secrets of successful platesolving via synch?

[prefetch]

hi all,

 

i've been using sequence for many months now, and one thing that i've never really gotten to work consistently is the synch function in sequence.

 

through experimentation i've found that i have to be almost within about 15 minutes of center otherwise synch will fail.

 

however, if i use pinpoint through maximdl, i can be off by quite a bit.  it seems that pinpoint "tries harder" than sequence.  sequence fails after just a few seconds, whereas pinpoint keeps trying for up to a couple of minutes and many times succeeds after this long.

 

i've switched catalogs, i've played with the "Expansion %" variable, (which i don't believe actually does anything!!) the 5x5 spiral search option is disabled on sequence.  i've adjusted the Max Magnitude variable - i've increased my exposure time, decreased it (usually 7 seconds seem to get a good amount of stars) but nothing seems to help me get more area coverage for plate solving, unless of course i just use pinpoint from maximdl.

 

i just don't know what else to do, and since MLPT and sequence fundamentally requires platesolving to actually work through a long exposure, i feel like i'm kind of crippled here.

 

does anyone else feel like sequence synch is a lot weaker than pinpoint (even though they are supposed to be one in the same) ???  or is it just me??

[lukepower]

Hrm, I do admit that I tried last night a few Syncs, even without moving the scope, and Sequence had everytime some offsets to find (note: the image was the same). Dunno if there is a calculation error in Sequence's routine, as it fetches the results from Pinpoint, or whatever. At the end of the game, when leaving it taking a Sequence of images, it is working quite well nonethless... Which version are you using?

[prefetch]

lukas, thanks for sharing your thoughts.

 

i use sequence beta 0.2.0.5.  

 

i guess the strange thing to me is that synch can fail so quickly, but manual pinpoint works for a long time to figure out how to solve something.  it seems like synch is giving up too soon and cutting things off prematurely as opposed to merely calling pinpoint and letting it do all the work and waiting for it to be complete.

 

perhaps i need to post in the beta section to find out more of what's going on.

[robertp]

To my understanding, Sequence uses PinPoint in the background for platesolving, so it should not really matter whether you platesolve via PinPoint directly or via Sequence. If you see different behaviour, I would guess that it's due to one of the following reasons:

 

* The platesolve settings in Sequence differ from the settings in MaximDL or PinPoint, e.g. the timelimit or the spiral search. I actually limit the search to 10 sec maximum as I have the impression, that in case the platesolve does not succeed within few seconds (it usually does not take more than 1-2 seconds), then it will fail anyway, so a long timeout is just a waste of time. I never use spiral search in Sequence and when I tried it way back (the first version of Sequence) I had the impression that it did not work properly (that might have changed, but I haven't tried it since then).

 

* The horizontal and vertical scale per pixel is not correct in Sequence. It can be off quite a bit and PinPoint might still solve some images correctly but fail with others. The pixel scale in Sequence has to be set to the pixel scale of an unbinned image even if you set binning to e.g. 2.

 

I use Sequence with synch and MLPT all the time and usually all my images platesolve very fast and correctly using the GSC1.1 catalog. I usually only encounter problems using a very short focal length like the Pentax 165 medium format lens.

 

Hope this helps, clear skies and happy platesolving,

 

Robert

Edited October 29, 2014 by robertp

[tbaehnck]

Hi,

 

my experience is that plate solving in Sequence will perform as good as in MaximDL but both solve worse compared with the solving directly in PinPoint.  Frames that failed in Maxim or sequence I was able to solve in PinPoint.

 

The problem I have also, is that the result in Sequence shows an offset/delta to the result in Maxim. For the same frame!

And the result in maxim is right when I compare the position in the thesky6 ore MaximDL itself.

First I thought it is a problem with jnow and j2000 but the offset is different.

Anyone who have the same problem or have an explantion for this?

 

BR Thomas

Edited November 1, 2014 by tbaehnck

[prefetch]

thomas, i'd be interested in checking into that - strange!

 

robert, thanks for your reply and thoughts.

 

so, it turns out that i upgraded by camera to a 16803 ccd, and my FOV is now about 46 minutes - and suddenly plate solving is a breeze.

 

i guess my previous small chip plus long focal length made plate solving really hard.

 

still - it is interesting to see evidence that sequence and pinpoint seem to be not 1:1 equivalent.  strange.  i guess we'd have to look at the code and understand how it's implemented to figure this out.

[robertp]

Hello Thomas,

 

I never checked whether platesolving with Sequence or Maxim/Pinpoint provides different solutions. That's interesting and I will try to verify that asap. How did you compare the results? I would recommend to adress that problem to Philipp in the bugs-section.

 

 

Hello "prefetch" (would you mind to share your real name?),

 

glad that with the bigger chip your problems went away. What was your FOV before?

 

Best regards,

 

Robert

[prefetch]

hi robert.  i just go by prefetch.  hope that's okay.  

 

my FOV was about 14 minutes square w/ my atik 460, so quite a bit smaller than the 46' i enjoy now.

 

i used USNO A2.0 and had some more success with the 14' FOV, but now w/ the larger one i switched backed to GSC 1.1.

 

so, problem solved for me, but i believe something is screwy with pinpoint and sequence.  my solution was just to use a bigger chip.

[tbaehnck]

Hello prefetch, Hello Robert,

 

you can check this easily if you:

 

- take a e.g. 5sec frame in maximdl

- platesolve it

- choose in observatory/telescope "image center from pinpoint" and "sync" in maxim

- then open sequence and sync

- in the status bar you see the delta in both axis

 

Because the telescope didn't move it should be the same but there is always a delta. And if I sync in sequence thesky6 shows an offset from the star but the star is dead center on the chip, so the sync/platesolve result in maxim seems to be better.

 

CS Thomas

[tbaehnck]

Have anyone checked this meanwhile?

 

BR Thomas

[robertp]

Hi Thomas,

 

sorry, the weather did not cooperate during the last weeks mainly due to my home cities infamous fog. I hope to test that soon, but the forecast is not very promising for the next few days.

 

best regards,

 

Robert

[MarkS]

 

"i've played with the "Expansion %" variable, (which i don't believe actually does anything!!)" - Prefetch

 

Just a side note to the main thread: I have found that when using Pinpoint to solve plates directly, it is possible to get severe position errors if you set the Expansion % too high - eg 40%.

 

Mark

 

 

Edited November 29, 2014 by MarkS