Exposure limit on SBIG cameras

[griz11]

I've decided on a 8300 based camera. I was just about to buy the SBIG when I discovered its exposure is limited to 60min or 3600sec. A lot of the NB images I see are 75 60 75 minute exposures so this camera couldn't do those. Is there a reason for this that anyone knows like a hardware limitation or it just goes white after 60min under typical conditions. In other words would going with the ATik 383L + that has the same chip but unlimited exposure a better way to go if you are going to do a lot of narrow band? I'm going with the Atik wheel and I also noticed that with the Atik 383 and my scope at f5.5 I can use 1.25 instead of 36mm filters. Which allows the 9 position wheel. So the Atik has some advantages other than the unlimited exposure. I'm going batty reading specs   And its a significant purchase so I want to get it right.  So any information is appreciated.

Griz

[johnrt]

I really don't think a lot of people shoot 60 minute plus subs, I know it can and has been done but it is certainly not the norm. 10, 20 or even 30 minutes are pretty much standard.

[perfrej]

I, for one, rarely go above 30 minutes, and I have my remote observatory in a very dark place; about as dark as it gets in mainland Europe. Even though I have an SBIG ST-8300M myself, it is not a camera I recommend. If you can afford it, QSI-683WSG8 is the best bet. It has the added advantage of having the filter wheel very close to the chip, so you get by with smaller filters without vignetting. Olly Penrice, whom I trust in these matters, speak dearly of Atik products so that might well be a second choice. If I were to get another and reasonably low-prices 8300-based camera today I would give Moravian instruments a serious look.

As for Atik's claim of 1.25" filters.. Nah, not sure about that. The distance to the filter wheel is too large I think. QSI barely makes it happen with 31mm unmounted (essentially 1.25") and I think they have the wheel much closer to the sensor than what you can get with the external filter wheel.

Between my ST-8300M and my QSI-683WSG8, the BIAS and noise is significantly higher in the former (quite a lot actually).

/per

[swag72]

I'd be interested to know why you'd not recommend an SBig Per over a QSI? I am not in the market, but a good friend is and I know that he'd like to know this as he is looking at an SBig.

[ollypenrice]

The Atik One has an integrated filterwheel close to the chip, nowadays.

Do people really take 75 minute subs? I'm impressed! I regularly use 30 min ones in all filters but I'm not an NB imager other than NB for enhancing LRGB so I'm not in that world, so to speak.

Olly

[steppenwolf]

I don't think you need to worry about the 60 minute limitation for one minute (oops, pun!) - it is hard to imagine when you would want to capture with such a long exposure, 30 minutes yes but not 60 even for narrowband.

As for camera choice, that's a little more difficult but I am VERY happy with my QSI 683 WSG, supremely well made and it works just fine with 1.25" filters. I have no personal experience of the SBIG so cannot offer any comparison advice.

[nightster]

Not that you asked this Griz, but if you factor in cost, the QSI w/ integrated FW is at least 1k $ more than a 383L and the Atik FW. As you know, I just went down this road over the last 3 months and battled between the 8300 vs the 694 chips, changing my mind weekly. I looked at the QHY9M also but in the end was dissuaded by reports of quirky behavior. In the end I can only recommend what I know and the quality of my new Atik is high and seemingly one of the best values if budget is a concern.

[griz11]

I was reading those exposure times wrong. Looks like people aren't getting close to the limit for NB after figuring this out. 2K is all I want to spend on one. Almost 2500 with the filter wheel. Lot of money for a retired guy.  I have really dark skies here. Its black all the way to the ground on 3 sides with minimal glow to the east. That should make for shorter exposures so a little additional noise will be minimized. I won't be tangled up with the skyglow so it will be easier to get rid of. To me its not the camera that makes a great image its the processing skills. Especially at my level. I wouldn't see the difference between the STF and a QSI or FLI or any of the other high end cameras. It will be several years before my skills develop to a point where I'll get everything out of the STF and by then everything will be different and better. I decided against going with the 1.25 filters. They might work ok but why go with a bigger ccd and then waste the corners with a smaller filter. And if the exposure limit isn't an issue I'd rather go with the STF and it has more distance between the filter wheel and camera so it will need a bigger filter. Don't know what filters I'd put in the extra slots anyways the 36mm has enough for LRGB and 3 NB filters. Not that much more money and I found out you don't have to glue them in these days so that is another worry I had that isn't a problem. I almost ruined one the last go round trying to glue it into an Optec unit. If you didn't scratch them getting them out of the holder then you had the glue to deal with. Sure thought I was going to be able to do some imaging tonight but it clouded up right about sundown.

Griz

[perfrej]

I'd be interested to know why you'd not recommend an SBig Per over a QSI? I am not in the market, but a good friend is and I know that he'd like to know this as he is looking at an SBig.

I have both and they are miles apart in terms of both build quality and performance. I have also taken both apart and found the same difference. Given that they share sensor, there is only one explanation for the difference in noise and general performance: read electronics design.

This parameter is what generally separates the more expensive ones from the cheaper. One can ask why most manufacturers gave up on the 29050, and why FLI continues to make excellent cameras based on that very sensor. They are at the top of the quality ladder and have the knowledge and the resources to develop good stuff.

I had a conversation with Moravian Instruments when they cancelled their 29050 camera. The reason was that it proved too complicated to tame the sensor. Add to that the fact that Moravian are fairly high up the ladder and apparently make good read electronics.

In the end, the old proverb still goes: you get what you pay for

/per