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martin_veasey

Guiding using NexImage 5 (and PHD2) ?

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I'm happy enough using my NexImage 5 for planetary photography - my images aren't as good as some that I've seen here taken with the same camera but I'm learning fast.

I would, however, like to guide my scope Skywatcher 200p with the NI5 through an Orion 50mm Guide Scope for longer exposure DSOs with a DSLR.

My problem is that I just can't get candidate stars up on PHD2 (or indeed on iCap) under the settings / focus that I'm using. The screen generally looks much like the attached image :

post-38267-0-41777300-1452340167_thumb.j

This is, I presume, just noise coming from running the NI5 on 1 second exposures but surely I should also be seeing stars on the settings I am running: 1s exposure, gain of roughly 60, PHD2 looping over 3-5sec? I get much the same running the camera through the Orion and, indeed, through the main eyepiece on the OTA.

I know that the NI5 is hardly the most sensitive camera available - I am tempted to either get an ASI120MC or QHY5L-II Colour (opinions on which would be welcome, though I am veering to the ASI) - but I'm wary about spending money without being sure that I know that I'm doing the best out of existing kit and that the upgrade will therefore fix the issue.

Does anyone here have any experience of the NI5 in this area and/or any good ideas for things to check?

Cheers,

Martin

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Hi,

The NI5 is not really a guide camera, it is as you know for planetary imaging, so maybe it is just not sensitive enough ??

If you try three second exposures and are still not getting any stars then I would guess it is down to sensitivity.

But others on here with more knowledge than me will surely get involved

:)

AB

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I have also just noticed that your camera setting and PHD are different, you do,raise that you must control the camera for guiding through PHD and not the native camera software, you need to have the correct drivers loaded for PHD to be ab,e to control the guide camera.

You say that PHD is looping over 3-5 seconds, but that is the camera exposure, you have it set on 3 secs in the image you show?? Which is the exposure that PHD had set for the camera...

You need to select your camera from the drop down menu in PHD and select the correct driver, have you done all this first ??

As for a good guide camera then the lodestar is the best and they come up second hand for around £230 from time to time.

:)

AB

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I have also just noticed that your camera setting and PHD are different, you do,raise that you must control the camera for guiding through PHD and not the native camera software, you need to have the correct drivers loaded for PHD to be ab,e to control the guide camera.

You say that PHD is looping over 3-5 seconds, but that is the camera exposure, you have it set on 3 secs in the image you show?? Which is the exposure that PHD had set for the camera...

You need to select your camera from the drop down menu in PHD and select the correct driver, have you done all this first ??

As for a good guide camera then the lodestar is the best and they come up second hand for around £230 from time to time.

:)

AB

Thanks AstroBoffin, that's really helpful.

I have the camera setup under the WDM Webcam driver in USB2, which I believe should be OK.

There is a difference between the time settings in the two parts of my capture.

1) The dialog box is the camera's own view of its settings - its also accessible via other programs such as the iCap program provided by Celestron with the camera. It's showing individual the camera's taking individual subs of 1 second each - which is high compared to (say) a 1/20 second for exposing Jupiter (but necessary to pull light in)

2) The PHD2 setting of 3 seconds at the bottom of the screen is, I believe, more to do with the frequency of refresh that the program uses so as not to react to transitory changes in the setup. My understanding is that PHD2 stacks sufficient subs together to make up the refresh interval, so 3 x 1sec over 3 sec. If the camera was more sensitive, I guess we could stack (perhaps) 6 x 0.5sec or 12 x 0.25sec

However, I don't think its PHD2 that is causing my problem, I can't get stars to show in Celestron's own iCap software. I don't think its a specific camera breakage (it works fine for Jupiter), so its likely down to a failure of comprehension / process on my part or perhaps the NI5 just isn't the right camera for the job.

I'll take a look at the Lodestar.

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Hi,

Well I am not sure what you are saying there, but I use PHD all the time, you should select your camera from the drop down list and then connect, then the camera for guiding is all controlled from within PHD, that number 3.0 at the bottom of the PHD screen is the exposure length that PHD has for the camera, you can set that to what you want, it is not anything to do with a refresh as you put it...!!

It is simply the exposure length.

