Veil & North America Neb from Tampines

[kimo]

I don't know about Extending time problem with DSLR. Yes, here we have serious problem with condensation.
I managed to Exp without condensation. hope I am not offending here to post a pic. this is the sample of single
12min Exposure of Ha. I have converted JPG for posting.

[orly_andico]

the problem with DSLR isn't condensation per se, it's thermal noise.

an IDAS LPS-V4 is almost a narrowband filter (it has 20nm passbands for OIII and Ha). A DSLR would need a 10-minute range exposure to get any signal, and without cooling the thermal noise is terrible.

kimo, i think your image is with cooled mono camera. That's a totally different situation from using a DSLR.

[kimo]

Thanks orly. I wanted to show that DIY cooling have no condensation problem so DSLR can be done for our weather right?

[orly_andico]

hi Kimo,

not sure. i have had condensation problems on my old QHY8 and now on the ST8300M. Because I could not get any desiccant i bought two cans (about 200 pcs) from Sigma Aldrich. Cost me over $100. but now I have enough desiccant for years and years.

because of this, i cannot really say that there are no condensation problems here... of course a better camera like a QSI has a nitrogen or is it argon-purged chamber so has much less (or no) condensation problems.

do you know what is the temperature for your DIY? if the temperature of the sensor is below the dew point you will get condensation, and in SG thanks to the high humidity, the dew point is only a few degrees below ambient temperature.

[kimo]

I ever had same problem and reconstructed CCD few times to get perfect. currently imaging at 3deg cel depends on my dark collection and ambient temp but mostly are below 10deg cel CCD sensor temp.

[orly_andico]

I noticed on the 8300 that even at 10 celsius i would get dewing (resolved now with the molecular sieve desiccant - ordinary silica gel doesn't work).

Maybe the chip in your camera is smaller so there is less area for the moisture to condense? (on the 8300, only about 20% of the chip surface gets condensation, and it's always a fixed pattern)

regardless.. cooling a DSLR is a much greater challenge, because you have to house the entire DSLR, and it has a much larger sensor (typical DSLR sensor is 2X the size of 8300). And the DSLR cooler isn't cheap, we're talking US$300 range unless you DIY.

[orly_andico]

I forgot.. the biggest enemy of DSLR for narrowband is the IR cut filter.

If the DSLR is modded you get 4X as much H-a signal. So that should be the first priority, before even cooling.

[PETER LOO]

Oh, btw this Canon 500D that i used for Nebula is already IR filter glass replaced, i bought it from Shirox, thinking of selling it off to get a Cooled one even though i already have a DIY cooler (too lazy to improve on it, in fact i spoiled it , sorry Kelvin ..)