C9.25 EdgeHD alignment - Forums

Topic starter

Apr 5, 2021

Dear friends

Yestarday I wanted to point my C9.25 to M 94, but I had great problems during the alignment process as this scope is only at f10. The lack of light makes it very difficult to see the alignement stars in the reticle eyepiece. I was not able to get a proper alignment and to center M 94.

What could the solution be? Would it be possible to do the whole alignment proces with the 0.7 reducer that offers a wider field of view and better light, and remove it once the alignemnt process is finished?

Thanks for your help in advance.

Kind regards
Markus

Björn Arnold

Apr 5, 2021

Hi Markus,

You're having two threads in the forum. I assume the other refers to the polar alignment and this to the mount alignment after polar alignment is done. A good polar alignment is the basis for the rest. Even if you just do visual, your polar alignment shouldn't be horribly off but you'd can allow some more arc minutes compared to astrophotography. You can see how bad your polar alignment is when you have an object centered and let the mount just track. If your polar alignment is bad, you'll see a strong drift in the field of view very quickly.

If you do initial alignment with your finder scope, make sure your finder scope and main OTA are well aligned to each other. Start the alignment of the mount and center on a bright and convenient star. This will give the mount a first idea how it's aligned. Then let the mount slew to a brighter star close to your final target. Center on that star and "sync" the mount (a feature every mount should have). This will inform the mount for any deviation of its alignment and make the next moves even more accurate. Then you can try to slew to the final target. With the mount you have, it should hit it directly.

I'm adding that I don't have the CGX but an iOptron CEM40. The basics remain the same however. I only do a one-star alignment and sync the mount to a star close to the faint target. With that my mount has a precision on the final target that I just love.

CS!

Björn

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Scott Badger

Apr 5, 2021

I'm a new owner of a C925/CGEM (and new all around), so fwiw….. Swapping the reducer on and off works if that helps, but I'm using a DSLR (Canon 5D) and find using the camera on 'live view' is a lot easier than the eyepiece. I generally have the reducer on (don't have auto-guiding yet, so need to reduce exp time as much as possible), but I don't think I've had trouble seeing stars without it either. With my Canon the live view is according to the camera's exp etc. settings, so set exposure as high as it will go and same with iso to 'see' the stars on the screen during alignment. Also, and only because it's caught me a couple times, you don't have to be too far out of focus for stars not to show…..

Cheers,
Scott

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Markus

Topic starter

Apr 5, 2021

Hi Scott!

Many thanks for your answer! I wil try to use the liveview of my Sony, that's a good idea!

Kind regards
Markus

Björn Arnold

Apr 5, 2021

Hi Scott and Markus,

Live View helps a lot but again: align your finder scope with your main optics. If both look at the same point in the sky, when you center the star in your finder, it will be (nearly) centered in the camera view (so no more guessing of where the scope points at) or at least visible in the field of view of the camera.

Another point: don't shoot without reducer. At least until you've checked the resolution per pixel (e.g., here: http://astronomy.tools/calculators/ccd_suitability).
If your resolution is much higher than average seeing, you won't get any benefit. And since both of you have a DSLR where you cannot bin the image, you should try to set your focal length to what is suitable.

CS,
Björn

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Scott Badger

Apr 5, 2021 · Edited: Apr 5, 2021

Thanks Björn! Agreed about getting the finder scope spot on. Another advantage to that with my set-up is the finder has a cross-hair while the camera live-screen has a center circle, so witht the live screen I'm estimating by a few arcsecs at least (you can add a grid pattern, but I can't see it at night).

According to the calculator you linked to, I'm a little oversampled without the reducer (0.47) and right on the lower end of the range with (0.67).

Cheers,
Scott

BTW Markus thanks for your likes!

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Björn Arnold

Apr 5, 2021

@Scott Badger It might be helpful to connect the EOS to a laptop computer and use Canon's EOS utility application. With that I always have much easier control over the camera than with the camera only.

Best,
Björn

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Scott Badger

Apr 5, 2021

Thanks @Björn Arnold , I've tried that and agree, but I occaisionally have issues getting my laptop to see the camera wifi for some reason. Also, the grid doesn't show up any better on my laptop screen and EOS Utilities doesn't have it's own grid display that I can find.

Cheers,
Scott

Björn Arnold

Apr 5, 2021

@Scott Badger ,
Hi Scott, I admit that I even haven’t found a crosshair or central circle in the EOS Utilities. I usually centered the object by naked eye and that was sufficient for me. The WiFi is also unstable in my case (I use it combination with an iPad but it’s convenient for quick checks or focus adjustment).

For the laptop, I can only recommend to use a 3 or 5meter USB cable.

Cheers,
Björn

Scott Badger

Apr 5, 2021

@Björn Arnold
Hi Björn, my laptop is nearing it's end and was at the top of my shopping list....until I stumbled on to Astrobin! Ha! Anyhow, I'm back to laptop shopping (actually, I'd rather add auto-guiding first, but since I'll need a laptop for it....). In the meantime, like you I'm using my iPad.

After sending my post, I started wondering why I can see the circle on my live-screen, but not the grid..... will need to look at that again when I get home tonight.

On the computing note, I'm trying to decide between a big laptop (17" screen with 1TB hard drive and 32GB memory) for processing and use with the scope or a desktop with the same memory, faster video card (8GB vs 6) and a larger screen plus a smaller, cheaper laptop for the scope, all for about the same amount of money. I'm leaning towards the bigger laptop so I have one machine for everything, but would welcome any feedback.

Cheers,
Scott

Björn Arnold

Apr 5, 2021

@Scott Badger ,
I have a MacBook Pro 16“ for post processing. I don’t see the need for 32 GB of RAM and an extreme graphics card (in the end compare prices). The software I have been using up to know worked very well with my 16 GB and „mid-size“ graphics chip. At the moment, I work with AstroPixelProcessor.

Also don’t look too much at internal storage. You‘ll run out of it one day. Just invested 110€ in a external 1TB SSD. That’s way more flexible and extremely fast.

Don‘t use your expensive laptop for shooting. At least at my place, I wouldn’t take my 2,5k€ Laptop out the whole night at -5 deg C. I‘m using a raspberry pi when I shoot with my mono (incl. guiding) and a cheap laptop when I need something more close to the scope.

Finally for the laptop: consider docking the laptop. Go for a mid size screen 15 (max 16“) and get a good Desktop Screen.

That’s how I am doing it and it works quite well that way. But sure, some things are a matter of taste.

Cheers,
Björn

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Scott Badger

Apr 5, 2021

@Björn Arnold
Not sure how they compare, but I'm using Pixinsight and for some processes on my current laptop (integration and local normalization in particular) I start it and let it run overnight, or all day while I'm at work, and hope it doesn't crash mid-way through.....or that I need to tweak any of the settings..... Anyhow, I have the same concerns about the cold and an expensive laptop. Last couple nights were around -10C. For some other non-astro use, though, the better laptop would be a lot more convenient than a desktop.

Cheers,
Scott