Topics

2-3 Star Alignment #iEXOS-100 #ExploreStars #alignment #sharpcap


Tommy
 

Hello all,

I have been having trouble performing a 2 or 3 star alignment, meaning I am not 100% sure I've locked into the correct star, so I usually take my best guess. This usually throws off my go-to performance, then I have to search my target. Is there a program that can aid with star alignment, like how Sharpcap does with polar alignment? 
--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100


Jeff Snell
 

Hi Tommy,
I had the same issue using ExploreStars.  I was pretty much told the database is what the data base is.  I was instructed to scroll thru the alignment star choices given until you get to stars that are easily recognizable and then align off of those.  It works relatively well though if you are patient.  However, I found that method to be too cumbersome/time consuming.  

I don't know how experienced you are ( I am a relative newbie), but with the above said I switched to a serial connection via a Lenovo 11e PC.  I bought a QHY Polemaster for Polar alignment (super easy), then downloaded and used CdC to "sync" on a known target (a single star).  I've been using Venus for a month or so now since it is readily visible and the brightest (non-moon) object in the sky.  Once I polar align with the Polemaster and "sync" on Venus my mount tracks near perfect.  Maybe I'm still doing that wrong but it works great (again, I'm a newbie).  All this is not really as easy as I make it sound but I can tell you that after a little work on a Saturday (6 hours or so) and help from folks on this forum, it all works and has been very nice to use.  I had previously downloaded ASCOM and all associated drivers, then I downloaded a configuration management tool from ES, configured a com port or two (which I have NEVER done), and then download CdC for tracking and APT for my astrophotography.  Also had to configure the serial cable to support two different interfaces but that's an easy download too.  Wish I could give you the step by step, but I haven't sat down and done that yet.  I muddled my way through but wished I had simple steps for my simple Alabama boy brain.

Trust me when I say though, I am NOT smart on this stuff!  So if I was able to make it work (with a little help) you can too and I highly recommend moving that way for your astrophotography.  The difference is remarkably noticeable between old photos and the new.

I'm sure others will weigh in here.  The community and this site in particular are awesome.  Just hope I didn't say anything to steer you wrong.
  
Jeff

PMC-Eight w/Explore Stars
APT, CdC, QHY Polemaster
Orion 50mm w/Starshoot AutoGuider
ES ED80mm APO
Celestron 8" Edge HD
Canon Ti-5 w/ Spencer Camera Astro-mod


On Mon, Mar 2, 2020 at 2:30 PM Tommy <darko7411@...> wrote:
Hello all,

I have been having trouble performing a 2 or 3 star alignment, meaning I am not 100% sure I've locked into the correct star, so I usually take my best guess. This usually throws off my go-to performance, then I have to search my target. Is there a program that can aid with star alignment, like how Sharpcap does with polar alignment? 
--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100


 

Tommy,
 
Yes, but not with Explorestars or visual.  It's called 'plate solving', and people generally use it for framing their target when imaging.  
 
Basically, your plate solving software asks the imaging camera for a picture, parses the picture for stars and compares it with an internal star map.  The coordinates from that matchup get compared with where your ASCOM (or INDI) - controlled mount is *supposed* to be pointing, and the software commands the mount to move to correct.  Rinse and repeat 2 or 3 times, and after that, your target is framed and your mount sync'd.  Magic.  Wonderful stuff!
 
So, if you're imaging and guiding, this is a natural step that helps you frame targets that you may not be able to see.  If you're visual, it's not as easy to see how to come out ahead with it.  Sharpcap apparently will do plate solving, but that's with your guidescope's field of view and aiming.  Whether that helps you at the eyepiece or not is another matter...
 
- Bob

--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Tommy
 

Jeff, thanks for all the input. I've got polar alignment down-solid using Sharpcap, so I don't get star trails in my photos anymore, up to 60-sec subs so far. My biggest issue is the go-to with star alignment. I wish you could just program the brightest star in your FOV into the Explore Stars app, instead of scrolling through dozens of unusable stars, but is what it is I guess.

