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New ZWO camera with built in guide chip?


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3 hours ago, Colin Haig said:

That made me chuckle.  Santa Barbara Instrument Group literally invented self-guiding cameras and patented the idea back in the late 1990's.

They were immensely popular - the ST-7 was the first in a long line of many self-guiding cameras.  This went on through to the STL-series with larger sensors and larger guide chips, and then on through to the late 2000's when narrowband filters became popular with the rise of light pollution and the reduction in manufacturing costs of the coating technology to make these interference based filters.  Eventually SBIG and later Diffraction Limited (the owners of SBIG since 2014) developed self-guiding filter wheels, so that the guide sensor was ahead of the filters, allowing for more guide star choices.

Apologies, I have a big gap in my Astro digital imaging knowledge, having only got back into the hobby in 2014. I am surprised that there has been virtually no mention of them on this forum since that time, but SBIG cameras don’t seem that popular in the UK. That’s a pity, because they were the real pioneers of digital imaging. I purchased one of the first ST-4 guiders in the UK back in 1990,  I know this because I got a call from SBIG shortly after delivery asking me if I wanted to be the UK agent for them!

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Interesting use case that I've been thinking about, rather than considering it as a guide chip on your main imaging scope, think of it as an imaging chip added to your guide scope (admittedely a bit expensive for a guide camera!)

This way you can image widefield thorugh your guide scope assuming it's good enough to cover the asp-c chip. Something like a zenithstar 61 or similar, probably not the evoguide 50ED.

On 09/05/2023 at 19:06, tomato said:

Apologies, I have a big gap in my Astro digital imaging knowledge, having only got back into the hobby in 2014. I am surprised that there has been virtually no mention of them on this forum since that time, but SBIG cameras don’t seem that popular in the UK. That’s a pity, because they were the real pioneers of digital imaging. I purchased one of the first ST-4 guiders in the UK back in 1990,  I know this because I got a call from SBIG shortly after delivery asking me if I wanted to be the UK agent for them!

They were not competitive on price in the UK for as long as I've been interested in photography, there aren't any UK dealers anymore as far as I can see.

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36 minutes ago, SamAndrew said:

Interesting use case that I've been thinking about, rather than considering it as a guide chip on your main imaging scope, think of it as an imaging chip added to your guide scope (admittedely a bit expensive for a guide camera!)

This way you can image widefield thorugh your guide scope assuming it's good enough to cover the asp-c chip. Something like a zenithstar 61 or similar, probably not the evoguide 50ED.

They were not competitive on price in the UK for as long as I've been interested in photography, there aren't any UK dealers anymore as far as I can see.

Yes, Ian King used to stock them but FLO didn’t pick them up when he moved over to them.

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On 12/05/2023 at 16:12, SamAndrew said:

Interesting use case that I've been thinking about, rather than considering it as a guide chip on your main imaging scope, think of it as an imaging chip added to your guide scope (admittedely a bit expensive for a guide camera!)

This way you can image widefield thorugh your guide scope assuming it's good enough to cover the asp-c chip. Something like a zenithstar 61 or similar, probably not the evoguide 50ED.

 

I am really not sure about this idea, I'm either missing something or it doesn't work the way you think.

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  • 5 weeks later...

Hi, Guys,

Very interesting...

From the above tests it looks very promising.  I owned a SBIG ST10 XME some years ago.   Very sensitive, the built in guide chip worked very well, even not too bad narrowband with careful selection of the guide star.  Prone to blooming, and when the QSI 683wsg came along with its built in filter wheel and off axis guider, I 'upgraded' to that in 2012, and still happily use it.  A lot of comment about imaging circles etc., so I thought this might be useful.  The attached image is a Skymap framing for both cameras at 2000 mm focal length (f8, but I have no problems with my f6.2 TMB105 refractor).  I use a 42 mm thread attachment, and have no guide star problems with any of my telescopes.  Of course my guide pick off prism is in front of the filter wheel, so 1.75" (44.5mm) ahead of the main sensor, and in a slightly better position in the light cone.  But as I say using a 42 mm adaptor with no problems.  So very positive for the Asi Duo.

Cheers,

Peter.

Framing.jpg

Edited by petevasey
Corrected typos
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There's no monochrome version shown on the ZWO web site.  Anyway, if you watch the 'First light results' video above, it would seem that the guide chip is sensitive enough to do well even with 3nm filters.

There is as always a caveat with a fixed guide chip, either off-axis as in my case or part of the camera as in this case.  A suitable guide star is not always available without rotating the camera, sometimes quite a bit.  But for me the advantages of off-axis guiding far outweigh the disadvantages.

