Couple questions about PHD2 and the NINA Orbitals plugin

[Paul Goelz]

I have used the NINA plugin "Orbitals" to successfully put comet
c/2022-E3 ZTF dead center in the frame. But I have some questions about
usage with PHD2. So I figured I'd ask here.

1. I'm using an OAG so guiding directly on the comet head is not
possible. If I accept trailed stars and would like the comet to remain
stationary in the frame over time, am I supposed to use Orbitals to
change the PHD2 guide star offset AND ALSO change the mount tracking
rate? In effect, cause the mount to track the comet so the stars move,
and then tell PHD2 to expect that movement while guiding so the net
result is that while still guiding on stars, the stars trail over time
but the comet head does not move in the frame.

2. If I use Orbitals to generate a PHD2 offset, what happens when the
guide star eventually moves out of the guide camera frame? What about
secondary guide stars?

Paul

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Paul Goelz
Rochester Hills, MI USA
pgoe...@gmail.com
www.pgoelz.com

[BruceS]

I'm pinging this post since it never received a reply. I'm doing something similar with Asteroid 1013 NK4. It passed somewhat close to earth yesterday and I imaged it last night. Guiding on stars was useless due to the fast movement of the asteroid. It would move off frame in about 15 mins. I used N.I.N.A. to set the custom tracking rate in PHD2. I verified it was set correctly in the Comet Tool and Enabled, but it was still tracking at Sidereal. I'm tried several things including closing and reopening PHD2 (don't remember exactly what else...it was early AM!) and it finally started working well. Small round comet, long star trails.
Is there a particular order to use to set the custom rate and start guiding? Also see Q #2  above.

[Brian Valente]

Hi Paul

the tracking rate is through the mount, and unrelated to the PHD2 custom guide rate (i.e., comet tracking). So if it's tracking sidereal, that's between NINA and the mount. 

the order in which you enable things doesn't really affect how things should work, but that's a question better answered in the NINA discord. If PHD receives a custom guiding rate, it will set and use it.I would probably set it after any custom tracking rate is set on the mount.

Some of this also depends on how you are doing this in NINA: are you using the advanced sequencer? if so, you need to make sure to set the custom tracking rate for the mount and the custom guiding rate separately. 

If the guidestar is lost, it will report lost a lost guidestar: It doesn't automatically move to any secondary stars.

Brian

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Brian 

Brian Valente

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[BruceS]

Hi Brian,
I don't think I was very clear in my original post. Late night!

Using NINA Orbitals plugin, I tried setting the mount tracking rate but I ended up with both elongated stars and elongated asteroid. Tried adding Guider Shift Rate but that made it worse.

Reverted to Sidereal tracking on the mount and then set the Guider Shift Rate from NINA to PHD2. At first I was still getting sharp stars / long asteroid. I checked Tools, Comet Tracking in PHD2 and it was enabled with the correct RA/DEC settings. You need to multiply the displayed NINA rates by 3600 since NINA displays in arcsecs/sec and PHD2 displays in arcsecs/hr but the result in PHD2 is correct. I either restarted NINA or just restarted guiding (it was 4 am) but it began working and the asteroid was nice and round. This 60 sec image is overstretched, but you get the idea of how fast the asteroid (center) was moving.

My question was, should I turn off everything, set the Guider Rate then begin guiding or should just setting the Guider Rate get it going (not what I saw).

Since this is a very fast asteroid, the other question is, what happens when the guide star moves off frame (which it did and stopped guiding). Should PHD2 pick a new star (I had multi-star enabled) or do I have to "babysit" and select and restart guiding as required.

I'll image and test more tonight weather permitting.

[BruceS]

Oops! didn't mean to leave the 2nd question in my post as you already answered it.

[Brian Valente]

Hi Bruce (apologies, i thought it was Paul)

>>>Using NINA Orbitals plugin, I tried setting the mount tracking rate but I ended up with both elongated stars and elongated asteroid. 

That sounds like the main problem you are experiencing is the mount tracking rate was not being set correctly: Either it's not the correct rate, or there is something else causing the issue. You probably should plate solve solve prior to the orbitals. At any rate, this is really an Orbitals question over at Discord.  

>>>Tried adding Guider Shift Rate but that made it worse.

If the tracking rate is incorrect, then the guider shift rate is probably also incorrect and as a result I would expect it to be worse

>>>what happens when the guide star moves off frame (which it did and stopped guiding). Should PHD2 pick a new star (I had multi-star enabled) or do I have to "babysit" and select and restart guiding as required.

For the scenario you are describing, you'll want to guide on the asteroid itself, or you'll have to babysit it. I"m not sure exactly how fast things are going but for something that fast and likely without a lot of detail, you may just consider tracking without guiding. I assume your exposures are relatively short?

To view this discussion on the web visit https://groups.google.com/d/msgid/open-phd-guiding/f5f226a6-d3f3-44c8-b6c0-cf45416c2b8fn%40googlegroups.com.