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SGPro - Auto Meridian Flip shortcoming

astrophotography
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8 replies to this topic

#1 AstroDaveNZ

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Posted 04 April 2020 - 01:03 AM

Hi. I’m using the awesome SGPro for my deep sky imaging. (I’ve switched from the competition to test it out, and it seems great so far!).

However my telescope has a large filter wheel and so I can’t let the scope point directly upwards towards the meridian. (regardless of whether a meridian flip has occurred yet or not).

 

It seems to me that SGPro does not handle this situation? There is only one configuration value ‘Minutes Past Meridian to Flip’. Setting this to +10 minutes saves a 'scope collision after the flip, but doesn’t prevent it beforehand.

Similarly, setting this negative means that my 'scope will collide with my tripod after the flip.

Am I misunderstanding something?

 

It would be great to have a second configuration value named ‘Minutes Before Meridian to Pause’ or similar to allow for my situation? Then I can set them both to 10 minutes and all will be good?

Thanks!
Dave



#2 Charlie B

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Posted 04 April 2020 - 07:08 AM

The best place for this question is on the SGP forum.  There may be work arounds for this.

 

Regards,

 

Charlie B



#3 Alex McConahay

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Posted 04 April 2020 - 08:13 AM

Have you tried mounting your filter wheel "upside down?"

 

Could you send us a picture of the rig?

 

Thanks.

 

Alex



#4 TimN

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Posted 04 April 2020 - 08:25 AM

If your setup is like mine, Alex is correct, mount the filter wheel upside down. Works perfectly.



#5 ChrisFC

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Posted 04 April 2020 - 05:57 PM

Don't you set it to a negative value to flip before?

#6 1DegreeN

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Posted 04 April 2020 - 10:06 PM

It would be great if SGP had an automatic mechanism to avoid collisions where you could specify by declination how close the scope can approach the meridian. What I do for targets in my danger zone of dec 6 to 20 is create two targets for the object in SGP - one target for ante-meridian and the second for post-meridian. I set the AM target end time and the PM target start time sufficiently before and after the transit time respectively to avoid any risk of the scope colliding with the tripod leg. I create another target between (in time sequence) the AM and PM targets for any object that is well away from its own transit time. So when SGP reaches the end time for the AM target it slews over to the dummy target for, in my case, typically around 40 minutes of imaging and then slews back to the PM target to resume imaging. The intermediate target can just be any object, I don't always keep the frames. It is certainly a kludge but it does the job. I was doing this with the Leo Triplet recently and choose Coma B as the intermediate target, getting about 50 minutes data on it each night.



#7 don314

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Posted 04 April 2020 - 10:50 PM

I was going to suggest what 1DegreeN just posted, he explains it well, so won't repeat.



#8 AstroDaveNZ

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Posted 04 April 2020 - 10:57 PM

Thanks all for the suggestions. 

I agree with "It would be great if SGP had an automatic mechanism to avoid collisions where you could specify by declination how close the scope can approach the meridian"

 

FYI, there is also a conversation I had in the SGPro forum about this: http://forum.mainseq...g-setting/12153



#9 pfile

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Posted 04 April 2020 - 11:47 PM

i think in general this is a problem that is very mount dependent. there isn't good handling in ASCOM for whether or not a particular pointing state is safe. there's an ASCOM property called SideOfPier, which if it's writable, an ASCOM client can write that property to cause the telescope to change pier sides. but (for instance) on A-P mounts, this property is read-only, and that's what SGP uses to determine if an early flip can happen. in other words if SideOfPier is read-only then negative values in the meridian flip dialog box are disallowed.

 

we had a long discussion about this stuff on the SGP forums a couple of years ago and it's clear that ASCOM needs more hooks to let mount control software tell ASCOM what's safe and what's not, how many minutes until a state becomes safe or unsafe, etc. but it doesn't sound like the ideas got any traction on the ASCOM dev side.

 

rob




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