If your camera is not capable of long exposures say above 0.5 seconds, then you can still set it to 3.0 seconds and it will just show a new image every 3.0 seconds, (or is that what you mean by refresh ?) but here is your problem, you need a camera that CAN take longer exposures for guiding to be successful.

I don't really think that camera will be up to the job of guiding, it is really a planetary cam.

:)

AB

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Hi,

Well I am not sure what you are saying there, but I use PHD all the time, you should select your camera from the drop down list and then connect, then the camera for guiding is all controlled from within PHD, that number 3.0 at the bottom of the PHD screen is the exposure length that PHD has for the camera, you can set that to what you want, it is not anything to do with a refresh as you put it...!!

It is simply the exposure length.

If your camera is not capable of long exposures say above 0.5 seconds, then you can still set it to 3.0 seconds and it will just show a new image every 3.0 seconds, (or is that what you mean by refresh ?) but here is your problem, you need a camera that CAN take longer exposures for guiding to be successful.

I don't really think that camera will be up to the job of guiding, it is really a planetary cam.

:)

AB

Thanks for getting back - I believe that you're right about the refresh in general. In the case of the Webcam dropdown, the driver does - I think - stack shorter exposures into the 3.0 sec window.

Oddly, the NI5 is claimed to be capable of multi-second exposures but I think the thermal noise catches up with you rather quickly ... best to dig in the wallet, I think, as I sounds like I'm not doing something intrinsically silly.

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I wonder whether this camera is really up to guiding and you may be making a rod for your own back.  You really need quite a sensitive camera for guiding with a finderscope because you can't manipulate the finderscope to find a suitable guidestar (well not much), and unless your camera can see very faint stars you'll sometimes find there isn't a guide star in the FOV.  

Lots of people rate the lodestar but it is expensive, and it has cable connection issues - at least some of the older ones did - perhaps they've fixed it with the newer ones, but you're likely to get an older one if you buy second hand.  

I have used a QHY5 for years now and use a finderguider and have never had a problem finding a guide star, and it comes in new less than a Lodestar would 2nd hand.

HTH

Carole 

Edited by carastro
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Good advice by Carole,

The newer lodestars have a new guide cable connector, so think they are ok now.

But there was a full guide set up on Astro buy sell a couple of days ago and in the classifieds on here, consisting of a finder and QHY guide camera for £100, that would be what Carole is talking about, and would be ideal.

:)

AB

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I see he doesn't have enough posts, I know he can't advertise, but will he be able to view the classifieds......I am not sure...

AB

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Just a note on the older Lodestar cable issue, i run one but use Pulse Guiding so it only has the USB cable connected, EQMod does the pulse guiding with PHD, I'm not about to try to explain how, but its mentioned in the EQMod help file...it does work with my ST-80/Lodestar very well.....

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Just a note on the older Lodestar cable issue, i run one but use Pulse Guiding so it only has the USB cable connected, EQMod does the pulse guiding with PHD, I'm not about to try to explain how, but its mentioned in the EQMod help file...it does work with my ST-80/Lodestar very well.....

Good point, Same here I don't use the guide port on my lodestar either, I find pulse guiding to be better for my older Meade LX90, and as it works well I am reluctant to try anything else to be honest, also one less cable to worry about.

AB

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What resolution are you trying to guide at ? The Neximage 5 has small pixels (2.2 micron) which will probably be not sensitive enough for guiding. The camera has the option to set the resolution to 640x480 (binned) which might increase the sensitivity.

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I see he doesn't have enough posts, I know he can't advertise, but will he be able to view the classifieds......I am not sure...

AB

Sadly not - 50 posts to read and 250 posts to post ...

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What resolution are you trying to guide at ? The Neximage 5 has small pixels (2.2 micron) which will probably be not sensitive enough for guiding. The camera has the option to set the resolution to 640x480 (binned) which might increase the sensitivity.

It has, on occasion, worked at 640x480 but I'm assuming this was only for the brighter stars ...

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Thanks for the steer on this. Time for some comparative research on a better solution !

Thanks again to all who helped. I've now got an ASI120MC and its working well on guiding with PHD2 settings almost "out-of-the-box" (I had to back the aggressiveness down a bit).

Now to work on fine-tuning.

Clear skies everyone.

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