Using ROI in a large MM camera with PHD2?

[Chris and Esme Ryan]

Hi Bruce, 

I'd like to drive PHD2 from an alternate mono camera to track a planet. I'd use a planetary camera (e.g. 585MC) on the main scope with a Powermate for F21. And then use another mono camera on a guide scope with the aim of keeping the planet in the FOV of the main scope (very small FOV). However, the mono camera I have available to use with small pixels is the 294MM. If the sub-pixels are freed, then it has 2.3 micron pixels. But the trouble is that then it becomes a 48 Megapixel camera. This seems to give PHD2 indigestion.

It'd like to either select a small ROI on the camera (say, use 1/4 to 1/2 of the width and height) or to select the "normal" mode, which has 4.63 micron pixels and 11 Megapixels in total.

But I can't see any way of selecting any of these camera features.  The camera properties button only seems to allow setting the binning. The New Profile Wizard seems to recognize the camera as 2.3 micron pixels.

If I press ahead, it fails with an exception starting the Dark Library creation, and seems to hang if I select "Ignore".

If I skip the Dark Library step and start "Looping", it crashes PHD2.

If I select the same camera, but use bin=2 (11 Megapixels) and skip Darks then it will Loop OK.

Is this a lost cause? Is there a way to set a ROI? It would be nice to use smaller pixels in a ROI. Ideally I would just buy another camera. But this one is available.

Cheers, Chris.

[Michael Waring]

Hi Chris

What FL is the guidescope ?

A 200mm one would give 4.78arcsec/pixel Binned to 4.63um.

120mm FL would probably be too short (7.96arcsec/pixel)

Michael

Wiltshire UK

[Geof Lewis]

Hi Chris,

I hope this isn't inappropriate for the Open PHD2 forum, but if you want to image the planets and guide at the same time, take a look at FireCapture which has a guide feature inbuilt using an ST4 cable from the imaging camera to the mount. It's easy to set up and I left my rig (C14 on AP1200 with ASI462MC camera) tracking on Jupiter recently while I stopped for dinner and 75 minutes later when I went back out Jupiter was still on-screen at the centre of the tight ROI that I'd placed around.

Good luck,

Geof

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From: open-phd...@googlegroups.com <open-phd...@googlegroups.com> on behalf of Chris and Esme Ryan <chrisand...@gmail.com>
Sent: 09 February 2025 06:27
To: Open PHD Guiding <open-phd...@googlegroups.com>
Subject: [open-phd-guiding] Using ROI in a large MM camera with PHD2?

 

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[Chris and Esme Ryan]

Hi Geoff,

That's an option. But my main imaging train at F21 is 7470 mm focal length with only a 0.09 degree FOV. It will be all too easy to jump out of view altogether with this FL. I use SharpCap, which can also drive the guiding in the same way. But it will be risky, with time lost "finding" the planet again.

But I guess you know about limited FOV with a 462MC on a C14 (with a Powermate/barlow?). I have even guided my C8 x2 with an OAG. But it's not exactly routine. Now going to a 14" also, I was trying to make a more reliable plan.

I like the idea of using the finder/guide scope at smaller focal length. The image scale is terrible, depending on camera. But it may be good enough to keep the planet in the main FOV. SharpCap can then track a ROI on the planet. And I can't "lose" the planet with the large FOV of the guide scope. Anyway, that's the idea ...

Cheers, Chris.

[Chris and Esme Ryan]

Hi Michael,

It's actually even shorter at 85 mm. Using the 294MM in bin1 mode that gives 5.2"/pixel. So not the best for guiding for DSO long exposures. But may work fine for keeping a planet in view at 100 FPS.

Cheers, Chris.

[Jens Scheidtmann]

Dear Chris, 

I would consider a larger focal length for your guidescope. There‘s a fork/patch of PHD2, that does guiding on extended objects, see here: 

https://github.com/Eyeke2/phd2.planetary they also have a facebook group.

(I have not tested this myself.)

