Re: Counterweight down setup??
That is possible...you just set up the mount normally at CWD, but you must enable, in a Gemini, the RA safety limit to surpass 90 degrees.? I do set my mount to pass the 90 degree RA limit for certain types of imaging, like Solar where I want to track the sun through the meridian while imaging the solar surface.??
As long as you have physically confirmed that your scope and dovetail are not going to crash into the RA motor or tripod legs etc, at any part of the tracking path.?
?I can get away with that for solar imaging as the scope is small, and?pointing near the celestial equator, and I use a GM8 DEC extension and a tripod vertical extension for example.? ??
To do that with a Gemini, you have to set the "RA safety limits" setting to be past 90 (degrees). Attached is a PDF about where to find those settings using the Gemini.net applet.? The settings are hidden in the "Advanced" panel of the Applet.
-----
Using an RA extender on a G11 helps keep the dovetail away from the RA motor end.??
On my GM8, I created a DEC extender to keep the dovetail from hitting the RA motor end, and that also allowed me to do this more easily.? (Contact me if you want one if these extenders, as I have a few spares. Here is a picture of that.)
All the best, Michael
Is it possible to perform a mount setup with the counterweight up so you can track an object from east to west and avoid a meridian flip?
|
Counterweight down setup??
Is it possible to perform a mount setup with the counterweight up so you can track an object from east to west and avoid a meridian flip?
|
Re: PEMPro Results Analysis Question
On Wed, Aug 19, 2020 at 02:03 PM, Arun Hegde wrote:
A bit curious how much value there is in a PEC exercise unless you have a really large and high frequency PE; you could detect if you have this by running GA in PHD2. I would think it depends on your skies? Under SE Wisconsin skies, without PEC, I consistently get an average of 0.65" RMS with numbers sometimes as low as 0.45" RMS.?
If your PE is fairly slow changing and smooth, then the value of PEC over guiding is reduced as the guider can correct before the error becomes large. That said, with good PEC you can reduce the frequency of corrections resulting in less chasing of seeing and less need to find a high quality guide star. At shorter focal lengths you may even get away with no guiding. And then, any error that an autoguider corrects is most likely already has happened, so it already has lowered the resolution a little. In your case, it doesn't sound like it'll be a huge improvement, but even an improvement of 0.2" on FWHM of 2" is not a bad thing, and may even become noticeable, especially at smaller pixel scales/longer focal length. Regards, ? ? -Paul
|
Re: PEMPro Results Analysis Question
Hi Brian - When the monsoons let up I will be rerunning PEMPro.
|
Re: PEMPro Results Analysis Question
A bit curious how much value there is in a PEC exercise unless you have a really large and high frequency PE; you could detect if you have this by running GA in PHD2. I would think it depends on your skies? Under SE Wisconsin skies, without PEC, I consistently get an average of 0.65" RMS with numbers sometimes as low as 0.45" RMS. This is purely by good PA, balancing, and cable management. Under my skies, that means I am probably seeing limited rather than guiding limited. Generally, if you? have 2" skies, improving guiding much below about 0.8" wouldn't result in meaningful improvement in IQ. If you're moving to a larger scope and your guiding becomes worse, I would think that's not a problem solvable using PEC but rather a limitation of the mount itself or the setup of the equipment (for example the inability of the mount to quickly enough compensate for the disturbance amplified by a large moment arm with a large scope). Just trying to see if my understanding is correct. In any case, you would want to be absolutely sure you're taken care of all the other fundamentals (weight limits of the mount, balance, clutch tightness, accurate PA? etc.) before looking to use PEC.
|
Re: PEMPro Results Analysis Question
not yet, but it's coming
I'd be happy to look at your results Jim, which I think i offered before ;)
If I recall correctly, your initial data gathering seemed suspect, with no clear periodic error at the fundamental or multiples of that. If you don't have good data to start with, you won't be able to do a good PEC, no matter how you fit it.
