Max exposure for dslr

[piprees]

Just wondering, perfect polar alignment, tracking and guiding, wonder what the maximum safe exposure time for a dslr, (canon 40D), would be before things went pear shaped? I have this vision of blue smoke coming from the chip!!!!

Phil

[D4N]

I don't think there is an upper limit if it's cold enough.

I do 20 min subs in mine when it's -10 out and there is very little noise.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

[lensman57]

Just wondering, perfect polar alignment, tracking and guiding, wonder what the maximum safe exposure time for a dslr, (canon 40D), would be before things went pear shaped? I have this vision of blue smoke coming from the chip!!!!

Phil

You are limited by your sky quality, LP and in no small measure the limited well depth of the DSLR sensor. Most DSLRs used in the light polluted areas are safe to about 300s with a suitable LP filter, if you are lucky to have nice dark sky then 600s ( with guiding ) is possible but you may find that stars lack colour due to early saturation. I have managed up to 1200s using a NB Ha filter with a 1100d. Some of the more recent full frame pro DSLRs seem to have better well depth but having looked at their prices it is cheaper to go for a full frame cooled CCD which is made for the job.

Regards,

A.G

[piprees]

Thanks guys, have to curb my enthusiasm a little.

[wxsatuser]

The histogram will give you the limit for your sky conditions.

For any combination of ISO and f ratio get your histogram somewhere between 25 and 50%.

In theory you should'nt have a problem, I have done 20minute exposures on really good nights.

The norm here is 300secs at f4 for a 25% histogram and I have moderate LP.

[piprees]

Thanks Mike, bit technical but I'll google it and check it out. I reckon 5mins will be enough for me for a while.

Regards,

P.

[D4N]

It depends on your camera - I have no experience of a Canon 40D, your focal ratio, your target and how dark your sky is.

This is an unprocessed 20min sub I took the other night with my DSLR. The only thing I have done to it is shrink it and convert it to jpg to post here.

I used a Baader UHC-S filter, I always use that even though I don't have much LP as I need the IR block from it.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

[RichM63]

Nicely aligned there D4N (but it looks like you have a squad of cloaked Clingons invading) sensor cleaning time?

[D4N]

Yep gave it a clean after that session.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

[Psychobilly]

I have been know to shoot 1800s (30 min subs)  for imaging and on one occasion 3600s (60 min)  subs when doing a long term guiding test...

Here's M27 Single 1800s sub @ ISO800 with my Badder BCF Modified Canon 1000D Badder with  my CPC800 at f6.3...

Peter...