Vroobel

The FMA230 is a great scope, but it's rare to have no problems with the back focus. I use it with the original reducer, so have a 230mm focal length. Unfortunately, the back focus isn't equal to the declared 55mm, presently it's 52.5mm and I'm not sure if it's the end. It worked with 2600MC earlier, now I use 2600MM with it, but the problem still exists. Unlike a typical refractor, the Askar doesn't follow the below-mentioned rule. 

Startrails from my backyard;
Canon 6D, Optolong L-Pro clip, Tamron 17-35mm F/2.8-4 Di OSD @ 17mm F/4, ISO1600, 348 x 5s;
PixInsight, Affinity Photo, IrfanView. 

https://www.astrobin.com/cnxsk3/

Registering startrails for the first time. 

1 hour ago, Startoucher101 said:

Ok, Also a really impotant question; How can I improve the goto accuracy?

Thank you again, clear skies!

My bad, I had to read it twice. The GoTo is a matter of a system controlling your mount like NINA, ASIair or others. As @AstroKeith mentioned above, the system captures an image of the sky and it recognizes the piece of the sky where your scope is aimed. Of course, a supported camera is needed.

I ask a third time: please describe your project, what is your idea. It would be easier if we know what you want to achieve. 

You can do it by using e.g. worm gear or harmonic gear together with (not too high) number of micro steps, like in the example provided earlier. 

Nice dual rig, indeed. 🙂

I think it's OK, as long as guys from the OnStep recommend it, or as long as it's supported. Take into account that it's deprecated boards, like my FYSETC S6 and MKS Gen-L (L-Gen?).  

Do you need a mobile app which means you will use BT/WiFi features, or like me, do you want to connect it to a NINA/ASIair using a USB cable?

I used both MKS L-Gen v. 1/2.5 and FYSETC S6 v.2 in my applications. They are custom 3D printer boards which offer at least 5 ready-to-work ports for any 12-24V steppers, but you need to buy stepper motor drivers, at least two of them. I would recommend LV8729 as they are quite cheap and silent.

You should choose your stepper motors depending on your project and the final gear you use, so please, tell us much more about your idea.

Edit.

I have to add that both the board I used are slow which means a GoTo slew will be 1-3 degrees per second. You can find better boards offering more features.

9 minutes ago, Ratlet said:

Because of the way stepper motors work, microstepping reduces the torque output of the motor.  The more microsteps, the less torque.

I'm not qualified enough to explain it scientifically, but roughly saying, every level of micro stepping (number of micro steps per full step) is based on a fraction of the magnetic field needed for turning the stepper by one full step. A 2-micro-steps mode offers smaller torque than a full-step mode, a 4-micro-steps mode offers less than the 2-micro-steps one, etc.

A 32- or 64-micro-steps mode gives you good fluency and accuracy to the torque ratio.

1 minute ago, Ratlet said:

I picked up a 27:1 nema 11 and 99:1 nema 17 and the gearboxes have next to no backlash.

 

Indeed, the planetary gearing provided with the stepper as assembly usually has the backlash, but I didn't take this case into account in my calculation above. By the 100:1 gearing, I meant a worm or harmonic gearing.

3 minutes ago, Vroobel said:

Edit. It may happen rather around 128 or more micro steps.

 

27 minutes ago, Vroobel said:

The stepper motors don't have any backlash...

 

You may face another problem related to the steppers itself. The torque lowers with a number of micro steps, so in the worst scenario, some micro steps may be lost because the stepper may have not enough power to move a significantly loaded and not balanced axis.

Edit. It may happen rather around 128 or more micro steps.

That's nice, you made my day better, thank you. ☺️ 

Share all your assumptions here, we can think about your project together with other SGL members.

And good luck, of course! 👍🤞

The stepper motors don't have any backlash, it appears in the gearing. Nema 23 steppers usually offer a higher torque than the Nema 17, but it depends on a strength of magnetic field generated inside the stepper - the longer the stepper the higher the torque.

That's right, you have to use a proper total gearing ratio for astrophotography. If you base on 400 steps per revolution and use e.g. 64 micro steps, and the gearing ratio is 100:1 then your theoretical final resolution of the axis equals ( 360 * 60 * 60 ) / ( 400 * 64 * 100 ) =~ 0.5 arcsec which is quite good for astrophotography. In practice, the resolution is smaller, you can find info about it in OnStep(X) documentation.

The iris isn't a problem, if your lens works like Canon lenses do. Set the iris with the body while a Bulb mode is turned on, press and hold a release button to close the iris and detach the lens from the body. 

The focusing is an another problem. 

8 hours ago, Tony Acorn said:

I too bought a wireless programmable remote release but it was from Aodelan. It is really good as I can start and stop it without touching the camera or the tripod although I can only programme it to take up to 199 images where my older hard-wired Rollei would do 399!
I hope you aren't intending putting a scope on that trripod though - I fear it would be too light to carry much more than a camera and lens, let alone a tracking mount.
I'm hoping that I get the AM3 delivered tomorrow.

Tony

My intervalometer offers several operational modes, but I need two: remote release and 1-999 shots separated by flexibly set intervals multiplied by 1-999 or even repeated infinitely. I should live on the North or South Pole and use it during their nights to fully use its features. 🙂

26 minutes ago, Tony Acorn said:

I too bought a wireless programmable remote release but it was from Aodelan. It is really good as I can start and stop it without touching the camera or the tripod although I can only programme it to take up to 199 images where my older hard-wired Rollei would do 399!
I hope you aren't intending putting a scope on that trripod though - I fear it would be too light to carry much more than a camera and lens, let alone a tracking mount.
I'm hoping that I get the AM3 delivered tomorrow.

Tony

Thanks, but no worries, its max load is 10kg. It will work with Canon 6D and <1kg lenses.

Two new items from Amazon today: an intervalometer with remote control and a very clever and very tall tripod - up to 2.3m, depending on its configuration. 😇

10 hours ago, RoryG said:

 

Should I take it as nothing to say about disadvantages? 🤔 Well, I'm jealous then! 🙂

Tell us something about disadvantages of living there to not make us too jealous... 😁

They are very good pictures, congrats. 👍

On 09/07/2024 at 17:48, Elp said:

Does this count, whilst video recording the aurora of 10/11th May a meteor had the audacity to enter the frame:

Lucky you! 🙂

I have an Optolong 6.5-7nm SHO and their LRGB. I can see that particularly OIII subs are very bright, so I consider replacing the wider OIII with 3nm one. Does it make sense? I know that the oxygen contains two wavelengths. 

The ZWO one works, I used it with the SharpCap which has a dedicated feature for it. 

Could you please write something about the stuff you used (I know that they are on AstroBin) ? 

Nice composition and details but I think it's stretched too much. 

On 06/09/2021 at 05:17, 900SL said:

They look good. I have the 17-35mm Tamron f2.8-4.0 OSD. It's pretty good at 17mm but a fair bit of vignetting at f2.8. Tracking at f4 is fine. I tend to use a Nikon 20mm f1.8 now for MW shots, it's sharp as a tack at f4.0

Hi, 

Recently I bought an used Tamron 17-35mm f/2.8-4 Di OSD. I thought to use it occasionally for some sky events, but I see that the 15-30mm one gives quite nice stars with Canon 6D. 

Do you have unprocessed (unsharpen) pics taken with your 17mm?