Brian
On Wed, Aug 19, 2020 at 10:34 AM Jim Waters < jimwaters@...> wrote: Is there a good tutorial on how to interpret the PEC curves and FFT waveform analysis results?
-- Brian?
Brian Valente portfolio
|
PEMPro Results Analysis Question
Is there a good tutorial on how to interpret the PEC curves and FFT waveform analysis results?
|
Re: G11 Mount Not Tracking Correctly
Hey everyone, first post here.
I have used the G11 mount before and had success with it, but this past weekend, it seems like no matter what I tried, I could not get the alignment correct. ?I purchased the GPS attachment thinking that would make things more accurate and simple, but that didn't seem to help. ?After setting up my mount, I aligned it due north with a compass and waited for sunset to align with Polaris using the polar scope. ?The app I have on my phone to match the reticle never seems to be in the same position when looking through the reticle of the polar scope, but I've never had difficulty aligning before. ?So after aligning Polaris between the correct lines in the reticle, I fired up the mount and used quick start. ?I verified the GPS data with another source and verified the time zone UTC -5, or Central Daylight Time, and ensured the time was also correct, and it was. ?However when using the two bright stars to perfect the alignment, (typically I use Vega and Deneb), the GoTo was way off. ?It would slew but point in totally different directions for either star. ?After using the buttons to slew to the correct position, it still would not go back to the correct spot and then trying to slew back to Polaris did not even work. ?I put everything back in the correct position with CWD and all that, all my cameras pointing at Polaris and tried again using Vega and Arcturus, and then Arcturus and Dubhe and never got good results. ?All my images ended up with trailing and I was using short focal lengths with relatively short shutter times of 3-4 minutes. ?I have previously done 8 minute exposures and had no trailing whatsoever at 24mm focal length on a 35mm full frame. ?For this past weekend I had three cameras mounted and balanced, with an 85mm lens, a 24mm lens, and a medium format camera with 23mm lens (18mm full frame equivalent).
I wanted to also do a series of Andromeda with my 600mm lens, but that would have been out of the question since I was getting trails at short focal lengths.
Any recommendations for how to fix this? ?Honestly, even if the GoTo doesn't take me to the exact position, I'm fine with using the buttons to slew to where I want to go, but I at least need it to track properly.?
Hi Doug,
Sorry to hear of your problems with the G11. First a GPS will only help the Gemini get its initial positional GOTO closer. Once polar aligned and even a single star model is built the Gemini knows where it is in that part of the sky.
A few questions, which Gemini are you using? Did you install a battery you tested @ 3.0V or higher? Do you know that Gemini GPS coordinates are entered using DMS format? If your GPS was a recent purchase do you know if it has the firmware fix for GPS rollover? If you are using well know navigational stars for Gemini alignment and your GOTOs are off and you cannot slew and return to a once centered location you have a few potential issues.
The troubleshooting checklist I use is: test battery, wipe battery clip contacts and install battery, do a full factory reset, verify GPS data you used is correct and entered using DSM format, enter UTC and only use UTC - no need for local offset, verify time format is entered using correct Gemini format is different, verify polar alignment. If you do this checklist 99.9% of all issues are resolved.?
--?
Chip Louie - Chief Daydreamer Imagination Hardware
|
Re: G11 Mount Not Tracking Correctly
In addition to verifying that you are not in lunar or solar, make sure that your dec wire is in fact to dec and RA to RA.? Sounds stoopid but I have confused the wires more than once.
Sometimes the wires are OK but one is not completely plugged in.
I would only use GPS if you can't see Polaris.
Greg, What does the GPS have to do with seeing Polaris?? -- Chip Louie - Chief Daydreamer Imagination Hardware
|
Re: Valid Guide Rates for PEC on Gemini Level 4
I avoid messing with these deep dark secret settings. ;^)
I just run the PEC, and have it start for me automatically, with the Gemini Telescope virtual hand controller I open on my display.
