the exposure"

I didn't know cameras could do that.
Can my QHY9 pause an exposure & then continue the rest of the sub frame when the guiding has settled?

cheers
Allan
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  #28  
Old 02-01-2014, 05:25 PM
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Originally Posted by Paul Haese View Post
That's a good question. 5 years ago when I bought the property the society's instrument officer tested the seeing conditions at Clayton with a DIMM. The readings showed that seeing peaked around 0.7 and mean values were around 0.9-1.0 arc. That night from my own experience was about average for Clayton. The seeing comes and goes but we get long sessions when the seeing is good. Anyone who has been there and either images or done viewing there can attest to the still conditions on many nights. I urge you all to buy property there as many blocks are for sale. And; having a bunch of observatories there will help to maintain the dark sky lighting limits.

The down side of course is the amount of cloud we get there due to the proximity to the southern ocean.

There are other sites around Australia such as Exmouth where seeing values are the same ir better. Damien Peach lives in Selsey which also has exceptional seeing. So good seeing at sea level is not out of the ordinary.
I'm a bit wary Paul, smack me if you like . SRO (sierra remote OBS, 4610 ft) has the best amature seeing I know, and they are chuffed with 1arc secs tops. Siding Spring can't touch that. Could you now rescale your guiding graph to arc secs, seems fair
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  #29  
Old 02-01-2014, 06:28 PM
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I'm a bit wary Paul, smack me if you like . SRO (sierra remote OBS, 4610 ft) has the best amature seeing I know, and they are chuffed with 1arc secs tops. Siding Spring can't touch that. Could you now rescale your guiding graph to arc secs, seems fair
Hmm?..what was it again Paul?..."looks like a case of averted imagination to me"

....just kidding, I am certain your seeing is better than mine

Mike
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  #30  
Old 02-01-2014, 07:06 PM
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Lewis is talking about the ability to set guider settle criteria in Maxim. It doesn't really pause the exposure. It just doesn't start it until the guide corrections get below a configured limit.

Same as CCDsoft with its min/maximum move. You set the minimum an error has to be for it to issue a correction and conversely the highest error to allow it to issue a correction.

I usually set max to 3 and min to .1

Greg.
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  #31  
Old 02-01-2014, 08:13 PM
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Same as CCDsoft with its min/maximum move. You set the minimum an error has to be for it to issue a correction and conversely the highest error to allow it to issue a correction.

I usually set max to 3 and min to .1

Greg.
Greg: Maxim has min/max move as well. Guider settle criteria are different and are only used to wait until guiding settles down after dithering between exposures.
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  #32  
Old 02-01-2014, 09:14 PM
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Originally Posted by Logieberra View Post
Paul, have you toyed with the idea of using direct guide of your paramounts via TheSkyX? Just wondering why Maxim. A case of, works well, ain't broke so don't fix it?
Just ever so briefly investigated this Logan, and as yet not used SkyX on the PME. I have been using the SkyX on the PMX and bug testing to get the whole thing sorted on the dome before transferring the SkyX to the roll off roof. In time though I will look at direct guide. For now I was just going with what I know works. Mind you on the PMX and dome I am only at the point of doing focusmax. PA is completed or very close to perfection and I don't intend just yet on doing any more modelling work to improve the pointing and PA. Maybe next full moon I will look at that, but focusmax was pointing well the other night with acquire star, however I discovered that the adapter I had made up between the focusor and the camera is in fact too long by 4mm. Since the atlas only has 10mm of travel; focus is around 2mm from totally in at present. Anyway that is entirely another story. I can once I get that sorted move onto direct guide if that will work with CCDAP5.
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  #33  
Old 03-01-2014, 08:17 AM
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Using direct guide is nothing Paul. You simply set it to direct guide in the autoguiding tab in CCDsoft. That's it. If you are using some other software then I am not sure. Its not a big deal. It gets rid of the autoguider USB cable so its one less cable. I have read it is better but haven't done any testing to know if that's true or not. It sounds like its more direct so anything that gets rid of a via is going to be better generally speaking.

