10micron hps1000 tracking accuracy with only 2 star align

[mbrickley]

Hi

Im considering this mount and will use it for a mixture of proper astrophotography, obviously what it’s designed for, but also for some visual observing and for some EAA with 30s- 1 minute subs. I’d obviously buy a mount of this calibration for the proper Astro sessions but would also want to use it for short EAA sessions with no fuss.

 

I understand the concepts of model building and accurate polar align but wonder if anyone has tried just aligning on the pole using sharp cap or the like , doing a  1 (2 if it doesn’t support 1) star align and then using it without model building etc.... I’d be very interested if anyone had tried doing this for visual how they found goto accuracy and if anyone has tried this and then taking short subs such as you use for EAA of say 1 minute.  When I’m doing EAA, which translates to the kids went to bed late and it’s work tomorrow, I would not want to spend half an hour building a complex model but just do a rough setup as above slew to several targets  and produce images of relatively low quality by stacking 30s-1min images using sharpstack for live viewing and documentation

 

Any info would be very gratefully digested 😎

mark 

[inFINNity Deck]

Hi Mark,

the HPS models offer 2-stars, 3-stars and refine-stars alignments. The first two are dedicated options. About the 2-stars alignment the manual explains:

Quote

Note that this procedure does not correct the orthogonality error of the telescope. If you are not sure that
your telescope’s optical axis is perfectly orthogonal to the declination axis, do a three-stars alignment or a
refinement.

About the 3-stars alignment it reads:

Quote

The three-stars alignment procedure measures the orthogonality error of the telescope’s optical axis in
addition to the polar axis misalignment, and uses it to improve the pointing accuracy. Furthermore, you can
choose among more stars than using two-stars alignment, since the selection is less critical. On the other
hand, you can choose stars in the same zone of sky, thus hampering the final accuracy.

...

Even after the three-stars alignment, you can improve the mount model by adding more stars.

Adding more stars is done using refinement-stars procedure, which can be done using any amount of stars (up to a total of 100 that is).

Then there are free tools like MountWizzard and ModelCreator that allow automation of multiple-star modelling. In order to make that work you will need to attach a camera and design a model (i.e. a number of alt-azimuth positions in a some kind of pattern). The software can create these patterns for you (and save them for later use), but you can built it manually as well. The software then uses these model points to take images of the sky that are then plate-solved, resulting in up to 100 artificial stars, which are then sent to the mount for processing. I currently use a 74 point model, which takes about 45 minutes to complete, but being in an observatory I only need to do this once a year or after each alteration of the set-up. For visual observing and short exposures you may do just fine with a 10 or 20 point model, which should complete in about 5-10 minutes. I remember having reasonable visual pointing accuracy with as little as 6 stars. Then remove the camera and start enjoying the sky. :-)

Modelling can also be done completely manual using a reticle-eyepiece, but my experience is that it is tedious and takes at least three times as long.

Nicolàs

[Davey-T]

No need for Sharpcap but modelling needs Maxim a bit expensive if that's all you use it for but otherwise a small model with a reticle eyepiece is feasible once you get the hang of it.

You can  do a small PA model of 10 /15 points and that is fine for general observing and short exposures but if you then adjust the PA you need to repeat the model.

The modelling can be left to it's own devices, mine is permanently mounted and I occasionally do an 80 point model which can be started at dusk and finishes by the time it's dark enough to image.

It's a bit overkill for occasional imaging especially with one of the newer CMOS cameras that can be used for short exposures, I generally take 20 minute exposures with the 10Micron but also have a Rainbow  RST-135 mount with a fast scope and CMOS camera that produces comparable results with 5 minute subs.

Dave

[inFINNity Deck]

4 minutes ago, Davey-T said:

No need for Sharpcap but modelling needs Maxim a bit expensive if that's all you use it for ...

Hi Dave,

MW4 is free and does not need any other software than a free plate solver (I currently use ASTAP and have used PlateSolve2) to create a model.

Nicolàs

[Davey-T]

1 minute ago, inFINNity Deck said:

Hi Dave,

MW4 is free and does not need any other software than a free plate solver (I currently use ASTAP and have used PlateSolve2) to create a model.

Nicolàs

I use Maxim and PinPoint  as I already had them, haven't tried Mount Wizard since an early version, liked the feature of just solving the path of intended target but the GUI was buggy, had a bit of correspondence with the guy developing it but stuck with Modelmaker, must give MW another go.

Dave

 

[inFINNity Deck]

The latest version (MW4) is really nice and Michael is doing a fine job extending it with requested features like the lateral scope-offset in dome-control for my observatory. It is amazing to see the mount and dome moving simultaneously in a kind of ballet while modelling. The other nice thing is that it assists in uploading object data (i.e. asteroids, satellites, etc) to the mount for tracking/imaging purposes.

