Approching and passing the Meridian

[gonzostar]

Hi 

Last night there was a couple of hours window of clear skies  Quickly set up etc, Calibrated for the Eagle Nebula. Got about a hours worth of data on the East side. Then it crossed meridian. Should i just let the system continue guiding as before (i did for 10mins untill the clouds rolled in) Or once a object passes the meridian should i immediately  re-slew the scope, re-sync and recalibrate? 

I am using a ST-4 cable to guide with PHD2 

What i would like to know is what do other people do once your object passes the meridian?

 

Clear skies

Dean

[alacant]

Hi. If your mount and telescope are well aligned e.g. with no cone error, it should flip to the same centre. On my (real world) eq6, that's not the case. My wf is:

• plate solve east
• record the centre coodinates
• flip
• plate solve west
• slew to same centre

APT's PointCraft solver makes this painless. HTH.

[ronin]

Not sure how good this is but sounds reasonable.

Someone said what they did if they expected a meridian flip kind of "soon" was to set the scope+mount up aiming at an object on the other side of the flip then manually slew the scope to the real target and start  collecting data. That way (they said) there was no meridian flip. Guess it would only work if the object wanted was reasonably close to the meridian but an hour is just 15 degrees and that seems close enough.

Seemed to be that the manual slew overrode any "automatic" flip, then when it got to and past the meridian the mount was correct so one was not needed.

Having seen a big mount and biggish scope perform an automatic flip it sort of worries me. It all returned to the exact target but there was a lot of weight being thrown around. Sort of "Yes officer it was a terriable accident, he was looking through the eyepiece, then his skull was smashed by the 50Kg counter weights."

[Stub Mandrel]

In my garden the target is likely to disappear behind a tree before the scope hits the tripod, so i don't bother with meridian flips. As long as the balance remains east-biased I can't see the need to flip if nothing is getting caught up.

Neil

[AKB]

Doesn't really help the OP, but I simply chose a mount that doesn't need a meridian flip.  What it does need, though, is good balance.  My other mount (belt-model HEQ5-Pro) also requires good balance (rather than weight-heavy) so I'm wondering if that helps when wanting to pass the meridian?  Not sure,  never tried. 

[gonzostar]

Thanks for your replays very useful ideas. I dont have APT and mount scope didnt seem to be perfectly aligned! thought there must be a simpler solution Hence starting again with  sync and calibration. Also everything moving around such as cables and counterweight! it all seemed a bit chaotic 

However do like your idea Ronin will give this a try next time. Around 15 degree west the Eagle will crash into a chimney pot anyway. But do like the idea of pre-preparing for the flip if its so close in terms of balance and calibration. Hopefully the AVX mount can cope  

[wimvb]

As long as the scope doesn't hit anything, you really don't need to do a meridian flip when the target passes the meridian. 'if it ain't broke, don't fix it.' Especially if doing a flip costs imaging time. You can always do a 'dry run' on a mediocre imaging night, to see how fast you can reframe a target after a flip. And if your scope does automatic flips, you can test it without a scope attached, just to make sure how it works. Some hand controllers let you choose when/if to do a flip.

[gonzostar]

Cool, Cheers Wim I like the statement if it aint broke dont fix it  Will next time continue after meridian as imaging time is limited this time of year. I think i can get away with it more with the refractor then the 8"SCT. Wasnt aware that my hand controller for the AVX you can choose when  to do a flip. Will investigate  

[kirkster501]

On 15/07/2017 at 19:23, Stub Mandrel said:

In my garden the target is likely to disappear behind a tree before the scope hits the tripod, so i don't bother with meridian flips. As long as the balance remains east-biased I can't see the need to flip if nothing is getting caught up.

Neil

There lieth the problem for most people Neil, track too far past the meridian and you will get a collision with the peer.  Some mounts will not track x number of configurable degrees past the Merdiean.  I am working this out for my rig.

[Stub Mandrel]

6 minutes ago, kirkster501 said:

There lieth the problem for most people Neil, track too far past the meridian and you will get a collision with the peer.  Some mounts will not track x number of configurable degrees past the Merdiean.  I am working this out for my rig.

The solution for me would be the vertical extension I was offered with my tripod for an extra £10....

[ollypenrice]

How soon your scope and camera will collide with the pier depends on...

- how wide it is. Side by side systems collide earlier.

- how near the zenith you are. The nearer, the sooner the collision.

- the design of the mount itself. Some collide with themselves soon, some don't. And piers beat tripods.

If you run an auto-flip your software can be set up to plate solve itself back on target and resume the run. It will also invert the Dec guide commands as necessary. Alternatively you can re-frame by hand. If you do so I'd suggest opening a pre-flip image in suitable software, rotating it 180 degrees on the screen, and using that as a comparator with your incoming post-flip test subs which you frame accordingly. Dec calibration needs to be flipped after the flip.

If your target is approaching the meridian as you start the run it would, indeed, be a better idea to start flipped, which is to say conterweights west and counterweights high. How you persuade your mount to do this depends on the mount and its software. My Mesus are easy. I just drive them into roughly the right position, counterweights west, and hit GoTo. The mount considers my counterwieghts west position as an instruction to run on that side.

Olly

[gonzostar]

Thanks Olly very informative as usual.  As  i dont currently have software as yet (thinking of Backyard EOS) for the DSLR, i am prefering the idea in the second paragraph ie starting as if already flipped. Will give this a try when moon is in the way  I have the AVX mount so may not like the idea!

 

[wimvb]

Skywatcher mounts (synscan) give you several options for if/when to do a flip. AVX may also have this, just check your manual. During daylight you can move your mount manually to test how far past the meridian it's safe to go. Do this for various dec settings. That way you'll be prepared for that perfect imaging night.