Greg.
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  #34  
Old 07-01-2014, 09:35 PM
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The seeing in Canberra lets me down here I think. Last night was the best I've seen in a long while, but nowhere near the envious flat line you have Paul. I think maybe AO might help here, then again so would a lot of $$$!

Does anyone know where I can get a grant to do this stuff?
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  #35  
Old 07-01-2014, 10:15 PM
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The seeing in Canberra lets me down here I think. Last night was the best I've seen in a long while, but nowhere near the envious flat line you have Paul. I think maybe AO might help here, then again so would a lot of $$$!

Does anyone know where I can get a grant to do this stuff?
Mate, that looks pretty good if you're guiding through an OAG with the C9.25. Looks very much like mine, only I have probably half the focal length (therefore half the image scale).

Cheers
Stuart
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  #36  
Old 08-01-2014, 09:27 AM
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In time though I will look at direct guide. For now I was just going with what I know works.
Paul, I'm using direct guide - gives me excellent results but I've also used PHD with great results. Either way, whatever works.
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  #37  
Old 08-01-2014, 10:54 AM
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Using the ST-I with an OAG on a system at 580mm at f5.6. I think that is somewhere around 1.89" per pixel or close to that. The later figure is the scale of the QSI/ TSA with reducer.
Hi Paul,

Thanks for providing that, always good to see what conditions others face.
In order to compare I calculated that your ST-i give a resolution of 2.63"/pixel at 580mm (assuming you guide unbinned) and RMS of 0.106 is then 0.28". That's actually very similar to mine which is around 0.25"-0.30" on good nights.
However, I don't think my loaction is exceptional and here FWHM is hovering around 2" on the best nights. Are you sure you really have sub arc second seeing? Not saying that you don't but it sounds extreme and in that case I would have expected much smaller RMS at your location.

Cheers,
Rolf
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Old 08-01-2014, 12:04 PM
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Hi Paul,

Thanks for providing that, always good to see what conditions others face.
In order to compare I calculated that your ST-i give a resolution of 2.63"/pixel at 580mm (assuming you guide unbinned) and RMS of 0.106 is then 0.28". That's actually very similar to mine which is around 0.25"-0.30" on good nights.
However, I don't think my loaction is exceptional and here FWHM is hovering around 2" on the best nights. Are you sure you really have sub arc second seeing? Not saying that you don't but it sounds extreme and in that case I would have expected much smaller RMS at your location.

Cheers,
Rolf
Rolf I can only go by the readings I was told and by my own experience here. Planetary imaging here is pretty good to exceptional. At focal lengths of around 11-12 meters the seeing can often be very still here. My only Saturn image last year was taken from Clayton, and I only needed to take one lot of data to satisfy my want to get a great image .My previous Saturn shot was the year before and the seeing that night was very good but a night before the seeing had been truly exceptional. I did not image Saturn that night but kicked myself later for not taking data. My Mars shots from 2012 were taken from Clayton too when it was just 13 arc seconds in diameter. The beauty is that seeing is so good that I only need to take a few nights or in the case of Saturn one night to get the shot I am looking for. You cannot do great planetary images unless the seeing is approaching sub arc seeing. Yes the software is very good but you cannot make great images from average data in planetary. Just a small amount of blurring is enough to reduce the data to an average looking image.

I think I am currently running binning 2x2 on this STi. That makes it 5.15 arc seconds per pixel, but I don't know if that makes the calculations better or worse. I am assuming better; to make it 1x1 I divided the RMS by 2 and get a figure of 0.14, but I could be completely wrong here. Feel free to correct me here if I am wrong. Certainly interested to know how the calculation works.