Hope this helps,

Jens

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[Brian Valente]

To answer your question, no PHD doesn't support ROI in the way you are describing

Have you tried sharpcap's ROI tracking and mount bump guiding? Does it not do what you need?

Alternatively a smaller guidescope and lower resolution camera combined with ROI tracking should be plenty to keep the planet wher you need it. In my planetary imaging which is roughly the same image scale, i just use ROI tracking and manually recenter every few minutes. Excellent polar alignment helps here as well (and if you have any sort of sky modeling, that helps too) 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/ab73bf54-3628-4ce1-9e99-73ca708a13f9n%40googlegroups.com.

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Brian 

Brian Valente

astronomy portfolio https://www.astrobin.com/users/bvalente/ 

[Chris and Esme Ryan]

Hi Brian,

Good suggestion to use (a second instance of ) SharpCap to drive the mount from the guide scope. That may be the way. I was hoping to exploit all the tricks in PHD2 (e.g. Periodic PEC). PHD2 does work at bin=2 in the 294MM case, so will work. And surprisingly gets about 2 FPS over USB 3.

Yes, a planet is not a ‘point’ like star. But I was thinking it may still work at this focal length and large image scale where Jupiter’s FWHM is only about 4 pixels. 

Yes, I have used the ROI tracking the same way, with my existing scope (EdgeHD8 at F20) and manually nudged the mount to keep it roughly centred. The new scope has a smaller FOV so I was trying to organise a better approach.

Thanks. Now I have two options to try.

Cheers, Chris.

[Geof Lewis]

Hi Chris,

I'm also imaging at around F21 (0.09 arcsec/px) and the guiding feature in FireCapture has no issues holding the target in view over several hours. I do have a permanent set up on a pier in an observatory, which means that my polar alignment is accurate from the get go, plus the AP1200 mount has excellent tracking performance, with very low period error.

Regards,

Geof

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From: open-phd...@googlegroups.com <open-phd...@googlegroups.com> on behalf of Chris and Esme Ryan <chrisand...@gmail.com>

Sent: 09 February 2025 09:37

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Subject: Re: [open-phd-guiding] Using ROI in a large MM camera with PHD2?

 

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[Chris and Esme Ryan]

Hi Geoff,

That's encouraging. My scope (Hubble Optics HNA 14") is still on order and will be shipped soon. All this is in preparation. 

Still, I would like options beyond keeping everything within a FOV of just 0.09 degrees. Hence, my thinking about the guide scope, just for mount tracking.

I will give SharpCap a go, or PHD2 in bin2 mode. Both should work. PHD2, in my mind, does have very nice algorithms for Periodic PEC and Resist Switch, which would be good to use.

Cheers, Chris.

[Geof Lewis]

Hi Chris,

I’m not familiar with the Hubble HNA, so had a look at their website - it looks great. PHD2 is a great product, which I use for guiding when DSO imaging, but I have never used it to guide when imaging the planets. It’s always good to have options though, so I wish you well with the new scope when it arrives.

Geof

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From: open-phd...@googlegroups.com <open-phd...@googlegroups.com> on behalf of Chris and Esme Ryan <chrisand...@gmail.com>

Sent: Wednesday, February 12, 2025 6:35:51 AM

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[Brian Valente]

Hi Chris

Is this notion of a guiding on planets solving a problem you have now, or are you thinking about what may happen in the future? 

There's a separate project on facebook regarding solar and planetary guiding, based on PHD, which may also interest you

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/06a07fad-e06f-45d0-b43b-fbd5ef31c160n%40googlegroups.com.

[Chris and Esme Ryan]

Hi Brian,

I have not tried guiding on a planet yet. But with the short FL guide scope, Jupiter will be just 4 pixels across, so I think PHD2 will handle that OK. This is all planning so far. I now have this guide scope setup, but with clouds for the next week. Hope to “just try it” when I get some clear sky. 

Cheers, Chris.

[Brian Valente]

Don't get too hung up on guiding exactly on Jupiter. It's an extraordinarily bright target and could saturate easily, not the greatest for guiding. Nearby stars are probably a better bet for guiding.

