Hi Guys,
I thought I would post this up here to show some of the people who don't have the equipment to guide, what can be achieved with good polar alignment. This is a 10 minute single sub CR2 to JPG convert straight out of the camera. Now I know there is some tracking in this image, however it is a 10 minute sub, so I could probably go at least 2 or 3 minutes without any tracking showing. Like I said I just wanted to show that longer subs are achievable with good polar alignment.
Like I said I just wanted to show that longer subs are achievable with good polar alignment.
Sorry to be party breaker but it's not really, at least not repeatable with low end mounts (or more or less with any mount without absolute encoders).
You can have a perfect PA but because of high PE you will have to throw away many subs.
Guiding is unavoidable.
When inspected closely, your star trails suggest round stars for approx.
2 minutes, which I can achieve with my HEQ5. If you are lucky enough to have a mount with lower than average PE, you could maybe get a little longer, say 2.5 mins, but other external factors come into play which
prevent repeatability for any longer than that. You have a comparatively short focal length scope Rex. If you had say an 8" SCT, you would struggle to get 60 secs.
raymo
The other night we were experimenting with software assisted drift alignment with my EQ6. I was getting 1 minute subs with a C8@f/7 with a tiny bit of trailing - have a look in my Orion thread for the images of the core. I threw out about half the frames due to excessive trailing IMO, but I wasn't guiding so I wasn't shocked about having to do that.
Naturally, I want more! But appreciate it's probably a case of diminishing returns and/or realistic expectations given the cost of the mounts
Wow. Shows how much I'm still struggling with alignment. 30 sec is the best I've managed
Just keep at it Peter, it takes practice to achieve good PA without spending half your night doing it. Read up on drift alignment and keep at it.
Quote:
Originally Posted by orion69
Sorry to be party breaker but it's not really, at least not repeatable with low end mounts (or more or less with any mount without absolute encoders).
You can have a perfect PA but because of high PE you will have to throw away many subs.
Guiding is unavoidable.
You are absolutely correct. This post wasn't meant to discourage anyone from guiding, or even suggest that it's totally unnecessary, it was meant to encourage those who don't have the means or equipment to guide, and show that slightly longer subs are possible.
Quote:
Originally Posted by cometcatcher
Rex, curiosity wants to know, what's the bright star and cluster?
Kevin, it's Antares and M4.
Quote:
Originally Posted by raymo
When inspected closely, your star trails suggest round stars for approx.
2 minutes, which I can achieve with my HEQ5. If you are lucky enough to have a mount with lower than average PE, you could maybe get a little longer, say 2.5 mins, but other external factors come into play which
prevent repeatability for any longer than that. You have a comparatively short focal length scope Rex. If you had say an 8" SCT, you would struggle to get 60 secs.
raymo
I have no doubt you could achieve the same with your mount Raymo. It's basically the same as mine.You're correct with all you have said, however, most new-comers, who this post was supposed to encourage, start out with short focal length scopes, ED80, f/5 newts etc, so that's why I thought it was relevant.
Quote:
Originally Posted by PeterEde
So I can stop panicking. I could never achieve much more than 1 minute or maybe 2 on my EQ3 unguided
Hi again Peter, I must be coming across wrong mate. I apologise if I made you panic, that was not the intention. Sorry mate. I don't know a lot about mounts mate, but I think the main difference between your mount and mine is the amount of weight it can carry.
What you said is quite right Rex. 2 min or slightly longer subs are
achievable with care, and with 500-1000mm f/l scopes. The struggle
with 60 sec subs with an 8" SCT did of course mean with it being used
at it's native f/10.
I myself have no means of guiding, and may probably never have, so I
am just seeing how far I can get without it. I used to guide manually, but have had enough of that.
raymo
Just keep at it Peter, it takes practice to achieve good PA without spending half your night doing it. Read up on drift alignment and keep at it.
Hi again Peter, I must be coming across wrong mate. I apologise if I made you panic, that was not the intention. Sorry mate. I don't know a lot about mounts mate, but I think the main difference between your mount and mine is the amount of weight it can carry.
I have since removed my dual battery grip. Which reduced the weight quite a bit. Now just scope and DSLR. Seems to do ok with that.
Ah of course. I was racking my brain trying to think which cluster was near a bright star, but didn't think of Antares. My brain is slow lately. Must be the lack of sleep.
The struggle with 60 sec subs with an 8" SCT did of course mean with it being used at it's native f/10.
IMO raymo you do a fantastic job with your polar alignment
When I first started taking images I was getting trails at 10s exposures with this scope I have yet to try f/10...but being slower that'll be reserved for when f/7 just won't do.
That's still a great demo Rex. Yes us chaps with shorter focal length scopes have it lucky, I just don't know how the 2000mm guys do it. Guiding I guess!
I'm finding guiding is giving me a leap in performance however and of course saves much time, esp using PHD2's excellent drift alignment routine.
I have yet to try f/10...but being slower that'll be reserved for when f/7 just won't do. 
