130 replies to this topic

[rockstarbill]

Looks like they are available. https://astronomy-im...tegory/usb-2-0/

Saw this link on another thread and thought I'd share it here.

Lets have a real talk here...

 

174 vs 290... If you wanted to buy once and take the cake, 174? 

[rockstarbill]

If the camera is available either with 290 or 174 then for OAG I would choose 174 over 290 because the sensor is so much larger due to the larger pixels.  I use oag with the qhy 174 sensor and it is close to the prism of the oag and is nearly fully illuminated - which means it has a wide field for guidestars.  Other oag setups may not yield as much benefit if the field is constricted - but it still wouldn't hurt to have that extra sensor size.

 

But the 290 would be a better choice if you also intend to use it with a guidescope - because of the smaller pixels.

 

The larger pixels may also give an impression of greater sensitivity - but that's just because the pixels are larger - just like with a binned lodestar.  When it comes to getting high snr from a faint guidestar and calculating an accurate centroid - it's the total light collected that matters as long as the read noise is small - which it is.

 

Frank

Just read this post, Frank. I'll be getting the 174 as well.

 

Order placed. Looking forward to better guiding. 

Edited by rockstarbill, 26 September 2017 - 09:34 PM.

[freestar8n]

Hi Rockstarbill-

 

Great - I hope it works out for you.  Depending on the prism size and distance there may be some vignetting and you may not be able to use the full field of the camera - but you will still be using as much of the field as possible and that will help find guidestars.  And if you do get coverage over most of the field - it's a big change from the qhy5l-ii, which I had used previously.  

 

Frank

[Stelios]

Just ordered the ZWO OAG and mini-174 from Tolga. 

 

The 290 would've probably been good enough, but I want to minimize the chances of not locating a star after a meridian flip... The 174 sensor is four times the size. 

[rockstarbill]

Just ordered the ZWO OAG and mini-174 from Tolga. 

 

The 290 would've probably been good enough, but I want to minimize the chances of not locating a star after a meridian flip... The 174 sensor is four times the size. 

Yeah, and for $200 more, if you are going to invest in a good guiding solution (which is fairly important to our craft) you might as well get the one that sets you up for the best success. Interested to see how this stacks up to Lodestar. 

[kingjamez]

Do any U.S. based vendors have these in stock yet? My guide cam died tonight and I'd prefer not to have to wait for a shipment from China.

 

-Jim

[rockstarbill]

I dont know about "in stock" but hit up Tolga. He might be able to help you.

 

tolgaastro.com or tolga AT tolgaastro DOT com

[kingjamez]

Done, thanks!

-Jim

[ChrisWhite]

Do any U.S. based vendors have these in stock yet? My guide cam died tonight and I'd prefer not to have to wait for a shipment from China.

-Jim

Also, with expedited shipping from zwo you will receive it in 1 to 2 days. It's stupid fast....

[mikertx]

Has anyone tried guiding at longer focal lengths (say > 2000mm) with the 174?  Does the driver support binning?

 

Thanks,

Mike

[rockstarbill]

So the ASI174 mini showed up. Shes already installed on my QSI camera, and pretty much looks the same as the 290 mini, just with a bigger sensor. The one thing I should probably suggest to Sam is to include the same T thread to 1.25" compression adapter they include with the ZWO OAG. Since my QSI690WSG-8 has a t-thread for the guide camera, the mini was too small and there was no included adapter for direct connection to a OAG with t threads only. Since I own the ZWO OAG, I just used the compression adapter they included with it to get it connected and it worked fine. Including this adapter with the mini guide cameras would be very helpful for folks that dont already have one on hand.

 

I should mention that they include two USB-C cables. One shorter one that would be wonderful for folks using the ZWO cameras with built in USB hubs, and another for us folks that use other imaging solutions. Nice touch! 

 

Clear night tonight, so I will get some data from PHD for folks thinking about the 174.

Edited by rockstarbill, 02 October 2017 - 07:18 PM.

[rockstarbill]

So here is PHD during my run tonight. There is quite of a bit of vignetting, which is likely due to the adapter I am using to connect this to the QSIWSG. I will need to look into changing this out for either the C or 1.25 adapter. Still trying to figure that out. 

 

Images have been very consistent in terms of FWHM which is at about 2.75" tonight with SII frames. 

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[mikefulb]

I'd say you have a few stars to choose from! 

[entilza]

So here is PHD during my run tonight. There is quite of a bit of vignetting, which is likely due to the adapter I am using to connect this to the QSIWSG. I will need to look into changing this out for either the C or 1.25 adapter. Still trying to figure that out. 

