Thank you SGL + PA question

[Denys]

Hello folks!

First of all, I would like to thank this community for being so open and helpful towards newbies like myself, and also for all the high-quality information that is available on this forum (which I am still trying to get a grasp on 😬).

Thanks to this forum I managed to get some astrophotography which I am very happy with (despite them being far from perfect). I hope you don’t mind with I share with you my attempts at the globular cluster in Omega Centauri and the Eta Carinae nebula...

Now, please bear with me once again: I have an EQM-35 mount and a SW 150-PDS, and the images above were taken with an old Canon 500D. But I have been really struggling with polar alignment… Yesterday I spent what felt like an hour trying to align with the DARV method, but I am not sure if I was really successful, as I was hoping I could achieve exposures at least one minute long, but only managed a few seconds… So first question: maybe I am expecting too much from my mount (maybe OTA + DSLR are already too heavy for it)? And if that is not the case, is there any software out there that I could use for polar alignment with my DSLR (on PC)? From my understanding, EKOS may be up for the task, but apparently it doesn’t run on Windows…

Thanks once again!

Denys

[vlaiv]

I'm rather baffled by your images.

They are object that I'm not that familiar with, so I might be wrong here.

Omega Centauri globular image looks like trailing is in fact in RA direction  - and that is something I would expect. I'll explain in a minute.

In second image - well, I simply can't figure out what is what. I'm looking at Stellarium and Eta Carinae and I can't figure out how to match them. If you can - well, first step is to figure out direction of elongation.

Now for explanation. Most people just starting out in AP when facing elongation - think, this must be poor polar alignment.

I've found that in majority of cases - it is actually something else causing the elongation and drift. Most people do rather good job of polar aligning and you really need to miss by a lot in order to have drift that happens in matter of seconds. That just does not happen. What does happen is drift in RA due to periodic error. If elongation is in RA direction on the image - you can be 99% sure it is down to periodic error.

Periodic error is rather difficult to overcome. One thing that you can do is to do periodic error correction if your mount supports it. Since you are using EQM-35 which is SW mount - you can use EQMod and control your mount via computer. EQmod has periodic error correction feature. That should help somewhat - but it can still be present.

Second thing that you can try is to do a belt mod. Not sure if there is belt mod kit for your mount.

If none of these help, and even if they do help - it is likely that they won't solve the problem 100% - you'll need to turn to guiding in order to correct that. In fact - people should not fear guiding - and should consider it from the start. Most affordable amateur mounts will need guiding. Only expensive models with encoders or with exceptional mechanical precision can do without guiding. Everyone else simply guides.

Guiding does not need to be expensive - web camera and 50mm finder scope with a bit DIY skill can be turned into guide scope. Then you just need a computer / laptop, but you can even do it with Raspberry PI.

HTH

[Denys]

15 minutes ago, vlaiv said:

In second image - well, I simply can't figure out what is what. I'm looking at Stellarium and Eta Carinae and I can't figure out how to match them. If you can - well, first step is to figure out direction of elongation.

Thanks for your answer vlaiv! This is something interesting that you have pointed out, I didn't think about checking the direction of elongation... Now, since you mentioned it, I just opened Stellarium and I myself struggled to recognized any star pattern there LoL... All I can say is that I typed NGC 3372 in my handcontroller and this is what appeared on my camera/screen, so I assume it was indeed eta carinae 😅

Anyhow, thanks for the suggestions, really helpful! Is it just me or does this hobby has a never ending list of accessories? When I first decided that would buy myself a telescope I thought all I would needed was the OTA! 🤣

Denys