HEQ5 Pro go to alignment, part of your startup routine?

[AstroLearnerWill]

Hi

My current startup routine looks something like this. 

Balance scope and mount

put heq5 pro roughly in home position and switch on

nina 3 point polar alignment to get roughly in the right place 

nina 3 point polar alignment to get more accurate 

Slew and center on a bright star so I can manually focus with a mask. 

Slew and center on target, start guiding, begin imaging. 

The thing is, every time I slew and center the mount is never very close to where the target is on its first attempt and usually goes through 3 or 4 re-slews and plate solves to get it right. 

Should I be doing some kind of goto alignment or home calibration so the mount knows where it is? Presumably it’s solely relying on the best guess home position I start it up in, at the very beginning of my process. 

Also, I’ve previously had the mount unable to move on occasion stating horizon limit, despite not being close to it, which makes me even more curious about the goto alignment.

Thanks for any advice! 

[Nicola Hannah Butterfield]

I use APT and plate solving, and it can take 3 or 4 attempts as currently setup, but I am experiencing other issues, re cable, but usually it requires at least 2, not sure if resolution and accuracy is an issue, ie 1000 pix 100pix 10pix

I find APT stops if 5-10pix or less

If polar alignment is rough 1000pix would be quite good. I can get a lot of pixels out and still find the object, mmph like I said other issuse

[Budgie1]

Before I moved into my Obsy over the summer, I used to setup every night in the garden and follow the same routine.

1. Level the mount - some say this isn't that important, but I like to start with it as close to level as I can get it.
2. Balance the mount with everything on it which I intend to use that night, including all cables, guidescope & cameras.
3. Start from the Home Position - I notice you say you put it roughly in the Home Position, this can start you off with a built-in error which you'll carry through the whole alignment routine. So set your Home Position as accurately as possible (see this video for assistance) and put marks on the mount with a Sharpie so it's easy to find the Home Position again. 
4. I also use APT but I assume the 3-point PA routine is going to be similar on both. Before APT had the PA routine, I used SharpCap to obtain PA.
5. Once Polar Aligned, I choose my target and slew to it, then use APT's Plate Solving to accurately locate the target. Once on the target, I don't need to do this again unless I have to do a meridian flip.
6. After the session has finished, I make sure to return the mount to the Home Position again before switching off, so the mount knows where it's pointing when I next switch it on.

[Cosmic Geoff]

I sometimes use an EQ5 Synscan on a fixed pillar.  Once aligned and parked at the Home position, there is no need to re-align on re-starting. The GoTo, I have found, is not very accurate unless one uses alignment stars not too far from the desired object and on the same side of the meridian. So I always plate-solve with Sharpcap, and when this gets a solution it places the object in dead center of the frame, first time. 

The OP's procedure seems to contain some unnecessary work.

3-star align I have found is a) hard work and b) not necessary if you either plate-solve or use alignment stars near the target.

Starting from scratch, the main function of putting the mount in Home  position is so (under the Synscan alignment routine) the first slew will aim the finderscope at the first alignment star so you can find and center it more easily.  Once you finish the alignment routine the mount will have recalculated the Home position.

Edited December 20, 2022 by Cosmic Geoff

[AstroMuni]

10 hours ago, AstroLearnerWill said:

My current startup routine looks something like this. 

Here is my routine with the HEQ5...quite similar to yours with a few differences..

1. Set up mount roughly pointing north, switch it on so I can see the reticle and do PA using the Polarscope. (I am fortunate that Polaris is visible, othewise I would have to do PA using Ekos)

2. Attach scope and balance it

3. Put scope in roughly home position

4. Check rough focus so platesolving will not fail

5. Slew to a bright star, platesolve and do fine focus adjustments manually

6. Attempt guiding. If I get too many errors then do PA alignment in Ekos

7. Slew to target and start imaging

As you are platesolving there is no need to do 3 star alignment. Everytime you platesolve with a different target the mount model will get updated and it will get better and better at pointing.

[StevieDvd]

I think you are missing one step. When you plate-solve are you doing a sync? This tells the mount to adjust its internal co-ordinates to match the plate-solved settings. As you said you are relying on your guessed home position, until you have star aligned or synched each goto needs a plate-solved nudge.

I don't use NINA but a quick scan of the online document shows the details for sync  here

 

[AstroLearnerWill]

Thanks all for the help, very insightful.

I'll be adding a step to do a manual platesolve and ensure the 'sync' setting is 'On' in Nina. This will ensure the mount knows where it is. I presume the automatic platesolving as part of 'skew and center' in the framing tab does not sync to the mount.

