Another which mono camera upgrade from DSLR question!
Hi guys,
Well, I envisage that in the next 6 -9 months at most, I would like to move on from my modified Canon DSLR - an ageing Canon 400D, to a mono camera.
Had aspirations initially that perhaps I would go to a cooled OSC camera or a cooled/modified DSLR, but I think if I can address the issues below, a mono could work for me.
Firstly, all my imaging is done with a portable set up with a 12.5" f/5 scope and a focal length of 1600 mm which currently uses a MKIII Baader Coma Corrector, OAG and Loadestar guide camera.
I already do mono work for planetary imaging and have a UK made True Technology filter wheel with 1 1/4 inch LRGB filters.
My criteria as follows:
1. Budget - absolute max $2000k tops, if I have to get a new filter wheel and filters, then max $2,500
2. As my mount is not high end - max exposure levels 5 mins per shot. This means I cannot do like 20 minute expsures, and 10 minutes is pushing ti for me without being in an observatory. This to me means that I need a high efficiency QE chip?? ie. high sensitivity?? and/or that the signal to noise ratio vs sensitivity needs to work in 5 minute increments for stacking.
3. Need to be able to shoot LRGB sequence for an object within one night and ideally 2.5 to 3.0 hours total LRGB exposure time. Most of my DSLR shots have been at this level, and I have been comfortably been able to shoot one object per night. So to me, this says 45 minutes per LRGB channel maximum exposure. HOW REALISTIC IS THIS?
4. Ideally still be able to use my filter wheel and 1 1/4 INCH filters. Optionally upgrade just the internal filter holder and to 2" filters. The True Technology never accepted square filters but I think I can get a 2" filter wheel holder with 5 filters.
5. My current CCD chip on the 400D is 22.2mm x 14.8mm and 3888 x 2592 in pixels. I don't need for the CCD to be bigger than this, but ideally I don't want it to be much smaller as I find it fits most deep sky nebulas perfectly in my 12.5" f/5
6. In terms of image scale, I am guessing that I would like image scale of around 0.7 arc seconds per pixel or thereabouts to allow me to do sharpening and some deconvolution. I could have this wrong. My shooting location (Heathcote, Vic) is not renound for the seeing conditions, but it can be ok.
7. I am not a brand freak - I am not into high end or low end brands. For me it's about value for money, and also about getting the latest technology. I know that QSI?? and Sony?? chips at the moment are being talked about highly. Not fussed - just want something that will be still producing results in 5 years. I have been able to get 8 years out of my DSLR and it's still going strong.
8. Weight. Not discussed very often, but the lighter the better - my scope has a rotating truss and if the camera weighs more than my Canon 400D 510 grams than perhaps I will be pushing it when I add my filter wheel.
9. Ideally needs to be usable with my Baader MKIII coma corrector so I don't have to buy a new one. Only have a spacer designed to be used with a DSLR.
10. Back focus - I currently appear to only have 15mm of back focus left. THIS COULD BE A SHOW STOPPER! But this already includes the OAG, coma corrector and DSLR adaptor and then the 400D. I hope this issue alone is not a show stopper indeerd! Otherwise perhaps the solution is simply a camera with a built in low profile filter wheel??
Am I dreaming here? A lot of things to consider.
Hope the people one IIS that have been on the same journey and moved on from a DSLR, but also with the above complicating parameters, can offer some advice.
To my limited knowledge, you won't be able to find a new astro camera with this size CCD sensor for 2000 AUD; I will be extremely happy if someone proves me wrong...
The dimensions of a common KAF-8300 sensor are 17.96mm x 13.52mm, which is bit smaller than what you already have, but at F5 you will probably get some vignetting with this CCD anyway when using 1.25 filters and external filter wheel. Anything larger will cause more severe vignetting in combination with 1.25 filter.
Perhaps you could consider a smaller sensor or a second hand camera with 8300 sensor could be a reasonable option?
I am sure more knowledgable and experienced imagers will soon provide you with a thorough answer.
To my limited knowledge, you won't be able to find a new astro camera with this size CCD sensor for 2000 AUD; I will be extremely happy if someone proves me wrong...
John, 8300 powered ones are closest in image size to your APS-C 400D. Gama has the QHY9S plus filter wheel listed for $2500. There's also the Atik 383L+ but even Andrews want close to $2800 for just the camera.
John, 8300 powered ones are closest in image size to your APS-C 400D. Gama has the QHY9S plus filter wheel listed for $2500. There's also the Atik 383L+ but even Andrews want close to $2800 for just the camera.
Good one thanks - looks like the SBIG 8300 and QHY9 will be in my budget. What other options are out there and what about some of the other issues raised?
I don't want to turn this thread however into another SBIG vs QHY thread as I just finished reading the last multi page thread on this!
Back focus will be your first hurdle to get over John. 15mm is not enough for any camera ever without filters. Get that eqation solved first.
Have double checked this.
In total, I have a total of 14 cm of total back focus which includes my main mirror moving up 1 cm. This is from where my eyepiece focuses to the inserted focuser.
If I add my current imaging train, I still have 2.5cm left (as I can move my main mirror up 1 cm), but I still need to add a filter wheel. But this includes a Lumicon Giant Easy guider which is not ultra thin, my Canon 400d, and my coma corrector.
