PHD help please

[Ewan]

I have a CG-5GT mount with a guide port, HITECASTRO USB guider & tge DMK 618 that has NO ST-4 port.

In PHD i HAVE to select MOUNT - ASCOM to get phd to tell me its talking to the mount, surely i am meant to be able to GPSUB as the mount selection ?

I pick TELESCOPE as Usb_Guider as well which i think is correct from what i have read.

Can anybody please confirm this is correct setup as i thought ASCOM was for controlling thd scope through the Handset only ?

I have posted similar question but didnt get very far so id really appreciate some guidance ( no pun intended)

[IanL]

You have RTFM right?

http://www.hitecastro.co.uk/support/Guider/USB_Guider.pdf

The instructions describe the process exactly as you have followed it, so it should work fine. As per the manual, when you get to the ASCOM telescope chooser dialog in PHD, click the 'properties' button and then click the 'test outputs' button on the properties dialog. This should send some short guiding pulses to the mount. You won't see it move as the guiding movements are small, but if you listen to the mount you should hear the motors responding (different whining/clicking type noises).

ASCOM is just a standard means for hooking up telescopes, cameras, etc. on Windows machines. The vast majority of software uses it for one purpose or another.

[Ewan]

Ok Ian, ill rig it up tonight & check it indoirs, i assume this can be done without getting a guide star etc but just s dry run inside ?

[IanL]

Ok Ian, ill rig it up tonight & check it indoirs, i assume this can be done without getting a guide star etc but just s dry run inside ?

Yes indeed. Another test after connecting to PHD; on the PHD tools menu there should be options to send guiding commands to the mount. Mind you if the first test in the ASCOM properties dialog works, there should be no reason why PHD wouldn't work as well.

[Ewan]

I think the mix up is from advice regarding me selecting the GPSUB on the mount options, this is what i have been trying to do with no luck at all, so i was assuming i DO use the ASCOM & it finally connected.

The only other problem & fix which i can confirm works is this, if you have 2 usb's on one side of the laptop (if using one) DO NOT plug guider & guide cam in these 2 next to each other it will not work, i moved one connection to the opposite side & it enabled ASCOM to connect.

I didn't want to use the ASCOM option as i thought it was ONLY meant for connection through the handset which i thought might generate a slight lag, obviously i want the connections talking to one another as quickly as possible.

Thanks for the help Ian.

[Ewan]

Got it working but clouding over now typical, from what i have read i turn off Dec in PHD from auto ?, the red graph line was going off the chart but the blue one has very small spikes so is this pretty good, after turning DEC off red stayed in a straight line.

Got 3 minute subs which double not guided & i was testing only so its better already.

Thanks again

[IanL]

Normally you would not turn off Dec guiding (red line) unless you have perfect polar alignment (unlikely unless you have a permanent set-up and have drift aligned to an obsessive degree). When starting out you should leave it set to 'Auto' and 'Resist Switching' in the 'brain' dialog box as this will usually figure out what do without your help.

The blue (RA) line sounds okay, but if you can post a screenshot of the graph next time that would help us to confirm it. If the red (Dec) line was shooting off the graph, that normally means either:

- Your Dec corrections are not being acted on by the mount for some reason.

Again, suggest you use the tools menu in PHD to check that you are getting responses to guiding in both Dec and RA.

- Your Dec corrections are undercorrecting due to poor calibration.

How many steps did PHD take to calibrate in each direction? If it only took a few (maybe five) or lots (maybe more than 20 or 30) you may need to change the calibraton step settings. You are aiming for more than 10 and less than 20 steps in each direction in my experience, and nearer to 10 is usually best otherwise calibration takes forever.

Try different values for the 'Calibration Step' setting. Maybe between 500 and 2000 (though even more might be needed in some cases). There is no one right value for this, as it depends on the image scale of your guiding setup (which depends on the focal length of your guidescope and the size of the pixels on your guider chip), plus the closer you are imaging to the pole, the higher the calibration step needs to be. As I said, experiment until you get a sucessful calibration with 10-20 steps in each direction.

Also every time you move the scope to a new target that is a fair distance from the current one, make sure you tick the 'force calibration' box under the brain settings, as you will need to re-calibrate in most circumstances.

- You have a mechanical problem.

This might be a loose clutch or a slipping gear or similar in the mount. It might be flexure under gravity between the guide scope and the mount so as the mount moves the scope doesn't follow exactly. We are talking about very small movements here, not usually visible by eye; check for loose bolts, that the guidescope is tight in the rings, that the camera is not drooping (e.g. the focuser tube may droop under gravity, so if you have a lock screw use it).

Here is a good all round guide to PHD that is well worth a read:

http://www.rosecitya...deToGuiding.pdf

Also, here is a slightly more advanced document from the author himself:

http://www.stark-lab...gPHDGuiding.pdf

[Ewan]

Thanks Ian, i will have to put a screen grab prog on laptop, i did tell PHD to create a log if thats any use.

My guidescope finder is f3.75 @ 225 fl, i set phd steps to 1300 after getting a calibration count of upto 50 which from what i gether is too high.

I will turn the DEC back to auto.

[IanL]

I would typically use a step of 1500 - 2500 with my 400mm FL ST80, and 50 steps is way too many I'd say. Don't be afraid to go for something in the 2000 - 4000 range as such a short FL. You may find the calibration is not reliable if you set the step size too high, so do a bit of trial and error until you can get reasonably stable guiding without spending 20 minutes calibrating!

[Ewan]

Yes your correct Ian, it was about 15 minutes calibrating but as i am new to PHD i thought this normal until i checked on the internet.

If i post my 'brain' settings can you have a look & advise if it's really obviously an error by me (i havn't fiddled that much with them though), if some items are going to be trial & error ie steps then ill just have to test when it's clear again.

[IanL]

Sure thing I'll take a look for you. You don't need a screen grabber, if you just hit the PrtScn key that will capture the whole screen (or hit ALT-PrtScrn to just grab the active window). You can then open paint, paste in the screen grab and save it. (If using a laptop you might need to hold the Fn key or similar if PrtScn is not a key by itself but one of the Fn type keys).