guide star lost, low mass

[Stuart Taylor]

Quite often I get this and I wonder if maybe I need to bin the guide camera? my guiding image scale is 1.15"/px and my imaging scale is 0.74"/px

Thanks

[mj.w...@gmail.com]

You haven't suppled the Logs for the experts to examine.

Try the "How to ask for help with PHD2" link at the top of the home page.

https://openphdguiding.org/getting-help/

[Stuart Taylor]

ok, thanks I'll read all that and maybe find my answer there

[Bruce Waddington]

You've got your camera saturation settings goofed up - the saturation level is set to zero.  Since the camera is 8-bit, the saturation value should be 255.  That's "Saturation by Max ADU value" on the camera tab of Advanced Settings.  This mistake is causing PHD2 to choose fainter stars than necessary.  It would be worth trying out binning on the guide camera - the resultant image scale should still be fine enough to produce good guiding results.  This should have the benefit of producing stars with higher SNR values.  If you try this, be sure to create a new, separate profile for 2x2 binning operations.  The new profile will have adjusted values for many of the guiding parameters and you should get good results without any fiddling around needed.  Once you have the second profile built, you can easily switch back and forth between binned and un-binned operations.

Regards,

Bruce

[Stuart Taylor]

that's odd. I just checked my advanced settings and the saturation value is set to 255. Assuming you mean this?

[bw_m...@earthlink.net]

It looks like we automatically repaired that for you at 00:06 on 8/9.  Prior to that, you were running with a zero value.  It’s probably not worth the time to figure out what happened, it should be fine going forward.

 

Bruce

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[Stuart Taylor]

ok. Not sure how that got fixed but anyway. good. Thanks

[Stuart Taylor]

what happens when your particular view of the sky has no guide stars? I am just getting endless 'bing' from PHD2

[Brian Valente]

>>> what happens when your particular view of the sky has no guide stars? I am just getting endless 'bing' from PHD2

that depends - presumably you are using your imaging app (NINA, right?) and it is controlling PHD. So you control the guiding behavior via the imaging app

What is your fov on your guidescope? there are always stars out there, unless it's weather-related or you are shooting at really long focal lengths

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[Stuart Taylor]

I have an OAG-L (large prism) on an Esprit 150 (1050mm FL). Guide scale is 1.15"/px

 I tried increasing the guide cam exposure time to 4 sec and upped the gain to 200

but I am still getting endless 'bing'

[Brian Valente]

you should have plenty of guidestars at that focal length. I'm not sure how familiar you are with troubleshooting OAGs, etc. but you should look at focusing/spacing and being parfocal to your camera. That setup you has sounds like a nice one, but many people use that setup (or nearly that) and have no problem with guidestars

Has it worked before or is this a new setup you are trying to dial in?

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[George Shoup]

Out of focus?

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[Stuart Taylor]

this exact setup was working perfectly last night. It's not focus, or obstruction. and I am in a part of the sky with plenty of stars and a bright scope (Esprit 150 f/7)

[Stuart Taylor]

ugh!

[Stuart Taylor]

here is the relevant log https://openphdguiding.org/logs/dl/PHD2_logs_p3nv.zip

[bw_m...@earthlink.net]

The data in the log files show there were basically no usable stars in the guide frames – just faint objects with very low SNR values.  When you encounter the problem again, you should do a File/Save in PHD2 so you can capture the image.  You can post that on a publicly accessible cloud store or look at it yourself with whatever imaging app you like.  I think you will see a pretty sorry looking image from the standpoint of well-focused, sharp stars.

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[Stuart Taylor]

Ok. So basically I was pointed at the wrong part of the sky. Nothing to do with my PHD2 settings. That’s reassuring (in a way). I’d not be surprised if this were a long FL scope, but 1050mm is not extreme. Oh well.

Next time I attempt this target I’ll rotate the camera 180 degrees and see if there are any stars on the other side.

Thanks for looking at it for me.

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[Brian Valente]

>>>Next time I attempt this target I’ll rotate the camera 180 degrees and see if there are any stars on the other side.

or your guidescope isn't well focused?

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[Stuart Taylor]

I’m not using a guidescope. It’s an OAG and it’s parfocal with the telescope (that’s why I’m suggesting rotating the camera to find more stars on the other side)

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[mj.w...@gmail.com]

I plan my imaging using a Planetarium to position the guidecam on suitable guide stars.

Michael

Wiltshire UKJ

[Rick Cohen]

Michael,

What program did you use to get that image?  Is it a screenshot?  It would be really helpful to see exactly what part of the sky my OAG is pointing at relative to the imaging camera.

Thanks,

Rick

[Stuart Taylor]

I agree Rick! This looks super useful!

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[Graeme Durden]

Don't know what programme that is, possibly Carts du Ciel. I use Stellerium for this. Rotate to a suitable star and check the angle. Rotate the camera to match and check the rotation in NINA. The chosen star will then be visible in the OTA for PHD to find.

[mj.w...@gmail.com]

It's COELIX, but looks like CdC does a good job too/

Michael

Wiltshire UK

[Stuart Taylor]

Thanks Michael. So do you enter the details of your camera, scope and OAG to get that view reticle?

Stuart

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[mj.w...@gmail.com]

Hi Stuart.

All it needs is:

Focal Length

Guidecam sensor size (it assumes the prism matches)

Radius, the distance of the prism from the centre of the imaging FOV.

After I've set the prism to just not vignette, I take the OAG off and roughly measure the prism distance (Radius) from the centre line.

Then I centralise a bright star like Vega in the imaging FOV, with the prism located to the north (or south).

Slowly slew in Dec until the star appears in the guidecam display in PHD2 etc, and centralise in the guidecam display.

If the COELIX display doesn't match, then adjust the Radius in COELIX until the COELIX box frames the star on the COELIX display

Note that due to inversions in the scope optics, in my setup the prism is actually located "above" the imaging camera, although COELIX shows it to be "below".

So that slew may not be in the direction you thought it should be.

This catches people out, when they have focused the imaging camera, then can't find the same star to focus the guidecam.

Michael

Wiltshire UK