 

Images have been very consistent in terms of FWHM which is at about 2.75" tonight with SII frames. 

 

You don't have corrections showing?  I love having those visible   Extra info always helps!

[freestar8n]

Rockstarbill that looks good and the vignetting shouldn’t matter much. But you are free to rotate the camera 90 degrees and you may get more uniform illumination.

Looks like you have a good setup.

Frank

Edited by freestar8n, 03 October 2017 - 04:40 PM.

[rockstarbill]

Thanks Frank, I will rotate and see how that works out tonight. 

 

As for corrections, no I dont turn those on. What is the point? 

[rockstarbill]

Hey Frank,

 

Great suggestion, much nicer field now for picking guide stars with the 174 Mini

 

 

 

 

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[Andy Grant]

I was considering the 290mm as a lunar/solar/planetary cam that I could dual-purpose as an autoguider. Is the normal, 'fat' 290mm seriously handicapped as an OAG (with an 8" sct)? Is the mini seriously handicapped as a solar system cam? How important to OAG is the 1.25" barrel?

[freestar8n]

If your setup allows you to have the imaging camera very close to the oag and at the same time you can still focus a wide body guide camera on the guide port without needing to slide it in, then the 1.25" won't matter.  But in many cases the guide port will place the guide camera too far away from the prism and you will need to put a spacer on the imaging side.  That would mean the guide camera has a less wide view of the prism and there will be loss of light - plus more aberration in the guidestar.

 

But if your guide port doesn't let you slide the camera in anyway then it won't help.  Some guide ports are just narrow tubes with a big flange on the end for the camera.

 

If you aren't using a fast newtonian or something that requires a very thin oag, then I recommend one with a big prism around 12mm and a 1.25" tube that gives a good view of it - so you can slide the guide camera in.  That will give a wide and bright view of guidestars like rockstarbill has.  His image is quite a contrast from all the people who bemoan oag as hard to find guidestars.  If you set it up right and focus well with a recent cmos camera - they are easy to use.

 

I think the only issue with the small asi ones is that they are usb2 - which won't affect guiding but would decrease frame rate if you want to use it for planetary video.  And the 174 is great for guiding because it is bigger - but for planetary and use with a small guidescope its bigger pixels are less ideal.  So there are trade offs.

 

Frank

[Andy Grant]

Is there a way I can tell if the bigger 290 will work 'before' buying it and an imaging camera?

 

The OAG I have is a Celestron Radial Guider (for SCTs) that's no longer in production.  It screws onto the scope where the visual back normally would and has T-threads for a camera.  It was designed for 1.25" eyepieces.  The prism angle can be adjusted and the eyepiece holder can rotate through about a 135° angle.

 

What specs would I need to know about the guide/imaging cameras and/or what would I need to measure on the OAG to know if a pair of cameras would work together well with my particular OAG?  Or is experimentation the only way to know for sure?

[kingjamez]

If you have t threads on the output port of your prisim, I’d buy one of the helical t thread focusers that gives you a 1.25” barrel to fit the camera too. I like my baader unit.

If you get one of these mini’s you be “most able” to make it work since you’ll have the maximum amount of flexibility. If any camera will work, these likely will.

-Jim

Edited by kingjamez, 04 October 2017 - 06:49 PM.

[freestar8n]

For Andy the passage through the prism is optically shorter than in air by about 4mm or so. As a result the distance from the middle of the long side of the prism to the imaging sensor should be about 4mm less than from that point on the prism to the guide sensor.

If you can measure things you may be able to tell if a camera will work or not.

A helical focuser is nice and good focus of the oag guidestar is important. But I find that if the guide camera can operate at high frame rate like video then it is easy to focus accurately just with the draw tube and thumb screws.

Often the helical focuser takes up too much backfocus but you may be able to slide the camera into it and use it.

Frank

[gotak]

Looks up some specs. Seems the 290 sensor is actually the more sensitive one. Wondering if anyone has seen actual guiding comparison?

[Andy Grant]

Thanks for the info. I only have T-threads on the imaging side. But at least I know what it should take to make it work. I will see if I can get decent measurements of my oag and compare with some camera dimensions.

[FiremanDan]

In the process of sorting out tracking/guiding issues it was brought up that my Lodstar's 8+μm pixels could be too big. With my SV80 and OAG 1 pixel is over 1 arc second. It sounds like smaller pixels might be better. 
The 290 has smaller pixels and higher QE. I am thinking that might be the camera to get. The larger sensor would be nice though.