In total, I have a total of 14 cm of total back focus which includes my main mirror moving up 1 cm. This is from where my eyepiece focuses to the inserted focuser.
If I add my current imaging train, I still have 2.5cm left (as I can move my main mirror up 1 cm), but I still need to add a filter wheel. But this includes a Lumicon Giant Easy guider which is not ultra thin, my Canon 400d, and my coma corrector.
CM or MM John. If it is 140mm then that is ok. In your original post you said you had 15mm.
Personally if you could afford either a QSIWSG or SBIG with integrated filter wheel then you would be ok.
The 8300 series sensor is a good sensor. 5 and 10 minute subs are fine, but in my opinion the sensor works best at longer exposure lengths. I am now doing 20 minutes as a minimum to get the best performance out of my QSI. I am certain others will not agree with me about exposure length. The QHY camera which contains this sensor has good deep cooling but might not suit your setup for length. I don't know the specs with filter wheel attached.
The 8300 series sensor is a good sensor. 5 and 10 minute subs are fine, but in my opinion the sensor works best at longer exposure lengths. I am now doing 20 minutes as a minimum to get the best performance out of my QSI. I am certain others will not agree with me about exposure length. The QHY camera which contains this sensor has good deep cooling but might not suit your setup for length. I don't know the specs with filter wheel attached.
Thanks Paul. In terms of the QHY9 camera I might ask this question on the QHY Forums and speak with the local OZ distributor.
Any other suggestions from anyone regarding a camera that will give good results superior to OSC or a DSLR with 5-10 minutes subs and 45 minutes per LRGB channel with a budget $2,500k budget?
I guess my other option is to be on the look out for a second hand unit as well.
I think the 8300 would be good with only ~10 minute subs on your 12.5". I've only done a couple of LRGB images with my STT-8300, NGC253 was 10min bin1x1 L and 5min bin2x2 R, G, and B, and that was with my TSA120 so nowhere near the aperture of your scope.
I always do 30 minute subs when I'm doing narrowband though.
If time is really tight for you then you could sacrifice some resolution and use binning to speed up acquisition of dimmer objects.
I think the 8300 would be good with only ~10 minute subs on your 12.5". I've only done a couple of LRGB images with my STT-8300, NGC253 was 10min bin1x1 L and 5min bin2x2 R, G, and B, and that was with my TSA120 so nowhere near the aperture of your scope.
I always do 30 minute subs when I'm doing narrowband though.
If time is really tight for you then you could sacrifice some resolution and use binning to speed up acquisition of dimmer objects.
Ok, thanks.
Also, in terms of the data I have been reading, the new SONY chips seem to be more sensitive which might suit my limit of ideally only doing 5 mins subs (maybe 10 at best) at 4 mins per channel.
What CCD mono cameras are out there in the $2k to $2.5k mark using the SONY chips?
Also, in terms of the data I have been reading, the new SONY chips seem to be more sensitive which might suit my limit of ideally only doing 5 mins subs (maybe 10 at best).
The biggest advantage of the Sony chips for short exposures is the low read noise.
The biggest advantage of the Sony chips for short exposures is the low read noise.
Cheers,
Rick.
Ok - so what does this mean in terms of 5-10 minute subs? Simply lower noise?
The issue I think as well with SONY chips is that for the equivalent size probably double the cost?? e.g. QHY9 vs ATIK equivalent in a SONY (in terms of chip size) - although I should be more accurate and say in terms of the ATIK offering which then starts to use larger KODAK chips in the larger format cameras.
My Canon 400D provides a 47.9' x 32.0' field. I really don't want to go below about 40' x 30'
I can see why even though it's been around for a long time the KAF 8300 chip is so popular! and why perhaps the QHY9 is such good value.
Ok - so what does this mean in terms of 5-10 minute subs? Simply lower noise?
For best SNR you need to take subs that are long enough that the read noise becomes insignificant. If the read noise is small then you can take short subs. It's difficult to say whether that's one, two, five or ten minutes since that depends on a number of factors, including sky glow.
Quote:
Originally Posted by John K
The issue I think as well with SONY chips is that for the equivalent size probably double the cost?? e.g. QHY9 vs ATIK equivalent in a SONY (in terms of chip size) - although I should be more accurate and say in terms of the ATIK offering which then starts to use larger KODAK chips in the larger format cameras.
My Canon 400D provides a 47.9' x 32.0' field. I really don't want to go below about 40' x 30'
I can see why even though it's been around for a long time the KAF 8300 chip is so popular! and why perhaps the QHY9 is such good value.
Yes, it's a shame the Sony chips that are available in astro cameras are relatively small. The KAF-8300 is good value because it was made in large volumes for non-astro applications and that pushed the price down.
Just going to throw a wild card out there - have you considered the new Sony A7s?
Fritz Helmut Hemmerich took this shot Very cloudy night. In a gap in the clouds of less than 10 minutes length with some constant faint clouds in the upper atmosphere.
A less than suboptimal sky: 10 shots of 40 sec. H-Alpha 7 nm. Sony A7s uncooled. ISO 3200. Calibration (flats and darks, no bias). Hyperstar 1400. F1.9. EQ8 unguided. PixInsight processing. Date: 2014-12-03 21h. Tenerife south at 1200 m altitude.m altitude.
It's a helluvan amazing performing camera and it's in your budget. There are at least 2 IIS member who have either just received or ordered one.
