How good are the ASI guide cameras?

[gregbradley]

I am interested in perhaps getting an ASI camera to work as a guide camera.

Anyone using one care to give some advice?

Greg.

[The_bluester]

I am using an ASI290MM mini and it has worked flawlessly since I bought it about a year ago. It is probably overkill sensitivity wise on my 80mm refractor/OAG combo but when I bought it I took the advice to go to the more expensive and sensitive one as I was using it with an OAG on my 9.25 SCT, where finding guide stars can be a lot tougher. I am using a dark frame library in PHD2 that I shot 6 months ago without any visible issues so it seems pretty stable sensor wise.

The USB-C connection is handy cable wise as it is not polarity conscious.

[Startrek]

Greg,
I’ve been using 2 set ups with a ZWOASI120MM-S camera as a guide camera in my Orion 60mm guide scope with helical focuser for 2 and 3 years respectively with PHD2 and no real issues.
This camera is USB3 and I use a 5m long USB2A to USB2B from laptop to camera which has no connection or operational issues at all
When I first started guiding I originally purchased a ZWOASI120MM USB2 Camera and had intermittent connection problems for weeks. I googled some various forums and found out his camera had driver issues and required a patch or upgrade of some kind from ZWO. I didn’t muck around and was advised to buy the USB3 version so I bought the USB3 camera and it’s been working perfectly for 3 years ( The old USB2 Camera is still in a drawer gathering dust )
Cheers

[glend]

I have found the 290 Mini to be the better of the ASI guide cameras. I had a 120 initially but really liked the higher QE of the 290.

[Imme]

Second this....asi120 on 2 x separate rigs with a zwo 60mm guidescope has worked fine for me. I have the color and mono versions....mono picks up a lot more stars however color works fine as well.

[gregbradley]

Thanks for all the responses. The 290 seems the go then.

I am currently using an SBIG STi guider which has a mechanical shutter which is handy for doing autodark subtracts. I don't use PHD2 but have in the past.
I don't think the Sky X will allow me to use a dark from a library.

Is the 290 pretty clean without it? I am not worried about a few hot pixels, I am more concerned with white bars, interference patterns that can be confused with the guide star like I had with an SX Lodestar.

I get guide stars resonably easily in most situations but there is the odd one where its hard. M104 comes to mind as an example of no nearby guidestars. 80% QE would help there.

Greg.

[glend]

Greg I have never had interference patterns with the 290, and zero hot pixels that I could find.

[The_bluester]

I am likewise, mine displays nothing noticeable by way of hot pixels or any odd interference patterns.

The only issue I have ever had is more related to PDH2. If stars are hard to come by it stretches the image harder and harder to try to find some and can stretch it so heavily it starts picking out noise and trying to call it a star. That only happens when conditions are so bad that imaging is worthless anyway. The only issue would be if your capture software tries to keep ploughing on instead of restarting the guiding. But I really cant call it an issue with the camera as I assume PHD would do the same with any attached cam.

I have been meaning to reach out to the developers to see if there is a config in a file somewhere that I can alter to limit the ultimate stretch of the guide images.

[Merlin66]

Greg,
A little surprised to hear your comments on the Lodestar.
I’ve been using one with the spectroscope for guiding on a reflective slit plate on the C11@ f10 for the past ten years, sure some hot pixels but for me a great performer. No white bars or interference patterns.

[Benjamin]

Hey Paul, Is this not solved by adjusting minimum HFD value for the selection of a suitable guide star? I’ve had a few occasions where I’ve guided on a hot pixel and have adjusted the minim HFD value to avoid this.

[lazjen]

I've been using a mini ASI174MM for a guider for a while now. It works quite well, but I use PHD2 and its dark library setup. No idea how it would go without it.

So far I've never had an issue with getting multiple stars to choose from for guiding.

[The_bluester]

It is not so much hot pixels Ben as random noise. If the sky gets bad enough it stretches the guider images to a high degree to try to find stars and it can try to latch on to random noise frame by frame and it can pass the minimum HFD test, the problem can come when the passing cloud (As an example) clears and PHD latches on to the wrong star.

It is probably something that would happen with more or less any guide cam and if it is a problem or not depends on how your imaging software handles it.

