PHD calibration

[Demonperformer]

For initial calibration manual says to use a star within 10d of the equator and 1hr of the meridian. At the time I am setting up the only thing brighter than about 5th mag within that area is Mars. Would the small movement of the planet during the time it takes to calibrate invalidate the result or will it be OK?

Thanks.

[Stargazer33]

I would imagine that using Mars would not work as it isn't a point light source. Wouldn't PHD think that it was either a star that is too bright or out of focus?

[Dr_Ju_ju]

Get PHD2 to auto select a star by typing ALT S....

[david_taurus83]

If your using an EQDir cable then it doesn't matter where you calibrate, as long as it's not too high up. It will let you know anyway. I've not had any issues by calibrating close to or on my intended target.

[Demonperformer]

That is great to know. Must admit I was thinking intuitively that calibrating near my target made sense when it starts guiding once calibrated. Moving to another star at that point seemed a little (excuse the pun) pointless.

Thanks.

[Rob63]

I only tried calibrating near the target after being clouded out in the south but having the east (target area) clear, it resulted in some of the best guiding stats I have ever had with my EQ6-R (under 0.6").

 

Rob

 

[Demonperformer]

Thanks.

Friday evening's session didn't happen unfortunately (despite the really clear skies). Tried on Saturday morning ... perfectly clear at 2.30, but by 3 when I had the mount and scope outside 100% cloud cover (which we have kept ever since).

[bottletopburly]

Phd2 or 1, if 2 it says, as you say 10 degrees  and hour from meridian as it works out and allows for rotation speed, read page 7/ 8 https://openphdguiding.org/PHD2_BestPractices.pdf

[Demonperformer]

@david_taurus83 & @Rob63

As above, can you please confirm if you are using PHD2 or PHD1 to calibrate near your object. I should perhaps have made it clear at the start that I have PHD2.

Thanks.

[david_taurus83]

PHD2

[Demonperformer]

Thanks, David.

[Rob63]

PHD2 as well.

[Demonperformer]

Would help if I learned how to focus the guidescope. Trying to calibrate on what appears to be a hot pixel does not make for a good guiding experience! 

[Dr_Ju_ju]

The guide camera doesn't need perfect focusing, if its slightly out, it gives PHD2 a better chance of selecting a usable target....

[michael8554]

1 hour ago, Dr_Ju_ju said:

The guide camera doesn't need perfect focusing, if its slightly out, it gives PHD2 a better chance of selecting a usable target....

The PHD2 developers only suggest that if you have a very short focal length guidescope, eg finder-guider, that gives tiny stars.

Otherwise to get sub-pixel guiding they recommend spot-on focus.

Michael

[Demonperformer]

It is a 9x50 finder with an adapter on it for a DMK camera. When I opened it in sharpcap with 10 second exposures (pointing in the vauge direction of andromeda) it showed just a load of bright dots, which did not move when I slewed the scope at top speed.

I was told that it can be focussed and there is a ring near the top, but I wasn't going to mess around in the dark. I will get it out and see if I can get it somewhere near focus in daylight today.

Thanks.

[Dr_Ju_ju]

While your at it, also build a dark\bad pixel map (PHD2 Tools), to stop selecting hot pixels etc.

[Demonperformer]

On 08/01/2019 at 21:43, Demonperformer said:

Would help if I learned how to focus the guidescope.

Well, a little playing has now got it focussed on my most distant pylon, so hopefully when I next try it "in anger" I will at least see something on the screen, even if not perfectly focussed, other than hot pixels. Speaking of which ...

On 09/01/2019 at 12:31, Dr_Ju_ju said:

While your at it, also build a dark\bad pixel map (PHD2 Tools), to stop selecting hot pixels etc.

Done that now with the setup in a changing bag from my old film photography days. 346 hot pixels and 615 cold pixels, on a 640x480 chip. In one way 961 bad pixels sounds a lot, but I guess as a proportion (961/307200, or just over 0.3%) it isn't so bad.