Comments - A Post I Sent To The Stark Labs Group on PHD Settings - AstroGab2024-03-29T10:09:06Zhttps://astrogab.ning.com/profiles/comment/feed?attachedTo=6354305%3ABlogPost%3A48818&xn_auth=noHere's some more tips on PHD…tag:astrogab.ning.com,2011-05-21:6354305:Comment:494112011-05-21T01:52:30.328ZGreg Marshallhttps://astrogab.ning.com/profile/GregMarshall
Here's some more tips on PHD settings:<br />
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1. DEC guide mode (Off/Auto/North/south): Normally you would leave this set at "Auto". If your polar alignment is excellent you might prefer "Off" to avoid spurious corrections. If DEC is drifting you can note which way it's drifting (easy in "Off" mode) and enable corrections only in the opposite direction.<br />
2. DEC Algorithm (Lowpass filter/Resist switch): Although the default is "Resist", it is probably slightly better to use the lowpass filter. What…
Here's some more tips on PHD settings:<br />
<br />
1. DEC guide mode (Off/Auto/North/south): Normally you would leave this set at "Auto". If your polar alignment is excellent you might prefer "Off" to avoid spurious corrections. If DEC is drifting you can note which way it's drifting (easy in "Off" mode) and enable corrections only in the opposite direction.<br />
2. DEC Algorithm (Lowpass filter/Resist switch): Although the default is "Resist", it is probably slightly better to use the lowpass filter. What this does is to effectively calculate your DEC drift rate and apply correction for it in very steady increments, greatly reducing the effects of seeing, etc.<br />
3. DEC slope weight (N): Craig doesn't explain this well and I certainly have no insight, but suggest taking him at his word and leave it at "5".<br />
4. Search Region (N pixels): The default of 15 pixels (i.e., a 30 x 30 area) is generally quite adequate. Larger areas take more time to process and if it gets that far off you've got a serious problem that is probably not going to recover anyway.<br />
5. Noise reduction (none/2x2/3x3): Normally set at "none", but if you're working with a dim guide star and can't increase the exposure time, you might want to try one of the other settings. What it does is to trade off resolution for sensitivity (like binning, but done after the capture rather than in the camera). This can be especially useful for cameras that have very small pixels. Such cameras may provide more resolution than is useful, but suffer from low sensitivity and noise that degrades the accuracy with which PHD can calculate the centroid of the guide star.<br />
5. Time lapse (N milliseconds): A delay after a guide movement before the next guide camera exposure. In some cases the mount movement may not be complete or may not have settled when the "pulse" is done. Setting some delay here will provide time for the mount to settle so that the next exposure is done entirely at the new position.<br />
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Another good debate on guiding is how critical it is to focus the guide scope. If you have a sufficiently bright star for the sensitivity of your camera, focus is not critical. In fact, in a camera with very large pixels it may be difficult for PHD to find the centroid of a tightly focused star because it doesn't cover enough pixels to get useful relative values. However, the much more common and likely situation is that the guide star is not as bright as PHD would like. In that case, getting better focused will increase the brightness, albeit over fewer pixels. That's a good summary, Neil,…tag:astrogab.ning.com,2011-05-20:6354305:Comment:485532011-05-20T15:46:02.090ZGreg Marshallhttps://astrogab.ning.com/profile/GregMarshall
That's a good summary, Neil, thanks. I would add to (5) that you can trade off between calibration step size and the mount's setting for guide rate. If you have to go really high in cal step size, maybe you should increase the guide rate - it would certainly make calibration go faster. But after you've done calibration don't change the guide rate. That's the same as changing aggressiveness. Guide rate is usually best kept at 0.5X (aka 1.5X or 50%), but might go as low as 0.25X and as high as…
That's a good summary, Neil, thanks. I would add to (5) that you can trade off between calibration step size and the mount's setting for guide rate. If you have to go really high in cal step size, maybe you should increase the guide rate - it would certainly make calibration go faster. But after you've done calibration don't change the guide rate. That's the same as changing aggressiveness. Guide rate is usually best kept at 0.5X (aka 1.5X or 50%), but might go as low as 0.25X and as high as 1X. You should NEVER go above 1X, even if your mount allows it.<br />
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I agree that it's a good idea to minimize DEC corrections because they will delay RA corrections that are more urgent. But you seem to be suggesting that PHD will always do DEC corrections first. Is that right?<br />
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I dislike the term "pulse guiding" because as a description it better suits the OTHER method, the ST-4 guide port. I have sometimes referred to it as ASCOM driver guiding, but that's not really good either, since it doesn't always involve an ASCOM driver. It's an annoying little bit of AP trivia - like the many different ways of specifying guide rate. Nice contribution Neil. I'm s…tag:astrogab.ning.com,2011-05-20:6354305:Comment:488292011-05-20T11:53:26.014ZSteve Coateshttps://astrogab.ning.com/profile/SteveCoates
Nice contribution Neil. I'm sure this will clear up a lot of confusion in using PHD.
Nice contribution Neil. I'm sure this will clear up a lot of confusion in using PHD.