All I know is my shots with the TSA here are very sharp coming out of the camera and I never use decon at all. I use some subtle selective sharpening on my final image sets, but not a lot. I don't think the scope has exceptional optics (good for sure) and I have to put the quality of the image sharpness down the seeing conditions. The mount I am using is certainly a factor in this too.

I have also noted in the last month that the images seem slightly sharper now since changing over to full robo focus. I was using the MHP to control the focusor but now am using the Robofocus module to totally control focusing. The images have picked up a little in sharpness, but again it could simply be some better seeing conditions and transparency. Nothing else has changed

In any event I think I will have to get the instrument officer back here to do some more tests. The 36" scope the society is building needs to be housed in a spot of good seeing and hence why testing was performed here. It will be certainly interesting. I know the Freeling tests in the Flinders outperformed Siding Springs by a significant factor and the only real reason why the telescope was not built there was due to remoteness of the location at the time. Yes that is 700km away from here but Freeling gets laminar seeing just like here.

I think this is certainly an interesting debate and welcome others experience. Excellent guiding can be dictated by a lot of factors such as mount, stability of pier, flexure and settings as well as seeing. I am certain though I have good seeing here and that it is far better than two arc seconds on many nights. Feel free to comment guys.
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  #39  
Old 08-01-2014, 12:16 PM
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From how you describe it sounds like you have exceptional seeing. My seeing here is good to excellent I would describe. However its a bit subjective. On a usual winter night there is usually no star scintalltion above about 20 degrees or minimal. Even in summer I had that on several nights.

What wrecks it though is wind. If there is wind star scintillation picks up noticeably.

I would describe my dark site as being way above average in darkness, and above average in seeing but not like you describe. I have seen it though.

One early morning I looked at Jupiter through a Tak FS152 scope and thought at the time it was remarkably still. I think that was what you would describe as superb seeing. That was around 3am or so.

It would be nice to experience exceptional seeing so you have a reference point subjectively to compare it to other conditions.

I certainly know the CDK17 will show up the seeing very clearly and when the seeing is good the images are very noticeably sharper and tighter.

Greg.
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Old 08-01-2014, 02:40 PM
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Hi Paul, it is certainly an interesting debate. I have often wondered how the conditions rate at my site, but there is not much to compare with as these things are not discussed often.
Your guiding graph is very helpful in that regard. I have calculated the numbers for our respective guiding systems as follows:

Camera: ST-1
Pixel size (microns): 7.4
Binning: 2
Focal length (mm): 580
Resolution ("): 5.26
RMS (pixels): 0.106
RMS ("): 0.56

Camera: Lodestar
Pixel size (microns): 8.2
Binning: 2
Focal length (mm): 1273
Resolution ("): 2.65
RMS (pixels): 0.100
RMS ("): 0.27

I changed binning to 2x2 and as a result your RMS of 0.106 now corresponds to 0.5" (so twice as high as I thought, had it been 1x1).

I would think that if you do have sub-arcsecond seeing but your guider resolution is 5.26"/pixel then you might not be getting the full advantage of it? I don't know though since guiding works on a sub-pixel scale. But based on these numbers I'm actually thinking of going to 1x1 binning on my guider. I only bin to get higher sensitivity, but when the guide star is bright enough I'll try 1x1 instead - it's worth a try at least.

When speaking of seeing I consider this to be measured as FWHM over a certain period of time. That is what determines the final resolution of a deep sky image, which must be what we care about. For deep sky purposes FWHM must be measured with exposures equal to or greater than the guiding frequency. I'd say planetary imaging is different because exposures are a lot shorter and as a result of lucky imaging much finer detail can be picked up. I have taken planet images with the ToUCam that show much better resolution than the ~2" I get with longer deep sky exposures.

I'd be interested to know your FWHM's on typical deep sky exposures, are they sub 1"? If they are then you could comfortably be imaging at an image scale of say 0.3-0.5"/pixel (Nyqvist sampling) and take absolute killer images in terms of resolution.
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