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MX+ First Light

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#1 csauer52

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Posted 17 January 2020 - 10:35 PM

Well Clear Sky Clock called for clear skies until midnight so I thought I'd take a chance to get the mount dialed in as a means to get ready for the new moon next weekend. The plan was to obtain a TPoint model, accurate PA and then train the PEC in order to assess how well the mount can image unguided. Well, I managed to get the TPoint model and accurate PA and that was it. I suppose the PEC and unguided testing will need to wait for another day.

 

Overall the mount is a dream to operate. Smooth and relatively quiet slews and I managed a 44 point model in around 10 minutes which I don't find to be terribly excessive. I'm really looking forward to seeing what this mount can do as I become more acquainted with it.

 

Question - I'm a setup/tear down guy every night I image. How does one approach PA with this mount on subsequent setups? Do you run a fresh TPoint model each time you setup and turn on the mount? Seems like there would be easier ways to obtain "close enough" PA therefore I'm wondering what others do in my situation? I upgraded to the Paramount to maximize my data collection potential therefore looking to minimize setup but not sacrifice accuracy (as much as possible anyway).

 

Interested to hear how others start their sessions....

 

Additionally - how does one read the report output? Clearly I managed a fairly accurate alignment but I don't understand why some of the text further down the report seems to suggest I need more mechanical correction. Appreciate any advice the more seasoned PM users tend to have.

 

Chris

 

 

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#2 Ken Sturrock

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Posted 17 January 2020 - 10:46 PM

Congratulations on the mount.

 

There are different ways to polar align the mount. In most cases, you're best served over-all with the standard "refracted pole" instructions. Moreover, if you choose the refracted pole then you can also use the "Advanced Polar Alignment" (APA) routine under the tools which is kind of nice because, instead of telling you to adjust a certain number of "ticks" it uses a closed-loop process where you use the mechanical adjusters to align the star with the on-screen reticle.

 

The standard answer to your setup question is that for field use, you'll perform a "portable recalibration" which uses a smaller TPoint model to recalibrate your previously-recorded larger TPoint model. You could, of course, run the whole thing from scratch during twilight, but it's probably not necessary.

 

You can read all the details in the TPoint manual.

 

In my case, I benefit from a pier in the backyard. I just plunk it down, home the mount, and go. I'll re-shoot my TPoint model and re-do the polar alignment every few months on a clear full moon night. I don't bother with unguided, though. So, my needs aren't as precise as yours.


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#3 rgsalinger

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Posted 17 January 2020 - 11:02 PM

You'll figure this out eventually but what I do with TPoint is to run it binned 3x3 and with a subframe of 1/2 (if memory serves). That way I get very fast slews and solves and I think I can do about 3 points per minute that way. You just have to get the image scale settings correct. My mount has such low PE that I don't bother with PEC. It was 1.5 arc seconds peak to peak after Bisque repaired it. 

 

Rgrds-Ross


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#4 LPA

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Posted 17 January 2020 - 11:10 PM

Everything Ken said is what I did before I had a RoR built. I'll just add a few things. Do a larger tpoint model, say 100 targets, one time followed by APA. That will nail down the internal mount-related parameters. From then on when you setup you can just do the portable recalibration with say 20-30 targets followed by APA during twilight before it's dark enough to image so you won't lose any imaging time. Also, if you want to go unguided, then PEC training will help somewhat if your seeing is really good. You only need to do that one time and skies only need to be clear around the meridian and celestial equator for it.

 

Larry


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#5 Ralph Paonessa

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Posted 18 January 2020 - 02:49 AM

 - how does one read the report output? Clearly I managed a fairly accurate alignment but I don't understand why some of the text further down the report seems to suggest I need more mechanical correction.

If you uncheck the "Show alternate polar alignments (advanced)" box (bottom right), the alternate connections will not be shown. And it's much better to use the reported tics to adjust as a preview of what you need to do, but actually dial in the adjustments with APA (Accurate Polar Alignment). 

 

Another tip: It only takes about 15 samples (both sides of meridian!) to dial in a good PA, so that plus Accurate Polar Alignment is a pretty efficient way to polar align. After you do this, you can just run a completely new 15 point model to verify your PA, or fine tune it (or as a sanity check).

 

As others have said, you can run and save a large model once for your setup; and then run a Portable Recalibration each time you set up after that. But keep in mind that this assumes you are using the same scope and image train, and attaching it to the mount the same way each time (and screwing everything down tight). It's not really valid to use the same model if you switch to a field corrector or reducer, for instance (or a different camera), because this would alter the image train and could change the flexure of the system that TPoint is trying to account for.

 

When I had time to spare, I ran a 300 point model, and typically do a 15-40 point recal after that. (It's important to sample well on both sides of the meridian.)

 

Also, once you have a large model, remember to activate ProTrack, which isn't on by default.

 

PEC is worth trying, so you can see how large or small the PE is for your mount. (If it's over 7" peak-to-peak, it's out of spec and SB will probably replace your worm.) If you create a PEC curve, it's important to apply it and immediately check your PE again, because it's easy to get it backwards (in which case you'll see your PE double, and you can go back and reverse it).

 

I have the MYT and my intrinsic PE was 2.8", and PEC reduced this to 1.0". Best to do this on a night of good seeing.

 

Out of curiosity, what focal length and image scale are you working with?

 

I love my Paramount and TheSkyX Pro! Congratulations on your MX+.

 

Ralph



#6 csauer52

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Posted 18 January 2020 - 07:37 AM

You'll figure this out eventually but what I do with TPoint is to run it binned 3x3 and with a subframe of 1/2 (if memory serves). That way I get very fast slews and solves and I think I can do about 3 points per minute that way. You just have to get the image scale settings correct. My mount has such low PE that I don't bother with PEC. It was 1.5 arc seconds peak to peak after Bisque repaired it. 

 

Rgrds-Ross

Thanks for reminding me about this Ross. Every video I watched related to running TPoint models suggested to use 3x3 binning and that fairly important tidbit slipped my mind when I actually used the real thing rather than simulators. I ran my model using 1x1 binning. confused1.gif

 

The weather forecast is looking favorable for tomorrow night and hopefully I’ll have a chance to give it another go as I’m off for MLK day on Monday. 


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#7 csauer52

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Posted 18 January 2020 - 07:49 AM

PEC is worth trying, so you can see how large or small the PE is for your mount. (If it's over 7" peak-to-peak, it's out of spec and SB will probably replace your worm.) If you create a PEC curve, it's important to apply it and immediately check your PE again, because it's easy to get it backwards (in which case you'll see your PE double, and you can go back and reverse it).

 

I have the MYT and my intrinsic PE was 2.8", and PEC reduced this to 1.0". Best to do this on a night of good seeing.

 

Out of curiosity, what focal length and image scale are you working with?

 

I love my Paramount and TheSkyX Pro! Congratulations on your MX+.

 

Ralph

Hi Ralph. I’m imaging at 1000mm (130mm refractor) at 1.8”/px. Typical seeing where I live isn’t great and we have very few nights where it’s really decent. I would say on average seeing is usually 2.5” to 3.0” FWHM. The MX+ should be capable of tracking better than that which is why I’d like to,see if I can get away with unguided imaging. In my view it will be one less variable to manage in a very complex system and tbh, LP is so bad where I live that unless you’re doing NB imaging, integration times beyond 10 minutes aren’t of much benefit. Further, I use a NABG camera which also limits my exposures when brighter objects are in the FOV. 

 

Thanks for the tips!

 

Chris


Edited by csauer52, 18 January 2020 - 07:49 AM.



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