Focusing LRGB

[Bottletopburly]

So I have a set of Astronomic type 2c  LRGB  filters how parfocal do filters tend to be from each other , i’am using an auto focuser and using APT you can run the wheel to autofocus to work out offsets , do parfocal filters tend to be out from focus from each other much .

[+Graham]

I use a set of Astrodon LRGB filters are they are pretty much spot on with each other even at the extremes when using the 10 inch RC.

[Bottletopburly]

1 hour ago, Graham said:

I use a set of Astrodon LRGB filters are they are pretty much spot on with each other even at the extremes when using the 10 inch RC.

Cheers graham hopefully these Astronomik will be similar 🤞

[+Ibbo]

It is good practice to re focus between filter swaps and every couple of hours sooner if temp changes.

 

 

Note to self to remember this advice.😀

[Bottletopburly]

6 minutes ago, Ibbo said:

It is good practice to re focus between filter swaps and every couple of hours sooner if temp changes.

 

 

Note to self to remember this advice.😀

Cheers steve the Newtonian does change focus a bit with temp change I usually set  it to refocus every 1.5 deg change refractor more stable .

[Bob Dobber]

I've never bothered with offsets, I don't trust them and would rather the AF routine just did its job every time. I wouldn't switch filter more than once or twice in an evening usually, although I guess in the depths of winter I might go through a whole LRGB sequence in an evening, obstructions permitting. But then in broadband the AF exposure times are pretty quick so the routine doesn't take that long. In narrowband I might be doing 15s exposures in the AF routine so it will have more of a time impact if re-focusing every time I switch the filter. But as someone else mentioned, I might force an AF every couple of hours anyway... I do set it to AF with temperature change too, but that doesn't seem to happen as often as you might expect, maybe I need to lower the temp change amount. But then it doesn't seem to affect things hugely anyway. Of course, re-focusing is a risk if you've had some clouds come past just at that moment, so if it's looking changeable and I know it's going to have done AF OK at the start, I might just leave it to ride it out, even though NINA at least will ignore any re-attempt to AF if the result is worse than what it was already. Just lost time, and we've got plenty of that, right? 😉 

[Bottletopburly]

35 minutes ago, Bob Dobber said:

I've never bothered with offsets, I don't trust them and would rather the AF routine just did its job every time. I wouldn't switch filter more than once or twice in an evening usually, although I guess in the depths of winter I might go through a whole LRGB sequence in an evening, obstructions permitting. But then in broadband the AF exposure times are pretty quick so the routine doesn't take that long. In narrowband I might be doing 15s exposures in the AF routine so it will have more of a time impact if re-focusing every time I switch the filter. But as someone else mentioned, I might force an AF every couple of hours anyway... I do set it to AF with temperature change too, but that doesn't seem to happen as often as you might expect, maybe I need to lower the temp change amount. But then it doesn't seem to affect things hugely anyway. Of course, re-focusing is a risk if you've had some clouds come past just at that moment, so if it's looking changeable and I know it's going to have done AF OK at the start, I might just leave it to ride it out, even though NINA at least will ignore any re-attempt to AF if the result is worse than what it was already. Just lost time, and we've got plenty of that, right? 😉 

 

4 hours ago, Bob Dobber said:

might be doing 15s exposures

Do you really take 15 sec exposures for Af , Apt inverse method I only take 4sec ,and 10 points min 8 , i should use shorter exposures but didn’t realise, recommended times are 0.5- 1.5 sec  but 4 sec worked , though will try shorter exposures too see how it goes ,I thought by now Nina would have implemented the inverse method, ivo from Apt recently did an interview with the Astronomy channel he goes into depth regarding focusing methods pros and cons ,I’m sure the method will turn up in Nina sooner or later as it’s open source code .

 

ivos interview on TAIC 

https://www.youtube.com/live/OzvZCvz0t4Q?feature=share

 

[Bob Dobber]

37 minutes ago, Bottletopburly said:

 

Do you really take 15 sec exposures for Af , Apt inverse method I only take 4sec ,and 10 points min 8 , i should use shorter exposures but didn’t realise, recommended times are 0.5- 1.5 sec  but 4 sec worked , though will try shorter exposures too see how it goes ,I thought by now Nina would have implemented the inverse method, ivo from Apt recently did an interview with the Astronomy channel he goes into depth regarding focusing methods pros and cons ,I’m sure the method will turn up in Nina sooner or later as it’s open source code .

 

ivos interview on TAIC 

https://www.youtube.com/live/OzvZCvz0t4Q?feature=share

 

I really do use 15s yes, for Ha and Oiii narrowband filters. I find that my curve isn't very reliable if I go much less.

[Bob Dobber]

18 hours ago, Bottletopburly said:

 

Do you really take 15 sec exposures for Af , Apt inverse method I only take 4sec ,and 10 points min 8 , i should use shorter exposures but didn’t realise, recommended times are 0.5- 1.5 sec  but 4 sec worked , though will try shorter exposures too see how it goes ,I thought by now Nina would have implemented the inverse method, ivo from Apt recently did an interview with the Astronomy channel he goes into depth regarding focusing methods pros and cons ,I’m sure the method will turn up in Nina sooner or later as it’s open source code .

 

ivos interview on TAIC 

https://www.youtube.com/live/OzvZCvz0t4Q?feature=share

 

 

Just had a quick watch of the bit of the video about the inverse method - no way I'm switching back to APT but will keep an eye out in NINA in case this is either already in there (or if there's a plugin) or if it is added. Looks interesting! Currently nothing is broken but if I can fix it painlessly anyway, I may be interested 😉 

[Bottletopburly]

3 hours ago, Bob Dobber said:

 

Just had a quick watch of the bit of the video about the inverse method - no way I'm switching back to APT but will keep an eye out in NINA in case this is either already in there (or if there's a plugin) or if it is added. Looks interesting! Currently nothing is broken but if I can fix it painlessly anyway, I may be interested 😉 

I did look yesterday at Nina algorithms I couldn’t see it’s been implemented but I’m sure it will turn up at some point , the open source code is there to use .