Concerning focus, have a look at this thread:

www.indilib.org/forum/general/6167-for-t...-issues.html?start=0

I would not focus on such a bright star, unless it was with a narrow band filter. I prefer bright but not that bright stars, and I do full frame, so a number of fairly but not too bright stars is perfect.

Magnus

Mohamed,

I still work through things a step at a time. If you have a cooled camera, start it cooling as soon as you start. Magnus says he uses the capture tab. The connect tab for the camera is another place where the temperature can be set. (After needing to not auto connect for a debugging issue years ago, I manually connect each device in turn. When the cooled camera connects, I set the temperature.)

I found that, for me, polar alignment with the imaging camera and scope worked best. (I now have a pier and tend not to fiddle with polar alignment any more.) PHD2 doesn't need to be started before you slew to a target location, but starting at any time before is OK, just make sure you aren't tracking when you slew (I did that once).

I tend to work in the alignment, focus and capture tabs. After a slew, I always do a slew to target in the alignment tab. If I am returning to a location where I have imaged before, I'll use one of the subs for "load and slew".

Here is another reference for focusing.

I still haven't moved to using the scheduler tab.

We each need to sort out our individual process for repeatability.

Richard

Thank you Richard. I have a question regarding the tracking timing. When I connect for the 1st time, my scope tracking is automatically on. I tried without success internal and PHD2 for guiding, but I think it is my camera (which I’m replacing).

So shall I turn tracking off before adjust guiding? Also, at what step you do plate solving? And so you turn on tracking or leave this for the guider?

I’m sorry my questions looks very basic even for me, but I’m confused what to do and clear nights are not that many where I live to give it try and error...


Thank you
Mohamed

Mohamed,

You should track sidereal whenever your mount isn't parked. Guiding occurs on top of sidereal tracking and applies adjustments required because of tracking errors which come primarily from mechanical issues and polar alignment.

To use guiding, ensure your guide camera is in good focus. I had many a struggle related to poor guide focus. Of course, the camera has to work. You can rough focus and test your camera during the day. If you are focused or near focus during the day, the camera will generally need to move towards the scope.

To help us give you support, please advise what equipment you are using. You can put that information in a reply, but it can also be useful to include it in your signature (see mine below).

Richard

Thank you Richard,

I have Celestron Nexstar 8SE with a sky sync GPS, Canon T3i as the main camera, JMI moto-focus, Orion Deluxe Mini 50mm Guide Scope with Helical Focuser as a guide scope, ZWO ASI120MM Mini Monochrome CMOS as a guide camera (ordered to replace bad quality eyepiece camera), and of course the Ekos running on RPi4 as astroberry.


Thank you
Mohamed

Mohamed,

I hate to tell you this, but an Alt-Az mount will lead to significant field rotation if you use it for astrophotography. It might work if you have an equatorial wedge.

I initially tried to use a Celestron Nexstar 90SLT (also Alt-Az) and the field rotation made stacking exposures impossible for me.

For guiding, two warnings: the separate guide scope and long focal length will give you guiding issues (flexure) and Alt-Az mounts will be different than equatorial mounts. I found a recent article on cloudy nights which you might find helpful ( www.cloudynights.com/topic/697479-guidin...az-mounts-with-phd2/ )

Mohamed,
I have a friend that does astrophotography with an Alt-Az mounted telescope and he achieves quite a bit but all done with lots of 30 second shots.
He does not guide, and throws out and failed shots, and I think you may need to do the same.
In the long term equatorially mounted is far better.
Paul

Hi Richard

I’m totally aware about field rotation for alt/azimuth mount. I just decided to slow down on purchase one till I’m able to make other components work.

What I don't understand and appreciate if you can explain is why it will be difficult to use the guide scope?

I'm aware about the f/10 of the 8SE where I can use field reducer to fix it.


Thank you
Mohamed

Hi Paul

Thank you for the tip. I found the below link in Richard response below. I’m attaching it as I found it useful

telescopemount.org/short-exposure-alt-az...o-get-great-results/


Thank you
Mohamed

I've imaged Altaz a long time ago, it does work with short exposures, less than 30 seconds usually. One thing that helps is to image objects as they are passing through east or west because in those directions the image rotation rate is smaller. Never tried guiding but the problem may be that if your guide star is not at the centre of rotation of your image the rotation will cause your guide star to move.

BTW, the focal length of an 8" F/10 scope is a bit long, even with a FR it has a focal length of 1260 mm. What I find is that for a budget imaging system an 80mm F/5 ED refractor is good. The shorter focal length reduces all you pointing issues and the light weight doesn't troube the mount. I have one on an AVX. I'm using an 80mm F/4 scope mounted side by side as a guider, that's a bit OTT but at least I never need to worry about finding a guide star.

Mohamed,

Generally with SCTs it becomes necessary to use an off-axis guider where the guide camera is using the main telescope. Reasons for this include mirror flop (which may be less of an issue for Alt-Az mounting) and the ability to keep a guide scope from moving differentially to the main scope.

If I've done the math right, 1 micron of movement of your guide scope (assumes 50mm f4 -- fl of 200mm) will equate to an angle of ~1 arc-second.

Using the same assumptions, your guide scale will be ~3.75 arc-seconds / pixel. With the reducer, your imaging scale will be about 0.6 arc-seconds / pixel. This may be OK if everything else is spot on.

[mention]RDBeck [/mention]
Thank you, Richard. Do you advise using OAG with the separate guide camera or use the main camera as a guide camera as well?


[mention]ChrisRowland [/mention]
I've read some posts about doing astrophotography with AltAz mount and I'm very interested in giving it a try before investing another $1k for the GEM


Thank you
Mohamed