Cheers,

Peter.

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  • 4 months later...

What a great idea! How come no other camera manufacturers thought if this? 

I'm slightly puzzled by all the comments like "but will this guide through narrowband filters?" - How is that any different from using an OAG? I use an OAG on the back of my 2600MC Pro for almost all my imaging and I generally use an L Extreme filter. My guiding is just fine, so I can't really see why there would be a problem with this new Duo.

A larger concern for me would be the image circle, as the guide chip looks a little further from the centre than my prism is. Need to check that.

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1 hour ago, StuartT said:

How come no other camera manufacturers thought if this? 

SBIG did and they held the patent for a decade. They must have asked for a fortune in royalty. Unfortunately sensor tech was not as sensitive or advanced as it is today and it did not work well if at all.

That's probably why you did not see it elsewhere.

It differs from OAG in a sense that the filters come after OAG in the imaging train. With duo filters are in front.

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1 hour ago, StuartT said:

What a great idea! How come no other camera manufacturers thought if this? 

I'm slightly puzzled by all the comments like "but will this guide through narrowband filters?" - How is that any different from using an OAG? I use an OAG on the back of my 2600MC Pro for almost all my imaging and I generally use an L Extreme filter. My guiding is just fine, so I can't really see why there would be a problem with this new Duo.

A larger concern for me would be the image circle, as the guide chip looks a little further from the centre than my prism is. Need to check that.

As mentioned above, SBIG did it years ago.

The filter problem arises because the guide chip is in the same plane as the imaging chip, so any filters in front of the camera are also in front of the guide chip, and narrowband filters considerably reduce the signal level.  I'd be very surprised if your OAG is behind your L Extreme filter, i.e. on the camera side of the filter.   Even if it is on the camera side, because the filter has two transmission peaks, it is letting through twice as much light as a single narrow band filter.

The image circle isn't too bad, in fact it'sonly slightly more than the built in off-axis unit on my QSI 683.  See my June 19th post in this thread.

Cheers,

Peter

Edited by petevasey
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On 09/12/2023 at 13:05, Dark Raven said:

It differs from OAG in a sense that the filters come after OAG in the imaging train. With duo filters are in front.

Not in my setup. The Esprit has the filter screwed into the focuser, then OAG then the camera. In fact, I'm not sure how it could be otherwise as the OAG is actually mounted on to the camera.   

On 09/12/2023 at 13:06, petevasey said:

I'd be very surprised if your OAG is behind your L Extreme filter, i.e. on the camera side of the filter.  

Again, I am not sure how it could be otherwise with an OAG? (see photo) Where would the filter go if not in front of the OAG?

15-connect-with-2600.jpg

As for the image circle the Duo requires, I make this 41.5mm which is fine for my Esprit at full FL which has 44mm

image.png.62d1000da8f73ddc5e090e2022717f4a.png

Edited by StuartT
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21 hours ago, StuartT said:

Not in my setup.

That is suboptimal position and you are loosing a lot of light for the OAG camera.

See proper positioning here: 5. Using OAG-L and 2” EFW

image.png.93645fd15daad2ae956350e7ccb3916f.png

I've noticed that stars in my DUO guider are not round due to 2" filters vignetting but it guides just fine. If I remember correctly it is also mentioned in the above video as well.

Edited by Dark Raven
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17 hours ago, Dark Raven said:

That is suboptimal position and you are loosing a lot of light for the OAG camera.

See proper positioning here: 5. Using OAG-L and 2” EFW

Now this is very interesting! It may even be a game changer. It may explain why I get quite a lot of 'lost star' beeps in PHD2. I have the filter screwed into the back of the telescope focuser.

I just dismantled mine and it seems to have a M54 15mm spacer in there which I assume is to produce the correct back focus distance. So perhaps I could replace that with a filter drawer of the same thickness?

Thanks for this!!

IMG_4348.jpeg

IMG_4349.jpeg

Edited by StuartT
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7 minutes ago, Elp said:

Bit confused here. Isn't this thread about the 2600 duo where no second guide camera or oag is needed?

Apologies for diverting. Entirely my fault. Just that this may be a Eureka moment for me! (I'll take it offline)

Edited by StuartT
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No need it's fine. Just in case someone without knowledge comes to read.

Hope you've sorted your issue, I do the same, OAG after flattener, then filter drawer then camera.

The duo must have some sort of magic if it can see through some narrowband filters without issue.

 

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