Home-made Autoguiding

[Jm1973]

Hi All!

 

I'm currently imaging with an EQ5 pro goto synscan mount, Skywatcher Explorer 200P, and D3300 DSLR attached to the focusser. It is all run from a PC via USB cables. I am aware that this is considered an underspecced mount for this weight but it works ok. I am able to get subs of 90 seconds with no issue, and with good polar alignment I can push up to about 2 minutes before stars start to get oval-shaped.

I am considering making the move to auto-guiding to get longer subs. I am aware that many would say I am already pushing my luck weight-wise with this mount, so I am trying to keep the setup streamlined. I have been reading up on the subject and am hoping to attached a webcam (maybe a QuickCam Pro 4000) to my existing finderscope, which is the stock 9x50 type. I am thinking of attaching this to my PC via USB cable and controlling via EQMOD.

The advantages of this are 1. it's cheap, 2. it only adds the weight of the webcam to my mount.

Does anyone here do anything similar, or know whether this is feasible, or know of any potential pitfalls I should look out for?

Thanks for any replies!

Clear skies!

 

[vlaiv]

I'm sure it will work, however, I'm not certain how well it will work.

I used modified webcams for planetary imaging and there is drawback in most models. They don't do raw format, but rather use compression for video data (limitation of usb 2.0 port and need for 30fps support).

Compression used will create artifacts and these artifacts are going to impact centroid precision needed for guiding. Guiding via web camera is not going to be very precise, but depending on how much precision you need - it will be certainly feasible.

In fact - metaguide software was developed to work with web cameras (only requirement is WDM driver I believe).

https://smallstarspot.com/metaguide/

 

[tooth_dr]

Having tried to guide with a webcam my suggestion would be continue with the finderscope method (which is excellent for keeping weight down) and buy a used ZWO120MM for the camera.   It will work 100%

[almcl]

I started almost exactly the same way (EQ5 with home added drive motors and a Logitech C270 webcam butchered to fit a spare SW finder scope using GPUSB to control the mount via a modified handset).

It works, just not always.  The Logitech webcam wasn't sensitive enough to find stars in every situation, and the EQ5 sometimes struggled with the SW200P but it did work most of the time. 

Tooth_dr's advice about getting a ASI 120 mono (mini is a tad more expensive but a bit lighter) is good - mine always finds loads of stars when used with the SW finderscope (it does a pretty good job with an OAG as well) and PHD2 reports guiding oscillations around about 1 arc second most of the time although I now use an AstroEQ to drive stepper motors on the EQ5.

 

 

 

[Budgie1]

+1 for the ASI120MM Mini on the 9 x 50 finder as a starter.

I started by using a Phillips SPC900 webcam attached to an adaptor for the 9 x 50 and it did work with PHD2 for guiding but the image was nasty and PHD2 often lost the guide star. Too much noise in the camera.

I swapped over to the ASI120MM Mini and it's that good I can see both cores of M51 on the 2 second PHD2 image. Plus it's not that much extra weight when compared to the SPC900.

[Jm1973]

Thanks for the replies. It sounds like the ASI120MM Mini could be the way to go.

I've not seen any of the mono ones on sale second hand, but I have seen a few of the colour ones for sale at around the £100 mark.

I assume there is no problem using a colour instead of mono version?

Also is the USB3 version necessary or would I get away with a USB2?

Thanks again!

Edited October 28, 2020 by Jm1973

[vlaiv]

USB 2.0 is more than enough for guiding. It is only when you want to use the same camera for planetary imaging that USB 3.0 has advantage.

You can still do very decent planetary shots with USB 2.0 cameras, mind you.

For guiding, mono is a bit better, but you can guide with OSC as well - there won't be any issues except for slightly smaller sensitivity (bayer matrix lowers overall sensitivity of camera and not each pixel is sensitive in whole spectrum).

So far I always guided with OSC cameras and never had any issues because of that.

[Jm1973]

53 minutes ago, vlaiv said:

USB 2.0 is more than enough for guiding. It is only when you want to use the same camera for planetary imaging that USB 3.0 has advantage.

You can still do very decent planetary shots with USB 2.0 cameras, mind you.

For guiding, mono is a bit better, but you can guide with OSC as well - there won't be any issues except for slightly smaller sensitivity (bayer matrix lowers overall sensitivity of camera and not each pixel is sensitive in whole spectrum).

So far I always guided with OSC cameras and never had any issues because of that.

Thanks. I'll consider getting the OSC if I can't find a mono version then.

[toxic]

hi i use the Microsoft lifecam 300 hd with a home made adapter to the 9x50 finder (remove webcam lens attach 35mm film canister to front of webcam housing dont forget to cut the bottom of the canister off lol and unscrew back from finder and added a home made tube to it with a 1.25 inch hole to fit the film canister or eye piece) and its still going strong even on the 250 quattro S and thats since 2011 no need to change what works.

 

Edited October 31, 2020 by toxic
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