I use only 5min subs actually, to avoid differential flexure (yeah I know, I should do something about it..I will, I will...). checking the peak of the histogram curve, ADU background on a single 5min sub is about 2500, on a 90 min stack of 5min subs about 500...?
Wow that makes a huge impact. Just by comparison I have on single Lum subs with the 4" at 10 minutes are 1111 ADU. The colour of course is around 430 ADU with 5 minutes subs. That means so much more time involved. I really must go back to 10 minutes subs overall. Thanks for the reminder.
Once you go to OAG you will never look back Mike. No more differential flexure again. If you do go that way, I can recommend the SBIG ST-i guide camera. Very nice and lots of bright stars. Mind you the light bucket you have it gets the job done in a quarter of the time I need with the 102.
Wow that makes a huge impact. Just by comparison I have on single Lum subs with the 4" at 10 minutes are 1111 ADU. The colour of course is around 430 ADU with 5 minutes subs. That means so much more time involved. I really must go back to 10 minutes subs overall. Thanks for the reminder.
Once you go to OAG you will never look back Mike. No more differential flexure again. If you do go that way, I can recommend the SBIG ST-i guide camera. Very nice and lots of bright stars. Mind you the light bucket you have it gets the job done in a quarter of the time I need with the 102.
I have this (SX H694, Loadstar, OAG, SXCFW and full set of Astronomik filters) galaxy gun waiting for me to pull my finger out ...I hate change in my imaging rig, once I have a system chugging nicely I am loathed to change it, I baulk at tinkering and getting technology to work, it is the imaging I like
I have this (SX H694, Loadstar, OAG, SXCFW and full set of Astronomik filters) galaxy gun waiting for me to pull my finger out ...I hate change in my imaging rig, once I have a system chugging nicely I am loathed to change it, I baulk at tinkering and getting technology to work, it is the imaging I like
Mike
Yeah I know what you mean. Took me ages to attempt focusmax and got it going in a couple of hours and wondered why on earth I had procrastinated for so long. Well you have the gear that is the main thing.
Halleluluja brother! I agree. Having a few setups makes for trouble every time I switch.
Greg.
I am also hesitant to get the SX gear attached until I have the protection of a dome, I am concerned the main benefits of the new system (small pixels and OAG) would be mostly negated by the pesky wind I get here..?
Quote:
Originally Posted by Stevec35
Very nice Mike. Incredibly good considering the moon.
I am also hesitant to get the SX gear attached until I have the protection of a dome, I am concerned the main benefits of the new system (small pixels and OAG) would be mostly negated by the pesky wind I get here..?
Cheers Steve, yes I was desperate I guess
OAG could give you a big gain. You may be able to do 10 minute exposures with that. I'd be whacking that on first. OAG are the way to go even if they are a tad fiddly. Focus your main imaging camera. Then focus the guide camera. Put a bit of masking tape on the guide camera so you know where it comes to focus next time in case you take it off.
That can save a lot of time. Distance from start of OAG to main camera sensor has to be the same as start of OAG to guide camera. That will help get it focused. If you are too far off guide stars are so out of focus they become invisible. You have to be reasonably close to focus on the guide camera to see the guide stars. It also helps to go to an area of bright stars when doing this for the first time.
OAG could give you a big gain. You may be able to do 10 minute exposures with that. I'd be whacking that on first. OAG are the way to go even if they are a tad fiddly. Focus your main imaging camera. Then focus the guide camera. Put a bit of masking tape on the guide camera so you know where it comes to focus next time in case you take it off.
That can save a lot of time. Distance from start of OAG to main camera sensor has to be the same as start of OAG to guide camera. That will help get it focused. If you are too far off guide stars are so out of focus they become invisible. You have to be reasonably close to focus on the guide camera to see the guide stars. It also helps to go to an area of bright stars when doing this for the first time.
I almost gave up on using my MMOAG at first as I could not get the guide camera to focus until I got the guide cam quite close to focus. I tried a few times and got nowhere. There was no evidence of a star in the too out of focus guide camera image. It was really frustrating. It really has to be relatively close to focus to see any guide star from the guide cam - at least with the MMOAG.Once I measured the distances I saw the guide cam holder had to be the 2nd focus tube they provided. The first focus tube was way off.
Yummy, the colour version that we've been waiting for! Nothing less than stunning, Mike. There really isn't anything quite like a nice smooth galaxy field
Quote:
Originally Posted by strongmanmike
I use only 5min subs actually, to avoid differential flexure (yeah I know, I should do something about it..I will, I will...). checking the peak of the histogram curve, ADU background on a single 5min sub is about 2500, on a 90 min stack of 5min subs about 500...?
Mike
Some interesting comments regarding sub length. I notice that many people swear to use very long sub exposures, but I found that S/N in the stacked image is actually higher for a correspondingly larger number of shorter subs (10x300s has higher S/N than 5x600s).
Depending on your equipment and sky conditions you may not have to increase your sub lengths Mike. Have you tried a test, as in stacking 10 subs of 5mins versus 5 subs of 10mins etc. and see which give you the highest S/N in the final image?
I experimented to find the optimal sub length for my combination of sky and equipment, which seems to be when background ADU reaches 1500-2000. The optimal ADU count is only dependent on the sensor properties, and optimal sub legth is then simpy the time it takes to reach that count. For me it is typically 5 minutes, so I stick to that.
Also, when the Moon is up I use correspondingly shorter exposures to keep the background ADU count in the optimal range in order to still gather maximum S/N under the brighter conditions. It's all about optimising the data collection during those precious clear hours
Beautiful image Mike. Nothing better than swimming around in an ocean of galaxies. Gawd help us when you start getting some pwoper data together from the Obsy.
Yummy, the colour version that we've been waiting for! Nothing less than stunning, Mike. There really isn't anything quite like a nice smooth galaxy field
Some interesting comments regarding sub length. I notice that many people swear to use very long sub exposures, but I found that S/N in the stacked image is actually higher for a correspondingly larger number of shorter subs (10x300s has higher S/N than 5x600s).
Depending on your equipment and sky conditions you may not have to increase your sub lengths Mike. Have you tried a test, as in stacking 10 subs of 5mins versus 5 subs of 10mins etc. and see which give you the highest S/N in the final image?
I experimented to find the optimal sub length for my combination of sky and equipment, which seems to be when background ADU reaches 1500-2000. The optimal ADU count is only dependent on the sensor properties, and optimal sub legth is then simpy the time it takes to reach that count. For me it is typically 5 minutes, so I stick to that.
Also, when the Moon is up I use correspondingly shorter exposures to keep the background ADU count in the optimal range in order to still gather maximum S/N under the brighter conditions. It's all about optimising the data collection during those precious clear hours
Cheers,
Rolf
No haven't tested that yet but all sounds about right to me too Rolf ...30min subs baaah...maybe 10 min once I have the SX OAG running
will be very interested to see your new cam come online - should only need 2 minute subs with that one. Regards Ray
Quote:
Originally Posted by DJT
Beautiful image Mike. Nothing better than swimming around in an ocean of galaxies. Gawd help us when you start getting some pwoper data together from the Obsy.
Cheers Ray and David...I made the first moves on the road to getting the pier and slab under way...went and saw the neighbour to organise borrowing his Bobcat and post hole digger sometime over the next week
...I hate change in my imaging rig, once I have a system chugging nicely I am loathed to change it, I baulk at tinkering and getting technology to work, it is the imaging I like 
baaah...maybe 10 min once I have the SX OAG running 