So when using CdC, once you sync on Venus, or any other bright object, your go-to accuracy is good? Meaning you have the target in view every time? If so, that may be the route I take.
--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100


Tommy
 

Robert, 

Next on my list was auto-guiding. Its been really cold the past couple months and didn't want to get into till summer. I will look into plate solving with Sharpcap. Thanks for the info.
--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100


 

Tommy,

If you're imaging, you'd want to plate solve using what your imaging camera sees, not your guide camera.  
Lots of options for that, just depends on what software you're using to manage the D5600.  

--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64


Wes Mcdonald
 

Tommy:

If you are doing visual, you will want to get good at this alignment.  If you are ding astrophotography, you will need to get good at mechanical polar alignment for tracking purposes, and then use plate solving to center up objects as Bob described.

To do the 2-3 star alignment you must, as you have seen, identify the correct star as selected by the algorithm.  You can however always skip the selected star and try another.  But even with a star you think you recognize before you look into your eyepiece, it can be difficult to be sure you have centered the correct star.

BUT, if you are good at getting a mechanical polar alignment, then you are almost able to do visual without doing a 2-3 star alignment.  2-3 star alignment is needed if you don't have a polar alignment.   With a polar alignment this is not necessary.

The issue with GOTO accuracy is that there are three or four things that impair it that mechanical alignment do not address.  These are:

1.  Cone error
2.  Dec home error
3.  RA axis home error
3.  Miss-level.

Cone error:

Cone error changes where the scope is pointing by lowering or raising its line of sight relative to the altitude of the RA axis.  Sharpcap and polemaster remove cone error when aligning, that is they correctly get you aligned to the north celestial pole (NCP) in the face of cone error.  The thing is they align your RA axis not your telescope.  So your mount is good, but your scope is not pointing at the NCP when the mount is placed in polar home.  This error will contribute to GOTO apparent error as you go around the sky -- the cone error will cause your scope to point in the wrong place (subtly) even tough your mount may be correct.  You perceive this is GOTO error as you might no see the object in your eyepiece.  You can correct cone error once.  Jerry posted a link to the astronomy shack method to do this.  I suggest you perform this procedure to eliminate cone error from your rig.

2.  Dec Home error and RA home error.  These are errors in where the mount RA and DEC axes are when you turn on the PMC8.  The PMC8 expects the mount to be aligned at polar home (PH).  If there were no cone error, and of the mount was polar aligned, the scope would point to the NCP -- if you could see an object there it would be in the center of the telescope field of view.  The problem is, especially with the iEXOS 100, setting the mount at polar home after performing a PA is not obvious.  For one thing there are no marks on the mount indicating where the RA and DEC axes are supposed to be to put the thing into PH.  I published a method for finding polar home, it is posted in the Mounts subgroup files section.  With the mount level, you can execute this procedure and then put some fiducials onto your axes so that you can always find PH.  Note the PH you need is dependent upon the level, so perform the procedure with the scope level and always set it up level.  If you do this then your RA and DEC home will be correct.  While RA home error is removed with a SYNC, I am not sure DEC is, so you want to find it manually, as close as you can.  If you have home error, these errors get added in to the pointing of the mount, and thus you will experience GOTO errors.

3.  You will hear, correctly, that miss-level will not affect polar alignment.  Or maybe it will be stated that if polar aligned miss-level will not affect your tracking.  These statements are true.  But they do not consider GOTO accuracy, which miss-level in the east-west direction (I call this tilt, while miss-level in the north south direction i call tip) most certainly does.  Tip which is present in the same axis as the PA alt adjustment, is removed in the PA process.  But there is no PA adjustment that address tilt.  As a result tilt affects the pointing angle of the telescope as a function of the DEC angle.   So you must have the mount level.  But you will also need it t be level to ensure your PH is correct anyway.  

If you get all that right, then your GOTOs will be pretty good.  Once you get it down pat, you will find you do not need 2-3 star alignment.