But then, I only use my single telescope/imaging rig, and have things set for repeat accuracy with each assembly.
I believe PEC is a good thing to implement. But I don't find it to be overly critical for my Fly-on-an-Elephants-Back equipment load.
I'm more concerned with the hobble-wobble in my telescope and focusser. ;^)
Simple Life = Simple Strife's.
--
SonnyE
(I suggest viewed in full screen)
|
Re: G11 Mount Not Tracking Correctly
I always like posts like this. I can come along after the usual prospectors and usually pick up a few nuggets.
I've never extended the legs on my tripod. Never had the need. But I think Michael's Point 4 has merit for me. So I will check that my leg clamps are tight.
That nugget was not missed by me, Michael. ;^)
I've almost always checked my tripods level and plumb as I begin my set up for the evening. (Which hasn't been lately due to heat, smoke, and clouds.)
My tripod remains set up on it's leveling pads I made for it, covered but ready to assemble my "chunks" and begin a session.
If I was to be accused of anything, it would probably be of tightening a smidgen too tight. I often notice this when breaking down and I look around for the gorilla who tightened my clamp on my D-bar.
I always handle my mount like it was made of glass. Not because I think I will hurt it, but out of my respect for how well made and beautiful I think it is.
And not banging it around keeps things as set from the previous sessions.
But for those who do extend their tripods legs, making sure they are tight is a very prudent point.
To me, .001" (0.0254 mm) on Mother Earth, can amount to a clear miss in Deep Space Objects. 8^0
--
SonnyE
(I suggest viewed in full screen)
|
Re: Valid Guide Rates for PEC on Gemini Level 4
Eric, The issue with PEMPRO is not the difference between East and West moves, but I don't want to get off topic. At the time you were using PEMPro there was an issue introduced when adding the two-cyle PEC programming for the Gemini, but that has been long since fixed. Hopefully someone else can measure their residual PE/drift at different guide rates using the same PEC curve
so we have more than one sample. PEMPro has been able to program the Gemini controllers since 2005, so I've seen hundreds of curves where drift was introduced by using the wrong guide rate. Hopefully a few people will report if the amount of drift changes depending on guide rate. It could well be that the latest firmware has changed the behavior. That said, the amount of drift change when changing guide-rate will depend on the PEC curve. The lower the periodic error of the mount, the less drift will be introduced when changing guide rate. So, one arc-sec/minute could be right for your mount and a small change in guide rate. It could be a lot more under different circumstances. -Ray Gralak Author of APCC (Astro-Physics Command Center): Author of PEMPro V3: Author of Astro-Physics V2 ASCOM Driver: -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Cyclone
Sent: Tuesday, August 18, 2020 8:25 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Valid Guide Rates for PEC on Gemini Level 4
Ray,
You seemed pretty stubborn about me being wrong about the move distances being different between
East/West
The issue with PEMPRO is not the difference between East and West moves, but I don't want to get off topic.
According to your PDF when you had mismatched guide and PEC rates you observed drift.
The report does not say that. The mount reports its state as slewing periodically and momentarily, but there is
no change in drift. I assume that because the PEC divisors are different than the guide divisors, the mount
reports its state as slewing at each PEC correction, but there does not seem to be any other side effect.
Have you tried measuring drift with mismatched guide/pec rates?
I did measure the drift with the same PEC curve and different guide rates and the drift in RA does not change
(approximately 1 arcsec/min).
Hopefully someone else can measure their residual PE/drift at different guide rates using the same PEC curve
so we have more than one sample.
Eric
|
Re: Valid Guide Rates for PEC on Gemini Level 4
On Tue, Aug 18, 2020 at 11:20 AM, Michael Herman wrote:
I still think it's a mis translation or a mis statement.
I think the statement should be:
?
...the PEC data is recorded at the present Tracking speed....