I'm a bit confused why I don't need to polar align necessarily. My understanding is that this is important to reduce any field rotation in long exposure images and to give the guider higher accuracy and therefore better sharper images.

 

[Cosmic Geoff]

13 minutes ago, AstroLearnerWill said:

I'm a bit confused why I don't need to polar align necessarily. My understanding is that this is important to reduce any field rotation in long exposure images and to give the guider higher accuracy and therefore better sharper images.

 

A good mechanical polar alignment will minimise field rotation.  But you don't need it just to find stuff. Even an alt-azimuth GoTo can do that. 🙂

[pipnina]

I've found with my own HEQ5 that the first slew attempt is miles off. Kstars/Ekos shows errors in the order of 8000+ arcsecond on ra and 3000 on dec quite often. But then it narrows in very fast.

I've tried things like resetting the alignment data and all, but it's not helped much. I consider it a rather untroubling issue as the computer gets it to the right spot relatively quickly regardless.

I imagine some get their HEQ5s to work very nicely, but it has all the flaws from my perspective that you would expect from an entry level scope-AP mount.

[StevieDvd]

On an EQ mount with expectations to image then the best PA you can get is always a good idea, especially if you wannt long exposures and guiding. If you only intend to do a visual session then it's not so important.

With good PA and a platesolved sync you will get the best out of your tracking (unguided) and may be able to take short exposures, but that is needed for a serious guided session.

 

[AstroLearnerWill]

Thanks all, again, that makes perfect sense re PA now.

Thats cleared things up. I've also marked the mount where 'home' is using the video linked above. I'll set the mount to this position at the beginning of every session to make things a bit easier.

[AstroMuni]

1 hour ago, AstroLearnerWill said:

I presume the automatic platesolving as part of 'skew and center' in the framing tab does not sync to the mount.

In Ekos, there are 3 options

The first one just Syncs scope to the coordinates found in platesolve, 'Slew to target' syncs and Slews to target and last option does exactly what it says, just platesolves. So I would suspect NINA would do something similar as option 2 with 'slew and center'. Someone who uses NINA could confirm.

[Gumminess8083]

On 20/12/2022 at 02:12, Budgie1 said:

Start from the Home Position - I notice you say you put it roughly in the Home Position, this can start you off with a built-in error which you'll carry through the whole alignment routine. So set your Home Position as accurately as possible (see this video for assistance) and put marks on the mount with a Sharpie so it's easy to find the Home Position again. 

Sorry to hijack the post, but I was wondering something.

 

Is starting from the home position really that important?

I initially set my home position with my mount perfectly aligned, pointing the scope straight forward (I did this like a couple of months ago).

Now, whenever I bring my scope outside, I don't really bother pointing my scope forward perfectly. I just start it wherever it is, usually pretty close to home position but not perfectly, polar align, and then platesolve, which usually fixes any error I could have made and properly recognizes the scop position relative to the home position.

 

Is this procedure wrong? 'Cause so far it hasn't caused me any problems

[Budgie1]

1 hour ago, Gumminess8083 said:

Is starting from the home position really that important?

I initially set my home position with my mount perfectly aligned, pointing the scope straight forward (I did this like a couple of months ago).

Now, whenever I bring my scope outside, I don't really bother pointing my scope forward perfectly. I just start it wherever it is, usually pretty close to home position but not perfectly, polar align, and then platesolve, which usually fixes any error I could have made and properly recognizes the scop position relative to the home position.

Is this procedure wrong? 'Cause so far it hasn't caused me any problems

There's nothing wrong with your procedure because you use platesolving to find your position and that accounts for any errors. If you weren't using platesolving and relied on the handset to do a 3-star alignment for the Go-To function, then an accurate home position is more critical because it gives the mount a known starting position. This in turn will mean the alignment process is more accurate from the start, as long as you remember to return the mount to the Home Position before turning it off after a session.

I have a Home Position and a Park Position set on my mount because I have to have the scope as low as possible to be able to close the obsy roof. So normally I start from the Park Position, slew to target and platesolve. That works fine for me, and I don't have to PA every night because it's a permanent setup.  

[Steve Ward]

People still getting PA and Go-To interlaced and confused it appears , making it all way more complicated than it need be.

Step One ... Read and reread the instructions that come with the mount ... an oft overlooked step due to the usual bravado.

An accurate input  by the user of the required data ... Location , date and especially time is needed , the more accurate the data the more accurate the initial pointing , rough guessing and especially endless faffing about means everything will have apparently moved from where the mount thinks it is.

Step Two ... reread the instructions.

 

Edited December 23, 2022 by Steve Ward