Regards,
Wes.
 


--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired


Jeff Snell
 

Tommy,
Yes.  I use APT to control my camera, use live view on the canon T5i and slew to the selected target, center it in live view, then hit the sync button in CDC.  Works like a champ.  I slewed to multiple targets this evening and was always in the field of view of the camera at completion. 

Jeff


On Mar 2, 2020, at 4:46 PM, Tommy <darko7411@...> wrote:

Jeff, thanks for all the input. I've got polar alignment down-solid using Sharpcap, so I don't get star trails in my photos anymore, up to 60-sec subs so far. My biggest issue is the go-to with star alignment. I wish you could just program the brightest star in your FOV into the Explore Stars app, instead of scrolling through dozens of unusable stars, but is what it is I guess.

So when using CdC, once you sync on Venus, or any other bright object, your go-to accuracy is good? Meaning you have the target in view every time? If so, that may be the route I take.
--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100


Tommy
 

Wes,

Thank you for all the input. I will digest all the info you provided and try to get my mechanical alignment down using the steps you provided.

--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100


Jerry Hubbell - Explore Scientific VP Engineering
 

On Mon, Mar 2, 2020 at 04:30 PM, Tommy wrote:
I have been having trouble performing a 2 or 3 star alignment, meaning I am not 100% sure I've locked into the correct star, so I usually take my best guess.
Hi Tommy,

The Explore Stars 2 or 3-star "virtual polar alignment" system is designed to make it as easy as possible (within reason) for beginners to get a good alignment so that the GOTO navigation (Pointing) to stars is accurate. The default setting is to slew automatically to the first suggested star when selecting 2 or 3-star alignment. If you have set up your tripod and mount to have a good physical polar alignment (within a couple of degrees), then with a wide field finder the slew will take you to the alignment star and you should be able to identify it as the brightest star near the center of your finder. If it is behind an obstruction, then just hit NEXT to go to the next suggested star.  It should not be hard to identify the correct star as Explore Stars will show you which star in the constellation it is pointed to. 

There is the option to turn off the "Auto Slew" function so that you can select your stars without the mount slewing to every star in the list until you get to the one(s) you are after.

This is how it is designed to work for beginners.  I hope this helps to understand.

--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


Tommy
 

Thank you Jerry for the input. That was a question I had about locking onto the brightest star in my FOV with my 50mm guidescope. I will give that a try tonight.


On Tue, Mar 3, 2020, 7:58 AM Jerry Hubbell - Explore Scientific VP Engineering <jrh@...> wrote:
On Mon, Mar 2, 2020 at 04:30 PM, Tommy wrote:
I have been having trouble performing a 2 or 3 star alignment, meaning I am not 100% sure I've locked into the correct star, so I usually take my best guess.
Hi Tommy,

The Explore Stars 2 or 3-star "virtual polar alignment" system is designed to make it as easy as possible (within reason) for beginners to get a good alignment so that the GOTO navigation (Pointing) to stars is accurate. The default setting is to slew automatically to the first suggested star when selecting 2 or 3-star alignment. If you have set up your tripod and mount to have a good physical polar alignment (within a couple of degrees), then with a wide field finder the slew will take you to the alignment star and you should be able to identify it as the brightest star near the center of your finder. If it is behind an obstruction, then just hit NEXT to go to the next suggested star.  It should not be hard to identify the correct star as Explore Stars will show you which star in the constellation it is pointed to. 

There is the option to turn off the "Auto Slew" function so that you can select your stars without the mount slewing to every star in the list until you get to the one(s) you are after.

This is how it is designed to work for beginners.  I hope this helps to understand.

--
Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

www.explorescientificusa.com
1010 S. 48th Street
Springdale, AR 72762
1-866-252-3811

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home


Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
Mounts
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!


--
Cameras: Nikon D5600, ASI ZWO120
Scope: Astro-Tech 60ed, Orion 50mm
Mount: ES-iEXOS-100