Michael, there are two steps and you keep talking only about the first one. Step one is recording PE data, the other is programming it into Gemini. Recording data into Gemini requires knowing the guide rate, otherwise Gemini doesn't know the size of the corrections you are sending.
|
Re: Valid Guide Rates for PEC on Gemini Level 4
Ray,
You seemed pretty stubborn about me being wrong about the move distances being different between East/West
The issue with PEMPRO is not the difference between East and West moves, but I don't want to get off topic.
According to your PDF when you had mismatched guide and PEC rates you observed drift.
The report does not say that. The mount reports its state as slewing periodically and momentarily, but there is no change in drift. I assume that because the PEC divisors are different than the guide divisors, the mount reports its state as slewing at each PEC correction, but there does not seem to be any other side effect.
Have you tried measuring drift with mismatched guide/pec rates?
I did measure the drift with the same PEC curve and different guide rates and the drift in RA does not change (approximately 1 arcsec/min). Hopefully someone else can measure their residual PE/drift at different guide rates using the same PEC curve so we have more than one sample. Eric
|
Re: Valid Guide Rates for PEC on Gemini Level 4
I still think it's a mis translation or a mis statement. I think the statement should be: ? ...the PEC data is recorded at the present Tracking speed....
It cannot be guide speed since there is no guiding being performed during PEC recording.? But Tracking rate surely would affect the PEC recording, since that determines the RA rate of speed and the corrections are matched to the worm rotation period.? ?
So in recording PEC data, I'd avoid using King rate, etc...just stick to Sidereal.??
Stay well, ...
Michael?
On Tue, Aug 18, 2020, 7:13 AM Brian Valente < bvalente@...> wrote: >>>
Periodic error correction pulses are recorded and stored? at the current guide speed?by Gemini, regardless of how PEC is programmed
yep - glad you guys added some meat to that bone
On Tue, Aug 18, 2020 at 5:36 AM Paul Kanevsky < yh@...> wrote: On Mon, Aug 17, 2020 at 08:23 PM, Ray Gralak wrote:
That's incorrect if you are using an autoguider to program PEC data. The autoguider keeps the star centered so it MUST send pulse guide commands via the ASCOM interface. The Gemini moves the mount and keeps track of the movement at that autoguider rate. What gets stored are indicators to move forward or backward (at autoguider speed) at each internal clock "tick".
Gemini PEC data is recorded based on the autoguide speed. If you change the autoguide speed after collecting periodic error playback will be either under or over-emphasized.
Ray is exactly right. This is what I was trying to say, albeit a little less clearly :) Periodic error correction pulses are recorded and stored?at the current guide speed by Gemini, regardless of how PEC is programmed. If you change the guide rate later, the pulses will no longer match the speed and the result will be overshoots or undershoots by PEC. Both not desirable.
--
Brian?
Brian Valente portfolio
|
Re: G11 Mount Not Tracking Correctly
In addition to verifying that you are not in lunar or solar, make sure that your dec wire is in fact to dec and RA to RA.? Sounds stoopid but I have confused the wires more than once.
Sometimes the wires are OK but one is not completely plugged in.
I would only use GPS if you can't see Polaris.
|
Re: Valid Guide Rates for PEC on Gemini Level 4
I still cannot get PEMPRO to work with my mount, but I wrote my own PEC programming software :) PEMPro works well on other Gemini equipped mounts if you follow the directions. You seemed pretty stubborn about me being wrong about the move distances being different between East/West, so maybe you didn't follow the directions? You state "the Gemini firmware is using the current guide rate instead of the rates defined by the divisors".