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/f4eb4a31-e506-44e1-bbd7-1495cfdc7115n%40googlegroups.com.

[Chris and Esme Ryan]

OK, I’ll keep that in mind. On another note- I usually get an object centred by starting guiding after tweaking it to the centre in the main scope. Once guiding is running, is there a way to adjust this position (e.g. if Jupiter is well off centre in main scope)? Can I nudge the search target box in some way? Is there some trick that can be used making use of PHD2’s spectroscopy slit target, for example? 

Cheers, Chris.

[Brian Valente]

I would do the opposite - center jupiter, then start guiding. 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/6cee5dd4-eb4f-4b19-b58c-606cecc261c8n%40googlegroups.com.

[Geof Lewis]

Chris,

At the risk of repeating myself, FireCapture and I believe, though am less certain, Sharcap have these tools built in specifically to create, centre, and anchor an ROI around the planet and guide on it directly. I don’t understand why you want to guide on planets using PHD2 with a guide scope when you can guide on the planet itself through the main scope.

Best regards,

Geof

PS Apologies for promoting an alternative product on this forum, but I'm trying to help as someone who nowadays is primarily a planetary imager.

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[Chris and Esme Ryan]

Hi Geoff,

I use SharpCap for planets. It’s great, especially with new planetary stacking/sharpening capabilities. But it’s mount guiding abilities are no where near as good as PHD2. You can browse the forum to see this. Perhaps not surprising as PHD2 has been developed and tuned over decades, specialised to this sole task. The other point is guiding in a 0.09 degree FOV is fine while it works. But a small wind gust and you’re totally lost. And you need to refine the planet. Guiding in a wider FOV guide scope and cam enables you to get it back quickly.

Anyway, that’s the plan.

Cheers, Chris.

[Geoffrey Lewis]

Chris,

I don't use SharpCap for planetary imaging, but I do use FireCapture and I've never had any issues with FireCapture's inbuilt guiding tools even when imaging at 0.08"/px. I have never used PHD2 for guiding on a planet, but of course the choice is yours, so I leave you working with PHD2 and wish you well.

Best wishes, Geof

[Chris and Esme Ryan]

Hi Geoff,

You’re probably right about guiding on a planet. I’ll probably just guide on a star field. It was just an idea I floated to see what people thought. Tested the guide scope last night and it worked just fine despite the large image scale of around 7”/pixel. For various reasons, I wasn’t well balanced, but it guided at about 1-1.5 arc-sec RMS total, which will do just fine, as SharpCap will take it from there and centre the planet as part of stacking. 

Good to hear that you have no problems at long FL. I do get the occasional wind gust that can catch the dew shield. Hence, my efforts to build in some latitude.

Cheers, Chris.

[Brian Valente]

Chris

I agree with Geof's feedback. Planetary imaging is not new, and guiding via PHD has not been something holding anyone back. In my years of imaging planets, I have never experienced"a small wind gust and you’re totally lost" nor have I had a need to guide more than the exceptional ROI guiding capabilities of sharpcap. 

It seems to me like these are hypotheticals or maybe you have a novel approach, and while I can't disagree in concept, in practice guiding outside of sharpcap (or firecapture) just isn't really a factor. 

To view this discussion visit https://groups.google.com/d/msgid/open-phd-guiding/7bd0db7c-9e38-4053-8a2c-4da57ba76b54n%40googlegroups.com.

[Chris and Esme Ryan]

Hi Brian,

Yes, it is just hypothetical at this stage. With a planned jump from about 4m to 7.5m focal length, I was thinking of what would avoid issues. Yes, I too have had great success using SharpCap’s ROI tracking with the occasional ‘nudge’ manually to adjust the mount. That may well be enough with the new telescope and image scale. Anyway, I now have a plan B, guiding with PHD2 on the guide scope, or at least just plate solve and re-centre there, if I “lose” the planet, and continue with ROI. 

Cheers, Chris.