Alignment and focusing issues

[Shahd]

Hello,

I have a few questions 

1. How to get accurate GoTo results (Orion Atlas EQ-G)? I've read somewhere that polar alignment is important; I always do a rough polar alignment and get different results each time I begin star alignment. Will controlling the mount through a PC give better results? 

2. I've recently upgraded my DSLR camera to the ZWO ASI1600 MM-COOL; using a CCD is much harder than I thought. At first I tried to star align using the camera to get the stars centered on the chip, but nothing appeared on the screen. I gave up, removed the camera and used an eyepiece instead. I had to wait for the moon to rise to learn that the camera was waaay out of focus, that's why I couldn't see anything on the computer screen. 

So my question is, is there an easier way to focus in moonless nights? and does removing the camera and replacing it with an eyepiece affect the accuracy of alignment (since the balance has changed)? 

 

Thanks.

[IanL]

1. The PC won't intrinsically make it easier - if your polar alignment is bad, your home positioning is bad or you have significant cone error (scope not perfectly square with the mount axes) then you're always going to be off the first alignment star. This can make life hard with a camera if you don't have a wide-field finder attached to the scope. That said, if you're going to get serious about imaging then you really want to switch over to PC control through EQMOD anyway, as that can then interface with capture software (e.g. Sequence Generator Pro).

For imaging with PC control the best solution is to use plate solving (which SGPro has built in). It needs a bit of setting up, but once working it's like magic as you just need to do polar alignment and that's it. You can then tell the software to go find the target by name or coordinates and it will use the camera to work out where to point in a minute or two with no alignment needed.

2. Once you've got reasonable focus, measure the distance from some identifiable point on the focuser body to an identifiable point on the camera. Setting the focuser to the same position next time out will mean you are close to focus. If your focuser drawtube has a scale printed on it then you can use that, but most don't. You could make a measure by cutting a bit of stick or similar to the correct length to fit between the focuser body and the camera. Simplest of all I often use my fingers to measure the amount of drawtube extension (assuming it isn't too far), e.g. on my Lunt Ha scope, I know that two fingers' of width is where I need to be.

[wimvb]

If you don't want to swap camera/eyepiece, you need some form of platesolving. The solution that works for me (asi174 & sw 150pds on an az eq6, with motor focus) is ekos/kstars. It doesn't use star alignment as a hand controller does, but uses plate solving. Here's my approximate workflow:

Set up mount and scope with camera

Have scope pointing in approximate park position (northern celestial pole).

Focus on stars visible. I know at what step position I have approximate focus. I always start at focuser all the way in (= 0). I then set the focuser position to the approximate target position.

Slew scope to any position away from pole

Image and platesolve

(Polar align with drift alignment if necessary)

Repeat this a couple of times. Ekos will add each image to build a pointing model.

Slew to imaging target.

Refocus

Start imaging.

[Shahd]

5 hours ago, IanL said:

1. The PC won't intrinsically make it easier - if your polar alignment is bad, your home positioning is bad or you have significant cone error (scope not perfectly square with the mount axes) then you're always going to be off the first alignment star. This can make life hard with a camera if you don't have a wide-field finder attached to the scope. That said, if you're going to get serious about imaging then you really want to switch over to PC control through EQMOD anyway, as that can then interface with capture software (e.g. Sequence Generator Pro).

For imaging with PC control the best solution is to use plate solving (which SGPro has built in). It needs a bit of setting up, but once working it's like magic as you just need to do polar alignment and that's it. You can then tell the software to go find the target by name or coordinates and it will use the camera to work out where to point in a minute or two with no alignment needed.

2. Once you've got reasonable focus, measure the distance from some identifiable point on the focuser body to an identifiable point on the camera. Setting the focuser to the same position next time out will mean you are close to focus. If your focuser drawtube has a scale printed on it then you can use that, but most don't. You could make a measure by cutting a bit of stick or similar to the correct length to fit between the focuser body and the camera. Simplest of all I often use my fingers to measure the amount of drawtube extension (assuming it isn't too far), e.g. on my Lunt Ha scope, I know that two fingers' of width is where I need to be.

3 hours ago, wimvb said:

If you don't want to swap camera/eyepiece, you need some form of platesolving. The solution that works for me (asi174 & sw 150pds on an az eq6, with motor focus) is ekos/kstars. It doesn't use star alignment as a hand controller does, but uses plate solving. Here's my approximate workflow:

Set up mount and scope with camera

Have scope pointing in approximate park position (northern celestial pole).