Nicolàs

[mbrickley]

2 hours ago, Davey-T said:

No need for Sharpcap but modelling needs Maxim a bit expensive if that's all you use it for but otherwise a small model with a reticle eyepiece is feasible once you get the hang of it.

You can  do a small PA model of 10 /15 points and that is fine for general observing and short exposures but if you then adjust the PA you need to repeat the model.

The modelling can be left to it's own devices, mine is permanently mounted and I occasionally do an 80 point model which can be started at dusk and finishes by the time it's dark enough to image.

It's a bit overkill for occasional imaging especially with one of the newer CMOS cameras that can be used for short exposures, I generally take 20 minute exposures with the 10Micron but also have a Rainbow  RST-135 mount with a fast scope and CMOS camera that produces comparable results with 5 minute subs.

Dave

Thanks very much for replying... the RST-135 was another mount I was considering exactly for the EAA use as you describe using 1 minute subs but the consensus seemed to be you couldn’t image unguided at all with it due to the high unguided pe... can I ask are you  guiding the 5 min subs and are you polar aligning this using the QHY polemaster that I think just bolts on to it?

 

Thanks

 very much for taking the trouble to reply

Mark 

[Davey-T]

1 minute ago, mbrickley said:

Thanks very much for replying... the RST-135 was another mount I was considering exactly for the EAA use as you describe using 1 minute subs but the consensus seemed to be you couldn’t image unguided at all with it due to the high unguided pe... can I ask are you  guiding the 5 min subs and are you polar aligning this using the QHY polemaster that I think just bolts on to it?

 

Thanks

 very much for taking the trouble to reply

Mark 

The RST-135 is probably a better mount for your purposes with its very light weight and not needing weights it's very portable, it has the attachment for the Polemaster but I've got an ASIAIR Pro and all ZWO setup on it which controls cameras, guiding, autofocus, and mount by WiFi from the app on iPad.
It has a really good PA routine in it so no need of the Polemaster, it has built in version of PHD  which works fine for my purposes using a fast short focal length scope and I haven't altered any of the default guide settings it came with so could probably be improved upon. Curiously the unguided Dec graph is better than the guided one.
Another good thing about the RST-135 is it's ability to run well out of balance although you need to be wary of a power disconnection when it will simply rotate down until it hits something and the more unbalanced it is the faster it will fall.

Its not without it's design faults, the handset seems to have been designed by a computer programmer or someone trying to reinvent the wheel, the on off switch mounted on the top surface of the mount has nothing to prevent heavy dew running into the interior likewise the RS232 socket, the cables rotate with the mount so can get pulled or tangled and the azimuth adjustment screws are a bit delicate so best not to use them to push a heavy load around when PAing.

Dave 

[mbrickley]

On 01/04/2021 at 18:11, Davey-T said:

The RST-135 is probably a better mount for your purposes with its very light weight and not needing weights it's very portable, it has the attachment for the Polemaster but I've got an ASIAIR Pro and all ZWO setup on it which controls cameras, guiding, autofocus, and mount by WiFi from the app on iPad.
It has a really good PA routine in it so no need of the Polemaster, it has built in version of PHD  which works fine for my purposes using a fast short focal length scope and I haven't altered any of the default guide settings it came with so could probably be improved upon. Curiously the unguided Dec graph is better than the guided one.
Another good thing about the RST-135 is it's ability to run well out of balance although you need to be wary of a power disconnection when it will simply rotate down until it hits something and the more unbalanced it is the faster it will fall.

Its not without it's design faults, the handset seems to have been designed by a computer programmer or someone trying to reinvent the wheel, the on off switch mounted on the top surface of the mount has nothing to prevent heavy dew running into the interior likewise the RS232 socket, the cables rotate with the mount so can get pulled or tangled and the azimuth adjustment screws are a bit delicate so best not to use them to push a heavy load around when PAing.

Dave 

Hi Dave
Thank you so much for coming back to me, sorry for the delay posting a response... I have two little ones and they were soooo full on over Easter! 
I think this sounds like a great Mount ., can you tell me have you Tried using it unguided and if so are you able to get 1 min or so subs from it (I’m at 540mm fl) 

thanks so much and have a good day

Mark

[Davey-T]

On 06/04/2021 at 10:19, mbrickley said:

I think this sounds like a great Mount ., can you tell me have you Tried using it unguided and if so are you able to get 1 min or so subs from it (I’m at 540mm fl) 

Haven't actually tried it unguided on short subs but it may work better with just RA guiding looking at the PHD graph, I'm running at f/2.8 and haven't altered any default settings in PHD.

Dave