My scopes are too good. Help with guidance please

[Catanonia]

Let me explain.

I am using an Opticstar PL130m camera as guidance on a Skywatcher Pro II 80ED.

Now I have noticed that the regions I am looking into (galaxies and nebula) do not have bright is stars (mag 6 or above) around them and hence I am having amazing problems getting a guding star.

So a few questions please to those in the know.

1. Is my ED80 too tight a image to be able to guide properly with this camera unless a constellation star in FOV ?

2. Do you guys that guide use a wider field of view to pick a brighter star to guide on ?

I am guessing that my guidance is down to not finding a bright star in the ED80 FOV as it is too tight.

If I go to an area in the sky with a bright (ish) star in the FOV for the ED80, then guidance is no probs. Probably talking one of the stars in the standard constellations as a rough rule of thumb.

Any where else where one of these stars is not in the FOV the guidance with PHP fails always.

So 2 other questions.

1. Is my guide scope to narrow a FOV for the camera.

2. Why should it matter as long as the ED80 shows the stars? Surely the guidance camera should pick up the stars no matter what magnitude as the guidance camera is doing all the work presenting them to the camera nice and bright. ???

Confused and need some help. Really considering ditching the ed80 but don't want to as such a nice scope. But currently logic tells me it is not good for guidance for me unless I have a brightish star in FOV of it.

[Kai]

I would say that your scope is fine (just look at the amount of images taken with a 80mm scope) but your guide camera is not sensitive enough.

Is the scope mounted in guide rings or is it piggybacked ?

If its in guide rings then just adjust the scope until it points towards a brighter star.

[blinky]

I use and ED80 as well as a ZS66 (66mm apreture) and have no problems finding guide stars at all with a Meade DSI Camera. I assume as does Kai that it must be the guide cam not being sensitive enough but I am surprised as that cam is sold as a guide cam.

[jgs001]

I've had an issue with locking guidestars in my ST80 with DSI, it turned out that I hadn't nailed focus, and the stars were too blobby. I wonder if you need to ensure you have the focus nailed down as best as possible. And the reason you're only seeing the real bright ones is they blob into view when a little out of focus, but the fainter ones you're wanting to use, just can't be made out. I don't know that camera (hell, I barely know the DSI), but it's worth checking in the camera software for a focus assistance option and use that.

[Psychobilly]

I guide with a 500mm f8 telephoto lens and DSI II c no problems finding guidestars never as yet failed to find one with exposures of less than 3s normally only need to use 1s exposures... Never had to offset the guidescope so now its ridgidly fixed...

I would think about trying a decent guidecam...

Use a focus mask to nail focus ... I normally ever so slightly defocus the guidescope but just a smidge...

Peter...

[Aza]

There is no problem with your scope!

Like has been said:

Check your focus is spot on

Use guide rings so you can move the scope a little if needed

Failing that get a better guide cam

It also depends on your target, I cant seem to frame M51 in the centre of my cameras FOV because I cant get a guide star. Some areas of the sky a more 'barren' than others

[moondog]

Checking on the Opticstar website it says your camera is a 'Planetary - Video Camera'. For Solar System objects Opticstar give the camera 5 stars and for Deep Sky only 1 star. This probably indicates that the camera is not particularly sensitive. Although it does say that the camera is suitable for guiding.

As a few people have said make sure you nail the focus of the guide cam. I've often thought that I couldn't find a guide star, but after a few attempts focussing a few have appeared. Also your problem may be the bright night sky at the moment - it makes faint stars even fainter. I sometimes use my SW ED80 as a guide scope with my QHY5 guide cam and the scope works well.

Hope you sort it soon

MD

[beamish]

just to add my 2c worth, I'm guiding using a 50mm finder, around F7/8 and still have never failed to find a guide star. The pertinent points have been covered, focus and lack of sensitivity in your cam-scopes are fine mate !

[Catanonia]

Thanks guys, for the last 2 sessions it has been doing my head in.

Most of the time messing with the guide camera.

I now tend to point to a brightish star, set guide cam to that and focus and then move to the target and spend ages changing very little amounts of focus to try and get a guide.

The guide scope ED80 is piggy backed and rigid to the ED120 so moving its aim is not an option yet.

I am beginning to think this camera sucks as a guide camera as I only manage to actually use it as such about 10% of the time.

Also the image in php seems to jump all over the place.

For example.

I am perfectly focused on M81 and I get some stars on php. But php say no star..... even though I can clearly see stars on the php screen. The every other frame the php screen will change to a completely different star field !!!!!!

No idea what is happening, all this on 4 second loops and dark taken.

I am going to give this guide camera 1 last go before I give it back to opticstar as it was sold as a guide solution and just doesn't work 90% of the time.

[Ant]

Try altering the Gamma setting on the guide cam. On the DMK it was full of noise and had trouble telling what was a star untill I lowered the gamma.

Also make sure that you click on the "brain" and put tick in "force Calibration" box. This will force PHD to calibrate each and every time you click on the guide button.

It add's a little time (maybe a minute or two), but without doing that PHD often loses the guide star completely with a few sections.

The ED80 is absolutely spot on as a guide scope.

Ant

[Beyond_Vision]

You may find that you are trying to select a 'hot' pixel and not a star. If a hot pixel is selected it will fail to calibrate.

[beamish]

Kev, would that be resolved thru doing a "dark" in PHD ??

[Catanonia]

Kev, would that be resolved thru doing a "dark" in PHD ??

I am taking the dark and then trying to guide with the same loop rate. It is getting rather annoying.

The camera works fine in daylight on distant trees, works fine if I focus on a bright constellation star, but when I try deep space, I can see random star patterns happening on the PHD even after the dark is taken.

To make it easier to explain

Imagine seeing the outline of Orion for 4 seconds, then a totally different star pattern, then orion again for a bit longer etc etc.

It is very wierd. I will try the gamma changes and see if that makes any difference.

[Ant]

What sort of exposures are you using...?

I use the QHY5 and DMK21 to guide with (whichever one I pick up first from the case). The exposures are usually 0.3 - 2 seconds depending on the brightness of the stars.

I have never failed to find a guide star (ever) with the ED80.

Cheers

Ant

[Catanonia]

Exposures of 4 seconds on the PL130m guide camera through PHD. Take the dark and then set the exposure loop.

[Milamber]

You may find that you are trying to select a 'hot' pixel and not a star. If a hot pixel is selected it will fail to calibrate.

Yup - have to agree here, either that or noise... especially given:

Imagine seeing the outline of Orion for 4 seconds, then a totally different star pattern, then orion again for a bit longer etc etc.

[Tim]

Forget the PL 130 for guiding, use it for lunar and planetary work where you will be pleased with the quality.

get a guidecam with an exview HAD chip, they are many times more sensitive. I use a DSI like many others. I also own a pl 130.

[blinky]

I think you should return it though, if it was sold as a guide cam and cannot find any stars then it's no good!