[Benjamin]

Ah, yes. I see what you mean Paul :thumbsup:

[LewisM]

I tried the ASI120 years ago. Not bad and quite sensitive, but I did have driver issues. Not QHY driver bad, but still made for some headaches.


I went back to Lodestar. Never an issue finding a star, never an issue connecting, never drops out. Since coming back to Astronomy, I bought myself a Lodestar X2. (my CCD is self guiding, but we'll see how that goes and keep the Lodestar as fall-back, especially for H-a subs)

[peter_4059]

Ive got 2 120mms no issues with either of them

[Camelopardalis]

The 290 mono works very well, the only real downside is that the sensor isn’t very big.

It also has an uncanny knack of guiding through cloud... (with a 60mm guide scope)

[The_bluester]

I would agree with that, my 290MM mini will guide away through conditions that produce absolutely rubbish subs, just big coloured halos instead of stars. It has to be pretty atrocious to get the effect I was mentioning with PHD2 over stretching the images to try to get stars.

[gregbradley]

I may have had a poor one.

I usually only hear good things about the Lodestar. Maybe it was a USB issue or cable issue as I do see interfence often with the STi but auto dark subtract usually gets rid of that and its reliable as a result.

I am not too worried about hot pixels as I usually do 6 second guide exposures as the PME or the AP1600 don't need much correction and do better with the longer guide exposures.

Greg.

[loc46south]

Hi Greg - I use a 174 in a MMOAG on an AGiDK 12.5 and with PHD2 and its predictive PEC guiding gives excellent results. I am getting sub pixel guiding on 5 or 6 hours exposure runs with a Losmandy Titan 50 mount.

[Nikolas]

I have the 120 mm mini no issues

[gregbradley]

Sounds good. Wha is predictive PEC guiding? Isn't all PEC predictive in that its a file of errors that repeat and used to add or subtract from the current correction?



Thanks for the feedback.

Greg.

[Startrek]

Greg
Some detail on PHD2 Predictive PEC guiding -

Advanced Functions for PHD2 - Predictive PEC ( Periodic Error Correction) in PHD2

PPEC is an alternative to the Hysteresis algorithm normally used for your mounts RA guide corrections and can provide improvements to your mounts overall guiding
Go to Brain
Select Algorithms
In ‘Right Ascension’ select “Predictive PEC”
Use all default settings for Predictive Weight, Reactive Weight and Min Move ( Period Length can be adjusted to suit your mounts worm cycle period but always leave “Auto Adjust Period” checked or ticked )
Do your normal Calibration then start guiding
PPEC takes time to train itself and perform
It starts out using the normal RA Hysteresis algorithm then shifts seamlessly to the PPEC algorithm after about 2 worm cycles of the mount when it learns the mounts performance
HEQ5 mount worm cycle period is 638 sec or 10 minutes 38 seconds
EQ6-R mount worm cycle period is about 480 sec or 8 minutes
PPEC will remain whilst guiding , stopping and starting guiding for focusing and dithering on the same target
If you stop and slew to a new target , PPEC must be turned off and then on again , start guiding and then re train itself again on the new target
Once training is complete after 2 worm cycles, the PPEC algorithm uses both reactive and predictive guide corrections which in principle is usually more accurate than just Hysteresis on its own
EQMOD has a feature to store your mounts PEC curve which is created by a third part software like PECprep and allows PHD2 to retain and use this data when running the PPEC algorithm. This saves PHD2 time when setting up and guiding for the next imaging session
The mounts Synscan handcontroller also has a function to record PEC and store it in the mount for PHD2 to use along side the PPEC function

Cheers
Martin

[gregbradley]

Thanks Martin.

That sounds very sophisticated. I did use PHD2 for quite a while but my mount was overloaded and also the camera would put a bump on stars that I mistook for guide errors so I stopped using it. It also dropped out too easily when a cloud went over at least in that version of PHD (was about 5 years ago now).

Greg.

[loc46south]

Hi Greg - I use it for Differential; Photometery where limited pixel shift is desired and it works like a dream - provided you keep an eye on it. But I wouldn't recommend it for unattended photography. The software is still in a beta + stage and there is the odd occasion when it does not perform as expected. The 174 is is best guiding camera I have used - it 's red band capability lets you hang on to guide stars better, especially when there is that pesky high cloud about.

Geof

[gregbradley]

Thanks Geoff.

Greg.