I've had a frustrating intermittent problem with flats for some time now.
This morning was a good example - half way through capturing a series of early morning sky flats, under more or less evenly lit cloudy skies the images appear to have a series of vertical bands or stripes running through them.
Previously, suspecting electrical interference, I'm managed to somehow resolve the problem by separating all cables and cords from one another, switching on /off the camera, removing and replugging in the cables, restarting Nebulosity and sometimes even the laptop.
But here it is again - this time though the effect appears mid sequence.
It's a QSI 8300wsg8 camera, I capture with Nebulosity 3.0 on a mac.
I've had this issue in the past, but not with flats, just generic light frames. This is typical of a cooling failure. Check your camera TEC if you have a log of the temperature.
I've had this issue in the past, but not with flats, just generic light frames. This is typical of a cooling failure. Check your camera TEC if you have a log of the temperature.
Marc, image info says they're all the same temp - 30C
Quote:
Originally Posted by Moon
Are you 100% sure the exposure time is 30 sec for all of them?
James, the image info says they're all the same time @ 120 secs (not 60, my mistake)
This is exactly what my QSI looks like before its cooled down, so is there a way of double checking that the TEC is working? How often does nebulosity actually poll the camera for temp?
Perhaps try some other capture software like a trial of SGPro?
Cheers,
Andrew.
Ok, thanks for that tip Greg, Andrew, Marc & James.
I've posted this on the QSI group and emailed QSI support direct as well. I dont know if there's any other way I can check if the tec is working. The camera ran all night without problems. My 20mins subs appear to be fine (see my M16 post today in the Deep Sky section).
Just the 120 sec flats show the banding when taking them this morning.
James the flat sub duration is based on very early morning light, in overcast foggy conditions through 5nm NB filters at f5.6.
Looks like you might have a problem. Kevin from QSI should be able to help you out. I think maybe -30 is a bit steep though ever for a 683. How much head room did you have left?
Can you get hold of a lightbox and try "constant" flats?
Does Nebulosity show an instantaneous temp readout during the exposures? MaxIM has "active" temp readout. I do have Nebulosity, but never used it only ever using MaxIM.
Those results are precisely how my SXVR-M25C behaved after TEC failure before I sent it back to SX for repair.
Folks, the problem continues - here is a sequence of 5 consecutive 30sec "t-shirt" sky flats (ie: white t-shirt stretched over the objective).
These images were taken through the 5nm Astrodon Ha filter, one after another, in sequence, no changes were made to anything during the capture sequence.
Paul/Lewis, a screenshot of the last frame shows the TEC settings at -30C, 68% ambient temp 19.
James/Tigerdes, what is a "mean ADU"?
You can clearly the sequence starts normally, as frames 5-7 are "normal but the banding appears on frame 8 and gets worse on frames 9 &10.
(I didn't post frames 1-4, as they're the same as 5-7 - let me know if you want to see them).
Same stripes appear through the O3 & S2 filters immediately when taken afterwards on the same settings.
QSI support have asked to see the fits files for analysis by their lead engineer, so I've dropboxed them as requested.
This has been going on intermittently since december last year. The camera is less than 12 months old, I'm hoping the camera doesn't need to be sent back to the states again!
I am definitely no expert but to me it looks like a camera read issue or signal build up (discharge error). The only suggestion I can think of as a test would be to run a bias frame in between the flats and see if that helps. It might work kind of like a purge of previous data that may potentially be left behind from the previous flat.
IF that helps then it'll probably have to be sent back to repairs anyway.
And back to the factory it goes today for the second time in less than a year! Hmmm, these unreliablity issues were part of the reason I didn't buy a new SBIG either after my previous experience with a return.
Is it just me or how hard is it really to make these expensive bespoke cameras perform reliably?
(Insert heavy sigh)
Anyway, off to Singapore and Legoland Malaysia for a fortnight with the family & kids tmrw. Time to relax and have some fun in the sun
And back to the factory it goes today for the second time in less than a year! Hmmm, these unreliablity issues were part of the reason I didn't buy a new SBIG either after my previous experience with a return.
Is it just me or how hard is it really to make these expensive bespoke cameras perform reliably?
(Insert heavy sigh)
Anyway, off to Singapore and Legoland Malaysia for a fortnight with the family & kids tmrw. Time to relax and have some fun in the sun
Man I feel your pain. Just been through this with my SBIG camera. Interestingly I have had two QSI camera's and never once had a problem. No doubt the same can be said for SBIG. Kevin will make sure the camera is sorted before it comes back.
My experience with FLI cameras so far are they are very reliable and solidly made. I think they may have had some teething issues early on and that they are a bit more expensive initially but they have the best of everything in their components. I just wish they made an AO and OAG setup.
My experience with Apogee was the same. The 2 SBIG STL's I had were very reliable and my STi guider is wonderful. My Starlight Express Trius is also very reliable and well made. I had Lodestars' though that had a white line at the top and another had one along the side that the autoguiding software (CCDSoft) confused with guide stars and would throw the autogudiing badly sometimes.
QSI cameras seem to be high performers and the built in filter wheel and OAG is like the SBIG STL type convenience that was so popular.
I am sorry that your camera needs fixing. I am sure QSI will do their best to find an effective solution quickly.
I have also been using Nebulosity for quite some time, but did not like that it does not have an option for a gradual warming up of the CCD (as well as gradual cooling). Therefore quite recently I swapped Nebulosity for Sequence Generator Pro. To avoid rapid temperature changes I set a gradual cooling and also warming up of the sensor at the end of imaging session. Also, since SGP has much more options and automation (including autofocus and plate solving - great for multi-night imaging sessions of the same target), I have not not looked back at Nebulosity. I am sure that Nebulosity is fine, but I like to look after my equipment as well as I possibly can so that it hopefully will last longer