Focus on stars visible. I know at what step position I have approximate focus. I always start at focuser all the way in (= 0). I then set the focuser position to the approximate target position.

Slew scope to any position away from pole

Image and platesolve

(Polar align with drift alignment if necessary)

Repeat this a couple of times. Ekos will add each image to build a pointing model.

Slew to imaging target.

Refocus

Start imaging.

1. I'll give plate solving a go. I don't think SGPro works on Mac but ekos/Kstar does. 

2. The focuser does have a scale printed on it, but whenever I add an extension tube or a spacer (still adjusting the back focus of the field flattener) the focus point changes and I have to start all over again. 

Thanks Ian and Wim.

 

[adyj1]

The biggest help I found with accurate star alignment for my goto mount was an illuminated reticle (eyepiece with an illuminated red cross in the middle). I found that my beginner's eyes weren't correctly centring the alignment stars in the eyepiece, and with the illuminated reticle I was able to get them dead centre - with much-improved tracking.

HTH

Ady

[Guest Tuomo]

23 hours ago, adyj1 said:

The biggest help I found with accurate star alignment for my goto mount was an illuminated reticle (eyepiece with an illuminated red cross in the middle). I found that my beginner's eyes weren't correctly centring the alignment stars in the eyepiece, and with the illuminated reticle I was able to get them dead centre - with much-improved tracking.

HTH

Ady

But goto aligment and tracking are very different thing. Only good polar aligment improves tracking.

[newbie alert]

Think you need to step backwards and accurate polar align first..a rough job isn't good enough for imaging..also making sure you have the correct spacing for the camera is a big must..no good collecting data if it's not the best that you can collect..ironing out poss faults narrows problems out at a later date.. dot the i's and cross the t's..

[adyj1]

20 hours ago, Tuomo said:

But goto aligment and tracking are very different thing. Only good polar aligment improves tracking.

Just using my many minutes of beginner's experience to comment on question 1; "How to get accurate GoTo results (Orion Atlas EQ-G)?"

[mikey2000]

I'm a bit of a newb using low end equiment but here's my setup routine, and it's now yours for the princely sum of 2p:

 

1. Get a reasonable polar align with the polarscope. 

2. fire up guide cam.  Use Sharpcap for polar alignment.  Hopefully it's a bit off to allow 'unidirectional dec guiding' as I have a cheap EQ3 mount

3.Make sure the scope/mount is in The Home position.

4. Start eqmod and stellarium.   Slew somewhere to a really bright star

5. use a hand controller to center roughly, thene resync eqmod.  Use a bhatinov mask to nail then lock focus,  THIS IS A KEY STEP - ALL FOCUSING IS DONE NOW.

5. Use stellarium to slew to Tonight's Target.

6. Take a pic and AstroTortlla will platesolve the result and re-sync /reslew via EQMOD for me.

7. That normally gets you *very* close to the target with a DSLR field of view and 150mm scope..  Maybe repeat step 6 to make sure.

8. get the guiding up to speed then start taking pics.

9. Bask in Glory

10. (optional) Curse the Gods of Intergalactic Photography as sometihing goes wrong in any of the above steps.

11. (Optional) Praise the Gods of Intergalactic Photography if nothings goes wrong at all.

12. Post photos here

13. Realise you could have done better with a bit more care. (!!!)

14. Realise there is always someone with a better mount/location/scope/camera etc

15. Realise that you should probablyt not sell your roof to keep up :-)

 

16.  Reflect on all of that the next day and enjoy the ride.

 

 

I love it!   I think #16 is the most important part.

[newbie alert]

16 hours ago, adyj1 said:

Just using my many minutes of beginner's experience to comment on question 1; "How to get accurate GoTo results (Orion Atlas EQ-G)?"

I have no experience with your mount so not really my place to comment but with any mount accurate PA improves tracking, accurate star alignment improves the goto accuracy..theres so many different ways to do PA.. 

You could use a polar scope and use the reticle to place Polaris where it should be at the time ( assuming you're northern hemisphere)

Use sharpcap software with a finder/guider 

Use polemaster

Find out how to drift align either on the handset,phd2..or just the old fashioned way...

Some of these suggestions can or can't be used on the mount you own as i  have no experience with the mount you have..