Marc
@corpsmoderne@mamot.fr  ·  activity timestamp last week

Hey #astrophotography #astronomy , my Skywatcher Skyadventurer 2i has a noticeable "wobble" on the Y axis (RA I presume?) . Here I shoot @ 400mm , shutter-speed 15s . Is it normal or is my unit faulty? Or something I'm doing wrong?
Marc
@corpsmoderne@mamot.fr  ·  activity timestamp 6 days ago

Update on my periodic error issue: I did a second night trying a better arrangement for balance and... it didn't go well 😅

I believe that the collapse near the end is due to a worst polar alignment? I'm surprised I thought I did better than the first night.

It's strange that the "calm" periods are synchronous among the two nights, must be a coincidence?

(to try to make a better balancing I added a ball-head so more weight, seems it didn't helped)

#astronomy #astrophotography
mjr
@madjohnroberts@mastodon.social  ·  activity timestamp 6 days ago
@corpsmoderne do you have images from this session? If it's a polar alignment issue, it should be relatively straightforward to evaluate from a subframe. I'd compare one from the low PE region and the high PE region.

Also worth checking for a cable snag, it might be that as the night progressed a cable was pulled taut, and that could easily vary between nights
mjr
@madjohnroberts@mastodon.social  ·  activity timestamp 6 days ago
@corpsmoderne well, if there was a particular pattern of star elongation then we would know there was an alignment issue. If we don't see it, we'd have to keep looking 😅. So I guess it would be the first thing I'd check, since you mentioned you suspected an alignment problem.

Not dragging your previous images at all (they are good!), but I do see evidence of polar misalignment in your M31 picture from a week ago. If you are using similar exposure times, I think we'll see any alignment problems
RaphAstronome
@raphastronome@mamot.fr  ·  activity timestamp last week
@corpsmoderne It is the periodic error. It is due to the gears in the mount and the quality (and price) of it. Also it can be worst if mechanical stress occurs (counterweight not correctly placed for exemple). I don't now exactly the specifications of the Skyadventurer but normally you can calculate the value in arcsec on sky and compare it with others but numbers in pixels knowing you shot with a 400mm doesn't seems enormous for this setup.
RaphAstronome
@raphastronome@mamot.fr  ·  activity timestamp last week
@corpsmoderne I notice the mount have a ST4 port. Normally it can give possibility to add a autoguider with a small guider telescope in parallel. This is a camera checking for displacement of a star and controls the mount to correct the movements. I don't now if it is reasonable with weight can handle the mount. It is also complex, generally it require a computer.
Erik
@pleiotrope@fosstodon.org  ·  activity timestamp last week
@corpsmoderne what’s the scale on the y-axis, and is this consistent night-to-night? Assuming you’re not using a guider, it could be issues with your counterweight balance in either the RA and Z-axis (or both). It’s sort of hard to describe, but you can check the latter by ensuring it balances horizontally even across different rotations of the DEC saddle.
Erik
@pleiotrope@fosstodon.org  ·  activity timestamp last week
@corpsmoderne oh that’s very fair. You could also try guiding on just RA if you have a guide scope and camera- if it’s a technical issue with your RA gear, guiding may help a lot. I think the sky adventurer can take guider inputs?

And yeah… technically drizzle requires random offsets in both RA and DEC for best results, so I never bothered when using star tracker type mounts. It *might* reduce the noise from the color array on your sensor, maybe?