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iEXOS and PHD2

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#1 Danoglide63

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Posted 10 April 2020 - 08:18 AM

Hello everybody,

The last two nights were the first chance I had to get going with PHD2 on my new iEXOS mount. The first night I used my Revolution2 Imager camera and Orion 50mm guide scope. I PA'd with Sharpcap Pro and ran the calibration (see the screenshot) and for some reason the PHD2 log is gone now and the Guide Assistant. I two star aligned using Starry Night8 and slewed to Alnitak just to see what I'd see. I tried several 6 minute exposures and got nice round stars but the Red/Blue lines looked like Picasso's rendering of a lumberjack's saw. Last night I changed to my ZWOASI224MC camera did the calibration, Guide assistant which told me I was 20 arc-min off PA so I re-did PA on Sharpcap.

 

I slewed to Rosette Nebula and tried some 5-6 minute exposures and got nice round stars but that's all I got. Not a good night for "seeing". Anyhoo.....the graph on PHD2 looked terrible to me but the stars are round. I'll attach the screenshot's and the one log from last night. Please look them over and let me know if I'm doing good or I need to change something.

 

Thanks and hope everyone is safe!

Dano

 

Screenshot (79).png

 

Attached File  PHD2_GuideLog_2020-04-09_192832.txt   90.74KB   4 downloads


Edited by Danoglide63, 10 April 2020 - 09:47 AM.


#2 Danoglide63

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Posted 10 April 2020 - 08:19 AM

And the other screenshot too big for the first post.

Dano

 

Screenshot (78).png


Edited by Danoglide63, 10 April 2020 - 08:20 AM.


#3 OTA

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Posted 10 April 2020 - 10:15 AM

Couple of questions.

 

Are you using Explore Star's or the ASCOM driver?

 

If it is Explore Star's are in you Point or Track mode?

 

steve,



#4 Devonshire

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Posted 10 April 2020 - 10:31 AM

Dano,

 

Round stars is the objective, and at 300-360s, no less - good show!  :-)

 

I see a couple of interesting things going on your log (using the PHD2 log reader).  Nine short guide sessions, rather than fewer, longer ones, but I'm not sure what changed between them.

 

Some of your sessions have a huge bump in them.  Looks to me like you may have touched the mount in that time...or maybe dropped an anvil nearby?  :-))

 

I also see some sessions with star lost/low SNR popping up, so presumably you had a bit of cloud messing things up.

 

The 14 min session looks like a good one to study.  The star scatter diagram looks pretty well distributed.  The twin bumps at 21:08 and 21:18 are probably the main periodic error (~600s) showing up and being compensated for.

 

- Your calibration looks reasonable to me, although your guide camera angle may be off a bit from the mount axes.
- You may benefit a bit from biasing your balance east-heavy, camera-heavy to help with backlash
- Don't touch the mount when imaging
- If not already, you tripod legs should be set low
- Your polar alignment could be a bit better, and that plus backlash and unbiased balance may explain the DEC activity. 
- If you feel ambitious, you might try adjusting your mount to reduce backlash on both axes, but if you're already getting round stars at this exposure length, I wouldn't feel in any rush at all.

 

Having said all that... ya got round stars, and at a very decent exposure length! :-)

 

My $0.02, FWIW...

 

- Bob



#5 Danoglide63

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Posted 10 April 2020 - 10:55 AM

Thanks for the replies,

I'm using ASCOM Steve.

 

Bob, I had short sessions at several DSO's that I couldn't get a good shot of. The tripod is slightly extended so that I can look through the Polar tube when I have to. Yes it was kind of cloudy, the kind that is very faint like smoke? There are/were some fires in the mountains. I'll try to shift the weight like you suggested. I don't remember dropping my anvil and I'm back from the tripod so I don't kick it again.....the sessions in the log showed some smooth flowing lines and some look like jagged gravel roads.  Why the differences?

 

Thanks anyway, hope everybody is safe!

Dano



#6 Devonshire

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Posted 10 April 2020 - 11:39 AM

Dano,

 

A bit of high cloud would do it. The lost star/SNR drop shows up in the log and you should see a msg go by on the console as well.

 

Re: Anvils - well, *something* delivered some notable bumps!  :-)

 

One thing to bear in mind when looking at the logs/tracks is that PHD2 can change presentation scale on the fly.  That puzzled me too for a while - those sessions with the big bumps have pretty flat tracks and a very tight star scatter diagram.  Took me a while to realize that the flat track/tight scatter I was seeing was due to a scale change. 

 

Most of your sessions have such a bump - anywhere between 40" and 100", just a few seconds long, and all by itself, but a couple (like the 14min one) do not.  Sticks up like a mountain on a rolling plain, and the plain looks flat by comparison.  Zoom in on that flat plain and once you get to a more appropriate scale, it doesn't look so flat any more. 

 

Question:  If you're using Sharpcap for PA, why do you need to use the Polar tube?  

 

HTH...

 

- Bob


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#7 Danoglide63

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Posted 10 April 2020 - 02:07 PM

Out of habit I guess, I use the Polar Scope on my AVX too. The closer I start off the easier I guess. You mentioned the change of the scale, I noticed that too, the graph doesn't look as bad when viewed by the Log viewer. I'm set up outback on the concrete pad around the pool. I often wonder if a car drives by will it show up on the graph? I don't have the rubber shock pads yet. Maybe when my clogs wear out.........

 

Thanks again,

Dano



#8 Devonshire

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Posted 10 April 2020 - 04:34 PM

Car?  Maybe.  Soil conditions may be a factor.  Might also be something else.  You're sure about that anvil?  :-))

 

I have trains that go by in the evening, perhaps ~200m away.  Lots of other properties and trees in the way, but we also have clay and a high water table, so I felt the bounce when they passed, despite setting up on well-compacted concrete pavers. 

 

I bought a couple of Celestron-clone pads from Steve and glued a layer of cork on the bottom to mess with vibration transmission from the pavers.  Seems to help.


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#9 Danoglide63

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Posted 10 April 2020 - 06:49 PM

What's odd is the spike happens right there in the begining most of the time. I must admit I'm guilty of not going Right/Up each time I centered a star. I'm trying to look through my Rigel finder scope while I look at the laptop and push the NSEW keys on the POTH control.

 

Dano




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