However, as I described in my previous post, this is not my observation. I can change the guide rate to any
value, it does not change PEC behavior. You should get some correction when the rates are different, but not the best possible correction. The more severe effect is the extra drift introduced, which can cause poorer autoguiding RMS than if you turned PEC off. The first time I noticed this is when I forgot to match the guide rate to
the currPEC rate and collected residual PE data. The residual PE with PEC ON was well corrected regardless
of the guide rate. According to your PDF when you had mismatched guide and PEC rates you observed drift (mount would indicate "slew"). I've definitely seen logs where there has been extra drift when the rates do not match. I don't have a mount myself to test with but others can try this test. There is always the possibility that there has been a firmware change to account for this. Have you tried measuring drift with mismatched guide/pec rates? -Ray Gralak Author of APCC (Astro-Physics Command Center): Author of PEMPro V3: Author of Astro-Physics V2 ASCOM Driver: -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Cyclone
Sent: Tuesday, August 18, 2020 7:27 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Valid Guide Rates for PEC on Gemini Level 4
Ray,
I still cannot get PEMPRO to work with my mount, but I wrote my own PEC programming software :)
You state "the Gemini firmware is using the current guide rate instead of the rates defined by the divisors".
However, as I described in my previous post, this is not my observation. I can change the guide rate to any
value, it does not change PEC behavior. The first time I noticed this is when I forgot to match the guide rate to
the currPEC rate and collected residual PE data. The residual PE with PEC ON was well corrected regardless
of the guide rate.
Do you have data that shows that the guide rate affects PEC? That behaviour does not match my mount.
Eric
|
Re: Valid Guide Rates for PEC on Gemini Level 4
Ray,
I still cannot get PEMPRO to work with my mount, but I wrote my own PEC programming software :)
You state "the Gemini firmware is using the current guide rate instead of the rates defined by the divisors". However, as I described in my previous post, this is not my observation. I can change the guide rate to any value, it does not change PEC behavior. The first time I noticed this is when I forgot to match the guide rate to the currPEC rate and collected residual PE data. The residual PE with PEC ON was well corrected regardless of the guide rate.
Do you have data that shows that the guide rate affects PEC? That behaviour does not match my mount.
Eric
|
Re: Valid Guide Rates for PEC on Gemini Level 4
>>>
Also, note that serial command 502 always returns 0.5, regardless of the actual guide rate used to train PEC, so it cannot be used to determine the PEC rate; you have to look at the clock divisors in thew currPEC.pec file to determine the PEC rate.
this was the part i remembered about something in Gemini always returning 0.5x
[Edited Message Follows]
Good morning all,
Based on my observations using my G11 with Gemini 2 in the past few years, the guide rate does not affect PEC once a PEC file is loaded. The currPEC.pec file contains all the information required for PEC to run independently of the guide rate.
Also, note that serial command 502 always returns 0.5, regardless of the actual guide rate used to train PEC, so it cannot be used to determine the PEC rate; you have to look at the clock divisors in thew currPEC.pec file to determine the PEC rate.
Attached is the first section of a draft document I am writing on guiding and PEC.
Eric
-- Brian?
Brian Valente portfolio
|
Re: Valid Guide Rates for PEC on Gemini Level 4
>>>
Periodic error correction pulses are recorded and stored? at the current guide speed?by Gemini, regardless of how PEC is programmed
yep - glad you guys added some meat to that bone
On Tue, Aug 18, 2020 at 5:36 AM Paul Kanevsky < yh@...> wrote: On Mon, Aug 17, 2020 at 08:23 PM, Ray Gralak wrote:
That's incorrect if you are using an autoguider to program PEC data. The autoguider keeps the star centered so it MUST send pulse guide commands via the ASCOM interface. The Gemini moves the mount and keeps track of the movement at that autoguider rate. What gets stored are indicators to move forward or backward (at autoguider speed) at each internal clock "tick".
Gemini PEC data is recorded based on the autoguide speed. If you change the autoguide speed after collecting periodic error playback will be either under or over-emphasized.
Ray is exactly right. This is what I was trying to say, albeit a little less clearly :) Periodic error correction pulses are recorded and stored?at the current guide speed by Gemini, regardless of how PEC is programmed. If you change the guide rate later, the pulses will no longer match the speed and the result will be overshoots or undershoots by PEC. Both not desirable.
-- Brian?
Brian Valente portfolio
|
Michael Herman
Paul Kanevsky
Chip Louie