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By Rob Glos
I've been guiding using PHD on my EQ5 & Orion Starshoot Autoguider for a while. I recently hooked up a QHY5-ll to do some planetary work om my main scope using SharpCap (successfully). However since then I've gone back to my deep sky work and the AutoGuiding is now failing with an Error - 22 (sometimes when connecting the camera and sometimes when trying to calibrate). Last night, having got past the error 22 on connection (connected the Orion late after starting the App) I then got an "start didn't move enough" error even though the settings hadn't changed from when I successfully guided (as far as I can remember). Also using the same cables to the same Win10 laptop. Not sure if the QHY camera is a red herring or a possible cause. Any pointers would be appreciated.
I connect my mount to PHD2 using ASCOM and most nights I have the error "Star did not move enough" as well as "Suspicious blah blah, axis may not be perpendicular". This does not happen when I connect the mount via ST4 cable. I read somewhere that I can do a Calibration Sanity Check in PHD2. I am however unable to find that function in the software. Is it some pop up feature or does it have a location in the settings/brain icon?
Any help will be highly appreciated.
I am using the SA with a Canon 650D and a 300/4.0 L USM for some months now. In order to get longer exposure times (>30 sec) I just got a little guiding cam (TSGM120M: https://www.teleskop-express.de/shop/product_info.php/language/en/info/p8963_TS-Optics-Mono-Planetenkamera-und-Guidingkamera-mit-Aptina-CMOS-Chip.html).
Stand alone guiding like the M-GEN II is way to expensive from my point of view, so I decided to use PHD(2) on a laptop to do the guiding. I use the Orion 50 mm Guide-Scope mounted on the second port of the L-Mount. But I don't know how to set up PHD2 to work with the SA. The guider-cam will be connected over USB to the laptop and over the ST-4 cable to the ST-4 port of the SA - now question about that.
There are some users in the forum, who already work with PHD and the SA as far, as I have seen. So maybe someone could help me about what "Mount" and "Aux Mount" do I have to choose in the connection dialogue of PHD? How do I switch off DEC-guiding, as the SA doesn't provide it?
Any experience with the dither function BackyardEOS provides with PHD2 connectivity?
Many thanks in advance!
Now that I have my CGEM on a permanent pier, I figured that I should get much better accuracy in guiding quality, especially at 2032mm (F10) focal length on my 8" SCT.
I spent a bit of time getting guiding results that are at the very least acceptable and thought I’d share my experience with anyone who is looking for info on PHD autoguiding.
In the pasten setting up for each astro session and using PHD I was generally getting RMS about 2.2-2.6ish and after stacking and processing, the soft effects were able to be negated to a great point, revealing detail and with results that I was quite happy with (on a good night) imaging at 2032mm using a modded Canon 40D.
The stars were round and generally I was able to use most (if not ALL) of the subs generated, even when I was exposing through Halpha or SII for 30-40 minutes per sub. That in it self, I thought, was pretty good for the setup that I'm using... or... I'm just easily pleased.
I use a OAG for my exposures so guiding on the same FL as imaging.
That said I did spend a bit of time playing with PHD settings, as well as the backlash setting on the CGEM, along with autoguide rates to try to get better guide graph.
After a spending a bit of time on both polar alignment as well as tweaking the autoguiding parameters in PHD, I was still getting a graph that showed large jumps, see pics… Nowhere near the near flat line that a few imagers were getting. Although the RMS level at 2032mm did improve, now I’m getting numbers of between 0.83-1.3, so it is definitely an improvement but still didn’t look flat.
The test exposures I done at those RMS levels using the 40D at ISO100 on a 40 minute exposure showed round stars and the frame exposure looked good.
I decided to investigate to try to improve the graph, and when turning off the guide commands the graph showed large bumps generated by star movement caused by the atmosphere, the graph was very similar, although slightly higher RMS, due to the star moving around obviously due to seeing.
At this stage I put my larger graph RMS in comparison to other very flat graphs to perhaps me guiding at 2032mm on a 1/4” CCD and others guiding using a much smaller/shorter FL guidescope where such large seeing related star movements are not picked up at a shorter FL, I base this on the fact that when imaging and guiding while using my 80mm/500mmFL frac where I generally got a RMS of 0.3ish.
Using the size of the pixels and CCD on the focal length the results are 0.548 arcsecs per pixel so multiplying that by the RMS I get the guiding is 0.45 – 0.71 arc seconds accuracy (?) which if I’m right, sub arc sec accuracy is OK for AP. I used http://www.celestialwonders.com/tools/imageScaleCalc.html for the calculation.
NOTE That until I had decent backlash set on the handset I was still getting intermittent saw tooth like spikes in DEC and RA, and the guide star did spontanously jump large distances periodically.
The way I adjusted the backlash on both RA and DEC was by centering a star on the laptop screen and at 1X guide speed moving forward, forward, back, forward, back, back, adjust the backlash and repeat until the star responded instantly.
Also my autoguide rate is set at 40% for both DEC and RA.
My PHD parameters that seem to give the best guiding at 2032mm are below:
RA Aggressive: 50
RA Hyster: 10
Max RA Dur: 350
Search Reg Pix: 15
Min motion: 0.15
Calib Step: 500
Time Lapse: 0
Dec Guide Mode: Auto
Dec Alg: Resist Switching
Dec Slope: 4.5
Max Dec Dur: 350
Star Mass Tolerance: 1.00
Dither Scale: 0.05
Hopefully some of this helps someone.
Also if I'm missing something and anyone has advice to improve that graph, please feel free to share.
By Gerry Casa Christiana
Ive been through this a few times but I thought I would look at what other people think on this.
Is the time spent on dithering really worth it? Or is it better to use that time to get more subs?
It seems to me in my experience that im spending at least 2 minutes between shots for dithering. When I look back through my pictures when I wasn't even guiding they look much better. One thing I have changed is not using darks anymore. I used to always use them. Now I use flats and bias shots but they seem noisier than my older shots.
What sort of times are others getting in dithering? Is there a way to speed it up? I'm using APT. EQMOD PHD2 eq6.